Handbook for Waterworks Operator Certification: Fundamental Level, Volume I

FUNDAMENTAL LEVEL

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VOLUME 1

FUNDAMENTAL LEVEL

The Handbook for

Waterworks Operator Certifleation Frank R. Spellman, Ph.D.

TECHNOMIC

(WBusHING Co., lNcJ

1 ,ANCASTER

BASET ,

Fundamental Level, Volume 1 aTECHNOMICfhblication Technomic Publishing Company, Inc. 851 New Holland Avenue, Box 3535 Lancaster, Pennsylvania 17604 U.S.A. Copyright O 2001 by Technomic Publishing Company, Inc. All rights reserved No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of the publisher. Printed in the United States of America l 0 9 8 7 6 5 4 3 2 1 Main entry under title: The Handbook for Waterworks Operator Certification-Fundamental A Technomic Publishing Company book Bibliography: p. Includes index p. 273 Library of Congress Catalog Card No. 00-107613 ISBN NO. 1-56676-866-7

Level, Volume l

To Waterworks Operators Everywhere

Table of Contents

Preface

...

xi11

1. INTRODUCTION

1.1 1.2 1.3 1.4 1.5

..............................................................................................................

Introduction 1 The Waterworks Treatment Process: The Model Key Terms Used in Waterworks Operations 3 Summary 8 Chapter Review Questions 8

2

2. CERTIFICATION/LICENSURE REQUIREMENTSAND SWDA

2.1 2.2 2.3 2.4 2.5 2.6

................................................................................................

Introduction 19 An Abbreviated History of Waterborne Disease and Hydraulics Waterborne Disease 21 Indicator Organisms 27 Multiple Barrier Concept 27 Summary 28 Chapter Review Questions 28

4. WATER MICROBIOLOGY

4.1 4.2 4.3 4.4 4.5 4.6 4.7 4.8

........................................

11

Introduction 11 Safe Drinking Water Act (SDWA) 11 Operator Certification 12 Typical Classes of Waterworks 16 Summary 17 Chapter Review Questions 17

3. WATERBORNE DISEASES

3.1 3.2 3.3 3.4 3.5 3.6 3.7

1

19

.............................................................................................

Introduction 31 Microbiology: What Is It? Bacteria 34 Protozoa 36 Viruses 38 Algae 39 Summary 39 Chapter Review Q1 ons

19

31

31

39

5. BACTERIOLOGY: SAMPLING AND EXAMINATION

........................................................ 41

5.1 Introduction 41 5.2 Water Sampling 42 vii

viii

Table of Contents

5.3 5.4 5.5

Sampling Followed by Testing: Why and for What? Summary 51 Chapter Review Questions 51

6. WATERWORKS MATH: BASIC

46

........................................................................................

53

Introduction 53 Calculation Steps 53 Mathematical Terms 54 Sequence of Operations 54 Fractions 55 Decimals 60 Rounding Numbers 63 Determining Significant Figures 63 Powers 64 Averages 65 Ratio 67 Percent 68 Units and Conversions 69 Measurements: Areas and Volumes 72 Pressure and Head 76 Flow 78 Detention Time 80 Summary 82 Chapter Review Questions 82 7. BASIC WATER CHEMISTRY

.............................................................................................

87

Introduction 87 Chemistry Definitions 87 Water Chemistry Fundamentals 88 The Water Molecule 91 Water Solutions 91 Water Constituents 93 pH 96 Alkalinity 96 Hardness 97 Summary 97 Chapter Review Questions 97 8. BASIC ELECTRICITY

........................................................................................................

Introduction 99 Basic Electricity : Definitions 100 100 Basic Electricity : Theory Measuring Electricity 102 Ohm's Law 102 Electrical Circuits 103 Electrical Motion 103 Electrical Phases 105 Electrical Power 106 Electromagnetics l06 Transformers 107 Electrical Equipment Used in Waterworks Operations Summary 109 Chapter Review Questions 109

108

99

ix

Table of Contents

9. BASIC HYDRAULICS

......................................... .. .. . . . . . . . . . . ..

Introduction 111 Basic Hydraulic Definitions 111 Weight of Water 112 Pressure and Head 114 Static (at Rest) and Dynamic (in Motion) Conditions 12 1 Distribution System Hydraulics Summary 122 Chapter Review Questions 122 10. POTABLE WATER SOURCES

. ... . . ... . .

111

115

........................................................................................

125

Introduction 125 Key Definitions 125 A Cycle without Beginning or End 128 Sources of Water 128 Surface Water 129 Groundwater 133 GUDISW l36 Surface Water QualityITreatment Requirements 136 Public Water System Quantity Requirements 138 Summary 139 Chapter Review Questions 139 11. WELL SYSTEMS

....................................... .. . . . . .

. ........ . . . . .

Introduction 141 Developing a Well Supply 141 Well Site Requirements 142 Types of Wells 142 Components of a Well 144 Well Evaluation 146 Well Pumps 147 Routine Operations and Recordkeeping Requirements Well Maintenance 148 Well Abandonment 150 Summary 150 Chapter Review Questions 150 12. WATERSHED PROTECTION

......................................... .

Introduction 153 Water Management: Current Issues 154 What Is a Watershed? 154 Water Quality Impact 155 Watershed Protection and Regulations 155 How to Develop a Watershed Protection Plan Reservoir Management Practices 156 Watershed Management Practices 156 Summary 157 Chapter Review Questions 157 13. DISTRIBUTION AND STORAGE

13.1 13.2

Distribution 159 Storage 163

... .

141

. . . ... .. . . . . . . . . . . .

153

147

156

................................................................................... 159

Table of Contents

X

13.3 13.4 13.5 13.6

Types of Storage 163 Tank Maintenance and Inspection Summary 164 Chapter Review Questions 168

14. CROSS CONNECTION CONTROL

14.1 14.2 14.3 14.4 14.5

................................................... ....................... .... 169

Introduction l69 Cross-Connection Control 170 Cross-Connection Control Program Summary 175 Chapter Review Questions 175

15. WATER TREATMENT

l63

174

..............,.................................................... .............. .. .. ...... . .... 177

Introduction 177 Pretreatment 178 Coagulation 186 Flocculation l89 Sedimentation 190 Filtration 190 Corrosion Control 195 Role of the Waterworks Operator 196 Summary 197 Chapter Review Questions 197 16. DISINFECTION

16.1 16.2 16.3 16.4

......................................... . . . . .. . . . ...................... . .

. . . . ..

201

......................................................................................................

215

Introduction 20 1 Chlorination 202 Summary 213 Chapter Review Questions

17. PUMPING SYSTEMS

213

l l 17.2 17.3 17.4 17.5

Introduction 2 15 Pumps 215 Pump Maintenance 220 Summary 221 Chapter Review Questions

221

18.1 18.2 18.3 18.4

Introduction 223 Fluoride Addition 224 Summary 225 Chapter Review Questions

225

19. SAFETY

19.1 19.2 19.3 19.4 19.5 19.6 19.7

......................................................................................................................

Introduction 227 Safety Precautions 228 OSHA-Required Safety Programs for Waterworks Specific Hazards Related to Waterworks Operation Storage Tank Safety 238 Safety Inspections 239 Accident Investigations 239

229 235

227

xi

Table of Contents

19.8 19.9

Summary 239 Chapter Review Questions

20. FINAL EXAM

239

.................................................................................................................

20.1 Introduction 20.2 Review Exam

24 1 241

255 Appendix A: Answers to Chapter Review Questions 263 Appendix B: Answers for Final Review Examination: Chapter 20 Appendix C: Commonly Used Formulae/Equivalents in Waterworks Operations Index

273

269

241

Preface

Safe Drinking Water Act Amendments of 1996 (SDWA)(Public Law: 104-1 82) Section 123 specifically require that all operators of community and non-transient noncommunity waterworks systems be certified. These amendments also require the United States Environmental Protection Agency (USEPA) to issue guidelines for state programs and to reimburse small system operations (those serving under 3,300 people) through state grants for the costs associated with training and certification-states not implementing the program stand to lose up to 20 percent of their funding grants. States have implemented their own regulations, along with USEPA requirements, for waterworks operator certification. For example, Virginia, under Chapter 23, Title 54.1, Code of Virginia, requires waterworks operators to be licensed: "No person shall operate a waterworks without a valid license" (p. 1.7). All states have similar requirements for waterworks operators. Each state has its own definition and guidelines for certification andor licensure. Basically, "certification" means that someone in responsible charge of a waterworks "certifies" in writing that a waterworks operator is qualified to perform certain duties. "Licensure," on the other hand, "is a method of regulation whereby the State, through the issuance of a license, authorizes a person possessing the character and minimum skills to engage in the practice of a profession or occupation which is unlawful to practice without a license" (p. 1.3). Basic qualifications for licensure include experience, education, and examination (the 3E7s). Licensure is set at various levels, with each state setting the level and criteria required to fulfil1the requirements for qualification at each level. For example (using Virginia's regulations as a model), the state maintains five classes of licensure for waterworks operators: Class V through Class I (least to most responsibility). State licensure levels from Class I through Class V or V1 (least to most responsibility) are fairly common. In other locations, qualification levels may be listed by Grade (e.g., Grade I through Grade V or VI), or certain qualification levels may differentiate Grade or Class levels by area of expertise. For example, a Class Ia licensure level may indicate level of experience and designate the area of expertise, with the "a" signifying expertise for groundwater source supplies only. Class IIb might indicate expertise in surface water supplies. At the lowest qualification level in one region of the U.S., Class 5a level licensure indicates qualification for water operators at day care centers. A 5b license qualifies operators for water operations in schools. In short (keeping in mind that each locality has its own requirements), generally, the primary difference between "certification" and "licensure" as a waterworks operator is that certification requires the signature of only the responsible person in charge (Note: some states also require the passing of an examination for certification); for licensure, passing a written examination is mandatory. Exactly what knowledge is required for waterworks operator certification/licensure?The answers vary with location. Generally, to achieve certification or licensure as a waterworks operator, the operator must demonstrate both the ability to operate the waterworks system and unit processes and a knowledge of concentration/dosages (chemical addition), water chemistry, microbiology,

T

HE

xiii

xiv

Preface

laboratory testing, cross-connection control, distribution, storage, sources of supply, and mastery of a certain level of general knowledge in the field. The knowledge needed to qualify for waterworks operator certification andlor licensure is gained primarily through on-the-job experience. To pass Class- or Grade-Level examinations for licensure, candidates sometimes pursue correspondence course study or trade school attendance. They study such guides as the Water Work's Operator's Manual-Alabama Manual (1989), Manual of Water Utility Operations-Texas Manual (1988) or attend state operated Short Schools. Over the years, the American Water Works Association's Operator Certification Study Guide: A Workbook for Treatment Plant Operators and Distribution System Personnel 20206 (1989) was the principal study guide (the closest thing to a practice exam) used by many water operators to prepare for licensure or a higher level of licensure. However, this study guide is no longer available. California State University (Sacramento) offers four courses for waterworks operators. But now, states and candidates for certification face a problem in light of these new amendments: most of these publications are outdated, out of print, or not current to the recent changes in SDWA. The 1996Amendments of SDWA brought about several changes and new requirements. The amendments place more emphasis on protecting the public from pathogenic protozoans such as Giardia lamblia, Cryptosporidium,and Cyclospora. The effects of disinfection by-products on public health are a new regulatory concern. These new areas of concern are not discussed in the older study guides to the level necessary (or at all) for current waterworks operators to operate their waterworks up to present regulatory standards. At this time, an information gap exists between what is available to waterworks operators for study and what they need to know. This handbook bridges this gap. The Handbooks for Waterworks Operator Certification is a study guidelreference text in three volumes: Volume 1 for entry-level operators; Volume 2 for intermediate operators; and Volume 3 for advanced operators. The three volumes of the Handbook are designed for use as handheld ready reference books--ones that waterworks operators will find offer several benefits. They give waterworks operators instant information to expand their knowledge. They aid operators in the efficient operation of water treatment plants. They provide the user with basic information and sample problem-solving sets for state licensing/certification examinations. They provide fundamental reference material for waterworks personnel. From surface/groundwater intakes through pumping to the treatment works, to storage, pumping, and distribution to the consumer's tap, these handbooks provide easy to understand state-of-the-art information. The Handbookfor WaterworksOperator CertiJicationbegins with Volume l at the fundamental level (Small Water Systems) for those preparing for Class V/VI or Grade U11 operator examination; Volume 2 proceeds to the intermediate level for Class IIIlClass I1 or Grade 111111operator examination. Volume 3 finishes at the advanced level for Class IlGrade I V N waterworks operator license examination. Note that the Handbooks do not discuss the specific content of the examination. They review the waterworks operator's job-related knowledge-the information identified by examination developers as essential for minimally competent applicable Class or Grade levels for waterworks operators. Every attempt has been made to make the three volume Handbook as comprehensive as possible while maintaining the compact, practical format. The Handbook is not designed to simply "teach" the operator licensing exams, although users will immediately find that the material presented will help them pass licensing exams. We present applied math and chemistry by way of real-world problems-the kinds of problems operators face daily. These volumes are intended for practical use and application.

Preface

xv

Though formatted at three separate levels (entry, intermediate, and advanced), overlap between each volume ensures continuity and a smooth read from volume to volume. In essence, each volume enables practitioners of the science of waterworks operation to qualify for certification andor refresh their memory in an easy, precise, efficient, effective manner. For seasoned, licensed veteran operators, continuous review is also critical, because waterworks operations is an evolving, dynamic, ever-changing field. This series (which we think of as "Answer Books") provides the vehicle for reaching these goals.

CHAPTER 1

Introduction

Living things depend on water but water does not depend on living things. It has a life of its own.-E. C, Pieloul

1.l INTRODUCTION

first book of the series, The Handbook for Waterworks Operator Certification, Volume l : Fundamental Level, is primarily designed to provide a readily accessible, user-friendly source of information for review in preparing for the ClassIGrade VIIV State Water Operator Certification1 Licensure Examinations. Along with providing much of the necessary information to help the user successfully pass the ClassIGrade VIIV CertificationILicensure Examinations, Volume 1 sets the stage by providing the basics for Volumes 2 and 3, which are intended to prepare users to sit for examinations for ClassIGrade IIIIII and ClassIGrade I Certification or Licensure. We've made every attempt to format these books in a way that allows users to build upon the information presented, step by step and page by page, as they progress through the material. This handbook presents a summary of expert information available from many other sources (see Table 1.l) and in many formats. Those who seek additional information or more specific material on any of the topics presented should consult one or more of those references. This fundamental-level handbook assumes that the user is an operator-in-training (OIT) currently preparing to sit for the ClassIGrade VIIV waterworks operator certification or licensure examination. This handbook is also suitable for students attending technical colleges or other technical schools who are studying for careers (at the operator level) in waterworks operations.

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HE

J Note: In this handbook, we refer to the "fundamental level" as those first two steps in certification/licensure, which is the case in many states (check your local requirements to determine exactly what classlgrade level you need to prepare for at the entry or fundamental level). The symbol J displayed in various locations throughout the handbook indicates or emphasizes an important point or note that the reader should read carefully.

However, the Handbook is more than just a study guide. For example, individuals with limited experience who do not qualify (see Chapter 2) to sit for certification/licensure examinations may find the material helpful for a wide variety of purposes but should also augment the content of this handbook with other, more in-depth training, such as the various field study programs currently available from state W ater control boards, short courses presented by various universities (e.g., Virginia Tech7sannual waterlwastewater short courses presented each August on campus) andlor 'From E. C. Pielou's Fresh Water. Chicago: University of Chicago, preface, 1998.

2

l NTRODUCTION TABLE 1.I. Recommended Reference Material.

Small Water System 0 and M, Kerri, K. et al. California State University, Sacramento, CA. Water Distribution System 0 and M, Kerri, K. et al. California State University, Sacramento, CA. Water Treatment Plant Operation, Vol. Iand 2. Kerri, K. et al. California State University, Sacramento, CA. Basic Mathematics, #3014-G. Atlanta: Centers for Disease Control. Waterborne Disease Control. Atlanta: Centers for Disease Control. Water Fluoridation, #3017-G. Atlanta: Centers for Disease Control. lntroduction to Water Sources and Transmissio~Volume1. Denver: American Water Works Association. lntroduction to Water Treatment-Volume 2. Denver: American Water Works Association. fntroduction to Water Distribution-Volume 3. Denver: American Water Works Association. lntroduction to Water Quality Analysis-Volume 4. Denver: American Water Works Association. Reference Handbook: Basic Science Concepts and Applications. Denver: American Water Works Association. Handbook of Water Analysis, 2nd ed., HACH Chemical Company, P.O. Box 389, Loveland, CO, 1992. Methods for Chemical Analysis of Water and Wastes, U.S. Environmental Protection Agency, Environmental Monitoring Systems Laboratory-Cincinnati (ESSL-CL), EPA-600014-79-020, Revised March 1983 and 1979 (where applicable). Standard Methods for the Examination of Water and Wastewater, American Public Health Association, Washington, D.C., current edition. Basic Math Concepts: For Water and Wastewater Plant Operators. J . K. Price. Lancaster, PA: Technomic Publishing Company, Inc., 1991.

technical schools and correspondence studies from such sources as California State University, Sacramento (The Sacramento Manuals). Note that changes in technology and regulations occur frequently-the waterworks profession is dynamic. Because of this, certificatiordlicensure candidates must stay abreast of these changes to successfully complete their examinations. The Handbook is divided into chapters covering specific topic areas. At the end of each chapter, a series of practice problems andlor review questions is provided. Upon completion of each chapter, solve the practice problems, answer the review questions, and check your answers with those given in Appendix A. The final chapter includes a comprehensive practice examination designed to test the level of knowledge users have attained through study of this handbook, from practical experience gained through on-the-job experience and from other sources. A score of 75 percent or above is considered "goodv-more importantly, any questions missed signal to the user the need to go back and re-read and re-study the applicable areas. By using the final examination in this manner, users obtain a measuring stick to gauge mastery of the presented material. We provide answers to the final review examination in Appendix B. Appendix C is a formula sheet that should be used for reference; it can and should be used when taking the final examination.

1.2 THE WATERWORKS TREATMENT PROCESS: THE MODEL Figure 1. l shows a basic schematic of the waterworks treatment process. This is the model, the prototype used in all three volumes of the handbook. Although other unit processes are used in treating water (e.g., fluoridation) that are not represented in Figure 1.1, we discuss them in detail within the handbook. The purpose of Figure 1.1 and its subsequent renditions is to allow readers to visually follow the water treatment process step by step as we present it (and as it is often configured in the real world) to help in understanding how the various unit processes sequentially follow and tie into each other. To visually indicate the process flow of water through the system, in certain chapters dealing with unit processes, we show Figure 1.1 with the applicable process under discussion added to any previous processes. In essence, what we do is start with a blank diagram and fill in unit processes as we progress. Displaying water treatment as the series of individual steps (unit

Key Terms Used in Waterworks Operations Addition of Coagulant

Water Supply

I

//

11 Screening

F

) Mixing Tank

---) Flocculation -) Settling Basin

--)

Tank

To Storage and Distribution

Sand Filter

Sludge Processing

Disinfection

Figure 1.1 The water treatment model used in this handbook.

processes) that treat raw water as it makes its way through the entire process provides a pictorial presentation to go along with the pertinent written information.

1.3 KEY TERMS USED IN WATERWORKS OPERATIONS

Like any other field, water treatment has terms with accompanying definitions distinct to the profession. Many of the terms used in water treatment are unique, while others combine words from many different technologies and professions. Water operators without a clear understanding of the terms related to their profession are ill-equipped to perform their duties in the manner required. In the Handbook series, an early introduction to key words is provided to prepare readers for much of the material that follows. Additionally, an early introduction to key terms facilitates more orderly, logical, step-by-step learning. We define terms not included in this section when they are used in the handbook, often presenting specialized vocabulary at the chapter opening. J Note: A short quiz on many of the following terms follows the end of this chapter.

1.3.1 DEFINITIONS Absorb to take in. Many things absorb water. Acid rain the acidic rainfall that results when rain combines with sulfur oxides emissions from combustion of fossil fuels (coal, for example). Acre-feet (acre-foot) an expression of water quantity. One acre-foot will cover one acre of ground one foot deep. An acre-foot contains 43,560 cubic feet, 1,233 cubic meters, or 325,829 gallons (U.S.) (also abbreviated as ac-ft). Adsorption the adhesion of a substance to the surface of a solid or liquid. Adsorption is often used to extract pollutants by causing them to attach to such adsorbents as activated carbon or silica gel. Hydrophobic (water-repulsing)adsorbents are used to extract oil from waterways in oil spills. Aeration the process of bubbling air through a solution, sometimes cleaning water of impurities by exposure to air. Algae bloom a phenomenon whereby excessive nutrients within a river, stream, or lake cause an explosion of plant life that results in the depletion of the oxygen in the water needed by fish and other aquatic life. Algae bloom is usually the result of urban runoff (of lawn fertilizers, etc.). The potential tragedy is that of a "fish kill," where the stream life dies in one mass execution. Ambient the expected natural conditions that occur in water unaffected or uninfluenced by human activities.

4

INTRODUCTION

Aquifer a water-bearing stratum of permeable rock, sand, or gravel. Artesian water a well tapping a confined or artesian aquifer in which the static water level stands above the top of the aquifer. The term is sometimes used to include all wells tapping confined water. Wells with water level above the water table are said to have positive artesian head (pressure), and those with water level below the water table have negative artesian head. Beneficial use of water the use of water for any beneficial purpose. Such uses include domestic use, irrigation, recreation, fish and wildlife, fire protection, navigation, power, industrial use, etc. The benefit varies from one location to another and by custom. What constitutes beneficial use is often defined by statutes or court decisions. Biochemical oxygen demand (BOD) the oxygen used in meeting the metabolic needs of aerobic microorganisms in water rich in organic matter. Biota all the species of plants and animals indigenous to a certain area. Boiling point the temperature at which a liquid boils. The temperature at which the vapor pressure of a liquid equals the pressure on its surface. If the pressure of the liquid varies, the actual boiling point varies. The boiling point of water is 212" Fahrenheit or 100" Celsius. Connate water pressurized water trapped in the pore spaces of sedimentary rock at the time it was deposited. It is usually highly mineralized. Consumptive use (1) the quantity of water absorbed by crops and transpired or used directly in the building of plant tissue, together with the water evaporated from the cropped area; (2) the quantity of water transpired and evaporated from a cropped area or the normal loss of water from the soil by evaporation and plant transpiration; (3) the quantity of water discharged to the atmosphere or incorporated in the products of the process in connection with vegetative growth, food processing, or an industrial process. Contamination (water) damage to the quality of water sources by sewage, industrial waste, or other material. Darcy 's Law an equation for the computation of the quantity of water flowing through porous media. Darcy's Law assumes that the flow is laminar and that inertia can be neglected. The law states that the rate of viscous flow of homogenous fluids through isotropic porous media is proportional to, and in the direction of, the hydraulic gradient. DifSusion the process by which ionic and molecular species dissolved in water move from areas of higher concentration to areas of lower concentration. Dissolved oxygen (DO) the amount of oxygen dissolved in water or sewage. Concentrations of less than five parts per million (ppm) can limit aquatic life or cause offensive odors. Low DO is generally caused by excessive organic matter present in water as a result of inadequate waste treatment and runoff from agricultural or urban land. Dissolved solids the total amount of dissolved inorganic material contained in water or wastes. Excessive dissolved solids make water unsuitable for drinking or industrial uses. Domestic consumption (use) water used for household purposes such as washing, food preparation, and showers. The quantity (or quantity per capita) of water consumed in a municipality or district for domestic uses or purposes during a given period, it sometimes encompasses all uses, including the quantity wasted, lost, or otherwise unaccounted for. Drawdown lowering the water level by pumping. It is measured in feet for a given quantity of water pumped during a specified period or after the pumping level has become constant. Drinking water standards established by state agencies, U.S. Public Health Service, and Environmental Protection Agency (EPA) for drinking water in the U.S. Efluent something that flows out, usually a polluting gas or liquid discharge. Energy in scientific terms, the ability or capacity of doing work. Various forms of energy include kinetic, potential, thermal, nuclear, rotational, and electromagnetic. One form of energy may be changed to another, as when coal is burned to produce steam to drive a turbine, which produces electric energy.

Key Terms Used in Waterworks Operations

5

Erosion the wearing away of the land surface by wind, water, ice, or other geologic agents. Erosion occurs naturally from weather or runoff but is often intensified by human land use practices. Eutrophication the process of enrichment of water bodies by nutrients. Eutrophication of a lake normally contributes to its slow evolution into a bog or marsh and ultimately to dry land. Eutrophication may be accelerated by human activities, thereby speeding up the aging process. Evaporation the process by which water becomes a vapor at a temperature below the boiling point. Fecal coliform the portion of the coliform bacteria group that is present in the intestinal tracts and feces of warm-blooded animals. Field capacity the capacity of soil to hold water. It is measured as the ratio of the weight of water retained by the soil to the weight of the dry soil. Filtration the mechanical process that removes particulate matter by separating water from solid material, usually by passing it through sand. Graywater water that has been used for showering, clothes washing, and faucet uses. Kitchen sink and toilet water is excluded. This water has excellent potential for reuse as irrigation for yards. Groundwater the supply of fresh water found beneath the earth's surface (usually in aquifers) often used for supplying wells and springs. Because groundwater is a major source of drinking water, concern is growing over areas where leaching agricultural or industrial pollutants or substances from leaking underground storage tanks (USTs) are contaminating groundwater. Groundwater hydrology the branch of hydrology that deals with groundwater, its occurrence and movements, its replenishment and depletion, the properties of rocks that control groundwater movement and storage, and the methods of investigation and use of ground W ater. Groundwater recharge the inflow to a groundwater reservoir. Groundwater runof a portion of runoff that has passed into the ground, has become groundwater, and has been discharged into a stream channel as spring or seepage water. Heavy metals metallic elements with high atomic weights, e.g., mercury, chromium, cadmium, arsenic, and lead. They can damage living things at low concentrations and tend to accumulate in the food chain. Holding pond a small basin or pond designed to hold sediment or contaminated water until it can be treated to meet water quality standards or used in some other way. Hydraulic gradient a measure of the change in groundwater head over a given distance. Hydraulic head the height above a specific datum (generally sea level) that water will rise in a well. Hydrologic cycle (water cycle) the cycle of water movement from the atmosphere to the earth and back to the atmosphere through various processes. These processes include precipitation, infiltration, percolation, storage, evaporation, transpiration, and condensation. Hydrology the science dealing with the properties, distribution, and circulation of water. Impoundment a body of water such as a pond, confined by a dam, dike, floodgate, or other barrier, and used to collect and store water for future use. Infiltration the gradual downward flow of water from the surface into soil material. Inorganic chemical/compounds chemical substances of mineral origin, not of carbon structure. These include metals such as lead and cadmium. Leaching the process by which soluble materials in the soil such as nutrients, pesticide chemicals, or contaminants are washed into a lower layer of soil or are dissolved and carried away by water.

6

INTRODUCTION

Nonpoint source (NPS)pollution forms of pollution caused by sediment, nutrients, organic, and toxic substances originating from land use activities that are carried to lakes and streams by surface runoff. Nonpoint source pollution occurs when the rate of materials entering these water bodies exceeds natural levels. Organic chemicals/compounds animal- or plant-produced substances containing mainly carbon, hydrogen, and oxygen, such as benzene and toluene. Parts per million (ppm) the number of parts by weight of a substance per million parts of water. This unit is commonly used to represent pollutant concentrations. Large concentrations are expressed in percentages. Percolation the movement of water through the subsurface soil layers, usually continuing downward to the groundwater or water table reservoirs. pH a way of expressing acidity and alkalinity on a scale of 0-14, with 7 representing neutrality; numbers less than 7 indicating increasing acidity, and numbers greater than 7 indicating increasing alkalinity. Photosynthesis a process in green plants in which water, carbon dioxide, and sunlight combine to form sugar. Piezometric surface an imaginary surface that coincides with the hydrostatic pressure level of water in an aquifer. Point source pollution a type of water pollution resulting from discharges into receiving waters from easily identifiable points. Common point sources of pollution are discharges from factories and municipal sewage treatment plants. Pollution the alteration of the physical, thermal, chemical, or biological quality of, or the contamination of, any water in the state that renders the water harmful, detrimental, or injurious to humans, animal life, vegetation, property, or to public health, safety, or welfare, or impairs the usefulness or the public enjoyment of the water for any lawful or reasonable purposes. Porosity that part of a rock that contains pore spaces without regard to size, shape, interconnection, or arrangement of openings. It is expressed as percentage of total volume occupied by spaces. Potable water water satisfactorily safe for drinking purposes from the standpoint of its chemical, physical, and biological characteristics. Precipitation a deposit on the earth of hail, rain, mist, sleet, or snow. The common process by which atmospheric water becomes surface or subsurface water, the term precipitation is also commonly used to designate the quantity of water precipitated. Purveyor an agency or person that supplies potable water. Radon a radioactive, colorless, odorless gas that occurs naturally in the earth. When trapped in buildings, concentrations build up and can cause health hazards such as lung cancer. Recharge the addition of water into a groundwater system. Reservoir a pond, lake, tank, or basin (natural or human made) where water is collected and used for storage. Large bodies of groundwater are called groundwater reservoirs; water behind a dam is also called a reservoir of water. River basin a term used to designate the area drained by a river and its tributaries. Saturation, Zone of the zone below the water table in which all pore spaces are filled with groundwater. Sediment transported and deposited particles derived from rocks, soil, or biological material. Seepage the appearance and disappearance of water at the ground surface. Seepage designates movement of water in saturated material. It differs from percolation, which is predominantly the movement of water in unsaturated material. Septic tanks used to hold domestic wastes when a sewer line is not available to carry them to a treatment plant. The wastes are piped directly from a home or homes to

Key Terms Used in Waterworks Operations

underground tanks. Bacteria in the wastes decompose some of the organic matter, the sludge settles on the bottom of the tank, and the effluent flows out of the tank into the ground through drains. Soil moisture (soil water) water diffused in the soil. It is found in the upper part of the zone of aeration from which water is discharged by transpiration from plants or by soil evaporation. Specific heat the heat capacity of a material per unit mass. The amount of heat (in calories) required to raise the temperature of one gram of a substance 1°C; the specific heat of water is l calorie. Stream a general term for a body of flowing water. In hydrology, the term is generally applied to the water flowing in a natural channel as distinct from a canal. More generally, it is applied to the water flowing in any channel, natural or artificial. Some types of streams include the following: -Ephemeral a stream that flows only in direct response to precipitation and whose channel is at all times above the water table. -Intermittent or Seasonal a stream that flows only at certain times of the year when it receives water from springs, rainfall, or from surface sources such as melting snow. -Perennial a stream that flows continuously. a stream or reach of a stream that receives water from the zone of saturation. An -Gaining effluent stream. -Insulated a stream or reach of a stream that neither contributes water to the zone of saturation nor receives water from it. It is separated from the zones of saturation by an impermeable bed. L o s i n g a stream or reach of a stream that contributes water to the zone of saturation. An influent stream. -Perched a perched stream is either a losing stream or an insulated stream that is separated from the underlying groundwater by a zone of aeration. Subsugace water all water found below the ground surface. SurJace water lakes, bays, ponds, impounding reservoirs, springs, rivers, streams, creeks, estuaries, wetlands, marshes, inlets, canals, gulfs inside the territorial limits of the state, and all other bodies of surface water, natural or artificial, inland or coastal, fresh or salt, navigable or nonnavigable, and including the beds and banks of all watercourses and bodies of surface water that are wholly or partially inside or bordering the state or subject to the jurisdiction of the state; except that waters in treatment systems that are authorized by state or federal law, regulation, or permit, and that are created for the purpose of water treatment are not considered to be waters in the state. Surface tension the free energy produced in a liquid surface by the unbalanced inward pull exerted by molecules underlying the layer of surface molecules. Thermalpollution the degradation of water quality by the introduction of a heated effluent. Primarily the result of the discharge of cooling waters from industrial processes (particularly from electrical power generation), waste heat eventually results from virtually every energy conversion. Titrant a solution of known strength of concentration; used in titration. Titration a process whereby a solution of known strength (titrant) is added to a certain volume of treated sample containing an indicator. A color change shows when the reaction is complete. Titrator an instrument [usually a calibrated cylinder (tube-form)] used in titration to measure the amount of titrant being added to the sample. Total dissolved solids the amount of material (inorganic salts and small amounts of organic material) dissolved in water and commonly expressed as a concentration in terms of milligrams per liter.

INTRODUCTION

Total suspended solids total suspended solids in water, commonly expressed as a concentration in terrns of milligrams per liter. Toxicity the occurrence of lethal or sublethal adverse effects on representative sensitive organisms due to exposure to toxic materials. Adverse effects caused by conditions of temperature, dissolved oxygen, or nontoxic dissolved substances are excluded from the definition of toxicity. Transpiration the process by which water vapor escapes from the living plant, principally the leaves, and enters the atmosphere. Vaporization the change of a substance from a liquid or solid state to a gaseous state. VOC (volatile organic compound) any organic compound that participates in atmospheric photochemical reactions except for those designated by the USEPA Administrator as having negligible photochemical reactivity. Water cycle the process by which water travels in a sequence from the air (condensation) to the earth (precipitation) and returns to the atmosphere (evaporation). It is also referred to as the hydrologic cycle. Water quality standard a plan for water quality management containing four major elements: water use, criteria to protect uses, implementation plans, and enforcement plans. An anti-degradation statement is sometimes prepared to protect existing high-quality waters. Water quality a term used to describe the chemical, physical, and biological characteristics of water with respect to its suitability for a particular use. Water supply any quantity of available water. Waterborne disease a disease caused by a microorganism that is carried from one person or animal to another by water. Watershed the area of land that contributes surface runoff to a given point in a drainage system. Zone of aeration a region in the earth above the water table. Water in the zone of aeration is under atmospheric pressure and would not flow into a well.

1.4 SUMMARY

Water treatment is a dynamic, ever changing field. Changes in treatment technology and changes in regulation mean that operators and operators in training must study to remain current with changes in the field. We discuss recently announced changes to the Safe Drinking Water Act of 1996 in the next chapter.

1.5 CHAPTER REVIEW QUESTIONS Matching exercise Match the definitions listed in Part A with the terms listed in Part B by placing the correct letter in the blank. J Note: After completing this exercise, check your answers with those provided in Appendix A (Exercise 1.4).

Part A 1-1 Identifies water that is safe to drink.

1-2 The natural water cycle.

Chapter Review Questions

1-3 Water lost by foliage. 1-4 A compound derived from material that once lived. 1-5 Rain mixed with sulfur oxides. 1-6 Region in earth above the water table. 1-7 Plants and animals indigenous to an area. 1-8 Heat capacity of a material per unit mass. 1-9 A result of excessive nutrients within a water body. 1-10 Compound associated with photochemical reactions. 1-11 When dissolved ions move from areas of higher to lower concentrations. 1-12 Present in intestinal tracts and feces of animals and humans. 1-13 Change in groundwater head over a given distance. 1-14 Oxygen used in water rich in organic matter. 1- 15 Water trapped in sedimentary rocks. 1-16 Determines the quantity of water flowing through porous media. 1-17 Enrichment of water bodies by nutrients. 1- 18 A stream that receives water from the zone of saturation. 1- 19 The amount of oxygen dissolved in water. 1-20 Gradual downward flow of water from the surface into soil. 1-21 Used to measure acidity and alkalinity. 1-22 The addition of water into a groundwater system. 1-23 A stream that flows continuously. 1-24 A solution of known strength of concentration. 1-25 Discharge from a factory or municipal sewage treatment plant. Part B a. biota b. gaining c. potable

INTRODUCTION

d. e. f. g. h. i. j. k. 1. m. n. o. p. q. r.

titrant organic point source pollution DO BOD hydrologic cycle perennial fecal coliform eutrophication acid rain pH recharge transpiration infiltration connate water S. zone of aeration t. VOC U. Darcy's Law v. specific heat W. diffusion X. hydraulic gradient y. algae bloom

CHAPTER 2

Certification/Licensure Requirements and SWDA

Indecision is like a stepchild: I f he does not wash his hands, he is called dirty, if he does, he is wasting watex-African Proverb

2.1 INTRODUCTION December 1998, President Clinton announced two major drinking water rules designed to strengthen protection from waterborne microbial contaminants such as Cryptosporidiurn (see Chapter 3 for more detail) and to reduce potential health risks from the by-products of chemical disinfection. The new rules, which go into effect in two years, require 13,000 municipal water suppliers to use better filtering systems to remove cryptosporidium (which sickened 400,000 people and killed 100 people in Milwaukee, WI, in 1993) and possible cancer-causing by-products of disinfection chemicals.

I

N

2.2 SAFE DRINKING WATER ACT (SDWA)2 These drinking water rules comprise part of the new requirements under the Safe Drinking Water Act (SDWA)Amendments of 1996 (Public Law 104-182). SDWA requires that public water supplies be disinfected and that USEPA set standards and establish processes for treatment and distribution of disinfected water to ensure that no significant risks to human health occur. The USEPA Science Advisory Board ranked pollutants in drinking water as one of the highest health risks meriting USEPA's attention because of the exposure of large populations to contaminants such as lead, disinfectant by-products (DBPs), and disease-causing organisms (see Chapter 3). Disinfectants are used by virtually all surface water systems in the U.S. and by an unknown percentage of systems that rely on groundwater. Chlorine has been the most effective disinfectant. However, disinfection treatments can produce a wide variety of by-products, many of which have been shown to cause cancer and other toxic effects. Recently, anxieties have arisen concerning possible water quality deterioration during distribution, which can be dramatic when systems are not properly designed and operated. While disinfection is an integral part of water treatment, filtration is necessary to reduce pathogen levels and make disinfection more reliable by removing turbidity and other interfering constituents. Upgrading existing techniques and developing new approaches to address these problems takes innovation. Areas of interest include the following: 2 ~ u c of h the information provided in this section is from USEPA's Drinking Water Treatment, June 1998.

12

CERTIFICATIONILICENSURE REQUIREMENTS AND SWDA

alternatives to chlorine disinfection for removing pathogenic microorganisms, including innovative applications of ultraviolet radiation and processes that improve overall effectiveness while using reduced amounts of disinfectant development of innovative unit processes (particularly for small systems) for removal of organic and inorganic contaminants, particulates, and pathogens development of efficient, cost-effective treatment processes for removing disinfection by-product precursors (e.g., trihalomethanes, haloacetic acids, and for ozonation: bromate, aldehydes; for chlorination: chloropicrin, haloacetonitriles; for chloramination: organic chloramines, cyanogen chloride) improved methods for controlling pathogens through coagulation/settling, filtration, or other cost-effective means drinking water contamination control between the treatment plant and the user; especially considering potential chemical leaching from distribution system materials and surfaces (e.g., lead, copper, iron and other pipe materials, protective coatings) as a result of instability, interaction with microorganisms, disinfection agents, and water treatment chemicals development of a better understanding of fundamental principles of well-designed water treatment systems and development and implementation of proper operations and maintenance procedures may make it possible to keep operational problems under reasonable control because designing a waterworks system that never fails may not be possible

2.3 OPERATOR CERTIFICATION The sentence at the end of Section 2.2 is of significant interest: ". . . development and implementation of proper operations and maintenance procedures." The meaning of this statement is straightforward, but it entails the requirement for waterworks operators to be properly qualified, certified, and licensed to follow proper procedures to ensure protection of public health. Various rules and regulations at both the federal and state levels make certification and licensure essential. For example, typically, states require that anyone who performs the duties of a Waterworks Operator be licensed. Requirements vary, but typically, to become licensed, the operator must possess a specified level of experience and must pass an examination (many of the state examinations are of the multiple-choice variety). Certain operator training classes and correspondence courses can be substituted for some of the required experience (see Section 2.4). New operators usually start with a ClassIGrade IV or a ClassIGrade I11 license, progressing upward toward ClassIGrade I. (Note: Be advised that in some locations, ClassIGrade V or V1 is the highest level of licensure with ClassIGrade I the lowest level). Note that in some locations, not every person working for a waterworks needs to be licensed, but a licensed person must be available (either on-site or in contact by phone, beeper, or radio) whenever the waterworks is in operation. J Note: Because of the recent outbreaks of Cryptosporidium problems in Milwaukee, WI, Las Vegas, NV, and other areas (as well as other public health concerns), many licensing agencies are pushing for stricter licensing regulations that require all waterworks operators be licensed or at least be operators-in-training working toward licensure.

Pertinent to our purpose (water operator certification) and related discussion within the Handbook is the new emphasis placed on operator certification guidelines by SDWA and other local regulations. For example, the 1996 SDWA Amendments include the following waterworks operator certification requirements:

Operator Certification

13

Certificationpartnership: Within 180 days, the USEPA must initiate a partnership with states, Public Water Systems, and the public to develop information on recommended operator certification requirements. The information developed through this partnership must be published within 18 months of enactment. Certification guidelines Within 30 months of enactment, in cooperation with the states, the USEPA must publish guidelines specifying minimum standards from certification and recertification of operators of community and nontransient, noncommunity water systems. Existing state programs are to be considered substantially equivalent to the guidelines unless the existing program fails to achieve the overall public health objectives of the guidelines. State programs Beginning two years after guidelines are published, 20 percent of a state's funding allotment will be withheld if the state is not implementing an operator certification program. Training reimbursement The USEPA, through grants to the states (allocated on the basis of "reasonable costs"), is required to reimburse training and certification costs for operators of systems serving fewer than 3,300, including per diem for unsalaried operators who are required to undergo training as a result of the Federal requirement. Grants of $30 million are authorized, and other funds may be used if appropriations are not sufficient. In waterworks operations in the United States, states and local public health authorities have implemented certification or licensure requirements for waterworks operators. Usually, the rules or regulations requiring waterworks operator certification/licensure are based on the concern for preservation of health, safety, and welfare of the public. J Note: The following information is provided in "general" or "typical" terms, meaning that each certification or licensure candidate should check with local requirements to determine exact requirements and to ensure compliance.

Various state and local authorities (covered under pertinent rules and regulations) have laws in place dealing with waterworks operators' certification/licensure that generally state: "No person shall operate a waterworks without a valid license." The various agencies assigned the responsibility for ensuring public health regulate operators through these licensing regulations. Typically, the State Department of Health regulates waterworks owners (in staffing matters) through Waterworks Regulations. Waterworks regulations typically define the responsibilities of the State Oversight Board, operators, and owners. The State Board of Waterworks Operators is usually assigned the duty of attesting to the competency of the waterworks operator to protect and conserve the water resources of the State, to supervise and operate the waterworks, and to protect the public health. The Oversight Board does this through regulations. State Waterworks Regulations typically define certification or licensing requirements and describe the certification andlor licensure process. The regulations specify certification or licensure requirements based (usually) on the following: experience education reciprocity substitutions application The regulations, additionally, generally spell out any and all disciplinary actions to be taken if noncompliance with certification or licensure occurs.

14

CERTIFICATION/LICENSURE REQUIREMENTS AND SWDA

Under state certification/licensure regulations, certain definitions applicable to the waterworks operator are normally stipulated. As a case in point, consider the definitions provided in the following example (typical of most states): Operator "any individual employed or appointed by an owner and who is designated to be the person in responsible charge, such as a supervisor, a shift operator, or a substitute in charge, and whose duties include testing or evaluation to control waterworks operations. Not included in this definition are officials whose duties do not include actual operation or direct supervision of waterworks." Responsible charge "designation by the owner of any individual to have duty and authority to operate or modify the operation of waterworks processes." Operator-in-training "individual employed by an owner to work under direct supervision of an operator holding a valid license in the proper classificationlgrade for the purpose of gaining experience and knowledge in the duties and responsibilities of an operator." Certification/Licensure "a method of regulation whereby the State, through the issuance of a license, authorizes a person possessing the character and minimum skills to engage in the practice of a profession or occupation which is unlawful to practice without a license." Most state waterworks regulations make several other stipulations regarding licensure. For example, in the operation of a waterworks, a person who makes decisions and process changes without checking with someone else must have a valid waterworks operator license and must be the same classlgrade or higher than waterworks works class. If the waterworks operator does not have the proper license, then he or she is not the operator but the operator-in-training. Such a person must be supervised by someone who has a current license.

J Note: A waterworks license is required only for an operator in responsible charge. Many states have five classes or grades of waterworks operator license: ClassIGrade V through ClassIGrade I (least to most responsibility). Each classlgrade level is based on cumulative experience, education, andor substitution. Waterworks operator licenses are usually good for two years, and each operator is responsible for renewal.

2.3.1 QUALIFICATIONS FOR LICENSURE Qualification for licensure is typically based on the 3E's: experience education examination Note that prospective licensure applicants are not required to be working in a waterworks facility at the time of application (in most states) and that no specific training is required for licensure (in most cases).

2.3.1.l Experience Requirements The experience requirement for licensure varies from state to state, but typically, experience is based on full-time work (meaning attendance to the extent required for proper operation). Work accomplished in the waterworks laboratory and on maintenance activities usually does not count. In many locations, full-time work in distribution counts only for ClassIGrade V licensure.

Operator Certification

Additional experience requirements may include any or all of the following: some experience must be earned at a specific class of plant and cannot be substituted (see Section 2.4) partial credit is often given for some wastewaterlwater experience (e.g., one month credit for two months worked, etc.) in most cases, the experience requirement decreases with more formal education all experience must be certified by a supervisor (if at a plant classed higher than the current license, the supervisor must be a licensed operator) experience must be stated in total years required with a specific time for a specific class of plant some substitutions are allowed for training and education generally, no substitutions are allowed for ClassJGrade V and IV 2.3.1.2 Substitutions In many states, some substitutions are allowed for the required waterworks operation experience. Substitutions include the following: relevant, Board-approved operator training courses wastewater plant operating experience relevant college courses J Note: In many states, experience, training, and education substitutions cannot be more than 50 percent of the total requirement.

To gain some idea of how substitutions are generally equated with minimum hands-on operating experience after substitutions, refer to the following: Class V-no substitution allowed Class VI-no substitution allowed Class 111-1 year Class 11-1 -5 years Class 1-2.5 years Education used as substitution for experience must be relevant to waterworks operation at the class license to which it is applied. Generally, one month of experience per semester hour is approved by the applicable Board for college courses in waterworks operation, engineering technology, engineering, chemistry, physics, and biology. Note that in some states, the same education used for determining qualifications cannot be used for determining experience. For example, if a candidate claims a B.S. degree, those undergraduate college courses cannot be used for substitution. Training used for substitution of experience requirements includes operator training courses, seminars, and workshops, all of which must be approved specifically by the Board after the sponsor's application. Training must be relevant to classification. Usually, one month of experience is given for each training credit (TC) received. One TC is equivalent to 10 hours of classroom work or 20 hours of lablfield trip. Examples of approved seminars, workshops, and courses include "Sacramento" correspondence courses, Center for Disease Control (CDC) courses, state short courses, and statelcommunity college waterworks operator programs. Certificationllicensure examinations administered by state agencies typically are of the open book, multiple-choice question, machine-graded type. The exam itself varies with the ClassIGrade

16

CERTIFICATIONILICENSUREREQUIREMENTS AND SWDA

Level attempted with the relative importance of each category varying from Class/Grade to Class/Grade. Typically, each examination tests the following knowledge items (varying in complexity, from basic to advanced, with increasing Class/Grade Level): concentration/dosages water chemistry microbiology laboratory testing cross-connection control distribution storage sources of supply general knowledge Along with the subject areas listed above, operator Class/Grade level examinations also test knowledge items related to operator duties that include general knowledge, cost analysis, regulations, safety, and various calculations. Test items target actual waterworks operations and include specific test items such as chemical clarification, fluoridation, pumps and feeders, filtration, softening, and disinfection. Advanced examinations include questions dealing with corrosion control, aeration, organic chemical control, and metals removal (e.g., Fe, Mg, etc.).

2.4 TYPICAL CLASSES OF WATERWORKS Various locations classify their waterworks according to a standard classification system (with few exceptions). Virginia, for example, maintains five classes of waterworks. A Class V waterworks is a groundwater system that uses no treatment at all or that only disinfects with chlorine gas or hypochlorite. It can also be a water system that purchases all of its water from another water system; the second (or consecutive) system may rechlorinate the water using chlorine gas or hypochlorite. If a Class V system adds any treatment other than chlorine/hypochlorite disinfection (such as corrosion control), it is reclassified to a higher class. A Class N waterworks generally serves under 5,000 people and has treatment limited to a combination of one or more of the following processes: disinfection, corrosion control, iron and manganese removal, softening, and slow sand filtration. If a Class IV waterworks installs fluoridation, it will be reclassified as a Class I11 waterworks. A Class 111waterworks may be larger than a Class IV (limited to the same treatment processes but serving 5,000 people or more) or may be more complex using "conventional" treatment processes such as coagulation, sedimentation, filtration other than slow sand filtration, disinfection, fluoridation, aeration, and corrosion control to serve under 5,000 people (0.5 MGD capacity). A system using high-rate filtration (with a filtration rate greater than 2.0 gpm/ft2)is automatically classified as Class I1 or Class I. A Class 11waterworks is one that includes "c~nventional'~ treatment processes, but that has a service population between 5,000 and 50,000, a capacity between 0.5 MGD and 5.0 MGD, or any waterworks serving over 50,000 people (5.0 MGD). A Class I waterworks includes all treatment facilities serving over 50,000 people (5.0 MGD). J Note: Most small waterworks will be classified as Class V or Class IV. However, if the system feeds fluoride or operates a rapid-rate filtration process, it may be a Class I11 System. Waterworks operators must know their water system's classification.

Chapter Review Questions

2.5 SUMMARY While some may consider having to obtain certification or licensure a drawback, the reasons behind having employees demonstrate their ability to work to a certain level of proficiency are sound as are the reasons we treat water in the first place. We cover the critical reason for water treatment in Chapter 3.

2.6 CHAPTER REVIEW QUESTIONS

2-1 In a short, simple paragraph, explain in your own words why waterworks certification and/or licensure is important. Be sure to list at least three different factors.

CHAPTER 3

Waterborne Diseases

Life originated in the sea, and about eighty percent of it is still there.-IsaacAsirnov3

3.1 INTRODUCTION HE licensed waterworks operator has many duties and responsibilities. However, a waterworks operator's primary responsibility is to ensure that he or she provides the consumer with water that is safe for whatever use intended-absolutely nothing takes a back seat to ensuring public health. In this chapter, we discuss waterborne diseases and the waterborne pathogens that cause disease. In Chapter 4, we discuss the basics of microbiology, and in Chapter 5, basic bacteriology, both subject areas of essential knowledge for the person who operates a waterworks where the product treated is intended for human use and consumption.

T

3.2 AN ABBREVIATED HISTORY OF WATERBORNE DISEASE AND HYDRAULICS

Probably as early as the era that we call "Caveman," people fundamentally understood two basic factors about fresh water: (1) they needed to have a supply readily available (this helps to explain why many civilizations developed around river valleys), and (2) tainted water was not pleasant or refreshing to drink. Did our early ancestors understand that not all fresh water drinking supplies were good for their health? Before the onset of "civilization," probably not. In this earliest of era of human existence on Earth, the first clue to the unfitness of a potential drinking water source was probably its appearance. For example, a muddy or algae-filled water source was probably enough of an indication to the prospective user that the water was less than desirable for consumption (unless the observer was thirsty enough, of course, to ignore the physical condition of the water). During these early days of human life on Earth, water pollutants existed [as long as humans have been around and involved with the environment, pollutants have always been a by-product of their (our) existence]. During those early days, though, water pollutants were somewhat different than many of those present in our present-day water sources. Human-made chemicals are a relatively recent phenomenon. They were unknown and not available then and, thus, did not pollute water bodies used as supplies of potable water. The pollutants of the ancient past were primarily generated and put in place via the machinations of Mother Nature. For example, a stream, river, or lake could (and did) become polluted whenever floods, storms, forest fires (mostly caused by lightning), and other natural events occurred. 3From I. Asimov's Book of Science and Nature Quotations, p. 43, 1988.

20

WATERBORNE DISEASES

As to biological pollution, we can probably safely say that certain waterborne pathogens (e.g., Giardia lamblia, a protozoan, see Chapter 4) have been around since time immemorial. This includes the timeframe of human occupancy because many (if not most) waterborne pathogens are derived from human and animal contact with water, especially from their feces, which readily enters various surface water bodies. We definitively state that human-induced pollution of water bodies is not a recent phenomenon; it is a phenomenon with a very long history. The difference between and consequence of water pollution of the past and water pollution of the present is glaring. For example, in the era of primitive human civilization, when a source of water was polluted, the human population in many cases could simply move on to another water source and use that water for whatever purpose was desired. Today, of course, we do not have this luxurywe simply cannot abandon our "caves" and move on to greener (wetter) pastures. However, even today, in some underdeveloped regions of the world, for local populations, when it comes to drinking water, quantity is more important than quality. J Note: Realize that in the human civilization effort, quantity was often more important than quality because most of the water was used for irrigation purposes, not human consumption. Therefore, if we had to sum up the state of water during the age of prehistoric humans, the statement that quantity was more important than quantity probably sums it up best.

Even in the days of early humans (especially after the discovery of fire), our ancestors may have understood the wisdom of boiling water before drinking it. And even before fire, they may have allowed water drawn from a local source to sit in the open sunlight to be "purified." We are not sure, of course, but we do know that in later times, these practices were employed to "purify" water, even though those employing such practices didn't have a clue about waterborne disease or any disease, for that matter. About the only thing those humans could have known was that various means of water treatment worked to improve water's appearance or taste. In the history of water treatment, major progress (at least for that period of time) was made when early Romans refined distribution (the hydraulics of water) by developing aqueducts and irrigation channels. The early Greeks got involved with drinking water when Hippocrates (CA 460-377 BC) stated, ". . . water contributes much to health," and asserted that rainwater be boiled and strained prior to consumption. Others, much later (as late as 1771) made reference to water filtration. Around 1800, in Paisley, Scotland, the first municipal filtration works was constructed. A breakthrough of enormous consequence occurred in Great Britain in the mid 1850s. The people living in Great Britain during this timeframe still did not have a clue about disease and the cause of disease, but they had firsthand knowledge that people were dying around them, sometimes in large numbers, for unknown reasons. Even though they lacked understanding of disease, waterborne disease in particular, the British did pass, in 1852, a law that all water should be filtered. Not until the cholera outbreak in l854 in London (which caused 700 deaths over a 17-week period) was the "connection" made between tainted water and cholera (and thus waterborne disease). The connection was made when Dr. John Snow conducted the first epidemiological study. In this study, Snow provided some of the earliest evidence of the relationship between human waste, drinking water, and disease. He noted that individuals who drank from a particular well on Broad Street in London were much more likely to become victims of cholera (during the epidemic) than those from the same neighborhood who drank from a different well. He not only found a likely source of the contamination (sewage from the home of a cholera patient-a leaky sewer line from the patient's home passed near the well), he was able to effectively end the epidemic by simply removing the handle from the pump on the Broad Street well. However, only later in the nineteenth century (when Pasteur, Koch, Henle, and Budd convincingly established the germ theory of disease) was the role of pathogenic microorganisms in such epidemics understood.

Waterborne Disease

21

Over time, water treatment developed into a multidisciplined technology, to the point where professionals in the field are from such fields as or have backgrounds in hydraulics engineering, sanitary chemistry, engineering research, sanitary bacteriology, epidemiology, engineering design, engineering education, and public health engineering. We discuss many of the milestones associated with each of these disciplines below. In the United States, hydraulic engineering was off to a good start with 18 waterworks in place by 1800. In 1842, water began flowing from Croton reservoir to New York City via a 95-mgd aqueduct. In 1848, Boston, MA, began receiving water via the Cohchituate Aqueduct. In Chicago, IL, in 1855, a sewage system was under development. In the area of water treatment engineering research, significant milestones were achieved. In 1877, M.I.T.'s Sanitary Chemistry Lab was tasked to analyze water samples and supplies. In 1887, the Massachusetts Board of Health reorganized to include an engineering department. In 1890, the Lawrence Experiment Station demonstrated that wastewater treatment is a biochemical process. Early engineering design milestones include the installation in 1871 in Poughkeepsie, NY, of the first slow sand filter system. In 1893, slow sand filters were used to treat Merrimack River water, which demonstrated 98 percent bacteria removal, and the death rate from typhoid fever also dropped. In 1880, separate sewer systems were recommended. In 1890, bacteria as the cause of disease was still not widely accepted. However, a significant epidemiological milestone occurred in 1890 and 1891, when a typhoid epidemic in Lowell and Lawrence, MA, provided the data necessary to link bacteria with disease. In 1884, the bacteriological examination of water got its start when Escherich isolated organisms thought to cause cholera from stool samples. During this examination, the existence of coliform bacteria was proven and recognized as an inherent ingredient of the feces of humans (E. coli). However, another 10 years went by before the procedure to inoculate fermentation tubes was developed. In discussing the history of the discovery of waterborne disease and the development of water hydraulics, we can state that water treatment is relatively new (developed around the turn of the century). With the advances made in purifying drinking water, drinking water practitioners shifted their focus from "quantity" to "quality" issues. The major development from the earliest days of water treatment to the present was the realization that water treatment can effectively control outbreaks of waterborne disease.

3.3 WATERBORNE DISEASE

The first point we want to make about waterborne-disease generators (pathogens) is that water is not a medium for the growth of microorganisms, but instead is a means of transmission, a liquid conduit. This is contrary to the view held by the average person. Many people mistakenly assume that waterborne pathogens are at home in water. A water-filled ambiance is not the environment in which the pathogenic organism would choose to live if it had such a choice. These pathogens7natural habitat is actually (generally speaking) inside some mammal's gut, whether human or animal. Communicable diseases that may be transmitted by water include bacterial, viral, and protozoa1 infections (see Table 3.1). 3.3.1 WATERBORNE DISEASE TRANSMISSION FACTORS Disease does not necessarily follow exposure to a specific waterborne pathogen. Specific factors must exist for the transmission of disease, related to the diseased individual (the host), the microbe (the agent), and the environment. For disease to actually develop, six elements must be present. These include the following:

WATERBORNE DISEASES TABLE 3.1. Waterborne Disease-Causing Organisms.

Microorganism

Disease Bacterial

Escherichia coli Salmonella typhi Salmonella sp. Shigella sp. Yersinia entercolitica Vibrio cholerae Campylobacter jejuni Legionella

Typhoid fever Salmonellosis Shigellosis Yersiniosis Cholera Campylobacter enteritis Legionellosis Intestinal Parasites Amebic dysentery Giardiasis Cryptosporidiosis

Entamoeba histolytica Giardia lamblia Cryptosporidt'um Viral Norwalk agent Rotavirus Enterovirus

Hepatitis A Adenoviruses

Polio Aseptic meningitis Herpangina Infectious hepatitis Respiratory disease Conjunctivitis

( 1 ) Pathogen (or causative agent) a disease must be carried by an agent (a microbe). This agent is usually parasitic and lives at the expense of the host. (2) Reservoir the location where microbiological disease lives and multiplies and is transmissible to man; consists of man himself, as well as both domestic and wild animals. Agents are usually unable to multiply or grow outside the reservoir. ( 3 ) Flight may be from body openings (intestinal, respiratory, urinary), from infected open wounds, and by ticks, mosquitoes, or other invertebrates (by mechanical means, by vectors). The microorganisms responsible for causing disease are generally excreted in the feces or urine, whereupon they may gain access to water. If drinking water treatment is inadequate (or lacking altogether), these organisms may pass freely into water en route to the consumer, thereby engendering a risk of infection and possibly disease. J Note: The human intestines are the source of most of the bacteria, virtually all of the viruses, and the great majority of protozoan parasites that can be transmitted through water to man.

(4) Transmission two types of transmission exist: Direct transmission organisms pass immediately to a new host through physical contact Indirect transmission organisms are transferred mechanically by vectors or vehicles. Vectors are living and include ticks, fleas, mosquitoes, and other invertebrates. Vehicles are nonliving and include water, milk, food, and air. ( 5 ) Entry the pathogen must enter the new host through defensive barriers. (6) Susceptible host humans (and animals) possess mechanisms of defense against disease. For infection to begin, these defense barriers must be nonexistent or lowered.

WaterborneDisease

23

For disease to spread, the opportunity for spread must exist. Opportunities include biological, physical, and social elements. Sanitation, water supply, and crowding are environmental factors. Waterborne diseases (or agents) are usually spread by a carrier (an infected individual). The intestinal discharges of an infected carrier may contain billions of pathogens, which, if allowed to enter the water supply, can cause epidemics of immense proportions. Carriers may not even necessarily exhibit symptoms of their disease, which obviously makes carefully protecting all water supplies from any human waste contamination even more important. Mary Mallon was probably one of the most famous (infamous) carriers of disease and was unaware that she carried disease. Mary was an American cook in the later 1800s and early 1900s. While she was "cooking up" her daily food preparations and passing on typhoid to her unsuspecting victims (she may have infected more than 1,000 people), Mary (a.k.a. "Typhoid Mary") never demonstrated obvious symptoms of this deadly disease; she was a carrier. J Note: When disease occurs, it continues until death, disablement, recovery, andor development of resistance occurs.

3.3.2 AGENTS OF DISEASE TRANSMISSION IN WATER

In the following sections, we briefly discuss several types of agents that transmit disease via water. The specific diseases are classified by the type of pathogen that acts as agent. We discuss each agentbacterial, viral, and parasitic-in more detail in Chapter 4. 3.3.2.1 Bacterial Diseases

Not all bacteria are pathogenic, many are actually beneficial to human life and the environment (e.g., bacteria aid in the decomposition of organic materials for recycling and perform other important functions). However, the few that are pathogenic are of great importance to the water treatment specialist. The majority of bacterial diseases are transmitted by food, milk, direct contact under poor sanitary conditions, and water. The huge irony is that control of bacteria-induced disease is rather simple, but outbreaks still occur. In many areas of the world, they are considered endemic (habitually present). Even in the U.S., recent outbreaks have occurred.

3.3.2.1.1 Cholera From a medical standpoint, cholera is an acute bacterial infection of the small intestine, characterized by severe diarrhea and vomiting, muscular cramps, dehydration, and depletion of electrolytes. The disease is spread by water and food that have been contaminated by feces of persons previously infected. The symptoms are caused by toxic substances produced by the infecting organism, Vibrio cholerae. The profuse watery diarrhea (as much as a liter an hour) depletes the body of fluids and minerals. Complications include circulatory collapse, cyanosis, destruction of kidney tissue, and metabolic acidosis. Mortality is as high as 50 percent if the infection remains untreated. Treatment includes the administration of antibiotics that destroy the infecting bacteria and electrolytes with intravenous solutions. A cholera vaccine is available for people traveling to areas where the infection is endemic. Other preventive measures include drinking only boiled, bottled, or properly treated water, and eating only cooked foods. From the human point of view, we can simply state that cholera has caused the deaths, in the past (and the present), of countless numbers of lives. We can also state that in the United States, except for occasional outbreaks here and there, cholera is no longer a major health problem. The agent of the disease, Spirillum cholerae, has been effectively controlled through sanitation and safe drinking water practices.

24

WATERBORNE DISEASES

In other parts of the world, though, as we have said, this is not and has not always been the case. Indeed, history is replete with cases of cholera epidemics, with drinking water supplies often being the conduit for pathogens and thus the disease. Probably one of the best-known and documented cholera epidemics occurred in Hamburg, Germany, in 1892. J Note: There were nearly 17,000 cases of cholera with 8,065 deaths in Hamburg (population about 650,000).

Fortunately for epidemiological purposes (and for lessons learned for the future), the Hamburg epidemic allowed for complete documentation of the entire episode, and it occurred under conditions almost equaling those of a well-controlled laboratory investigation. The bacteriological and epidemiological findings corroborated each other in every aspect. The Hamburg Incident occurred because the city drew its water supply from the grossly polluted Elbe River. The intake for the water supply was at the river front, and the sewers of the city emptied into the river at various points. Hamburg furnished its customers with raw, untreated, unfiltered Elbe River water. The source of the epidemic was traced to Russian immigrants crowded in barracks on one of the wharves. All the infected waste from these people was discharged into the Elbe river at the wharf, and, of course, the same water was used as drinking water for Hamburg's residents. Hamburg's plight (and those of two other cities closely bordering the Hamburg area) points to the significance of water supply contamination and its ramifications. To gain a better understanding of these implications, refer to Figure 3.1. In Figure 3.1, we can clearly see that the four labeled communities all have one thing in common: the river. In addition to being close to or bordering the river, we see that each of the communities draws fresh water from the river and discharges its waste back into the river. The large community close to the watershed headworks area (close to the source) of the river system has a huge advantage over its downstream neighbors. The water coming from the mountain watershed area is relatively untainted. At this point, a human population has not added a large input of contamination to the stream. The large community draws from the river water that does not need extensive treatment to make it fit for human consumption. The story changes, however, as the large community's sewage and industrial wastestream is poured back into the river (out of sight, out of mind) and flows past the community. If this tainted wastestream were allowed to flow downriver for several miles, it would probably self-purify through natural processes before emptying into the ocean. However, self-purification takes time and distance--elements not present in this situation. First, Community A draws river water to serve its needs. Notice that nothing indicates any treatment process before the raw, Large Community-contaminated water is distributed through the community's water supply system. Herein lies the problem. People in Community A drink the upstream Large Community-contaminated water that contains human fecal material and industrial wastes. In short, when people in Community A drink water from their household taps, they are essentially drinking a Pathogen Cocktail. Leaving the waterborne-diseased Community A and proceeding downriver to Community B, notice that Community B also draws water from the river. Community B provides a huge difference, however. Notice that the supply pipeline is fed directly into a slow sand filtering system prior to being fed via the community's regular water distribution system. This basic treatment process supplies Community B customers with water to ingest-water that has at least been filtered to the point that most of the pathogenic microorganisms have been removed. Following the river course from the point where Community B dumps its wastestream into the river to Community C, you will notice that Community C also draws river water to supply its water

Figure 3.1 The cholera river.

26

WATERBORNE DISEASES

distribution system. However, unlike Community B, which filters it water, Community C draws the water and directly distributes it to its customers for use. Years of such incidents as the one just described and the statistics and other data taken from such occurrences has proven conclusively the effectiveness of filtering raw water, not only for choleracausing agents, but also for others that can affect consumers7health or worse.

3.3.2.2 Viral Diseases

Viruses are ultramicroscopic intracellular parasites incapable of replication outside of a host organism (see Chapter 4). Several hundred animal viruses have been discovered; many viruses can be passed among man and animal species. Infection usually takes place after viruses are ingested, possibly in contaminated water (or food). Some varieties can pass unharmed through the stomach and infect cells lining the lower alimentary canal. Infection many also start in the throat, or in some cases, in the upper respiratory tract, then spread downward to the gastrointestinal tract. Viruses do not survive long outside the host but can survive heat, drying, and chemical agents while living. Viruses remain active in chlorinated water long after bacteria have been killed. The exact role of water in the transmission of most viruses has not been determined, but the transmittal by surface water of viral hepatitis and the possible water transmission of poliomyelitis (caused by three different strains of virus) have been studied. One thing is certain: because they are excreted through the feces of an infected individual, human enteric viruses (infections of the intestinal tract) are the ones most often encountered at sewage treatment plants and, therefore, are the ones most likely to be released to environmental waters. The USEPA (1985)4 recognized that between 1978 and 1982, 18 reported waterborne disease outbreaks were caused by viruses, with over 5,700 cases. The USEPA considers these outbreaks in addition to the outbreaks of unknown origins caused by viruses. The USEPA also pointed out that some strains of waterborne viruses have a minimum infective dose at very low concentration. Because of the difficulty of routine procedures for detection of the most important waterborne viruses, the USEPA and World Health Organization standards have a zero goal for pathogenic viruses as measured by the enteroviruses. Additionally, animals contribute viruses to water, but as yet, viruses from this source do not appear to present a public health hazard.

3.3.2.3 Parasitic Diseases

As potential causes of waterborne diseases, protozoan organisms and helminths (worms) are high on the agenda of waterworks operators as a connection to the Entamoeba histolytica (the cause of amebic dysentery and amebic hepatitis) and Giardia lamblia and Cryptosporidium (the protozoan parasites presently causing a very large number of gastrointestinal outbreaks). Symptoms of giardiasis, for example, include skin rash, flu-like symptoms, and severe gas and abdominal pains. The diseases from these two protozoans often allow periods of remission when the host has no symptoms, then, unfortunately, the symptoms return. With better sanitation and health practices and more sophisticated water treatment, the incidence of most parasitic diseases decreases remarkably. However, the parasites Giardia lamblia and Cryptosporidium have been increasing throughout the United States. Sewage contamination transports the eggs and cysts of parasitic protozoa and helminths (tapeworms, hookworms, etc.) into raw water supplies, leaving water treatment and disinfection the task of diminishing the danger of contaminated water to the consumer. We discuss Giardia lamblia and Cryptosporidium in greater detail in Chapter 4. 4FromUSEPA-NPDW4O

CFR Part 141-November 13,1985.

Multiple Barrier Concept

27

3.4 INDICATOR ORGANISMS Public water supplies are not tested for pathogens to determine microbiological quality, because laboratory analyses for pathogens are difficult to perform and quantitatively unreliable. For some pathogenic microorganisms, under current available and practical technologies, such tests are impossible to perform. Therefore, microbial quality is based on testing for an indicator organism, i.e., a microorganism whose presence is evidence that the water has been polluted with feces of humans or warm-blooded animals. 3.4.1 THE COLIFORM GROUP

Escherichia coli, a nonpathogenic fecal coliform bacteria that resides in the human intestinal tract (averaging about 50 million coliforms per gram in feces) is one of the fecal coliforms. In laboratory testing, total fecal coliforms refers to coliform bacteria from feces, soil, or other origin. Total coliforms include the genera Escherichia, Citrobacteq Enterobacter, and Klebsiella. The term fecal coliform refers specifically to coliform bacteria from humans or warm-blooded animals. Testing for the fecal coliform E. coli is the preferred and most specific indicator of microbial water quality. In testing for fecal coliforms, the Multiple-Tube Fermentation Technique (MPN-most probable number) and the Membrane Filter Technique (MF) are the methods recognized (and preferred) for use. They are sufficiently reliable, relatively simple techniques and require inexpensive equipment, so they can be run as often as required by the monitoring activity of water quality control (see Chapter 5). At the present time, the MF technique is the fastest standardized method. Though these two tests for coliforms are reliable indicators of the possible presence of fecal contamination, and consequently, a correlation with pathogens, they do present several deficiencies, including the following: Reliability of coliform bacteria to indicate the presence of pathogens in water depends on the persistence of the pathogens relative to coliforms. Coliforms may be suppressed by a high concentration of other organisms-for pathogenic bacteria, the die-off rate is greater than for coliforms outside the intestinal tract of humans. Thus, exposure in the water environment reduces the number of pathogenic bacteria relative to coliform bacteria. False-positive results may be caused by aeromonas in warm weather. False-negative results may be caused by strains that are unable to ferment lactose (see Chapter 5 for a more detailed discussion of coliform testing). J Note: The maximum contaminant level goal (MCLG) in the Safe Drinking Water Act is zero coliforms. The recommended testing procedure is the presence-absence test, which does not provide a coliform count. On the other hand, the maximum contaminant level (MCL) allows for a limited number of positive samples (not more than 5 percent of the monthly samples) because of inadvertent contamination. For example, coliform bacteria are common in the natural environment on dirty water faucets, on the hands of the person collecting the water sample, and in dust and soil.

3.5 MULTIPLE BARRIER CONCEPT To ensure that water supplied to the consumer is safe for consumption, water monitoring agencies incorporate one or more strategies. Regardless of the strategy employed, most water supply protection efforts revolve around what is known as the multiple barrier concept. The essential elements of this concept include the following:

28

WATERBORNE DISEASES

source protection water treatment distribution system management and protection education The first protection barrier, source protection (as the name implies), involves not only protecting the community's river, stream, lake, or groundwater supply source from contamination, but also includes protection of the entire watershed. Water treatment is normally required no matter the source, unless water is withdrawn from a groundwater source that has been tested safe for use. Raw water is drawn from the source and conveyed to a treatment works where it is typically processed through treatment components such as coagulation, flocculation, sedimentation, filtration, and disinfection before being pumped through a distribution system. Once drawn from its source and properly treated, water is then distributed via a distribution system to the consumer. The distribution system also acts as an important element in the barrier protection strategy against contamination. Obviously, sending quality treated water into a distribution system that allows the water supply to become contaminated before it reaches the consumer does little good and could be quite harmful. Various factors affecting the distribution system include the following: quality of treated water deterioration of water within the system cross connections with nonpotable systems maintenance, construction, and rehabilitation practices management practices sound operating procedures

3.6 SUMMARY

The last barrier against water supply contamination is education. Training waterworks operators on the importance of maintaining a contaminant-free water supply system is essential, as is ensuring that local residents and consumers understand (through local educational programs) the importance and need to maintain contaminant-free local water supplies.

3.7 CHAPTER REVIEW QUESTIONS

3-1 In discussing disease, what is a reservoir?

What is a host?

What is an agent?

Chapter Review Questions

3-2 What are the two types of disease transmission?

3-3 Do bacteria live long outside a host? Why?

3-4 In chlorinated water, which dies off quicker, bacteria or viruses?

3-5 What are the symptoms of Giardiasis?

3-6 Is Giardiasis a new disease?

3-7 What are total colifonns?

3-8 What are fecal colifonns?

CHAPTER 4

Water Microbiology

Don 't think there are no crocodiles because the water is calm.-Malayan

Proverb

4.1 INTRODUCTION waterworks operators cannot fully comprehend the principles presented in Chapter 3 or the principles of effective water treatment without knowing the fundamental factors concerning microorganisms and their relationships to one another, their effects on the treatment process, and their impact on consumers, animals, and the environment. This chapter provides microbiology fundamentals specifically targeting the needs of entry-level water specialists.

S

IMPLY put,

4.2 MICROBIOLOGY: WHAT IS IT? Biology is generally defined as the study of living organisms. Microbiology is the study of microorganisms so small in size that they must be studied under a microscope. Microorganisms of interest to the waterworks operator include bacteria, protozoa, viruses, and algae. J Note: The science and study of bacteria is known as bacteriology (see Chapter 5).

As stated in Chapter 3, waterworks operators' primary concern is how to control microorganisms that cause waterborne diseases-waterborne pathogens. Understanding how to minimize growth and control pathogens involves studying the structures and characteristics of microorganisms. To effectively achieve this, microorganisms are categorized under a systematic classification scheme. All organisms are included in two major groups, the animal and plant kingdoms. We discuss the biological classification system and the commonly recognized groups in the following section. 4.2.1 CLASSIFICATION For centuries, scientists classified the forms of life visible to the naked eye as either animal or plant. Much of the current knowledge about living things was organized by the Swedish naturalist Carolus Linnaeus in 1735. Linnaeus' class~ficationof organisms was quite innovative and has proven to be extraordinarily logical and useful over the centuries. His binomial system of nomenclature is still with us today. Under the binomial system, all organisms are generally described by a two-word scientific name, the genus and species. Genus and species are groups that are part of a luerarchy of groups of increasing size, based on their nomenclature (taxonomy). Linnaeus organized the groups in order of increasing number and dwersity as follows:

WATER MICROBIOLOGY

Species Genus Family Order Class Phylum Kingdom Using this hierarchy and Linnaeus's binomial system of nomenclature, the scientific name of any organism (as stated previously) includes the generic and specific names. The first letter of the generic name is usually capitalized, hence, E. coli indicates that coli is the species and Escherichia (abbreviated to E.) is the genus. The largest, most inclusive category, the kingdom, is plant. The names are always in Latin, so they are usually printed in italics or underlined. Some organisms also have English common names. Microbe names of particular interest in water treatment include the following: Escherichia coli-a coliform bacteria Salmonella typhi-the typhoid bacillus Giardia lamblia-a protozoan Generally, we use a simplified system of microorganism classification in water science, breaking down classification into the kingdoms of animal, plant, and protista. As a general rule, the animal and plant kingdoms contain all the multicell organisms, and the protists contain all single-cell organisms. Along with microorganism classification based on the animal, plant, and protista kingdoms, microorganisms can be further classified as being eucaryotic orprocaryotic (see Table 4.1).

J Note: A eucaryotic organism is characterized by a cellular organization that includes a welldefined nuclear membrane. Aprocaryotic organism is characterized by a nucleus that lacks a limiting membrane. 4.2.2 DIFFERENTIATION Differentiation among the higher forms of life is based almost entirely upon morphological (form or structure) differences. Note, however, that differentiation (even among the higher forms) is not as easily accomplished as you might expect, because normal variations among individuals of the same species occur frequently. TABLE 4.1.

Simplified Classification of Microorganisms.

Kingdom

Members

Cell Classification

Animal

Rotifers Crustaceans Worms and larvae

Eucaryotic

Plant

Ferns Mosses

Protista

Protozoa Algae Fungi Bacteria Lower algae forms

Procaryotic

34

WATER MICROBIOLOGY

Because of this variation even within a species, securing accurate classification when dealing with single-celled microscopic forms that present virtually no visible structural differences becomes extremely difficult. Under these circumstances, considering physiological, cultural, and chemical differences, as well as structure and form, is necessary. Differentiation among the smaller groups of bacteria is based almost wholly upon chemical differences.

4.2.3THE CELL The structural and fundamental unit of plants and animals, no matter how complex, is the cell. Since the nineteenth century, scientists have known that all living things, whether animal or plant, are made up of cells. A typical cell is an entity, isolated from other cells by a membrane or cell wall. The cell membrane contains protoplasm and the nucleus (see Figure 4.1). The protoplasm within the cell is a living mass of viscous, transparent material. Within the protoplasm is a dense spherical mass called the nucleus. In a typical mature plant cell, the cell wall is rigid and is composed of nonliving material, while in the typical animal cell, the wall is an elastic living membrane. Cells exist in a variety of sizes and shapes, and vary in functions. Their average size ranges from bacteria too small to be seen with the light microscope to the largest known single cell, the ostrich egg.

J Note: The nucleus cannot always be observed in bacteria. 4.3 BACTERIA

Bacteria, among the most common microorganisms in water, are primitive, unicellular (singlecelled) organisms, possessing no well-defined nucleus, that present a variety of shapes and nutritional needs. Bacteria contain about 85 percent water and 15 percent ash or mineral matter. The ash is largely composed of sulfur, potassium, sodium, calcium, and chlorides, with small amounts of iron, silicon, and magnesium. Bacteria reproduce by binary fission. J Note: Binaryfission is when one organism splits or divides into two or more new organisms.

Bacteria, once called the smallest living organisms (now it is known that smaller forms of matter exhibit many of the characteristics of life), range in size from 0.5-2 microns in diameter and are about 1-1 0 microns long.

J Note: A micron is a metric unit of measurement equal to 1 thousandth of a millimeter. To visualize the size of bacteria, consider that about 1,000 bacteria laying side by side would reach across the head of a straight pin. Bacteria are categorized into three general groups based on their physical forms or shapes (though almost every variation has been found; see Table 4.2). The simplest form is the sphere. Sphericalshaped bacteria are called cocci. Rod-shaped bacteria are called bacilli. Spiral-shaped bacteria make up the third group (see Figure 4.2). Within these three groups are many different arrangements. Some exist as single cells, others as pairs, as packets of four or eight, as chains, and as clumps. TABLE 4.2.

Forms of Bacteria.

1

Technical Name

P

Form

Singular

Plural

Example

Sphere Rod Curved or spiral

Coccus Bacillus Spirillum

Cocci Bacilli Spirilla

Streptococcus Bacillus typhosis Spirillum cholera

Bacteria

Cocci -- spheres

Bacilli -- rods Figure 4.2 Bacterial shapes.

Most bacteria require organic food to survive and multiply. Plant and animal material that gets into the water provides the food source for bacteria. Bacteria convert the food to energy and use the energy to make new cells. Some bacteria can use inorganics (e.g., minerals such as iron) as an energy source and exist and multiply even when organics (pollution) are not available. 4.3.1 BACTERIAL GROWTH FACTORS

Several factors affect the rate at which bacteria grow, including temperature, pH, and oxygen levels. The warmer the environment, the faster the rate of growth. Generally, for each increase of 10°C, the growth rate doubles. Heat can also be used to kill bacteria. Most bacteria grow best at neutral pH. Extreme acidic or basic conditions generally inhibit growth, though some bacteria may require acidic or alkaline conditions for growth. Bacteria are either aerobic, anaerobic, or facultative. If aerobic, they require free oxygen in the aquatic environment. Anaerobic bacteria exist and multiply in environments that lack dissolved oxygen. Facultative bacteria (e.g., iron bacteria) can switch from aerobic to anaerobic growth or grow in an anaerobic or aerobic environment. Under optimum conditions, bacteria grow and reproduce rapidly. As stated previously, bacteria reproduce by binary fission. An important point to consider in connection with bacterial reproduction is the rate at which the process can take place. The total time required for an organism to reproduce and the offspring to reach maturity is called generation time. Bacteria growing under optimal conditions can double their number about every 20 to 30 minutes. Obviously, this generation time is very short compared with that of higher plants and animals. Bacteria continue to grow at this rapid rate as long as nutrients hold out--even the smallest contamination can result in a sizable growth in a very short time.

4.3.2 DESTRUCTION OF BACTERIA The destruction of bacteria is usually called disinfection. J Note: Inhibiting the growth of microorganisms is termed antisepsis, while destroying them is called disinfection.

Disinfection does not mean that all microbial forms are killed. That would be sterilization. However, disinfection reduces the number of disease-causing organisms to an acceptable number. Growing bacteria are fairly easy to control by disinfection. Some bacteria, however, form sporessurvival structures-that are much more difficult to destroy.

36

WATER MICROBIOLOGY

WATERBORNE BACTERIA All surface waters contain bacteria. Waterborne bacteria are responsible for infectious epidemic diseases. Bacterial numbers increase significantly during storm events when streams are high. Heavy rainstorms increase stream contamination by washing material from the ground surface into the stream. After the initial washing occurs, few impurities are left to be washed into the stream, which may then carry relatively "clean" water. A river of fairly good quality shows its highest bacterial numbers during rainy periods; however, a very polluted stream may show the highest numbers during low flows because of the constant influx of pollutants. Waterworks operators are primarily concerned with bacterial pathogens responsible for disease. These pathogens enter potential drinking water supplies through fecal contamination and are ingested by humans if the water is not properly treated and disinfected.

J Note: Regulations require that owners of all public water supplies collect water samples and deliver them to a certified laboratory for bacteriological examination (see Chapter 5) at least monthly. The number of samples required is usually in accordance with Federal Standards that generally require that one sample per month be collected for each 1,000 persons served by the waterworks.

4.4 PROTOZOA Protozoans (or "first animals") are a large group of eucaryotic organisms of more than 50,000 known species that have adapted a form or cell to serve as the entire body. In fact, protozoans are one-celled animal-like organisms with fairly complex cellular structures. In the microbial world, protozoans are giants, many times larger than bacteria. They range in size from 4 microns to 500 microns. The largest ones can almost be seen by the naked eye. They can exist as solitary or independent organisms [for example, the stalked ciliates (see Figure 4.3) such as Vorticella sp.], or they can colonize like the sedentary Carchesium sp. Protozoa get their name because they employ the same type of feeding strategy as animals. Most are harmless, but some are parasitic. Some forms have two life stages: active trophozoites (capable of feeding) and dormant cysts. The major groups of protozoans are based on their method of locomotion (motility). For example, the Mastigophora are motile by means of one of moreflagella (a whip-like projection that propels the free-swimming organisms-Giardia lamblia is a flagellated protozoan); the Ciliophora are motile by means of shortened modified flagella called cilia (short hair-like structures that beat rapidly and propel them through the water); the Sarcodina are motile by means of amoeboid movement (streaming or gliding action-the shape of amoebae change as they stretch, then contract, from place to place); and the Sporozoa that are nonmotile and are simply swept along with the current of the water. Protozoa consume organics to survive; their favorite food is bacteria. Protozoa are mostly aerobic or facultative in regard to oxygen requirements. Toxic materials, pH, and temperature affect protozoan rates of growth in the same way they affect bacteria. Most protozoan life cycles alternate between an active growth phase (trophozoites) and a resting stage (cysts). Cysts are extremely resistant structures that protect the organism from destruction when it encounters harsh environmental conditions, including chlorination.

J Note: Those protozoans not completely resistant to chlorination require higher disinfectant concentrations and longer contact time for disinfection than normally used in water treatment.

Figure 4.3 Protozoa.

WATER MICROBIOLOGY

The three protozoans and the waterborne diseases associated with them of most concern to the waterworks operator are as follows: Entamoeba histolytica-Amoebic dysentery Giardia lamblia-Giardiasis Cryptosporidium-Cryptosporidiosis

4.5 VIRUSES Viruses are intercellularparasitic particles that are the smallest living infectious materials known. Viruses are very simple lifeforms consisting of a central molecule of genetic material surrounded by a protein shell called a capsid and sometimes by a second layer called an envelope. They contain no mechanisms by which to obtain energy or reproduce on their own, thus, to live, viruses must have a host. After they invade the cells of their specific host (animal, plant, insect, fish, or even bacteria), they take over the host's cellular machinery and force it to make more viruses. In the process, the host cell is destroyed and hundreds of new viruses are released into the environment. The viruses of most concern to the waterworks operator are the pathogens that cause hepatitis, viral gastroenteritis, and poliomyelitis. Smaller and different from bacteria, viruses are prevalent in water contaminated with sewage. Detecting viruses in water supplies is a major problem because of the complexity of the nonroutine procedures involved, though experience has shown that the normal coliform index can be used as a rough guide for viruses as for bacteria. However, more attention must be paid to viruses whenever surface water supplies have been used for sewage disposal. Viruses occur in many shapes, including long slender rods, elaborate irregular shapes, and geometric polyhedrals (see Figure 4.4). Viruses are difficult to destroy by normal disinfection practices, requiring increased disinfectant concentration and contact time for effective destruction.

Figure 4.4 Virus shapes.

Chapter Review Questions

Euglenoids

Diatom Figure 4.5 Algae.

4.6 ALGAE You don't have to be a waterworks operator to understand that algae can be a nuisance. Many ponds and lakes in the U.S. are currently undergoing eutrophication, the enrichment of an environment with inorganic substances (e.g., phosphorus and nitrogen), causing excessive algae growth and premature aging of the water body. The average person may not know what eutrophication means, however, when eutrophication occurs and especially when filamentous algae like Caldophora break loose in a pond or lake and wash ashore, algae make their noxious presence known. Algae are a form of aquatic plants and are classified by color (e.g., green algae, blue-green algae, golden-brown algae, etc.). Algae come in many shapes and sizes (see Figure 4.5). Although they are not pathogenic, algae cause problems with water treatment plant operations. They grow easily on the walls of troughs and basins, and heavy growth can plug intakes and screens. Additionally, some algae release chemicals that give off undesirable tastes and odors. Many algae (en masse) are easily seen by the naked eye, and others are microscopic. They can be found in fresh and polluted water as well as in salt water. Since they are plants, they are capable of using energy from the sun in photosynthesis. They usually grow near the surface of the water because light cannot penetrate very far through the water. Algae are controlled in raw waters with chlorine and potassium permanganate. Algae blooms in raw water reservoirs are often controlled with copper sulfate.

4.7 SUMMARY

Controlling the microbial population present in the water sources a community draws from is a critical part of an operator's job. The means by which water operators determine what levels of treatment their water supply needs are covered in the following chapters.

4.8 CHAPTER REVIEW QUESTIONS 4-1 The three major groups of microorganisms that cause disease in water are:

40

WATER MICROBIOLOGY

4-2 Will freezing kill all bacteria?

4-3 When does a river of fairly good quality show its highest bacterial numbers?

4-4 Are coliform organisms pathogenic?

4-5 How do bacteria reproduce?

4-6 The three common shapes of bacteria are:

4-7 Three waterborne diseases caused by bacteria are:

4-8 Two protozoa-caused waterborne diseases are:

4-9 When a protozoa is in a resting phase, it is called a 4- 10 For a virus to live, it must have a 4-1 1 What problems do algae cause in drinking water?

CHAPTER 5

Bacteriology: Sampling and Examination

U.S. CHOLERA EPIDEMIC-18325

. . . the most important task in preventing the spread of cholera was to safeguard the common people against their dangerous habits of life. Accordingly, the Special Medical Council drew up thefollowing recommendations, which were distributed in handbills and published prominently in all of the city's newspapers. NOTICE Be temperate in eating and drinking, avoid crude vegetables and fruits; abstainfrom cold watel; when heated; and above all from ardent spirits and if habit have rendered it indispensable, take much less than usual. Sleep and clothe warm. Avoid labor in the heat of day. Do not sleep or sit in a draught of air when heated. Avoid getting wet. Take no medicines without advice.

5.1 INTRODUCTION LL water, even distilled water, contains microorganisms. A water supply containing pathogenic microorganisms is contaminated, of course. The only way sterile water can be obtained is by treating it with chemicals (such as chlorine) to destroy the bacteria, by heating it, or under special circumstances, by irradiating it with ultraviolet (UV) light. We can safely say that all natural waters, whether from surface or ground sources or from precipitation, are contaminated to some degree with bacteria. We can also safely say that water containing a large number of microorganisms may be perfectly safe to drink. The important consideration, from a microbiological or bacteriological standpoint, is the kinds of microorganisms present. Water treatment specialists are primarily concerned with bacteria in public water supplies. Public law requires that owners of public water supplies collect water samples and deliver them to a certified laboratory for bacteriological examination at least monthly. The number of samples to be collected is usually mandated by federal standards that generally require that one sample per month be collected for each 1,000 persons served by the waterworks.

A

'~rornC. E. Rosenberg's The Cholera Years: The United States in 1832, 1849, and 1866. Chicago: The University of Chicago Press, p. 3, 1987.

42

BACTERIOLOGY: SAMPLING AND EXAMINATION

J Note: In water analysis, the number and kind of bacteria in the water are determined by bacteriological examination.

Bacteriological tests on water determine whether pathogenic organisms are present by testing for certain indicator organisms. In practice, these indicator organisms are the focus of testing because identifying specific disease-producing organisms present in water is not practical; to check water for each pathogenic agent would be difficult, time consuming, and expensive. This chapter provides a brief discussion of sampling and examination (bacteriological practices) normally performed by waterworks personnel serving a public water supply system. 5.2 WATER SAMPLING When initially setting up a water sampling protocol, determining the objectives and the criteria for the sampling is critical. One important consideration is to determine whether sampling will be accomplished at a single point or at isolated points. Obviously, the water samples collected should reflect the quality of the water supplied to the consumers. The quality can vary greatly from one point in the distribution system to another, depending on how the pipes are laid out. Use a map or sketch of the water distribution system to locate general sampling locations that give samples representative of the various characteristics of the distribution system.

J Note: Representative samples are collected from designated sampling points (e.g., dead-end pipes, main lines, branch lines, loops, various water sources, storage tanks, pressure zones, and other distribution configurations) and tested. The results of these tests reveal the quality of the drinking water and should be recorded and filed. This permanent record of bacteriological quality is public information and must be maintained by the waterworks operator for up to five years, depending on location. Additionally, frequency of sampling must be determined (frequency of sampling is usually based on regulatory requirements). Whatever sampling frequency is chosen, the entire process will likely continue over a protracted period. 5.2.1 EXAMPLE SAMPLING POINTS IN DISTRIBUTION SYSTEMS

As we said, samples must be collected from representative locations. Consider the distribution systems shown in Figure 5.1. In distribution system 1 (Figure 5.1) a number of branch lines have dead ends. To provide samples that are representative of all the conditions in this system could require four different sampling locations: (1) Location A gives a representative sample from along the main line of the distribution system, (2) Location B gives one from along one of the branch lines, (3) Location C from a point near the dead end of the main line, and (4) Location D from a point near the dead end of a branch line. Distribution system 2 (Figure 5.1) is looped, allowing water to flow freely in all directions. In this system, we need only two sampling locations to provide samples representative of the main loop (Location A) and branch loop (Location B) conditions. Each sample location should be rotated to provide the required number of samples each month. Keep in mind that the number of samples required to be taken each month may be larger than the number of locations needed to provide representative samples. If this is the case, each location may be used more than once during a given month. Once enough general locations are identified to provide representative samples, select specific

Water Sampling

Distribution System 1: Branched water distribution system

Distribution System 2: Looped water distribution system Figure 5.1 Sampling locations.

points from which samples will be collected. Sampling points should be conventional-type water faucets, preferably in buildings where people consistently use water. Sampling points should be accessible during the time samples are normally collected, should provide reliable results, and should be free of conditions or equipment that could provide a sample that is not representative of the distribution system. Sampling points can be indoors or outdoors and can be in residences or in public or commercial buildings. If the location where sampling is normally conducted has no

44

BACTERIOLOGY: SAMPLING AND EXAM1NATION

buildings, a special sampling station should be installed. Sampling sites are permanent and are recorded as part of a particular water system's sampling site report. Because of sampling requirements, three sampling-site buildings for each general location should be identified including two "backup" sites that are needed on either side of the primary site at each location. The "backup" sites must both be located within five service connections of the primary site: one upstream and one downstream. The following locations should not be sampled from: locations with separate storage tanks (such as buildings with fire protection storage tanks and sprinkler systems) buildings with "point-of-entry" water treatment systems (such as water softeners, whole-house water filters, single-home chlorinators) abandoned buildings buildings with newly installed plumbing faucets with aerators or strainers, unless the aerators or strainers are removed before sampling faucets with swivel-type connections (such as kitchen faucets) faucets with water filters or "water purifiers" attached leaky faucets that allow water to run along the outside of them faucets with vacuum breaker backflow preventers attached directly to the outlets hot water faucets hoses (garden hoses, slop-sink hoses) fire hydrants or freeze-proof yard hydrants Local health departments are good sources of advice for help in determining sampling sites. 5.2.2 SAMPLING SITE RECORD

Record keeping is essential and required for proper waterworks operation. For sampling records, federal and state regulations require submission of a written report of sampling sites to the local health department. This report typically requires at least the following information: map of the water distribution system general sample locations marked on distribution map list of buildings that will be used as "primary" and "backup" sampling sites at each location (Identify buildings by name andlor address and code.) statement of the number of samples required each month statement regarding rotation of samples among sample sites statement of procedure to be followed in event of positive sample 5.2.3 SAMPLING REQUIREMENTS

Each public water supply system must take a minimum number of samples each month or quarter, based on the number of people served by the water system. Table 5.1 indicates the minimum number of bacteriological samples that must be collected each month or quarter by waterworks. Community waterworks (systems that serve a residential population, such as municipal water systems, subdivisions, mobile home parks and apartment buildings) and nontransient community waterworks (systems that serve a permanent nonresidential population, such as factories and schools) must collect the indicated number of samples each month they are in operation. Noncommunity waterworks (those that serve transient populations, such as campgrounds, motels, and restaurants) must collect the indicated number of samples each calendar quarter.

45

Water Sampling TABLE 5.1.

Minimum Bacteriological Sampling Requirements for Public Water Supplies.*

Population Served From

To

Minimum Number of Samples**

Population Served From

To

Minimum Number of Samples**

*From Federal Register, J u n e 29, 1989. "Community and non-transient waterworks: samples per month; noncommunity waterworks: samples per quarter

5.2.4 SAMPLING PROCEDURE If samples are properly collected and shipped to the laboratory, sample collection is a relatively simple task and does not take very much time. If incorrect procedures are followed, an otherwise good sample may be contaminated (which requires collecting additional samples and may lead to drinking water quality violations and public notification) or a sample that could not be analyzed by the lab may need to be replaced. If a waterworks has its own bacteriological laboratory, lab personnel should be able to provide samplers with the exact procedures to follow when collecting samples. The following general procedures apply to all samples submitted to state laboratories for analysis, and to most of those analyzed at other certified labs as well. Routine samples should be collected early in the month to provide enough time to collect replacement samples if the original samples are damaged in transit or cannot be analyzed in the lab. If more than one sample is collected per month, the samples should be spaced out somewhat, so the samples are also representative of the conditions in the distribution system at various times during the month. Procedure : (1) Fully open the sampling faucet and flush it for 20-30 seconds. If the faucet has an aerator or strainer, remove it first. (2) Using an alcohol flame, carefully flame the inside of the faucet long enough to evaporate any water present. Flaming the faucet is optional but highly recommended. J CAUTION: Many faucets contain plastic or rubber parts; too much heat can destroy the faucet. Do not use a blowtorch or other high-heat source; do not hold the alcohol flame on the faucet too long.

(3) Adjust the water flow to an even stream about the diameter of a pencil. Allow the water to run 3 or 4 minutes (5 or 6 minutes if the faucet was not flamed in Step 2) to assure that the water is flowing from the water main, not the building plumbing. Watch for a change in the temperature

BACTERIOLOGY: SAMPLING AND EXAMINATION

of the water, which indicates the water is coming from the service connection pipe. While the water is running, make sure the sample report form is filled out properly. (4) If the water system uses chlorine disinfection, collect a sample for chlorine residual analysis. Using the DPD colorimetric test kit, analyze for residual chlorine, and record the results on the report form. (5) Use only the sample container supplied by the laboratory that will analyze the sample-this may be a glass or plastic bottle or a plastic bag. The container has been sterilized for at least 1 hour at 170°F and contains a solution or tablet of sodium thiosulfate to neutralize any residual chlorine that may be present in the sample. Do not rinse or boil the container, place your finger in it, or otherwise tamper with it. A container should not be used more than six months after it has been received. Return outdated state lab containers to the appropriate agency. The screw caps on bottles may be loose when received; this is normal. If the cap is completely off the bottle, do not use it. Obtain a new container from the lab or appropriate agency. J Note: The preferred type of glass bottle used for sampling in the bacteriological examination

of water is a wide-mouth, ground-glass stoppered bottle.

(6) Open the sample bag or bottle only when ready to collect the water sample. Using a bottle: Hold the cap with the inside pointing down to avoid contamination from airborne bacteria. Do not put the cap down. Hold the bottle near the bottom to avoid contamination from fingers. Using a bag: Follow the instructions that came with the bag for opening the bag and holding it. (7) Keeping the water flow at a slow, even stream, fill the bottle just to the shoulder (see Figure 5.2) or fill the bag to the white line marked "4 oz. fill line." At least 100 milliliters (mt)must be collected or the sample cannot be analyzed. Ensure that an air space remains above the water in the bottle or in the bag. Do not let the container overflow, and avoid splashing water on the outside of the container. (8) Using a bottle: Immediately replace the cap, malung sure the bottle is tightly closed. Using a bag: Immediately close the bag by pulling the wire tapes to straighten them. Whirl the bag around the wires three or four complete revolutions to seal the bag tight. There should be a pocket of air inside the bag. Turn the ends of the tapes inward, opposite the fold, and twist the wire tape ends together. Be careful to turn the wire ends so the bag will not be punctured during transit. (9) Complete the sample report form according to local requirements, and transport the sample to the laboratory. If the sample is to be analyzed locally, it must be kept iced (temperature should be maintained between 0 4 0 ° C ) and reach the lab in time for analysis to begin the same day it was collected. If a state or regional laboratory is used, the sample must be kept iced until it is ready to be mailed. To be valid, typically, the sample must be received by the lab within 30 hours of collection.

5.3 SAMPLING FOLLOWED BY TESTING: WHY AND FOR WHAT? Sampling followed by testing for bacteria can reveal whether a public drinking water supply is safe. Experience has demonstrated that problems that may otherwise go unnoticed are often detected early enough to prevent the development of a major problem. Sources of contamination can be determined through proper sampling and testing. Common practice is not to sample for the pathogen itself (because of the impracticalities involved), but instead to sample for indicator organisms. The indicator organisms we are referring to, of course, are the fecal coliforms.

Sampling Followed by Testing: Why and for What?

Figure 5.2 Sampling bottle. Filling to shoulder assures collection of enough sample. Do not overfill.

5.3.1 SAMPLING FOR FECAL COLIFORMS

Among the organisms present in large numbers in the intestinal tracts of humans and warmblooded animals is a variety of coliform bacteria, including Clostridium perj-ringens and fecal streptococcus. The presence of these organisms in water indicates that the water has received contamination of an intestinal origin; we know that at least five diseases of bacterial origin are transmittable from person to person through sewage contaminated water. The Clostridium peq5ringens and streptococcus bacteria are pathogenic but are difficult to isolate and test for and can cause serious health hazards for the laboratory technicians who may be exposed to them. Therefore, in the US., we use the total coliform group of bacteria as indicator organisms for measuring and, thus, determining the bacteriological quality of drinking water. We test samples for the presence or absence of an organism or group of organisms specifically identified with sewage. The coliform group of bacteria is comprised of more than 30 individual species conforming to the requirements of an ideal index of sewage pollution. These requirements are: ( l ) always present when sewage is present, (2) always absent when sewage is absent, (3) survives longer in water than any of the pathogenic species, and (4) are easily isolated and identified. Standard Methods for the Examination of Water and Wastewater (current edition), published jointly by the American Public Health Association, the American Water Works Association and the Water Environment Federation, provides the official definition of the coliform group of bacteria: "The coliform group includes all of the aerobic and facultative anaerobic, Gram-negative, nonspore-forming, rod shaped bacteria which ferment lactose with gas formation within 48 hours at 35°C" (p. 327). Let's take a closer look at some of the terminology in this definition. We've discussed "aerobic" and "facultative anaerobic" previously, and will define them further shortly. "Gram-negative" refers to a technique of staining bacteria developed by Christian Gram, a noted scientist. With this technique, bacteria are separated into two broad groups, those that retain the applied stain despite washing with alcohol (these are designated "Gram-positive") and those from which alcohol removes the stain. The latter are designated as "Gram-negative," and as indicated by the official definition, coliform group bacteria belong in this category. That colifonn bacteria are rod-shaped needs no further discussion. However, the last specification (regarding fermentation of lactose) needs explanation. Lactose is a sugar, sometimes called milk

48

BACTERIOLOGY: SAMPLING AND EXAMINATION

sugar. Some bacteria (including the coliform group) are capable of decomposing this sugar to yield a gas that is chiefly carbon dioxide. The requirement specifies further that this gas production must take place within a definite period (48 hours) and at a definite temperature of incubation. The restrictions are intended to eliminate from consideration those species that are very slow gas producers. 5.3.2 METHODS USED TO ESTIMATE DEGREE OF SEWAGE CONTAMINATION

The two bacteriologic methods currently available for estimating the degree of sewage pollution of a water sample are the multiple tube fermentation method and the membrane filter method. The multiple tube fermentation method is the standard for all types of waters. The membrane filter method (the preferred method used today) is standard for waters free from turbidity, algae, and filterclogging materials after adequate parallel testing has demonstrated that it yields, for a particular water, information comparable to that of the multiple tube method.

J Note: The most recent edition of Standard Methods should be used as a reference in setting up a laboratory and making bacteriological tests. 5.3.2.1 Multiple Fermentation Tube Method

The multiple fermentation tube method (see Figure 5.3) for testing for coliforms consists of two steps known as the presumptive test and the confirmed test. Under certain conditions, testing must go one step further to include a completed test; however, this step is not always necessary. For the tests, small portions of the water sample are used in accordance with the following procedure.

J Note: If a completed test is warranted, among other things, it determines the Gram-stain characteristics of the organisms isolated. Agar slants and formate ricinoleate broth are used in the completed test.

5.3.2.1.1 Plate Count The plate count is a test made by the laboratory to determine the total number of bacteria present in the sample. This test does not differentiate between the many different types of bacteria and is thought of as giving index to general "housekeeping" practices. A "high" count indicates that some type of contamination is present and is undesirable. The test is performed by placing a portion of media in a petri dish. "Media" are types of plant food that favor the growth of most bacteria. J Note: The usual medium used for the standard plate count is tryptone glucose extract agar.

J Note: Other culture mediums commonly used in bacteriological examination include agar, beef extract, andlor peptone. Place a portion of the water sample in the petri dish along with the media, then place in an incubator with the temperature at 37OC or 98.6OF, which is body temperature. After 24 hours, the plate is removed, examined, and the colonies in and on the media are counted and recorded on the report form as "Bacteria per rnL at 37OC." We assume that each single bacterium in the media starts to grow, and because of its short generation time, develops so that a spot or colony visible to the eye can be seen on the plate. Count the colonies. Each colony is considered to represent an original bacterium.

Sampling Followed by Testing: Why and for What?

v Air

----

Figure 5.3 Fermentation tube.

5.3.2.1.2 The Multiple Tube Test The multiple tube test is much more significant than the plate count. It determines if coliform organisms are present. The presence of these organisms may indicate that harmful bacteria are entering the water supply. The presumptive test: Coliform bacteria are grown in test tubes containing Lactose Broth (primary fermentation tubes) in which a water sample is placed. The Lactose Broth provides the moisture needed for growth, and few other organisms grow in the broth. The test tubes are placed in an incubator at a temperature of 98.6"F (37°C). J Note: Nutrient broth used in bacteriological examination of water is generally sterilized at 121°C for 15 minutes. The pH of sterilized nutrient broth used in the bacteriological examination of water is approximately 6.0.

If we provide food, moisture, and proper temperature for the proper time, if organisms are present, they will grow. If coliform organisms or the few other types that will grow in Lactose are not present in the water, no growth occurs. If organisms are present, they will grow under these ideal conditions and will ferment the Lactose Broth and produce gas. Gas indicates the presence of the organisms. After 24 hours in the incubator, examine the tubes for gas. If no gas has formed, give the tubes an additional 24 hours. If, after 48 hours, gas has not formed, then no organisms were present, the report reads "Absent," and the water is considered safe for drinking.

50

BACTERIOLOGY: SAMPLING AND EXAMINATION

If organisms that reproduce in Lactose Broth are present in the sample, gas will be produced in any or all of the tubes within 18 hours. Because of the presence of gas, we then know that some type of organism is present and can presume that the organisms are coliforms. That is why the test is called the "presumptive test"-we presume that coliform organisms are present if gas is produced in Lactose Broth. The conJirmed test: The presumptive test would be complete if coliforms were the only organisms that grew in Lactose Broth. Unfortunately, other organisms will ferment the broth and produce gas. Thus, if gas is present, we must transfer a small amount of the contents of the Lactose Broth tubes showing gas into another more selective food called Brilliant Green Bile. Since coliform organisms are able to grow in the human intestine, bile is a preferred food. Other, non-coliform bacteria present are unable to grow in this medium. The tubes of Brilliant Green Bile containing some of the organisms from the Lactose Broth are placed in an incubator. At the end of 24 and 48 hours, they are examined for gas. If gas is present, the confirmed test is positive, and the results are reported as "Present." The water sample contained coliforms, so the water supply becomes questionable as safe drinking water. If no gas is present, the confirmed test is "negative," the results are reported as "Absent," and the water is considered safe. The presence of the Coli-aerogenous group of bacteria in the above tests does not definitely mean that harmful bacteria are present. Coliform bacteria are normally present in great numbers in the human intestine, and except in unusual circumstances, are not harmful to humans. When present in a water sample, they do, however, indicate the presence of fecal contamination and the possibility that harmful (pathogenic) organisms (such as typhoid fever germs) may be present. Therefore, the tests are not measures of actual disease-producing organisms, but are indicators of the possibility that they are present. Most Probable Number: Not only is detecting pollution of water important, estimating the degree of pollution is critical as well, specifically the number of coliform bacteria per unit volume. When testing using a medium in which the original number of bacteria introduced is greatly increased before their presence is evident, precise counting of bacteria cells is impossible. A suitable alternative is to inoculate several fermentation tubes with a series of dilutions of the sample to observe which produce gas and to calculate the number of bacteria using a mathematical formula based upon the laws of probability-a mathematical estimate of the mean density of coliforms in the sample. This sample becomes more accurate when a large number of sample portions are used in tubes to be incubated. Each sample may be diluted in a select way when a high coliform concentration is expected. In examining drinking water from the distribution system, a zero or negative result is expected, in other words, a minimum concentration of coliform. 5.3.2.2 Membrane Filter (MF) Method

Membrane (or MFMillipore) Filters have come into use in many fields of bacteriology and have supplemented or replaced some of the older methods of isolating and identifying bacteria. These filters are very thin films of cellulose manufactured to produce a porous structure. Water passes freely through the membrane with slight suction, but particles (even those as small as bacteria) are retained on the surface. Starting with the sterile membrane placed on a sterilized funnel-shaped holder mounted on a suction-type receiving flask, a sample of known volume is filtered with the aid of suction applied to the receiving flask. The membrane filter is then removed with sterilized forceps and placed in a sterile culture dish on a sterile absorbent pad and is saturated with special nutrient medium. Colonies develop after incubation for 18-22 hours at 35OC; these may be counted with the aid of a 10-power stereomicroscope. Only those that have a dark purplish-green color with a metallic sheen are considered members of the coliform group. Results are reported as colonies per 100mL of sample.

Chapter Review Questions

51

The membrane filter method yields results roughly comparable to the fermentation tube method when the sample is free from suspended matter. The more suspended matter present in the sample, the greater the discrepancy between the two methods. The technique is easier to perform than the fermentation tube method, results are obtained more quickly, and with a field testing kit, the test may be performed in the field. In this kit, the membrane filter disc and absorbent pad are assembled in a two-part sterile plastic device that serves as a filter holder and culturing dish. This assembly is called a "field monitor." To use the field monitoring set, force a sample of water through the properly prepared membrane, which is enclosed in a plastic holder for protection. Then, saturate the filter with medium (or food) for growing bacteria and plug the two openings in the monitor. Incubate in an inverted position in a portable incubator, or mail the filter to the laboratory for incubation and analysis of coliform colonies. 5.4 SUMMARY

Proper, accurate sampling and testing for the presence of bacteria in water is an essential part of the water operator's job. However, to determine and interpret the results demands that the operator take testing and sampling another step. Operators must also learn to "do the math" (the subject of Chapter 6). 5.5 CHAPTER REVIEW QUESTIONS

5-1 In water sampling, what is a representative sample?

5-2 When is the best time to sample? Why?

5-3 The presence of coliform in a bacteriological sample indicates:

5-4 Glassware used in the bacteriological examination of water is generally sterilized in the incubator for at least hour at "C. 5-5 Nutrient broth used in the bacteriological examination of water is generally sterilized at "C for minutes. 5-6 Water samples containing residual chlorine are generally dechlorinated by the addition of:

5-7 Water samples for bacteriological examination should be stored at a temperature between:

52

BACTERIOLOGY: SAMPLING AND EXAMINATION

5-8 The preferred type of glass bottle used to hold bacteriological samples is:

5-9 The standard tests used to determine the presence of members of the coliform group in water employ an incubating temperature of:

5-10 The pH of sterilized nutrient broth used in the bacteriological examination of water is approximately :

5- 11 Define bacteriological examination:

5-12 A presumptive test is negative if gas is not produced within

hours.

5- 13 The medium used in the standard plate count is:

5-14 The magnification of the lens typically used in counting colonies for the standard plate count is approximately power. 5-15 Primary fermentation tubes are used in the:

CHAPTER 6

Waterworks Math: Basic

To operate a waterworks and to pass the examination for a waterworks operator's license, you must know how to do certain calculations.

6.1 INTRODUCTION S the introductory statement points out, without the ability to perform basic mathematical calculations, waterworks operators would have difficulty in properly operating a waterworks and have extreme difficulty in passing a waterworks operator's licensing examination. In reality, most of the calculations operators need to know how to perform (especially at the entry level) are not difficult, but operators need a basic understanding of arithmetic and problem-solving techniques to be able to solve the problems they typically encounter. Keep in mind that mathematics is a universal language. Mathematical symbols have the same meaning to people speaking many different languages throughout the world. The key to learning mathematics is to learn the language, the symbols, definitions and terms of mathematics that allow you to understand the concepts necessary to perform the equations. In this chapter, we review and introduce the minimum math concepts critical to the "Qualified Operator" at the fundamental or entry level. However, this does not mean that these are the only math concepts that a competent operator would need to solve routine operation and maintenance problems. We review some of the basics of calculations: fractions and decimals, rounding numbers, determining the correct number of significant digits, raising numbers to powers, averages, proportions, conversion factors, calculating flow and detention time, and determining the areas and volumes of different shapes. While doing this, we explain how to keep track of units of measurement (inches, feet, gallons) during the calculations and demonstrate how to solve real-life problems that require calculations.

A

6.2 CALCULATION STEPS Many methods can be successfully used to solve waterworks problems. One of the standard methods of problem solving is listed as follows: (l) If appropriate, make a drawing of the information in the problem. (2) Place the given data on the drawing. (3) Determine "what is the question?" This is the first thing you should ask as you begin to solve the problem, along with, "what are they really looking for?" Writing down exactly what is being looked for is always smart. Sometimes the answer has more than one unknown. For instance, you may need to find "X' then find "Y"

54

(4) (5) (6) (7) (8) (9)

WATERWORKS MATH: BASIC

If the calculation calls for an equation, write it down. Fill in the data in the equation and look to see what is missing. Rearrange or transpose the equation, if necessary. If available, use a calculator. Always write down the answer. Check any solution obtained.

For some people, straightforward math such as addition, subtraction, multiplication, division, and other operations that are listed with numerical values are usually easier to solve than are word problems. However, certain key words aid in solving word problems. For example, the word of means multiply, and means add, per means divide, and less than means subtract. 6.3 MATHEMATICAL TERMS Probably the greatest single cause of failure to understand and appreciate mathematics is not knowing the definitions of the terms used. Each term used in mathematics (more than any other subject) has a definite and fixed meaning. In this section, we define some of the basic mathematical terms you should recall. Integer is a whole number. Thus, 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8,9, 10, 11, and 12 are the first twelve positive integers. Factor (or divisor) of a whole number is any other whole number that exactly divides it. Thus, 3 and 4 are factors of 12. Prime number is a number that has no factors except itself and 1. Examples of prime numbers are 1 , 3 , 5 , 7 , and 11. Composite number is a number that has factors other than itself and 1. Examples of composite numbers are 4 , 6 , 8 , 9 , and 12. Commonfactor (or common divisor) of two or more numbers is a factor that will exactly divide each of them. If this factor is the largest factor possible, it is called the greatest common divisor. Thus, 4 is a common divisor of 16 and 24, but 8 is the greatest common divisor of 16 and 24. Multiple of a given number is a number that is exactly divisible by the given number. If a number is exactly divisible by two or more other numbers, that number is their common multiple. The least (smallest) such number is called the lowest common multiple. Thus, 36 and 72 are common multiples of 12,9, and 4; however, 36 is the lowest common multiple. Even number is a number exactly divisible by 2.2,4,6, $, 10, and 12 are even integers. Odd number is an integer that is not exactly divisible by 2. 1, 3 , 5 , 7 , 9 , or l l are odd integers. Product is the result of multiplying two or more numbers together. Thus, 21 is the product of 3 X 7, and 3 and 7 are factors of 21. Quotient is the result of dividing one number by another. For example, 7 is the quotient of 21 divided by 3. Dividend is a number to be divided; a divisor is a number that divides. For example, in 100 + 25 = 4, 100 is the dividend, 25 is the divisor, and 4 is the quotient. 6.4 SEQUENCE OF OPERATIONS In a series of additions, the terms may be placed in any order and grouped in any way. Thus, 4 + 3 = 7 a n d 3 + 4 = 7 ; ( 4 + 3 ) + ( 6 + 4 ) = 17,(6+3)+(4+4)= 17,and[6+(3+4)]+4=17.

Fractions

55

In a series of subtractions, changing the order or the grouping of the terms may change the result. Thus, 100 - 30 = 70, but 30 - 100 = -70; (100 - 30) - 10 = 60, but 100 - (30 - 10) = 80. When no grouping is given, the subtractions are performed in the order written, from left to right. Thus, 100-30-15-4=51;orbysteps, lOO-30=70,70- l 5 = 5 5 , 5 5 - 4 = 5 1 . In a series of multiplications, the factors may be placed in any order and in any grouping. Thus, [(2 X 3) X 51 X 6 = 180 and 5 X [2 X (6 X 3)] = 180. In a series of divisions, changing the order or the grouping may change the result. Thus, 100 +10 = 10, but 10 + 100 = 0.1; (100 t 10) + 2 = 5, but 100 + (10 + 2) = 20. Again, if no grouping is indicated, the divisions are performed in the order written, from left to right. Thus, 100 + 10 + 2 is understood to mean (100 + 10) + 2. In a series of mixed mathematical operations, the convention is as follows: whenever no grouping is given, multiplications and divisions are to be performed in the order written, then additions and subtractions in the order written.

Example 6.1

by performing operations in the order in which they are given.

Example 6.2

Example 6.3

First perform the multiplications and divisions, then the additions and subtractions. J An easier way to complete Example 6.3 is indicated as follows:

Again, first perform the multiplications and divisions, then the additions and subtractions.

Example 6.4 In a series of different operations, parentheses ( ) and brackets [ ] can be used to group the operations in the desired order. Thus, 120 + 3 X 5 X 2 + 2 = {[(l20 + 3)5]2) +- 2 = 200. 6.5 FRACTIONS The number 8 divided by 4 gives an exact quotient of 2. This may be written 814 = 2. However, if you attempt to divide 8 by 9, you are unable to calculate an exact quotient. This division may be written 819 (read "eight-ninths"). The number 819 represents a number, but not a whole number. This is called a fraction. Simply put, fractions are used to express a portion of a whole. The waterworks operator is often faced with routine situations that require thinking in fractions,

56

WATERWORKS MATH: BASIC

and on occasion, actually working with fractions. One of the common uses for the rules governing the use of fractions in a math problem is dealing with units of the problem. Units like gpm are actually fractions, gallons per minute or gaVmin and cubic feet per second or cfs is actually ft31sec.As you can see, understanding fractions helps in solving other problems. A fraction is composed of three items, two numbers and a line. The number on the top is called the numerator, the number on the bottom is called the denominator and the line in between them means divide. 4 -

Divide

5

+

+

Numerator Denominator

The denominator indicates the number of equal-sized pieces the whole "thing" has been cut into. The numerator tells how many pieces there are. For example, the circle in Figure 6.1 has been divided into four equal pieces, so the denominator will be 4. Each single piece represents 114 of the circle. Three of the pieces are shaded, representing 314 of the circle.

6.5.1 FRACTIONS: PRINCIPLES

Like all other math functions, how we deal with fractions is governed by rules or principles. The following is a discussion of the principles associated with using fractions. (1) Same numerator and denominator When the numerator and denominator of a fraction are the same, the fraction can be reduced to l . For example:

(2) Whole numbers to fractions Any whole number can be expressed as a fraction by placing a "1" in the denominator. For example: 69 3 is the same as -,3 and 69 is the same as 1 1 (3) Adding fractions Only fractions with the same denominator can be added, and only the numerators are added. The denominator stays the same. For example: 1 9

+ - 3= 9

4 and 6 9 18

+ - 8- -

- 14 18 18

(4) Subtracting fractions Only fractions with the same denominator can be subtracted, and only the numerators are subtracted. The denominator remains the same. For example:

( 5 ) Mixed numbers A fraction combined with a whole number is called a mixed number. For example:

Fractions

Figure 6.1 An example of fractions. There are four pieces, so each piece is 114. The three shaded pieces represent 314.

These numbers are read "four and one third," "fourteen and two thirds," "six and three fourths," "forty and one half," and "twenty-two and thirteen thirty thirds." Changing afraction A fraction is changed by multiplying the numerator and the denominator by the same number, which does not change the value of the fraction. For instance:

1 - is thesameas - which is 3 3x3

3

-

9

Simplest terms Fractions should be reduced to their simplest terms by dividing the numerator and denominator by the same number. The result of this division must leave both the numerator and the denominator as whole numbers. For instance:

2 1 - is not in its simplest terms, by dividing both by 2 we obtain 6 3 The number 2 and the 3.

cannot be reduced any further since no number can be divided evenly into both the

Example 6.5 Problem: Reduce the following to their simplest terms.

WATERWORKS MATH: BASIC

Solutions: 2 - 1 - - --both 4 2

were divided by 2

14= 1-both

were divided by 2

18

9

3 - 3 -is 4 4

in its simplest terms

3 -both -- - 10 5

were divided by 2

3 = 1-both

were divided by 9

18

2

2= 1 7-is in its simplest terms 29

29

-24 - - 3-both 32 4

were divided by 8

Reducing even numbers When the starting point is not obvious, do the following: If the numerator and denominator are both even numbers (2,4,6, 8, 10, etc.), divide them by 2 and continue dividing by 2 until a division will no longer yield a whole number with the numerator and denominator. Reducing odd numbers When the numerator and denominator are both odd numbers (3,5,7, 9, 11, 13, 15, 17), attempt to divide by 3, continue dividing by 3 until a division will no longer yield a whole number with the numerator and denominator. It is obvious that some numbers such as 5,7, and 11 cannot be divided by 3 and may in fact be in their simplest terms. Different denominators To add andlor subtract fractions with different denominators, the denominators must be changed to a common denominator. The denominators must be the same before adding or subtracting the fraction. One of the simplest methods of obtaining a common denominator is to multiply the denominators. Each fraction must then be converted to a fraction expressing the new denominator. For instance to add 1and 2: 8 5 start by multiplying the denominators 8 X 5 = 40 change Lto a fraction with 40 as the denominator 8

40 8

-= 5 , 5 X

5 1 = 5 (the numerator), new fraction is 40

Notice that this is the same as 118 except 5/40 is not reduced to its simplest terms. Change i t o a fraction with 40 as the denominator 5

16 40 = 8, 8 X 2 = 16 (the numerator), new fraction is 5 40

Fractions

complete the addition

(1 1) Numerator larger Any time the numerator is larger than the denominator, the fraction should be turned into a mixed number. This is accomplished by the following procedure: Determine the number of times the denominator can be divided evenly into the numerator. This will be the whole number portion of the mixed number. Multiply the whole number times the denominator and subtract from the numerator. This value (the remainder) becomes the numerator of the fraction portion of the mixed number. 28 - 28 is divisible by 12 twice-2 12

2 - 2 = -,4 12

12

is the whole number

dividing top and bottom by 4 =- 1 3

12

The new mixed number is 2-.1 3 (12) Multiplying fractions To multiply fractions, simply multiply the denominators, then reduce to the simplest terms. For instance: Find the result of multiplying

8

X

2 3

(13) Dividing fractions To divide fractions, simply invert the denominator (turn it upside down), multiply, and reduce to simplest terms. For example: Divide 1by 9

$

J Note: The divide symbol can be + or 1 or -.

Fractions to decimals To convert a fraction to a decimal, simply divide the numerator by the denominator. For example:

Change inches to feet example:

To change inches to feet, divide the number of inches by 12. For

60

WATERWORKS MATH: BASIC

Change 5 inches to feet 5 = 0.42 feet 12

Example 6.6 Change the following to feet: 2 inches, 3 inches, 4 inches, 8 inches L -- 0.167 feet 12

-- - 0.25 feet 12 -- - 0.33 feet

12

8 0.667 feet 12

-=

6.6 DECIMALS

While we often use fractions when using measurements, dealing with decimals is often easier when we do calculations, especially when working with pocket calculators and computers. A decimal is composed of two sets of numbers. The numbers to the left of the decimal are whole numbers, and the numbers to the right of the decimal are parts of whole numbers, a fraction of a number.

Whole number 3

9

K Fraction of a number

Decimal The term used to denote the fraction component is dependent on the number of characters to the right of the decimal (see Figure 6.2). The first character after the decimal point is tenths; the second character is hundredths; the third is thousandths; the fourth is ten thousandths; and the fifth is hundred thousandths.

Figure 6.2 Values of positions.

Decimals

0.1-tenths 0.0 1-hundredths 0.001-thousandths 0.0001-ten thousandths 0.00001-hundred thousandths When we use a calculator, we can convert a fraction to a decimal by dividing. The horizontal line or diagonal line of the fraction indicates that we divide the bottom number into the top number. For example, to convert 4 to a decimal, we divide 4 by 5. Using a pocket calculator, enter the 5 following keystrokes :

The display will show the answer, 0.8.

Example 6.7 To determine the amount of chemical solution remaining in a circular mixing tank, we need to determine the volume of the liquid in the tank in cubic feet. Since the volume is equal to the surface area of the liquid times the depth of the liquid, we measure the tank and find it has a diameter of 2 feet, 8 inches, and the liquid is 1 foot, 5 inches deep. We cannot multiply mixed dimensions like feet-and-inches, so before we can proceed with the calculations, we must convert the feet-andinches measurements to feet-and-decimals-of-a-foot. We first state the dimensions as feet-andfractions-of-a-foot by stating the inches as a fraction of a foot. There are 12 inches in a foot, so 8 inches is of a foot: the diameter is 2 feet and $ of a foot, and the liquid depth is 1 foot and 5 of a foot. Doing the division of the fractions, we find that of a foot is 0.67 ft and of a foot 12 is 0.42 ft. The diameter is 2.67 ft, and the depth is 1.42 ft. We can then proceed with the volume calculation. When a calculator is not available, people often cannot remember the basic rules associated with working with decimals. Therefore, we provide a brief review. As we stated previously, when a number is less than one and is expressed as a decimal, we place a "0" (zero) to the left of the decimal. This makes it clear that the number is less than one. For instance, 0.33 is much less open to confusion than .33.

h

5

6.6.1 DECIMALS: PRINCIPLES

6.6.1 .l Subtracting Decimals When subtracting decimals, simply line up the numbers at the decimal point and subtract. For example:

62

WATERWORKS MATH: BASIC

6.6.1.2 Adding Decimals

To add numbers with a decimal, use the same rules as subtraction: line up the numbers at the decimal point and add.

6.6.1.3 Multiplying Decimals

To multiply two or more numbers containing decimals, follow these basic steps: Multiply the numbers as whole numbers, do not worry about the decimals. Write down the answer. Count the total number of digits (numbers) to the right of the decimal in all of the numbers being multiplied. For example, multiplying 3.55 X 8.4 yields the number 29820. A total of three digits fall to the right of the decimal point (2 for the number 3.55 and l for the number 8.4). Therefore, the decimal point would be placed three places to the left from the right of the 0.

6.6.1.4 Dividing Decimals

To divide a number by a number containing a decimal, the divisor must be made into a whole number by moving the decimal point to the right until we have a whole number. Count the number of places the decimal needed to be moved. Move the decimal in the dividend by the same number of places.

Divisor 3

K Dividend

8.12

424 Divisor 3

G K Dividend

Using a calculator, this problem would be set up as follows:

Determining Significant Figures

6.7 ROUNDING NUMBERS Numbers are rounded to reduce the number of digits to the right of the decimal point. This is for convenience, not accuracy. J Rule: A number is rounded off by dropping one or more numbers from the right and adding zeros if necessary to place the decimal point. If the last figure dropped is 5 or more, increase the last retained figure by 1. If the last digit dropped is less than 5, do not increase the last retained figure.

Example 6.8 Problem: Round off 10,546 to 4,3,2, and 1 significant figures. Solution: 10,546 = 10,550 to 4 significant figures 10,546 = 10,500 to 3 significant figures 10,547 = 11,000 to 2 significant figures 10,547 = 10,000 to l significant figure 6.8 DETERMINING SIGNIFICANT FIGURES

The concept of significant figures is related to rounding. It is used to determine where to round off. The basic idea is that no answer can be more accurate than the least accurate piece of data used to calculate the answer. J Rule: Significant figures are those numbers that are known to be reliable. The position of the decimal point does not determine the number of significant figures.

Example 6.9 Problem: How many significant figures are in a measurement of 1.35 in? Solution: Three significant figures: 1,3, and 5.

Example 6.10 Problem: How many significant figures are in a measurement of 0.000135? Solution: Again, three significant figures: 1, 3, and 5. The three zeros are used only to place the decimal point.

WATERWORKS MATH: BASIC

Example 6.11 Problem: How many significant figures are in a measurement of 103,500?

Solution: Four significant figures: 1, 0, 3, and 5. The remaining two zeros are used to place the decimal point.

Example 6.12 Problem: How many significant figures are in 27,000.0?

Solution: There are six significant figures: 2 , 7 , 0 , 0 , 0 , 0 . In this case, the .O means that the measurement is precise to L u n i t . The zeros indicate measured values and are not used solely to place the decimal 10 point. 6.9 POWERS

Powers are used to identify area as in square feet, and volume as in cubic feet. Powers can also be used to indicate that a number should be squared, cubed, etc. This latter designation is the number of times a number must be multiplied times itself. More specifically, when several numbers are multiplied together, as 3 X 4 X 5 = 60, the numbers 3,4, and 5 are thefactors; 60 is theproduct. If all the factors are alike, as 3 X 3 X 3 X 3 = 81, the product is called a power. Thus, 8 1 is a power of 3, and 3 is the base of the power. A power is a product obtained by using a base a certain number of times as a factor. Instead of writing 3 X 3 X 3 X 3, it is more convenient to use an exponent to indicate that the factor 3 is used as a factor four times. This exponent (a small number placed above and to the right of the base number) indicates how many times the base is to be used as a factor. Using this system of notation, the multiplication 3 X 3 X 3 X 3 is written as 34.The 4 is the exponent, showing that 3 is to be used as a factor four times.

Example 6.13 Problem: Rewrite 10 X 10 X 10 and calculate the product.

Solution: 10 X 10 X I O = 103= 1,000

Example 6.14 Problem: Rewrite 2 X 2 X 2 X 2 X 2 and calculate the product.

Averages

Solution: 2 ~ 2 x 2 ~ 2 ~ 2 = 2 ~ = 3 2

Example 6.15 Problem: Rewrite 3 X 3 X 4 X 4 X 4 and compute the product. Solution:

Example 6.16 Problem: What is 12 cubed? 12 squared? Solution: 12 cubed = lz3= 12 X 12 X 12 = 1,728 12 squared = 122= 12 X 12 = 144

6.10 AVERAGES

An average is a way of representing several different measurements as a single number. Although averages can be useful by telling "about" how much or how many, they can also be misleading, as we demonstrate below. You find two kinds of averages in waterworks calculations: the arithmetic mean (or simply mean) and the median. J Definition: The mean (what we usually refer to as an average) is the total of values of a set of observations divided by the number of observations. We simply add up all of the individual measurements and divide by the total number of measurements we took.

Example 6.17 Problem: A waterworks operator takes a chlorine residual measurement every day. We show part of the operating log in Table 6.1. TABLE 6.1.Daily

Day Monday Tuesday Wednesday Thursday Friday Saturday Sunday

Chlorine Residual Results. Chlorine Residual (mg/L)

WATERWORKS MATH: BASIC

Find the mean. Solution: Add the seven chlorine residual readings: 0.9 + l .0 + 1.2 + 1.3 + 1.4 + l . l + 0.9 = 7.8. Next, divide by the number of measurements (in this case seven): 7.8 -+ 7 = 1.11. The mean chlorine residual for the week was 1.11 mg/L. J Definition: The median is defined as the value of the central item when the data are arrayed by size. First, arrange all of the readings in ascending or descending order. Then, find the middle value.

Example 6.18 Problem: In our chlorine residual example, what is the median? Solution: Arrange the values in ascending order:

The middle value is the fourth one-1.1. So, the median chlorine residual is 1.1 mg/L. (Usually, the median will be a different value than the mean.) If the data contains an even number of values, you must add one more step, since no middle value is present. You must find the two values in the middle, and then find the mean of those two values.

Example 6.19 Problem: A water system has four wells with the following capacities: 115 gpm, 100 gpm, 125 gpm, and 90 gpm. What is the mean and the median pumping capacities? Solution: The mean is 115 gprn + 100 gpm+ 125 gpm-t 90 gprn 4

- 430 -=

4

107.5 gpm

To find the median, arrange the values in order: 100 gprn

115 gprn

125 gprn

With four values, there is no single "middle" value, so we must take the mean of the two middle values: 100 gprn + 115 gprn = 107.5 gprn 2 At times, determining what the original numbers were like is difficult (if not impossible) when dealing only with averages.

Ratio

Example 6.20

Problem: A water system has four storage tanks. Three of them have a capacity of 100,000 gallons each, while the fourth has a capacity of 1 million gallons. What is the mean capacity of the storage tanks?

Solution: The mean capacity of the storage tanks is

J Notice that no tank in Example 6.20 has a capacity anywhere close to the mean. The median capacity requires us to take the mean of the two middle values; since they are both 100,000 gal, the median is 100,000 gal. Although three of the tanks have the same capacity as the median, this data offers no indication that one of these tanks holds a million gallons, information that could be important for the operator to know. 6.11 RATIO

One place where fractions are used in calculations is in the ratios used to calculate solutions. Ratio is the comparison of two numbers by division or an indicated division. A ratio is usually stated in the form A is to B as C is to D, and is written as two fractions that are equal to each other:

We solve ratio problems by cross-multiplying; that is, we multiply the left numerator (A) by the right denominator (D) and say that A is equal to the left denominator (B) times the right numerator (C) :

If one of the four items is unknown, we solve the ratio by dividing the two known items that are multiplied together by the known item that is multiplied by the unknown. This is best shown by a couple of examples. Example 6.21

Problem: If we need 4 pounds of alum to treat 1,000 gallons of water, how many pounds of alum will we need to treat 12,000 gallons? Solution: We state this as a ratio: 4 pounds of alum is to 1,000 gallons of water as "pounds of alum" (or X) is to 12,000 gallons. We set this up this way:

WATERWORKS MATH: BASIC

4 lb alum 1,000 gal water

-

x lb alum

12,000 gal water

x = 48 lb alum

Example 6.22 Problem: If 10 gallons of fuel oil cost $5.25, how much does 18 gallons cost?

6.12 PERCENT Percent (like fractions) is another way of expressing a part of a whole. The term percent means "per hundred," so a percentage is the number out of 100. For example, 22 percent (or 22%) means 22 out of 100. If we divide 22 by 100, we get the decimal 0.22:

When percentages are used in calculations (such as when calculating hypochlorite dosages, and the percent available chlorine must be considered), the percentage must be converted to an equivalent decimal number. Divide the percentage by 100.

Example 6.23 Problem: Calcium hypochlorite (HTH) contains 65% available chlorine. What is the decimal equivalent of 65%? Solution: Since 65% means 65 per hundred, divide 65 by 100: 65-which is 0.65. 100'

Units and Conversions

69

Decimals and fractions can also be converted to percentages. First convert the fraction to a decimal, then multiply the decimal by 100 to get the percentage. For example, if a 50-foot high water tank has 32 feet of water in it, how full is the tank in terms of the percentage of its capacity? -32 ft - 0.64

50 ft

[decimal equivalent]

Thus, the tank is 64 percent full.

6.13 UNITS AND CONVERSIONS

Most of the calculations made in the waterworks business have units connected with them. While the number tells us how many, the units tell us what we have. Examples of units include inches, feet, square feet, cubic feet, gallons, pounds, milliliters, milligrams per liter, pounds per square inch, miles per hour, and so on. Conversions are a process of changing the units of a number to make the number usable in a specific instance. Conversions are accomplished by multiplying or dividing into another number to change the units of the number. Common conversions in waterworks are as follows: gpm to cfs million gallons to acre feet cubic feet to acre feet cubic feet of water to weight cubic feet of water to gallons gallons of water to weight gpm to MGD (million gallons per day) psi to feet of head (the measure of the pressure of water expressed as height of water in feet-l psi = 2.3 1 feet of head). To understand more clearly how various units are used and how to perform conversions, we illustrate by example. Consider when we add or subtract numbers, the units must be the same. If we add 3 feet to 9 feet, for instance, we get an answer of 12 feet. But if we add 2 feet to 3 yards, we cannot get an answer unless we convert the feet into yards or the yards into feet. Converting larger units to smaller units is usually easier, but the type of conversion may also depend on the answer we want. In our example, we can convert yards into feet by multiplying by 3, because there are 3 feet in one yard; then, we can easily add 2 feet to 9 feet.

In many instances, the conversion factor cannot be derived, it must be known. Therefore, we use tables such as the one below (Table 6.2) to determine the common conversions. J Note: Conversion factors are used to change measurements or calculated values from one unit of measure to another. In making the conversion from one unit to another, you must know two things :

(1) The exact number that relates the two units

WATERWORKS MATH: BASIC

TABLE 6.2.

I

I

Common Conversions.

Linear Measurements

Weight

1 inch = 2.54 cm 1 foot = 30.5 cm 1 meter = 100 cm = 3.281 ft = 39.4 in. 1 acre = 43,560 ft2 1 yard = 3 feet

1 ft3 of water = 62.4 Ibs 1 gal = 8.34 Ibs 1 Ib = 453.6 grams 1 kg = 1,000 g = 2.2 Ibs 1 % = 10,000 mg/L

Volume

Pressure

1 gal = 3.78 liters 1 ft3 = 7.48 gal 1 I = 1,000mL 1 acre foot = 43,560 cubic feet 1 gal = 32 cups 1 pound = 16 oz dry wt.

1 ft of head = 0.433 psi 1 psi = 2.31 ft of head

Flow 1 cfs = 448 gpm 1 gpm = 1,440 gpd

(2) Whether to multiply or divide by that number For example, in converting from inches to feet, you must know that there are 12 in. in 1 ft., and you must know whether to multiply or divide the number of inches by 0.08333 (i.e., 1 in. = 0.08 ft). When making conversions, confusion often occurs over whether to multiply or divide; on the other hand, the number that relates the two units is usually known and thus is not a problem. Understanding the proper methodology, the "mechanics" to use for various operations, requires practice. We provide examples of the types of conversions water operators must be familiar with in the following sections on temperature conversions and milligrams per liter. Most operators memorize some standard conversions. This happens as a result of using the conversions, not as a result of attempting to memorize them.

6.13.1 TEMPERATURE CONVERSIONS To illustrate how typical conversions are made, we discuss temperature conversion in this section. Waterworks operators should keep in mind that temperature conversions are only a small part of conversions that must typically be made in real world operations work. Most waterworks operators are familiar with the formulas used for Fahrenheit and Celsius temperature conversions: S "C = ("F - 32") 9

'

"F = -

5

("C + 32")

(6.4)

These conversions are not difficult to perform. The difficulty arises when we must recall these formulas from memory. J Probably the easiest way to recall these important formulas is to remember three basic steps for both Fahrenheit and Celsius conversions:

Units and Conversions

(1) Add 40" (2) Multiply by the appropriate fraction (3) Subtract 40"

(-$or

3

Obviously, the only variable in this method is the choice of 519 or 915 in the multiplication step. To make the proper choice, you must be familiar with two scales. On the Fahrenheit scale, the freezing point of water is 32", and it is 0" on the Celsius scale. The boiling point of water is 212" on the Fahrenheit scale and 100" on the Celsius scale. For example, at the same temperature, higher numbers are associated with the Fahrenheit scale and lower numbers with the Celsius scale. This important relationship helps you decide whether to multiply by 5 or % Let's look at a few conversion problems to see how the three-step process 9 5 works.

Example 6.24 Suppose that you wish to convert 220°F to Celsius. Using the three-step process, we proceed as follows: ( l ) Step 1: add 40°F

(2) Step 2: 260°F must be multiplied by either+ or -$Since the conversion is to the Celsius scale, you will be moving to a number smaller than 260. Through reason and observation, obviously we see that multiplying 260 by would almost be the same as multiplying by 2, which would double 260, rather than make it smaller. On the other hand, multiplying by $-is about the same as multiplying by 112, which would cut 260 in half. Because in this problem you wish to move to a smaller number, you should multiply by

%

+:

(3) Step 3: Now subtract 40"

Therefore, 220°F = 1O4.4"C

Example 6.25 Convert 22°C to Fahrenheit ( l ) Step 1: add 40"

72

WATERWORKS MATH: BASIC

Since you are converting from Celsius to Fahrenheit, you are moving from a smaller to a larger number and should use %in the multiplication: (2) Step2:

(3) Step 3: Subtract 40"

Thus, 22°C = 72°F. Obviously, knowing how to make these temperature conversion calculations is useful. However, in practical operations, you may wish to use a temperature conversion table. 6.13.2 MILLIGRAMS PER LlTER (PARTS PER MILLION)

One of the most common terms for concentration is milligrams per liter (mg/L). For example, if a mass of 15 mg of oxygen is dissolved in a volume of 1 L of water, the concentration of that solution is expressed simply as 15 mg/L. Very dilute solutions are more conveniently expressed in terms of micrograms per liter ( & L ) . For example, a concentration of 0.005 mg/L is preferably written as its equivalent 5 @ L . Since 1,000 pg = 1 mg, simply move the decimal point three places to the right when converting from mg/L to pg/L. Move the decimal three places to the left when converting from pg/L to mg/L. For example, a concentration of 1,250 pg/L is equivalent to 1.25 mg/L. One liter of water has a mass of 1 kg. But 1 kg is equivalent to 1,000 g or 1,000,000 mg. Therefore, if we dissolve 1 mg of a substance in 1 liter of water, we can say that there is 1 mg of solute per 1 million mg of water, or in other words, one part per million (ppm). Neglecting the small change in the density of water as substances are dissolved in it, we can say that, in general, a concentration of 1 milligram per liter is equivalent to one part per million: 1 mg/L = 1 ppm. Conversions are very simple; for example, a concentration of 18.5 mg/L is identical to 18.5 ppm. The expression mg/L is preferred over ppm, just as the expression & L is preferred over its equivalent of ppb. But both types of units are still used, and the waterworks operator should be familiar with them. 6.14 MEASUREMENTS: AREAS AND VOLUMES Waterworks operators are often required to calculate surface areas and volumes. Area is a calculation of the surface of an object. For example, the length of a water tank and the width of the tank can be measured, but the surface area of the water in the tank must be calculated. An area is found by multiplying two length measurements, so the result is a square measurement. For example, when multiplying feet by feet, we get square feet, which is abbreviated ft2. Volume is the calculation of the space inside a three-dimensional object and is calculated by multiplying three length measurements or an area by a length measurement. The result is a cubic measurement, such as cubic feet (abbreviated ft3).

Measurements: Areas and Volumes

12 ft Figure 6.3 Rectangular shape showing calculation of surface area.

6.14.1 AREA OF A RECTANGLE

The area of square or rectangular figures (such as the one shown in Figure 6.3) is calculated by multiplying the measurements of the sides. Area = Length

X

Width

(6.5)

To determine the area of the rectangle shown in Figure 6.3, we proceed as follows:

6.14.2 AREA OF A CIRCLE

The diameter of a circle is the distance across the circle through its center and is shown in calculations by the letter D (see Figure 6.4). Half of the diameter (the distance from the center to the outside edge) is called the radius (r). The distance around the outside of the circle is called the circumference (C). In calculating the area of a circle, the radius must be multiplied by itself (or the diameter by itself); this process is called squaring and is indicated by the superscript following the item to be squared. For example, the radius squared is written as r2,which indicates that the radius should be multiplied by the radius. When making calculations involving circular objects, a special number is required, referred to by the Greek letter pi (pronounced pie), the symbol for pi is z. Pi always has the value of 3.1416 (many calculators include a button for z, since it is used so often). The area of a circle is equal to the radius squared times the number pi.

Example 6.26 Problem: Find the area of the circle shown in Figure 6.4.

WATERWORKS MATH: BASIC

Figure 6.4 Circular shape showing diameter and radius.

Solution: A A A A

= n x r 2 = n X 12.5ft X 12.5ft = 3.1416 X 12.5 ft X 12.5 ft = 490.9 square feet or ft2

At times, finding the diameter of a circular object is necessary, under circumstances that allow you to measure only the circumference (a pump shaft, for example). The diameter and the circumference are related by the constant n:

6.14.3 VOLUME OF RECTANGULAR TANK

The volume of a rectangular object (such as a settling tank llke the one shown in Figure 6.5) is calculated by multiplying together the length, the width, and the depth. To calculate the volume, you must remember that the length times the width is the surface area, which is then multiplied by the depth. Volume = Length

X

Width

X

Depth

Figure 6.5 Rectangular settling tank illustrating calculation of volume.

(6-8)

Measurements: Areas and Volumes

Example 6.27 Problem: Using the dimensions given in Figure 6.5, determine the volume.

Solution:

V V V V

= L x W x D = Area X Depth

= 12ft X 6 f t = 432 ft3

X

6ft

For many calculations involving water, we need to know the volume of the tank in gallons rather than cubic feet. One cubic foot contains 7.48 gallons. In the case of the tank in Example 6.27, the volume is as follows (in regard to total gallons of water): 432 ft3 X 7.48 gaVft3 = 2,244 gal 6.14.4 VOLUME OF A CIRCULAR OR CYLINDRICAL TANK

A circular tank consists of a circular floor surface with a cylinder rising above it (see Figure 6.6). The volume of a circular tank is calculated by multiplying the surface area times the height of the tank walls.

Figure 6.6 Circular or cylindrical water tank.

WATERWORKS MATH: BASIC

Example 6.28 Problem: If a tank is 20 feet in diameter and 25 feet deep, how many gallons of water will it hold?

J Hint: In this type of problem, calculate the surface area first, multiply by the height, and then convert to gallons. Solution: r = D + 2 = 20ft+2 = loft A = n x r 2 A = n X lOft X lOft A = 3 14 ft2(rounded) V = A x H V = 314ft2 X 25 ft V = 7,850 ft3 X 7.5 gal/ft3 = 58,875 gal

6.14.5 AREA OF A CIRCULAR OR CYLINDRICAL TANK

If you were supervising a work team assigned to paint a water storage tank, you would need to know the surface area of the walls of the tank. To determine the tank's surface area, visualize the cylindrical walls as a rectangle wrapped around a circular base. The area of a rectangle is found by multiplying the length by the width; in this case, the width of the rectangle is the height of the wall, and the length of the rectangle is the distance around the circle, the circumference. Thus, the area of the side walls of a circular tank is found by multiplying the circumference of the base (C = n X D) times the height of the wall (H):

For the tank used in Example 6.28 (D = 20 ft, H = 25 ft):

To determine the amount of paint needed, remember to add the surface area of the top of the tank, which is 314 ft2.Thus, the amount of paint needed must cover 1570.8 ft2+ 314 ft2= 1884.8 or 1,885 ft2. If the tank floor should be painted, add another 314 ft2.

6.15 PRESSURE AND HEAD

Pressure is the force exerted on a unit area or the weight per unit area. Typical pressure units are pounds per square inch (lbs/in2-psi) and pounds per square foot (lbs/ft2). The pressure on the bottom of a container is not related to the volume of the container or the size of the bottom. The pressure is dependent on the height of the fluid in the container. The height of the fluid in a container is referred to as head. Head is the measure of the pressure of water expressed as height of water in feet: 1 psi = 2.3 1 feet of head.

Pressure and Head

To understand the relationship between feet and head, consider the following: (1) By definition, water weighs 62.4 pounds per cubic foot. (2) The surface of any one side of the cube contains 144 square inches (12" X 12" = 144 in2). Therefore, the cube contains 144 columns of water one foot tall and one inch square. (3) The weight of each of these pieces can be determined by dividing the weight of the water in the cube by the number of square inches. Weight = 62'4 lbs = 0.433 lbs/in2or 0.433 psi 144 in2 (4) Since this is the weight of one column of water one foot tall, the true expression would be 0.433 pounds per square inch per foot of head or 0.433 psilft.

J Key Point: 1 foot of head = 0.433 psi. 1 foot of head = 0.433 psi is a valuable parameter that should be committed to memory. You should also know the relationship between pressure and feet of head, in other words, how many feet of head 1 psi represents. This is determined by dividing 1 by 0.433. feet of head =

l ft = 2.3 1 ftjpsi 0.433 psi

If a pressure gauge were reading 12 psi, the height of the water necessary to represent this pressure would be 12 psi X 2.31 ftjpsi = 27.7 feet. J Again, the key points: 1 ft = 0.433 psi, 1 psi = 2.31 feet

Having two conversion methods for the same thing is often confusing. Thus, memorizing one and staying with it is best. The most accurate conversion is 1 ft = 0.433 psi, the conversion used throughout this handbook.

Example 6.29 Problem: Convert 50 psi to feet of head.

Solution: psi X 50 ft = 115.5 feet 1 0.433 psi

Problem: Convert 50 feet to psi.

Solution: ft X 0.433 psi = 21 .7 psi 50 1 l ft

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WATERWORKS MATH: BASIC

As the above examples demonstrate, when attempting to convert psi to feet, we divide by 0.433; when attempting to convert feet to psi, we multiply by 0.433. The above process can be most helpful in clearing up the confusion on whether to multiply or divide. Another way, however, may be more beneficial and easier for many operators to use. Notice that the relationship between psi and feet is almost two to one. It takes slightly more than two feet to make one psi. Therefore, when looking at a problem where the data is in pressure and the result should be in feet, the answer will be at least twice as large as the starting number. For example, if the pressure were 25 psi, we intuitively know that the head is over 50 feet. Therefore, we must divide by 0.433 to obtain the correct answer.

Example 6.30

Problem: Convert a pressure of 55 psi to feet of head.

Solution: psi 55 x lft =127feet 1 0.433 psi

Example 6.31

Problem: Convert 14 psi to feet.

Solution: psi l4-X ft = 32.3 feet 0.433 psi 1

Example 6.32

Problem: Between the top of a reservoir and the watering point, the elevation is 115 feet. What will the static pressure be at the watering point?

Solution:

6.16 FLOW

Flow is expressed in many different terms (English System of measurements). The most common flow terms are as follows: gpm-gallons per minute cfs-cubic feet per second

Flow

gpd-gallons per day MGD-million gallons per day In converting, flow rates, the most common flow conversions are l cfs = 448 gprn and 1 gprn = 1,440 gpd. To convert gallons per day to MGD, divide the gpd by 1,000,000. For instance, convert 150,000 gallons to MGD.

In some instances, flow is given in MGD but is needed in gpm. To make the conversion (MGD to gpm) two steps are required. Step l : convert the gpd by multiplying by 1,000,000 Step 2: convert to gprn by dividing by the number of minutes in a day (1,440 midday)

Example 6.33 Problem: Convert 0.135 MGD to gpm.

Solution: First convert the flow in MGD to gpd. 0.135 MGD

X

1,000,000 = 135,000 gpd

Now convert to gprn by dividing by the number of minutes in a day (24 hrs per day X 60 min per hour) = 1,440 midday. 135'000 gpd = 93.8 or 94 gprn 1,440 minlday In determining flow through a pipeline, channel, or stream, we use the following equation:

W here

Q = cubic feet per second (cfs) V = velocity in feet per second (ftlsec) A = area in square feet (ft2)

Example 6.34 Problem: Find the flow in cfs in an 8-inch line, if the velocity is 3 feet per second.

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WATERWORKS MATH: BASIC

Solution: Step 1: Determine the cross-sectional area of the line in square feet. Start by converting the diameter of the pipe to inches. Step 2: The diameter is 8 inches, therefore, the radius is 4 inches. 4 inches is of a foot or 0.33 feet. Step 3: Find the area in square feet.

Step 4: Q = VA Q = 3 ft/sec X 0.342 ft2 Q = 1.O3 cfs

Example 6.35 Problem: Find the flow in gprn when the total flow for the day is 75,000 gpd.

Solution:

Example 6.36 Problem: Find the flow in gpm when the flow is 0.45 cfs.

Solution: 0.45

cfs X 1

448 gpm = 202 gpm 1 cfs

6.17 DETENTION TIME

Detention time is the length of time water is retained in a vessel or basin, or the period from the time the water enters a settling basin until it flows out the other end. To calculate the detention period of a basin, the volume of the basin must first be obtained. Using a basin 25 ft wide, 70 ft long, and 12 ft deep, the volume would be:

Detention Time

V = L x W x D v = 7Oftx25ftx12ft v = 21,000ft3 Gallons = V X 7.48 gal/ft3 Gallons = 21,000 X 7.48 = 157,080 gallons

If we assume that the plant filters 300 gpm, 157,080 + 300 = 523 minutes, or roughly 9 hours of detention time. Stated another way, the detention time is the length of time theoretically required for the coagulated water to flow through the basin. If chlorine were added to the water as it entered the basin, the chlorine contact time would be 9 hours. That is, to determine the CT [concentration of free chlorine residual X disinfectant contact time (in minutes)] used to determine the effectiveness of chlorine, we must calculate detention time.

J Key point: True detention time is the "T" portion of the CT value.

J Detention time is also important when evaluating the sedimentation and flocculation basins of a water treatment plant. Detention time is expressed in units of time (obviously). The most common are seconds, minutes, hours, and days. The simplest way to calculate detention time is to divide the volume of the container by the flow rate into the container. The theoretical detention time of a container is the same as the amount of time it would take to fill the container if it were empty. For volume, the most common units used are gallons. However, on occasion, cubic feet may also be used. Time units will be in whatever the units are used to express the flow. For example, if the flow is in gpm, the detention time will be in days. If in the final result the detention time is in the wrong time units, simply convert to the appropriate units.

Example 6.37 Problem: The reservoir for the community holds 110,000 gallons. The well will produce 60 gpm. What is the detention time in the reservoir in hours?

Solution:

Example 6.38 Problem: Find the detention time in a 55,000 gallon reservoir if the flow rate is 75 gpm.

Solution:

WATERWORKS MATH: BASIC

Example 6.39 Problem:

If the fuel consumption to the boiler is 30 gallons per day, how many days will the 1,000 gallon tank last? Solution: Days = 19000ga1 =33.3days 30 galldays

6.18 SUMMARY

Once you master the equations and vocabulary, you will find that regular practice (provided every day on the job) will quickly make perfarming these essential calculations second nature.

6.19 CHAPTER REVIEW QUESTIONS

6-1 [ ( 2 5 - 4 - 6 ) + ( 3 ~ 5 ) ] + 4 ~ 3 =

6-4 213 is equal to how many ninths (?/g)

6-5 8/12 is equal to how many thirds (?/3)

Chapter Review Questions

6-9 217 - 1/4=

6-10 What is the fraction equivalent of 0.625?

6-11 What is the decimal equivalent of 3/4?

6- 12 What are the decimal and fraction equivalents of 45%?

6-13 What is 113 X 15% of 0.75 X 5/3?

6-14 What is the mean and the median of 3 , 5 , 6 , 8 , 11, 17?

6-15 Write 10,000,000 as a power of ten.

6-16 How many liters can a 250 gallon tank hold?

6-17 What is the area of a rectangle 9 ft by 30 ft?

6-18 What is the surface area of a circular tank with a 25 ft diameter?

6-19 What is the volume of a tank 25 ft X 60 ft X 8 ft deep?

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WATERWORKS MATH: BASIC

6-20 What is the volume of a round tank 10 ft deep, with a 35 ft diameter?

6-21 A pipe has a diameter of 8 inches. Water is flowing through it at 4 feet per minute. How much water is passing through in one minute? In one hour?

6-22 If the same water is passing through a 200 gallon tank, what is the detention time?

6-23 Find the volume of a fuel tank 5 feet in diameter and 12 feet long.

6-24 Find the volume of a chlorine cylinder 25 inches in diameter and 44 inches tall.

6-25 The average daily winter demand of a community is 14,000 gallons. If the summer demand is estimated to be 73% greater than the winter demand, what is the estimated summer demand?

J Demand (when related to use) is the amount of water used in a period of time. The term refers to the "demand" put onto the system to meet the needs of customers. 6-26 Convert 50 gallons to pounds.

6-27 Convert 4 lbs to ounces.

6-28 Convert 135 ft3of water to weight in pounds.

6-29 A reservoir is 40 feet deep. What will the pressure be at the bottom of the reservoir?

6-30 Find the flow in gpm when the flow is 1.5 cfs.

Chapter Review Questions

6-3 1 Find the flow in a 5 inch pipe when the velocity is 1.3 feet per second.

6-32 The sedimentation basin of a waterworks contains 6,575 gallons. What is the detention time if the flow is 160 gpm?

CHAPTER 7

Basic Water Chemistry

The waterworks operator lacking in knowledge of water chemistry is like the auto mechanic who does not know how to operate an engine analyzer and/or how to interpret the results of such analysis. 7.1 INTRODUCTION S the chapter opening suggests, waterworks operators perform and analyze the results of laboratory tests. Because of this, they must have a working knowledge of water chemistry to properly perform their jobs. In this chapter, we discuss basic water chemistry. Not all waterworks operators must be chemists, but all waterworks operators must be competent operators, and basic knowledge of water chemistry fundamentals aids in attaining competency.

A

7.2 CHEMISTRY DEFINITIONS As with any other science, water chemistry has its own language; thus, to understand chemistry, you must understand the following key terms. Chemistry the science that deals with the composition and changes in composition of substances. Water is an example of this composition; it is composed of two gases, hydrogen and oxygen. Water also changes form from liquid to solid to gas but does not necessarily change composition. Matter anything that has weight (mass) and occupies space. Kinds of matter include elements, compounds, and mixtures. Solids substances that maintain definite size and shape. Liquids a substance with a definite volume but not shape, liquid will fill containers to certain levels and form free level surfaces. Gases they have neither definite volume nor shape and completely fill any container in which they are placed. Element the simplest form of chemical matter. Each element has chemical and physical characteristics different from all other kinds of matter. Compound a substance of two or more chemical elements chemically combined. Examples include water (H20)that is a compound formed by hydrogen and oxygen, and carbon dioxide (CO2)that is composed of carbon and oxygen. Mixture a physical, not chemical, intermingling of two or more substances. Sand and salt stirred together form a mixture. Atom the smallest particle of an element that can unite chemically with other elements.

BASIC WATER CHEMISTRY

All the atoms of an element are the same in chemical behavior, although they may differ slightly in weight. Most atoms can combine chemically with other atoms to form molecules. Molecule the smallest particle of matter, or a compound that possesses the same composition and characteristics as the rest of the substance. A molecule may consist of a single atom, two or more atoms of the same kind, or two or more atoms of different kinds. Radical two or more atoms that unite in a solution and behave chemically as if they were a single atom. Solvent the component of a solution that does the dissolving. Solute the component of a solution that is dissolved by the solvent. Ion an atom or group of atoms that carries a positive or negative electric charge as a result of having lost or gained one or more electrons. Ionization the formation of ions by the splitting of molecules or electrolytes in solution. Cation a positively charged ion. Anion a negatively charged ion. Organic chemical substances of animal or vegetable origin made basically of carbon structure. Inorganic chemical substances of mineral origin. Solids as it pertains to water-suspended and dissolved material in water. Dissolved solids the material in water that will pass through a glass fiber filter and remain in an evaporating dish after evaporation of the water. Suspended solids the quantity of material deposited when a quantity of water, sewage, or other liquid is filtered through a glass fiber filter. Total solids the solids in water, sewage, or other liquids; this includes suspended solids (largely removable by a filter) and filterable solids (those that pass through the filter). Saturated solution the physical state in which a solution will no longer dissolve more of the dissolving substance-solute. Colloidal any substance in a certain state of fine division in which the particles are less than one micron in diameter. Turbidity a condition in water caused by the presence of suspended matter, resulting in the scattering and absorption of light rays. Precipitate a solid substance that can be dissolved but is separated from solution as a result of a chemical reaction or change in conditions such as pH or temperature.

7.3 WATER CHEMISTRY FUNDAMENTALS Whenever waterworks operators add a substance to another substance (from adding sugar to a cup of tea to adding chlorine to water to make it safe to drink) they perform chemistry. Water operators (as well as many others) are chemists, because they are working with substances, and how those substances react is important for them to know. 7.3.1 MATTER

Going through a day without coming in contact with many kinds of matter would be impossible. Paper, coffee, gasoline, chlorine, rocks, animals, plants, water, and air are all different forms or kinds of matter. Earlier we defined matter as anything that has mass (weight) and occupies space. Matter is distinguishable from empty space by its presence. Thus, obviously, the opening statement about going through a day without coming into contact with "matter" is not only correct, but avoiding some form of matter is virtually impossible. Not all matter is the same, even though we narrowly classify all matter into three groups: solids, liquids, and gases. These three groups are called the

Water Chemistry Fundamentals

89

physical states of matter and are distinguishable from one another by means of two general features, shape and volume. J Mass is closely related to the concept of weight. On Earth, the weight of matter is a measure of the force with which it is pulled by gravity toward the Earth's center. As we leave Earth's surface, the gravitational pull decreases, eventually becoming virtually insignificant, while the weight of matter accordingly reduces to zero. Yet, the matter still possesses the same amount of "mass." Hence, the mass and weight of matter are proportional to each other. J Since matter occupies space, a given form of matter is also associated with a definite volume. Space should not be confused with air, since air is itself a form of matter. Volume refers to the actual amount of space that a given form of matter occupies.

Solids have a definite, rigid shape with their particles closely packed together and stuck firmly to each other. A solid does not change its shape to fit a container. Put a solid on the ground and it will keep its shape and volume-it will never spontaneously assume a different shape. Solids also possess a fairly definite volume at a given temperature and pressure. Liquids maintain a constant volume, but change shape to fit the shape of their container; they do not possess a characteristic shape. The particles of the liquid move freely over one another, but still stick together enough to maintain a constant volume. Consider a glass of water. The liquid water takes the shape of the glass up to the level it occupies. If we pour the water into a drinking glass, the water takes the shape of the glass; if we pour it into a bowl, the water takes the shape of the bowl. Thus, assuming that space is available, any liquid assumes whatever shape its container possesses. Like solids, liquids possess a fairly definite volume at a given temperature and pressure, and they tend to maintain this volume when they are exposed to a change in either of these conditions. Gases have no definite fixed shape, and their volume can be expanded or compressed to fill different sizes of containers. A gas or mixture of gases like air can be put into a balloon and will take the shape of the balloon. Particles of gases do not stick together and move about freely, filling containers of any shape and size. A gas is also identified by its lack of a characteristic volume. When confined to a container with nonrigid, flexible walls, for example, the volume that a confined gas occupies depends on its temperature and pressure. When confined to a container with rigid walls, however, the volume of the gas is forced to remain constant. The constant composition associated with a given substance is maintained by internal linkages among its units, including between one atom and another. These linkages are called chemical bonds. When a particular process occurs that involves the making and breaking of these bonds, we say that a chemical reaction or a chemical change has occurred. Chemical changes occur when new substances are formed that have entirely different properties and characteristics. When a piece of wood burns or iron rusts, a chemical change has occurred; the linkages, the chemical bonds, are broken. Physical changes occur when matter changes its physical properties such as size, shape, and density, as well as when it changes its state, i.e., from gas to liquid to solid. When ice melts or when a glass window breaks into pieces, a physical change has occurred. 7.3.2 THE CONTENT OF MATTER: THE ELEMENTS Earth is made up of the fundamental substances of which all matter is composed. These substances that resist attempts to decompose them into simpler forms of matter are called elements. To date, there are 106 known elements. They range from simple, lightweight elements to very complex,

90

BASIC WATER CHEMISTRY

heavyweight elements. Some of these elements exist in nature in pure form and others are combined. The smallest unit of an element is the atom. For convenience, elements have a specific name and symbol but are often identified by chemical symbol only. The symbols of the elements consist of either one or two letters, with the first letter capitalized. All 106 elements are listed together on a chart called The Periodic Table. The periodic table shows all the elements arranged in order from 1 through 106, as well as the chemical name, symbol, and on some forms of the table, a lot of other information about each element's physical and chemical characteristics. We list the elements important to the water operator (about a third of the 106 elements) below. Those elements most closely associated with water are marked (*).

Element

Symbol

Aluminum* Arsenic Barium Cadmium Carbon* Calcium Chlorine* Chromium Cobalt Copper Fluoride* Helium Hydrogen* Iodine Iron* Lead Magnesium* Manganese* Mercury Nitrogen * Nickel Oxygen* Phosphorus Potassium Silver Sodium* Sulfur* Zinc 7.3.3 COMPOUND SUBSTANCES

If we take a pure substance like calcium carbonate (limestone) and heat it, the calcium carbonate ultimately crumbles to a white powder. However, careful examination of the heating process shows that carbon dioxide also evolves from the calcium carbonate. Substances like calcium carbonate that can be broken down into two or more simpler substances are called compound substances or simply

Water Solutions

91

compounds. Heating is a common way of decomposing compounds, but other forms of energy are often used as well. Chemical elements that make up compounds such as calcium carbonate combine with each other in definite proportions. When atoms of two or more elements are bonded together to form a compound, the resulting particle is called a molecule. J Note: This law simply means that only a certain number of atoms or radicals of one element will combine with a certain number of atoms or radicals of a different element to form a chemical compound.

7.4 THE WATER MOLECULE Just about every high school-level student knows that water is a chemical compound of two simple and abundant elements, yet scientists continue to argue the merits of rival theories on the structure of water. The fact is that we still understand little about water. For example, we do not really know much about how water works. Part of the problem lies with the fact that no one has ever seen a water molecule. While we have theoretical diagrams and equations, and we have a disarmingly simple formula, H20, the reality is that water is very complex. X-rays, for example, have shown that the atoms in water are intricately laced. Water is different from any other substance we know. Consider the water molecule, for example, where the two hydrogen atoms always come to rest at an angle of approximately 105" from each other, making all diagrams of their attachment to the larger oxygen atom look sort of like an on-itsside set of Mickey Mouse ears on a very round head. The hydrogens tend to be positively charged and the oxygen tends to be negatively charged. This gives the water molecule an electrical polarity; one end positively charged and one end negatively charged. In short, this 105" relationship makes water lopsided, peculiar, and eccentric (see Figure 7.1). In the laboratory, pure water contains no impurities, but in nature, water contains a lot of things besides water. Water is a very good solvent (in fact, water is known as the universal solvent). The polarity just described is the main reason water is able to dissolve so many other substances. For the water operator tasked with making water as pure as possible, this fact makes the job more difficult. Water contains many dissolved and suspended elements and particles, and the waterworks operator must deal with them.

7.5 WATER SOLUTIONS

A solution is a condition in which one or more substances are uniformly and evenly mixed or dissolved. A solution has two components, a solvent and a solute. The solvent is the component that does the dissolving. The solute is the component that is dissolved. In water solutions, water is the solvent. Water can dissolve many other substances; given enough time, there are not too many solids, liquids, and gases that water cannot dissolve. When water dissolves substances, it creates solutions with many impurities. Generally, a solution is usually transparent and not cloudy. However, a solution may be colored when the solute remains uniformly distributed throughout the solution and does not settle with time. When molecules dissolve in water, the atoms making up the molecules come apart (dissociate) in the water. This dissociation in water is called ionization. When the atoms in the molecules come apart, they do so as charged atoms (both negatively and positively charged) called ions. The positively charged ions are called cations and the negatively charged ions are called anions.

BASIC WATER CHEMISTRY

Basic Science Concepts

Figure 7.1 A molecule of water.

A good example of ionization occurs when calcium carbonate ionizes: CaC03 calcium carbonate

C)

Ca* calcium ion (cation)

+

CO,-2 carbonate ion (anion)

Another good example is the ionization that occurs when table salt (sodium chloride) dissolves in water: NaCl sodium chloride

Naf sodium ion (cation)

+

Clchloride ion (anion)

Some of the common ions found in water are listed as follows: Ion

Symbol

Hydrogen Sodium Potassium Chloride Bromide Iodide Bicarbonate

H+ Na+ K+ C1BrIHC03-

Water dissolves polar substances better than nonpolar substances. This makes sense when you consider that water is a polar substance. Polar substances such as mineral acids, bases, and salts are easily dissolved in water, while nonpolar substances such as oils, fats, and many organic compounds do not dissolve easily in water.

Water Constituents

93

Water dissolves polar substances better than nonpolar substances only to a point. Polar substances dissolve in water up to a point, only so much solute will dissolve at a given temperature, for example. When that limit is reached, the resulting solution is saturated. When a solution becomes saturated, no more solute can be dissolved. For solids dissolved in water, if the temperature of the solution is increased, the amount of solids (solutes) required to reach saturation increases.

7.6 WATER CONSTITUENTS Natural water can contain a number of substances (what we may call impurities) or constituents in waterworks operations. When a particular constituent can affect the good health of the water user, it is called a contaminant or pollutant. These contaminants, of course, are what the waterworks operator works to prevent entering or removes from the water supply. In this section, we discuss some of the more common constituents of water. 7.6.1 SOLIDS

Other than gases, all contaminants of water contribute to the solids content. Natural water carries a lot of dissolved and undissolved solids. The undissolved solids are nonpolar substances and consist of relatively large particles of materials such as silt. Classified by their size and state, by their chemical characteristics, and their size distribution, solids can be dispersed in water in suspended and dissolved forms. Sizes of solids in water can be classified as suspended solids, settleable, colloidal, or dissolved. Total solids are those suspended and dissolved solids that remain when the water is removed by evaporation. Solids are also characterized as being volatile or nonvolatile. The distribution of solids is determined by computing the percentage of filterable solids by size range. Solids typically include inorganic solids such as silt and clay from riverbanks and organic matter such as plant fibers and microorganisms from natural or man-made sources. J Note: Though not technically accurate from a chemical point of view because some finely suspended material can actually pass through the filter, suspended solids are defined as those that can be filtered out in the suspended solids laboratory test. The material that passes through the filter is defined as dissolved solids.

Colloidal solids are extremely fine suspended solids (particles) of less than one micron in diameter; they are so small (though they still make water cloudy) that they will not settle even if allowed to sit quietly for days or weeks. 7.6.2 TURBIDITY

Water's clarity is one of the first characteristics people notice. Turbidity is a condition in water caused by the presence of suspended matter, which results in the scattering and absorption of light rays. In plain English, turbidity is a measure of the light-transmitting properties of water. Natural water that is very clear (low turbidity) allows you to see images at considerable depths. High turbidity water, on the other hand, appears cloudy. Keep in mind that water of low turbidity is not necessarily without dissolved solids. Dissolved solids do not cause light to be scattered or absorbed, thus, the water looks clear. High turbidity causes problems for the waterworks operator-components that cause high turbidity can cause taste and odor problems and will reduce the effectiveness of disinfection.

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7.6.3 COLOR Earlier, we mentioned that water can be or is often colored-the color of water can be deceiving. First, color is considered an aesthetic quality of water with no direct health impact. Second, many of the colors associated with water are not true colors but are the result of colloidal suspension (apparent color). This apparent color can often be attributed to dissolved tannin extracted from decaying plant material. True color is the result of dissolved chemicals (most often organics) that cannot be seen.

7.6.4 DISSOLVED OXYGEN (DO) Gases can also be dissolved in water. Gases such as oxygen, carbon dioxide, hydrogen sulfide, and nitrogen are examples of gases that dissolve in water. Gases dissolved in water are important. For example, carbon dioxide is important because of the role it plays in pH and alkalinity.Carbon dioxide is released into the water by microorganisms and consumed by aquatic plants. However, dissolved oxygen (DO) in water is of most importance to us here, not only because it is important to most aquatic organisms, but also because dissolved oxygen is an important indicator of water quality. Solutions can become saturated with solute. This is the case with water and oxygen. As with other solutes, the amount of oxygen that can be dissolved at saturation depends upon temperature of the water. Note, however, that in the case of oxygen, the effect is just the opposite of other solutes. The higher the temperature, the lower the saturation level; the lower the temperature, the higher the saturation level.

7.6.5 METALS One of the constituents or impurities often carried by water is metals. Although most of the metals are not harmful at normal levels, a few metals can cause taste and odor problems in drinking water. In addition, some metals may be toxic to humans, animals, and microorganisms. Most metals enter water as part of compounds that ionize to release the metal as positive ions. Table 7.1 lists some metals commonly found in water and their potential health hazards.

7.6.6 ORGANIC MATTER Organic matter or compounds contain the element carbon and are derived from material that was once alive (i.e., plants and animals). Organic compounds include fats, dyes, soaps, rubber products, plastics, wood, fuels, cotton, proteins, and carbohydrates. Organic compounds in water are usually large, nonpolar molecules that do not dissolve well in water. They often provide large amounts of energy to animals and microorganisms. TABLE 7.1.

Common Metals Found in Water.

Metal

Health Hazard

Barium Cadmium Copper Lead Mercury Nickel Selenium Silver Zinc

Circulatory system effects and increased blood pressure Concentration in the liver, kidneys, pancreas, and thyroid Nervous system damage and kidney effects, toxic to humans Same as copper Central nervous system (CNS) disorders CNS disorders CNS disorders Turns skin gray Causes taste problems but is not a health hazard

95

Water Constituents TABLE 7.2.

Relative Strengths of Acids in Water. HCI04 bSO4 HCI HN03 H3PO4 HNO2 HF CH3COOH H2CO3 HCN H3BO3

Perchloric acid Sulfuric acid Hydrochloric acid Nitric acid Phosphoric acid Nitrous acid Hydrofluoric acid Acetic acid Carbonic acid Hydrocyanic acid Boric acid

7.6.7 INORGANIC MATTER Inorganic matter or compounds are carbon-free, are not derived from living matter, and are easily dissolved in water; they are of mineral origin. The inorganics include acids, bases, oxides, salts, etc. Several inorganic components are important in establishing and controlling water quality. Two important inorganic constituents in water are nitrogen and phosphorus. 7.6.7.1 Acids Lemon juice, vinegar, and sour milk are acidic or contain acid. The common acids used in waterworks operations are hydrochloric acid (HCl), sulfuric acid (&So4), nitric acid (HN03), and carbonic acid (H2C03).Note that in each of these acids, hydrogen (H) is one of the elements. J Note: An acid is a substance that produces hydrogen ions (H') when dissolved in water. Hydrogen ions are hydrogen atoms stripped of their electrons. A single hydrogen ion is nothing more than the nucleus of a hydrogen atom.

The relative strengths of acids in water (listed in descending order of strength) are classified in Table 7.2. J Acids and bases become solvated-they

loosely bond to water molecules.

7.6.7.2 Bases A base is a substance that produces hydroxide ions (OH-) when dissolved in water. Lye or common soap (bitter things) contain bases. The bases used in waterworks operations are calcium hydroxide [Ca(OH),], sodium hydroxide (NaOH), and potassium hydroxide (KOH). The hydroxyl group (OH) is found in all bases. Bases contain metallic substances, such as sodium (Na), calcium (Ca), magnesium (Mg), and potassium (K). These bases contain the elements that produce the alkalinity in water. 7.6.7.3 Salts When acids and bases chemically interact, they neutralize each other. The compound (other than water) that forms from the neutralization of acids and bases is called a salt. Salts constitute, by far, the largest group of inorganic compounds. A common salt used in waterworks operations, copper sulfate, is utilized to kill algae in water.

BASIC WATER CHEMISTRY

Neutral

Basic

Acidic

I HCl

gastric juices

I I

I blood

oranges tomatoes

sea water

household ammonia

1M NaOH

pure water Figure 7.2 pH of selected liquids.

pH is a measure of the hydrogen ion (H+)concentration. Solutions range from very acidic (having a high concentration of H' ions) to very basic (having a high concentration of OH- ions). The pH scale ranges from 0 to 14, with 7 being the neutral value (see Figure 7.2). The pH of water is important to the chemical reactions that take place within water, and pH values that are too high or low can inhibit the growth of microorganisms. With high and low pH values, high pH values are considered basic, and low pH values are considered acidic. Stated another way, low pH values indicate a high level of H+ concentration, while high pH values indicate a low H+ concentration. Because of this inverse logarithmic relationship, there is a tenfold difference in H+concentration. Natural water varies in pH depending on its source. Pure water has a neutral pH, with an equal number H' and OH-. Adding an acid to water causes additional + ions to be released so that the H+ ion concentration goes up, and the pH value goes down. HCl

-+

H+ + C1-

To control water coagulation and corrosion, the waterworks operator must test for the hydrogen ion concentration of the water to determine the water's pH. In coagulation tests, as more alum (acid) is added, the pH value lowers. If more lime (alkali) is added, the pH value rises. This relationship should be remembered. If a good floc is formed, the pH should then be determined and maintained at that pH value until the raw water changes.

7.8 ALKALINITY Alkalinity is defined as the capacity of water to accept protons; it can also be defined as a measure of water's ability to neutralize an acid. Alkalinity is caused by bicarbonates, carbonates, and hydrogen compounds in a raw or treated water supply. Bicarbonates are the major components because of carbon dioxide action on "basic" materials of soil; borates, silicates, and phosphates may be minor

97

Chapter Review Questions TABLE 7.3. Water

Hardness.

Classification

mg/L CaCO,

Soft Moderately Hard Hard Very Hard

0-75 75-1 50 150-300 Over 300

components. Alkalinity of raw water may also contain salts formed from organic acids such as humic acids. Alkalinity in water acts as a buffer that tends to stabilize and prevent fluctuations in pH. Having significant alkalinity in water is usually beneficial, because it tends to prevent quick changes in pH, which interfere with the effectiveness of common water treatment processes. Low alkalinity also contributes to water's corrosive tendencies. When alkalinity is below 80 mglL, it is considered low.

7.9 HARDNESS Hardness may be considered a physical or chemical parameter of water. It represents the total concentration of calcium and magnesium ions, reported as calcium carbonate. Hardness causes soaps and detergents to be less effective and contributes to scale formation in pipes and boilers. Hardness is not considered a health hazard; however, water that contains hardness must often be softened by lime precipitation or ion exchange. Low hardness contributes to the corrosive tendencies of water. Hardness and alkalinity often occur together, because some compounds can contribute alkalinity and hardness ions. Hardness is generally classified as shown in Table 7.3.

7.10 SUMMARY The tasks connected with water math and water chemistry are closely related, and both are essential to passing licensing and certification exams and for the skills needed in the water operator profession.

7.11 CHAPTER REVIEW QUESTIONS

7-1 The chemical symbol for sodium is

7-2 The chemical symbol for sulfuric acid is 7-3 Neutrality on the pH scale is 7-4 Is NaOH a salt or a base?

7-5 Chemistry is the study of substances and the

they undergo.

98

BASIC WATER CHEMISTRY

7-6 The three states of matter are 7-7 A basic substance that cannot be broken down any further without changing the nature of the substance is 7-8 A combination of two or more elements is a 7-9 A table of the basic elements is called the

table.

7-10 When a substance is mixed into water to form a solution, the water is called the , and the substance is called the 7- 11 Define ion:

7-12 A solid that is less than 1 micron in size is called a 7-13 The property of water that causes light to be scattered and absorbed is 7-14 What is true color?

7-15 What is the main problem with metals found in water?

7- 16 Compounds derived from material that once was alive are called 7-17 pH range is from

to

7- 18 What is alkalinity?

7-19 The two ions that cause hardness are 7-20 What type of substance produces hydroxide ions (OH-) in water?

chemicals .

CHAPTER 8

Basic Electricity

Electricity is the 20th century version ofAladdin 's lamp. But just as the genie in the lamp could be put to insidious uses, electricity, handled incorrectly, can kill and cause serious accidentx6 8.1 INTRODUCTION HE "genie in the lamp of the twentieth century" may be the element of the water operator's job that makes those working on licensure or certification understand thoroughly why waterworks operators are typically termed "Jacks and Jills of all trades." Consider that the competent waterworks operator must be well-versed in microbiology, water chemistry, mathematics, basic physics, hydraulics and hydrology, along with plant unit process operation and troubleshooting skills. Thousands of operators, on a daily or around-the-clock basis, are tasked with keeping the waterworks plant running-keeping the system on line and feeding safe drinking water to the public, to the user. The fact is, in many small waterworks operations, waterworks operators must be more than just operators; they must be able to perform many duties, because their facility may have no one else to do them. Because of this, waterworks operation and electrical work and troubleshooting go hand in hand. Just as important (especially to the waterworks operator in training) is the fact that on several licensure and certification examinations, a knowledge of the basics of electricity is required to score well. Yes, typically, waterworks operator licensure/certification exams include questions about basic electricity/electronics. Thus, in this volume of the Handbook (and in this chapter, in particular), we provide a basic presentation of those electrical terms, electrical circuits, and electrical components the entry-level waterworks operator is expected to know for use in the real world of waterworks operations and in successfully passing licensure/certification examinations.

T

J CA UTZON: The information provided in this chapter is no way intended to qualify anyone to perform work on electrical equipment. Electricity is a dangerous hazard-one that can kill. Great care and caution is advised anytime anyone works with or around electrical equipment. In many locations, only qualified competent electricians are authorized to perform electrical work.

8.2 BASIC ELECTRICITY: DEFINITIONS Before we begin a brief discussion of basic electricity, we first define some of the frequently used 6~rom the National Safety Council's SupervisorS Safety Manual,6th ed. Chicago: National Safety Council, p. 342, 1985.

100

BASIC ELECTRICITY

terms that make up the language of electricity. Many of these terms are commonly used in describing systems, electrical equipment, or amounts of electricity required or used. Waterworks operators should become familiar with their usage. AC abbreviation for alternating current. Alternating current an electric current that is continually reversing its direction of flow at regular intervals. Ampere or Amp a measure of electric current, either AC or DC. Conductor a material or substance that passes electrical current with ease. Cycle applies to AC current systems and refers to one complete change in direction of current flow from 0 to maximum to 0 in one direction, then to maximum and back to 0 in the opposite direction. DC abbreviation for direct current. Direct current electric current that follows continuously in one direction. Electromagnetism the magnetic force produced by an electric current. Electron negatively charged particle that travels around the nucleus of an atom. Frequency applies to alternating current and to the number of cycles that occur each second. Ground an electrical connection to earth or to a large conductor that is known to be at earth's potential. Hertz frequency at which a cycle repeats within one second. Horsepower denotes the rate of doing work. Insulator a substance, body, or device that prevents the flow of electrical current. Neutron neutrally charged particle in the nucleus of an atom. Ohm basic electrical unit used to quantify a material's opposition to current flow. Phase describes the type of electrical service being used (e.g., single or three phase). Power the ability of electricity to do a certain amount of work in a certain amount of time. Proton positively charged particle in the nucleus of an atom. Resistance the opposition to current flow in an electrical circuit. Sine wave the wave traced by the sine of an angle as the angle is rotated through 360". Single-phase power a circuit or generator in which only one alternating current is produced. Three-phase power a circuit or generator in which three power sources 120" out of phase with each other are produced. Volt the practical unit of voltage, potential, or electromotive force (EMF). Watt the practical unit of,electric power.

8.3 BASIC ELECTRICITY: THEORY

To develop a basic understanding of how electrical equipment works, you need to understand basic electrical theory. In this section, we review the concept of basic electricity based on the atomic theory (one of the basic electrical theories, widely accepted in most nations and especially helpful as a training model). Question:What is electricity? Answer: Electricity is the flow of electrons. Question: What is an electron? Answer: The best way to explain what an electron is and what electricity is, is to expla n basic atomic theory.

Basic Electricity: Theory

Figure 8.1 Structure of an atom.

The smallest and basic fundamental unit of all matter is the atom. An atom is composed of three components: protons, neutrons, and electrons (see Figure 8.1). The protons (positively charged particles) and neutrons (zero or neutrally charged particles) are contained in the nucleus (the center part of the atom). Orbiting the nucleus are one or more electrons. The electron (a negatively charged particle) is extremely small and travels at nearly the speed of light. Electrons remain at a constant distance from the nucleus of the atom (see Figure 8.1). Two forces hold them in this position. One is the electrical attraction between the negative electrons and the positive protons. This force has the tendency to pull the electrons into the nucleus. The second force is centrifugal force. Centrifugalforce (the force that acts radially outwards from a spinning or orbiting object) tries to make the electrons fly away from the nucleus. The two forces work to counteract each other and hold the electrons stable in their orbits (see Figure 8.1). As we see in Figure 8.1, the electrons in an atom form shells or orbits (or orbitals, in distinct energy levels) around the nucleus. Each shell can contain a certain maximum number of electrons. Each element has a different number of electrons. The atoms of the heavier elements have multiple shells.Atoms are most stable (regardless of the element) when they have eight electrons in their outermost shell. Atoms with fewer than eight but more than five electrons in their outer shells prefer to accept more electrons; these types of materials are called acceptors. Electrically, materials that are acceptors are known as insulators. Insulators do not easily allow the flow of electrons. Examples include rubber, wood, plastic, and glass. When an atom contains fewer than five electrons in its outer shell, it more easily donates electrons than accepts more electrons. Atoms with fewer than five electrons (as you might guess) are called donors, meaning they have "free" electrons available. Electrically, materials with fewer than five electrons (donors) are called conductors. Conductors allow their electrons (and thus current flow) to flow easily. Examples include copper, aluminum, iron, and gold. If we have an electron donor material (such as copper wire), we have one of the major elements

102

BASIC ELECTRICITY

needed to produce electricity, a conductor of free electrons. To make the free or donor electrons within the copper wire flow, however, we need to provide an energy source (sufficient energy must be applied to cause the negatively charged electrons to speed up enough to overcome the internal attraction of the positively charged protons). Energy can be applied by a generator, by light, by pressure, by friction, by chemical reactions (e.g., by a battery), and by heat. So that you can easily visualize the preceding explanation of electron flow (electrical current flow), compare the flow of electricity to the flow of water within a pipe. If we have a water pump of sufficient energy connected to a water source on one end (suction end) and to a pipe on the other (distribution end), we could expect the pump to force the water into the pipe under pressure and thus effect water flow through the pipe. In a simple electrical circuit, the water pump is the generator or battery, the pipe is the conductor or wire, and water flow is the electron flow through the conductor. J We must point out that the analogy above is provided for explanatory reasons only, and that in reality, electrons do not flow through a wire the same way water flows through a pipe. Electrons move from one atom to another in random patterns.

8.4 MEASURING ELECTRICITY Let's assume that the power source in the electrical counterpart of the water pump used above is a battery. The battery is in fact our electrical pump and works to force electrical current through the circuit in much the same way the water pump forces water through its piping system. The water pump is able to perform its pumping activity because of a difference in pressure between the suction and discharge of the pump. The battery creates a difference in pressure-what is called a difference in potential between the poles of the battery-between the negative and positive poles. This difference in potential, this electrical difference, is called electromotive force or simply EMF. The electrical pressure generated because of a difference in potential is called voltage. The units of measurement are volts. The symbol for volts can be "E" (for EMF) or "V" for volts. Voltage is measured with a voltmeter. A common voltmeter used by waterworks operators is a VOM (Volt-Ohm Meter). The flow of electrons from one point to another is called current. Current is measured as amperage or amps. Current or amps is similar to flow in gallons per minute in a water pipe. The electrical symbol for amps is "I" or "A". Amperage is measured using an amp meter. The resistance to the flow of electrons (or current flow) is called, as you might guess, resistance, similar to headloss or friction in a water line. Resistance is measured as ohms. Electrically, the symbol for resistance is "Q" (the Greek letter omega) or "R". We provide a summary of electrical units and symbols compared to the water equivalent in Table 8.1. 8.5 OHM'S LAW Along with knowing basic electrical terms and their importance, you must understand Ohm 2 Law to gain a fundamental understanding of electrical theory. TABLE 8.1. Electrical Measurement and Water

Equivalents.

Electrical Equivalent

Units

Symbols

Water Units

Equivalent

Pressure (EMF) Current Resistance

Volts Amps Ohms

EorV IorA Q or R

Pressure Flow Headloss

psi g Pm Feet

Electrical Motion

Figure 8.2 Ohm's law.

Ohm's Law simply states that one volt will cause a current of one ampere to flow through a resistance of one ohm. As a formula, the relationship is represented as follows:

E (volts) = I (amps) X R (resistance)

(8-1)

An easy way to remember this formula and the different ways it can be expressed is to put the symbols in a circle or pie chart (see Figure 8.2). Using Figure 8.2, put your finger on I-I= E/R; put your finger on R-R = E/I; and put your finger on E-E = I X R. With this basic formula and using the pie chart, you can better understand and explain electrical parameters such as voltage, current, and resistance. Let us point out, however, that formula (8.1) applies only to direct current (DC). In alternating current usage, Ohm's Law is

where Z = impedance. J Impedance is the sum of the resistance, the capacitive and inductance reactance. Capacitive and inductive reactance are beyond the scope of this text, but we explain them in greater detail in Volume 2 of the Handbook.

8.6 ELECTRICAL CIRCUITS

Two types of electrical circuits concern us in Volume 1 of the Handbook: open and closed circuits (see Figure 8.3). An open circuit is similar to having the light switch in the "off" position [Figure 8.3 (a)]. No electrical current flow occurs, because no connection (no complete circuit) is made between the light and the power system, thus there is no flow of electrons. A closed circuit [Figure 8.3 (b)] exists when the switch is closed (in the "on" position), so that electrons can flow from the power sources to the light, and the light comes on.

8.7 ELECTRICAL MOTION Electricity is electrons (current flow) in motion. Motion can be of two types: one in which the electric current flows continuously in one direction (direct current), and the second in which the electric current reverses its direction of flow periodically (alternating current).

-

No current flow

Open Circuit

Closed Circuit

Lamp

Battery Figure 8.3 Open (a) and closed (b) circuits.

Figure 8.4 Sine wave.

Electrical Phases

105

8.7.1 DIRECT CURRENT

Current that flows continuously in one direction is referred to as direct current (DC)-the trons always flow in a single direction. Batteries supply direct current.

elec-

8.7.2 ALTERNATING CURRENT

Electric current that reverses its direction in a periodic manner-rising from zero to maximum strength, returning to zero, and then going through similar variations of strength in the opposite d i r e c t i o n i s referred to as alternating current (AC). This is the type of power provided through local power companies to the electrical service and outlets in most buildings. At a waterworks (and at home), it is used to operate and control the pumping control systems and electric motors. The advantage of alternating current over direct current (as from a battery) is that its voltage can be raised or lowered economically by a transformer: high voltage for generation and transmission, and low voltage for safe utilization. 8.7.2.1 Sine Wave

Direct current electricity produces a steady flow and rate of electrons. A visual representation of the flow of direct current would be nothing more than a straight line. On the other hand, alternating current produces a distinct pattern called a sine wave (see Figure 8.4). The sine wave shows the oscillation from positive to negative and back to positive. A complete sine wave is the representation of one cycle, resulting from switching from positive to negative and back to positive (see Figure 8.4). The number of complete sine wave cycles produced in one second is called the frequency. The units of frequency are Hertz (hz). Normal household current alternates at 60 hertz, or 60 times per second. The distance from one end of a sine wave to the other is a measure of time and is marked off in degrees (see Figure 8.4). When the frequency is 60 hertz, the distance in time from one end of a sine wave to the other is 1160th of a second. This 1160th of a second is then divided into 360 equal parts called degrees. Direct current can be converted to alternating current and vice versa. To accomplish this, an electrical circuit called a converter is used. For example, most computer systems are fed alternating current that is converted to direct current.

8.8 ELECTRICAL PHASES Most large industrial motors (such as the ones normally used in pumping stations and waterworks unit processes) are three-phase motors. Figure 8.5 helps to explain what we mean by "three phase" and illustrates single phase. We can equate phases to sources. Single-phase power uses a single source of power. Single-phase systems use two line leads (power leads), one that is called the hot lead, and one that is called the neutral. You may have noticed that most homes have three leads going into the house, two hot leads and one neutral. While this is really two-phase power, it is called single phase. Three-phase power has three line leads, three power sources. Each source is a different phase. Typically, a treatment unit process at a waterworks uses three-phase power that has four wires coming from the outside power supply to the point of use (three hot leads and one neutral). Phase is a common term used in electricity to describe timing. In three-phase power networks,

BASIC ELECTRICITY

Power Single Phase

Power

Motor

0 [

1

Three Phase Figure 8.5 Single- and three-phase power.

each phase is energized a fraction of a second later in time. The voltage applied to each phase starts later in time (each phase actually starts 120" later in time). Remember, 360" is 1160th of a second.

8.9 ELECTRICAL POWER

Horsepower is a common term used to denote the rate of doing work. Work requires energy. One of the ways to measure the amount of energy required to do work is in foot-pounds. One foot-pound of work is the amount of energy required to lift one pound of water one foot in elevation. While defining work in foot-pounds has become conventional, commonly, for larger units of work, we use horsepower. When 33,000 foot-pounds of work is performed in one minute, it is called one horsepower. Originally a mechanical term, horsepower is now commonly used to rate electric motors. The output of the motor is called brake horsepower. To provide the horsepower to drive an electric motor, we need electricity. The amount of electricity used (power) is a combination of the voltage and the amperage and is given in units called watts. The following equation describes the relationship between horsepower and watts. l HP = 746 watts

Using Ohm's Law, we can determine watts by

8.1 0 ELECTROMAGNETICS An iron bar with coils of wire around it that acts as a magnet when an electric current flows through the coil is known as an electromagnet (see Figure 8.6). The magnetic field is very much like the field that exists between the north and south poles of a permanent magnet. If we wind a wire around a piece of metal and pass a current through the wire, the piece of metal becomes a magnet with a north and south pole.

Transformers

Figure 8.6 Electromagnetic field.

Electromagnets have many uses: in electric bells, solenoids, metal-lifting cranes, and switches (see Figure 8.7). In Figure 8.6, we use an electromagnet to operate a switch by placing a simple magnetic switch (a bar close to the end of the magnet) in the circuit. The bar is connected to one side of the electrical supply. A second bar is connected to the light and to the other side of the power supply (battery). When we c!mc witch #l, the ekctmmignet is energized, pr;!!ing the bzr d ~ w nby the electromagnetic field and bringing power to the light. Many of the electrical machines used in waterworks operations use electromagnetic devices such as relays, contactors, or contact relays. The basic function of these simple devices is to close or to open a switch. Large electric motors also use electromagnetic devices (magnetic starters) to control operation of the motor. The motors are typically high voltage devices (440+ volts), but the electromagnetic starters operate on lower voltages (typically 120 volts).

8.11 TRANSFORMERS A transformer is a device that allows energy to be transferred in an alternating current system from one circuit (the primary side of the transformer) to a second circuit (the secondary side of the transformer). The primary winding and secondary winding are essentially two independent circuits linked by a common magnetic circuit. Transformers are used to step voltage up or step voltage down; that is, 440 volts stepped down to 220 or 120 volts or 120 volts stepped up to 220 or 440 volts. Transformers are rated for single-phase or three-phase operation.

Voltage 1

1

= -

Switch 1

S Switch 2

Light Figure 8.7 Electromagnetic switching.

Voltage 2

BASIC ELECTRICITY

8.12 ELECTRICAL EQUIPMENT USED IN WATERWORKS OPERATIONS Waterworks operators soon come to realize that their jobs would be much more difficult (if not impossible) to perform without electricity. Specifically, typical waterworks facilities use all types of electrical equipment to perform a myriad of tasks. From electrical motors used to power various pumps, screening devices, and other unit processes, to the light provided to see inside buildings and throughout the plant site at night, to the computer in the office, to lab equipment in the laboratory, to the wide variety of contactors, coils, relays, contact relays, magnetic starters, and other appliances, we hold no doubt that electricity helps to perform a lot of important work at a waterworks facility. Electricity works to make the waterworks operator job easier and more efficient. For example, can you imagine how time-consuming constantly measuring when the level of the tank is high enough to turn off the pump, or low enough.to turn it on would be, if a waterworks had to penna-

Motor

Pump Figure 8.9 Electrical probe.

Chapter Review Questions

109

nently station an operator at a tank to accomplish it? Electricity allows this operation to be accomplished on its own with little operator interface. For example, consider the common mercury float switch. The float contains a glass vial with two electrodes and a small amount of mercury. When the float is tripped, the mercury runs across the electrodes, and the circuit is closed. This can be used to start or stop the pump needed to fill a tank to its operational level (see Figure 8.8). This same action can be accomplished using electrical probes (see Figure 8.9) instead of mercury switches. The electrical probes are used to determine the level of water in the tank and turn the pump on or off. Another electrical device that makes the waterworks operator's job easier and definitely more efficient (or accurate) is the simple electrical flow switch. Measurement of flow, obviously, is something the waterworks operator must be concerned about on a continuous basis.

8.13 SUMMARY Operators need electrical know-how to operate and troubleshoot the equipment necessary to keep the plant working and the water flowing. Keeping the water flowing, and the physical laws that govern the movement of water, is hydrology, the subject of Chapter 9.

8.14 CHAPTER REVIEW QUESTIONS

8-1 The frequency of AC current is measured in what units?

8-2 The unit of electrical pressure is what?

8-3 The unit of electrical current flow is what?

8-4 The unit of opposition to electrical current flow is what?

8-5 The symbols for voltage, current, and resistance are:

8-6 The atom is composed of what three particles?

8-7 Explain the difference between three-phase and single-phase power.

110

8-8 Work in water is measured as 8-9 In electricity, work is measured as 8-10 What is an electromagnet?

BASIC ELECTRICITY

CHAPTER 9

Basic Hydraulics

The study of water at rest and in motion in tanks, reservoirs, pipelines, and pumping systems is known as hydraulics.

9.1 INTRODUCTION the chapter opening quote points out, hydraulics is the study of fluids at rest and in motion, essential for an understanding of how water systems work, especially water distribution systems. Although hydraulics is important in gaining understanding of water distribution systems, the principles of hydraulics are also useful for understanding standard practice in treatment, storage, and cross-connection control, which we discuss in other chapters. We point out that even though water distribution systems are often excluded from the definition of a waterworks (you do not have to be a licensed waterworks operator to operate a distribution system), the distribution system is essential to the operation of the water system. Many water quality problems in water systems come from contamination of the water after it leaves the treatment plant. In small water systems, the distribution system may occupy a larger portion of the operator's time than the treatment process or system. This chapter provides a brief discussion of hydraulics to furnish the background necessary to understand basic hydraulics at the operator-in-training level. In short, the following brief discussion on hydraulics represents a simple and logical discussion of that portion of hydraulics the waterworks operator is likely to practice.

A

S

9.2 BASIC HYDRAULIC DEFINITIONS Pressure the force exerted on a unit area. Pressure = Weight X Height. In water, it is usually measured in psi (pounds per square inch). One foot of water exerts a pressure of 0.433 pounds per square inch. Force influence (as a push or pull) that causes motion. In physics, it is the mass of an object times its acceleration, F = mu. Head the measure of the pressure of water expressed as height of water in feet-l psi = 2.3 1 feet of head. Static a nonmoving condition. Headloss the loss of energy, commonly expressed in feet, as a result of friction. The loss is actually a transfer to heat. Velocity head the amount of energy required to bring a fluid from a standstill to its velocity. From a given quantity of flow, the velocity head will vary indirectly with the pipe diameter.

112

BASIC HYDRAULICS

Inertia the tendency of matter to remain at rest or in motion. Total dynamic head the total energy needed to move water from the center line of a pump (eye of the first impeller of a lineshaft turbine) to some given elevation or to develop some given pressure. This includes the static head, velocity head, and the headloss due to friction.

9.3 WEIGHT OF WATER In the operation of waterworks unit processes (and the entire system), operators continuously deal with pressures. Thus, water pressure is the "key" parameter. Water pressure is directly dependent upon the weight of water. Interestingly, before we can begin a discussion of the weight of water and, consequently, a discussion about water pressure, we must first begin our discussion with the weight of air. Earth is surrounded by a blanket of air (a combination of gases, not just oxygen) many miles in thickness. The weight of this blanket on a given square inch of the earth's surface will vary according to the thickness of the atmospheric blanket above that point. As sea level, the pressure exerted is 14.7 pounds per square inch (psi). On a mountaintop, air pressure decreases because the blanket is not as thick. Now let's change the focus of our discussion to the weight of water. As waterworks operators, we know that water must be stored and moved in water supplies. Logically, we should know or at least consider some basic relationships in the weight of water, the substance we are storing or pumping. In the United States, cubic feet and gallons are used to describe a volume of water, with a defined relationship between these two methods of measurement. The specific weight of water is defined relative to a cubic foot. One cubic foot of water weighs 62.4 pounds. This relationship is true only at a temperature of 4°C and at a pressure of one atmosphere (a.k.a. standard temperature and pressure). However, the weight varies so little that for practical purposes, we use this weight from a temperature from 0°C to 100°C. More specifically, consider Figure 9.1. The l' X l' X 1' container shown equals one cubic foot. If it were filled with water, the water would weigh approximately 62.4 pounds. The total pressure exerted against the bottom of the container is 62.4 pounds. J Key Point: 1 ft3of water = 62.4 lbs.

Since the container in Figure 9.1 is filled with water, and 1 ft3of water equals 62.4 pounds, each square inch of the bottom of the container has a pressure exerted against it of 0.433 lbs per square inch (62.4 lbs divided by 144 square inches). Because water pressure is usually stated in pounds per square inch (psi), a column of water one foot high exerts a pressure of 0.433 psi, or 0.43 psi. A gallon of water contains 231 cubic inches. The cubic foot container shown in Figure 9.1 contains 1,728 cubic inches ( l 2 X 12 X 12). By dividing the 1,728 cubic inches by 231 cubic inches, we

Figure 9.1 One cubic foot of water.

Weight of Water

113

find that there are 7.481 (we round this off to 7.48) gallons of water in a cubic foot. One gallon of water weighs 8.34 lbs (62.4 Ibs divided by 7.48 gal). Water one foot deep will exert a pressure of 0.43 pounds per square inch on the bottom area ( l 2 in X 0.0362 lb/in3).Thus, a column of water two feet high exerts 0.86 psi, one 10 feet high exerts 4.3 psi.

Example 9.1 Problem:

A column of water 55 feet high exerts how much psi? Solution: psi 55 ft X 0.43 - = 23.65 psi ft

Example 9.2 Problem: A column of water 2.3 1 feet high will exert 1.0 psi. To produce a pressure of 50 psi requires a water column how high?

Solution: ft 55 psi X 2.31 - = 115.5 psi PS1

Example 9.3 Problem: Find the number of gallons in a reservoir that has a volume of 788.5 ft3.

Solution: 788.5 ft3X 7.48 gaVft3= 5,898 gallons J Key Points: 1 ft3 water = 7.48 gallons 1 gallon water = 8.34 pounds

We stated that water pressure is dependent on weight. We must also point out that it is directly proportional to elevation. If the container shown in Figure 9.1 were 15 feet high instead of one foot, the pressure on the bottom would be fifteen times more than a one foot column or 6.45 psi (0.43 psilft X 15 ft = 6.45 psi). The conversion of psi to feet is made by dividing the psi by 0.433 psi/ft.

Example 9.4 Problem: Find the height of water in a tank if the pressure at the bottom of the tank is 14 psi.

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BASIC HYDRAULICS

Solution: Feet =

14 psi = 32.3 feet 0.433 psilft

9.4 PRESSURE AND HEAD

Pressure is directly related to the height of a column of fluid. This height is called head or feet of head. For example, a 10 feet column of water exerts 4.3 psi. This can be called 4.3 psi pressure or 10 feet of head.

Example 9.5 Problem:

If the static pressure in a pipe leading from an elevated water storage tank is 44 pounds per square inch (psi), what is the elevation of the water above the pressure gauge? Solution: Remembering that 1 psi = 2.3 1 ft and that the pressure at the gauge is 44 psi,

ft - 101.6 feet 44 psi X 2.3 l psi

When speaking of the weight of water, we must first speak of the weight of air. Why we emphasized the weight of water related to the weight of air factor may be clear to you, but in case it is not, consider that the theoretical atmospheric pressure at sea level (14.7 psi) will support a column of water 34 feet high. Consider the following:

14.7 psi X 2.3 1 ft -33.95ftor34ft psi In contrast, at an elevation of one mile above sea level, where the atmospheric pressure is 12 psi, the column of water would be only 28 feet high (12 psi X 2.31 ft/psi = 28 ft). The airlwater pressure relationship is only one of the relative factors involved with water pressure. For example, the pressure at the bottom of a container is only affected by the height of water in the container, not by the shape of the container. More specifically, if we were to take three differently shaped containers and fill them to the same level, the pressure at the bottom of each container would be the same (see Figure 9.2). J Key Point: The pressure exerted at the bottom of a tank is related only to the head on the tank and not on the volume of water in the tank.

Static (at Rest) and Dynamic (in Motion) Conditions

Figure 9.2 Three containers of different shapes, configurations and sizes. The pressure at the bottom of each is the same.

9.5 STATIC (AT REST) AND DYNAMIC (IN MOTION) CONDITIONS Before beginning a discussion of static and dynamic water conditions in this section, we must discuss the basics of velocity and flow of water. Velocity is the speed that water is moving along a pipe or through a basin. Velocity is usually expressed in feet per second (fvsec). Flow is commonly expressed in gallons per minute (gpm) andlor cubic feet per second (cfs). The relationship between gallons per minute and cubic feet per second is that one cubic foot per second is equal to 448 gallons per minute. J Key Point: 1 cfs = 448 gpm

In equation form, flow is determined by:

where Q = cfs V = fdsec A = ft2 9.5.1 WATER AT REST

In static conditions (water at rest), Stevin's Law states that "The pressure at any point in a fluid at rest depends on the distance measured vertically to the free surface and the density of the fluid." Stated different1y (as an equation), this becomes :

where p = pressure in pounds per square foot (psf) W = density in pounds per cubic foot (lb/ft3) h = vertical distance in feet

BASIC HYDRAULICS

Example 9.6 Problem: What is the pressure at a point 20 feet below the surface of a reservoir? Solution: Remembering that the density of water ( W ) is 62.4 pounds per cubic foot.

In waterworks operations, the operator generally measures pressure in pounds per square inch rather than pounds per square foot; to convert, divide by 144 in2/ft2(12 in X 12 in = 144 in2): lb 1,248 7 ft lb = 8.7 -or P= in ft2 144 ,

psi

In short, we can say that the pressure measured when no water is moving in a line or the pump is not running is called static pressure. This is the pressure represented by the gauges, which we discuss in the next section. 9.5.1 .l Gauge Pressure

Even though air has weight and therefore exerts pressure, water gauges are designed so that the readings indicate pressures caused by the head of water. Because atmospheric pressure is essentially universal, we usually ignore the first 14.7 psi of actual pressure measurements and measure only the difference between the water pressure and the atmospheric pressure; we call this gauge pressure. If we include atmospheric pressure in our measurement of pressure at the bottom of a tank, for example, this pressure is known as absolute pressure-gauge pressure + atmospheric pressure = absolute pressure. To understand the difference between gauge and absolute pressure, consider an open reservoir subjected to the 14.7 psi of atmospheric pressure. Subtracting this 14.7 psi leaves a gauge pressure of 0 psi. This indicates that the water would rise 0 feet above the reservoir surface. If the gauge pressure in a water main is 80 psi, the water would rise in a tube connected to the main: 80 psi X 2.3 1 ftjpsi = 185 ft

9.5.2 WATER IN MOTION

To this point, we have considered pressure and head in relation to bodies of water at rest; that is, static pressure and static head. Anyone who has studied water at rest and in motion knows that the

Static (at Rest) and Dynamic (in Motion) Conditions

117

study of water flow is much more complicated than that of water at rest. Waterworks operators must have a sound understanding of the complicated principles involved, because the water in a waterworks treatment facility and distribution system is nearly always in motion. To gain an understanding of the basic principles of water in motion, you must be well grounded in pumping hydraulics. In this section, we provide a basic explanation of pumping hydraulics, but we first introduce a couple of key concepts that will make the understanding of pumping hydraulics somewhat more clear. Discharge is the term used to describe the quantity of water passing a given point in a pipe or channel during a given period of time. It can be calculated by using Equation (9.1). Recall that Equation (9.1) stated

W here

Q = discharge in cubic feet per second (cfs) V= water velocity in feet per second (fps or ftlsec) A = cross-sectional area of the pipe or channel in square feet (ft2)

The discharge can be converted from cfs to other units such as gallons per minute (gpm) or million gallons per day (MGD) by using appropriate conversion factors.

Example 9.7 Problem:

A pipe 12 inches in diameter has water flowing through it at 8 feet per second. What is the discharge in (a) cfs, (b) gpm, and (c) MGD? Solution: Before we can use the basic formula [Equation (9. l)], we must determine the area A of the pipe. The formula for the area of a circle is

where

D = diameter of the circle in feet r = radius of the circle in feet So, the area of the pipe is

Now we can determine part (a), the discharge in cfs:

Q=VxA=8-

ft sec

ft2 sec

X 0.785 ft2= 6.28 X -- cfs

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BASIC HYDRAULICS

For part (b), we need to know that 1 cubic foot per second is 449 gallons per minute, so 6.28 cfs X 449 gprnkfs = 2,820 gpm. Finally, for part (c), one million gallons per day is 1.55 cfs, so

In dealing with water in motion or with pumping hydraulics, another basic fact that we need to know is the law of continuity. Provided that water does not leave or enter the pipe or channel, the law of continuity states that the discharge at each point in a pipe or channel is the same as the discharge at any other point. In equation form, this becomes:

Example 9.8 Problem:

A pipe 12 inches in diameter is connected to a 6-inch diameter pipe. The velocity of the water in the 12-inch pipe is 4 fps. What is the velocity in the 6-inch pipe? Solution:

Using Equation (9.4), we first need to determine the area of each pipe using Equation (9.3).

The continuity problem now becomes

Solving for V,, ft (0.785 ft2)X (4 F) v 2

(0.196 ft2)

ft

= 16 ---- or fps

sec

Generally, we assume that elevation is the key factor affecting pressure on water in motion. However, factors other than elevation affect pressures when water is in motion. Specifically, dynamic pressure is created whenever the mechanical force of a pump is exerted (to produce motion) on water.

Static (at Rest) and Dynamic (in Motion) Conditions

119

For example, if we had a pump at a source of supply that pumps water to a storage tank with an overflow elevation of 100 feet above the centerline of the pump, a pressure gauge placed at the outlet of the pump would indicate a pressure reading of 43 psi when the tank was full. This represents a back-pressure against the pump. To pump water, the pump would have to exert a force greater than the pressure exerted by the 100-foot column of water. In reality, we are saying that this pump would operate against a static head of 100 feet. If the source of water for this pump came from a reservoir 10 feet above the centerline of the pump, there would be a positive pressure on the suction of the pump of 10 feet (or 4.3 psi). This is called suction head and serves to relieve some of the work of the pump. It would only have to exert a force against a net static head of 90 feet (100 ft-l0 ft). Instead of a reservoir 10 feet above the centerline of the pump, let's say that the source of water came from a well where the groundwater stood at an elevation 10 feet below the centerline of the pump. In this situation, an increased force would have to be exerted as a result of the need to "lift" the water 10 feet to the pump. This is called suction lift and would increase the head against which the pump must operate to 100 feet. The maximum lift that can be accomplished by suction is 33.9 feet. This is the theoretical maximum, determined and limited by atmospheric pressure, and is not attainable in field operations (the real world). The key point to remember is that it takes just as much energy for a pump to lift water 10 feet by suction as it does to force water 10 feet in elevation by pressure. 9.5.2.1 Headloss

When water runs through a pipe and the pressure (called pressure head) is measured at various points along the way, we find that the pressure decreases the further we are from the sources. This occurs because as soon as water is in motion, certain factors come into play. Most important of these factors is friction loss. Water flow is retarded by the friction of the water against the inside of the pipe. The resistance to flow offered by this friction depends on the size (diameter) of the pipe, the roughness of the pipe wall, and the number and type of fittings (bends, valves, etc.) along the pipe. J Key Point: Each type of fitting has a specific headloss depending on the velocity of water through the fitting. For instance, the headloss through a check valve is 2 114 times greater than through a 90 degree elbow, and 10 times greater than the headloss through an open gate valve.

The resistance to flow offered by friction also depends on the speed of the water through the pipe. The more water you try to pump through a pipe, the more pressure is needed to overcome the friction. The resistance can be expressed in terms of the additional pressure needed to push the water through the pipe, either psi or feet of head. Because it is a reduction in pressure, it is often referred to as friction loss or headloss. Headloss is the loss of energy due to friction. The energy is lost as heat. Friction loss is usually measured in "feet per 1,000 feet of pipe" and may be easily converted to pressure loss in pounds per square inch. Factors that affect friction losses include the following: flow rate increases type of pipe pipe length increases pipe coating pipe diameter decreases pipe is constricted pipe interior becomes rougher

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BASIC HYDRAULICS

bends, fittings, and valves are added age of pipe smoothness or roughness of the interior surface of pipe

J Key Points: (1) If the flow through a pipe doubles, the friction loss in the pipe increases by almost four times (obviously, this factor, more than any other single factor, affects headloss); and (2) the diameter of a pipe determines the area of wall in contact with flowing water; for a given discharge, the diameter also determines the velocity of the water. Pumps are designed to operate under specific head conditions. In addition to the static head, all friction losses and minor losses should be computed to determine the total head against which the pump will operate. The pump is then specifically designed or selected from a standard design to provide the desired capacity for the potential conditions under which it will operate. The total pressure provided at the discharge side of the pump represents the discharge pressure of the discharge head. The actual calculation of friction loss is too complicated for this introduction to hydraulics. Adding friction losses for fittings further complicates the calculations. Usually, head loss from fittings is calculated by substituting the equivalent length ofpipe from tables. In addition, various published tables are available that make estimating the amount of water a given pipe will carry fairly easy. You can find these tables in a variety of waterworks operation references. To help you understand the basic terms (and what they are used for) employed in describing pumping hydraulics, we include a basic diagram (see Figure 9.3). As we explain the following terms, refer to the diagram. Static head is the distance between the suction and discharge water levels when the pump is not in operation. Static head conditions are often indicated by the letter Z. Suction lift is the distance between the suction water level and the center of the pump impeller.

Velocity Head V2/2g

Headless

Distribution System Hydraulics

121

This term is only used when the pump is in a suction lift condition. A pump is said to be in a suction lift condition when the eye (center) of the impeller is above the water being pumped. Suction head is the distance between the suction water level and the center of the pump impeller when the pump is in a suction head condition (i.e., anytime the impeller is below the water level being pumped). Velocity head is the amount of energy required by the pump and motor to overcome the tendency of water to remain at rest or in motion (inertia). Mathematically, velocity is V2/2g(g for acceleration due to gravity or 32.2 ft/sec2). Total dynamic head (TDH) is the static head (the elevation difference) plus the friction head (pressure losses due to the water moving through the pipes) in a given pipe system. Simply, it is the difference in water pressure between the beginning of the pipe (at the pump) and the end of the pipe (i.e., the end point-the tank being filled or the consumer's tap)-the pressure the pumps must overcome to provide water to the consumer.

9.6 DISTRIBUTION SYSTEM HYDRAULICS State waterworks regulations require waterworks to provide a set minimum working (under flow) pressure at service connection based on the greater of maximum hour or maximum day plus applicable fire flows. Typically, this requires a working pressure of 20 psi. Friction losses are greatest at the higher flows of maximum hour or day plus fire flow. If the working pressure is set at 20 psi, then the system must be designed to provide enough pressure to overcome friction losses and still provide at least 20 psi pressure. Ideally, the delivered water will be at pressures somewhat higher than 20 psi; 35 to 65 psi is the generally recommended range. When the distribution system serves an area with high hills, deep valleys, and long runs of pipe, accomplishing set hydraulic goals can be (and often is) quite difficult. The elevation differences can be directly translated into pressure differences, and long runs of pipe add to the friction losses. 9.6.1 HYDRAULIC GRADE LINE

Earlier, we described head as the height to which water would rise in a tube connected to a water line under pressure above atmospheric. If we drilled holes in a water line every few feet and installed tubes, the water would rise to a certain height in each tube, depending on the pressure in the pipe. We know that the pressure will decrease because of friction when the water is flowing, so we would expect the water to rise to lower levels further down the water lines. This is precisely what happens, of course. If we also connect the water surface levels in the tubes, we have an imaginary line called the hydraulic grade line or HGL. The HGL always slopes downward in the direction of flow in the water line, regardless of the slope of the line itself (see Figure 9.4). When water changes its direction of flow in a line or pipe, the direction of the slope of the HGL will also change. J HGL is important from an operating standpoint because it can be used to determine the pressure at any point in a water system.

The HGL is affected by such factors as a major fire, leak, or other unanticipated high demand for water. When any of these events occur, water might draw the HGL down to a point that a negative gauge pressure (a pressure below atmospheric, or vacuum) is created at some service connections. This negative pressure can create backflow and contamination of the water system. The HGL is also affected by obstructions in the pipeline, such as partially closed valves. If flows are too great or pipe diameters are too small, the HGL can drop quickly from high friction losses and give pressures below 20 psi.

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BASIC HYDRAULICS

Hydraulic Grade Line When Valves Closed

-

Figure 9.4 Hydraulic grade line.

9.7 SUMMARY

Hydraulics is essential in every phase of waterworks operation. But, to apply the principles of hydraulics, first you must have the water to distribute. Chapter 10 covers the common sources of potable W ater.

9.8 CHAPTER REVIEW QUESTIONS

9-1 Looking at the four water tanks in Figure 9.5, will the pressure at the bottom be: a. Greater in Tank A b. Greater in Tank B c. Greater in Tank C d. Greater in Tank D e. The same

9-2 One cubic foot of water weighs

pounds, and contains

gallons.

9-3 A tank contains 600 cubic feet. This converts to how many gallons?

9-4 One gallon of water weighs

pounds.

9-5 The flow of one cubic foot per second is equivalent to

gpm.

9-6 The term used to describe the difference between the level of water in a well and the level of water in the reservoir when the pump is shut down is

123

Chapter Review Questions

Feet

A

B

C

D

Figure 9.5 Four water tanks--Chapter Review Question 9-1.

9-7 Headloss is the result of 9-8 What is the difference between suction lift and suction head?

9-9 It is 80 feet in elevation from the level of water at the top of the reservoir to the pump house. What is the static water pressure at the pump house?

9-10 Describe Total Dynamic Head (TDH).

9-11 Find the height of water in a tank if the pressure at the bottom of the tank is 14 psi.

9-12 The number of gallons of water in a reservoir that has a volume of 823 ft3is 9-13 The supply tank is located at an elevation of 120 feet. The discharge point is at elevation of 210 feet. What is the static head in feet?

9- l 4 What is head?

CHAPTER 10

Potable Water Sources

So Moses brought Israel from the Red Sea; then they went out into the Wildernessof Shur. And they went three days in the wilderness andfound no water. Now when they came to Marah, they could not drink the waters of Marah, for they were bitter. Therefore, the name of it was called Marah. And the people complained against Moses, saying, "What shall we drink?" So he cried out to the Lord, and the Lord showed him a tree. When he cast it into the waters, the waters were made sweet.-Exodus 15:22-25

10.1 INTRODUCTION and processing a potable water supply in Moses' style is, obviously, beyond the ability of the waterworks operators we know. We're stuck with more conventional treatment methods for our potable water sources. Let's define potable water:

F

INDING

Potable water is water fit for human consumption and domestic use, which is sanitary and normally free of minerals, organic substances, and toxic agents, in excess or reasonable amountsfor domestic usage in the area sewed, and normally adequate in quantity and qualityfor the minimum health requirements of the persons sewed. For finding a potable water supply, the key words are "quality and quantity." Common sense tells us that if we have a water supply that is unfit to drink, we have a quality problem. If we don't have an adequate supply of quality water, we have a quantity problem. This chapter presents a discussion of the components associated with collecting water from its source and bringing it to the water treatment plant. We do not discuss the areas of operation and maintenance of the various components (including pumps and their related components) in this chapter. Instead, the chapter focuses on surface water and groundwater hydrology, and the mechanical components associated with the collection and transmission of water to the water treatment plant.

10.2 KEY DEFINITIONS Surface water the water on the earth's surface as distinguished from water underground (groundwater). Groundwater subsurface water occupying a saturated geological formation from which wells and springs are fed. Hydrology the applied science pertaining to properties, distribution, and behavior of water. Permeable a material or substance that water can pass through.

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POTABLE WATER SOURCES

Overlandflow the movement of water on and just under the earth's surface. Su$ace run08 the amount of rainfall that passes over the surface of the earth. Spring a surface feature where without the help of man, water issues from rock or soil onto the land or into a body of water, the place of issuance being relatively restricted in size. Precipitation the process by which atmospheric moisture is discharged onto the earth's crust. Precipitation takes the form of rain, snow, hail, and sleet. Water rights the rights, acquired under the law, to use the water accruing in surface or groundwater, for a specified purpose in a given manner and usually within the limits of a given time period. Drainage basin an area from which surface runoff or groundwater recharge is carried into a single drainage system. It is also called catchment area, watershed, drainage area. Watershed a drainage basin from which surface water is obtained. Recharge area an area from which precipitation flows into underground water sources. Raw water the untreated water to be used after treatment for drinking water. Caisson large pipe placed in a vertical position. Impermeable a material or substance water will not pass through. Contamination the introduction into water of toxic materials, bacteria, or other deleterious agents that make the water unfit for its intended use. Aquifer a porous, water-bearing geologic formation. Water table the average depth or elevation of the groundwater over a selected area. The upper surface of the zone of saturation, except where that surface is formed by an impermeable body. Unconfined aquifer an aquifer that sits on an impervious layer, but is open on the top to local infiltration. The recharge for an unconfined aquifer is local. It is also called a water table aquifer. Confined aquifer an aquifer that is surrounded by formations of less permeable or impermeable material. Porosity the ratio of pore space to total volume. That portion of a cubic foot of soil that is air space and could therefore contain moisture. Static level the height to which the water will rise in the well when the pump is not operating. Pumping level the level at which the water stands when the pump is operating. J Note: The following definitions are included here for clarity but apply to well systems presented in Chapter 11.

Drawdown the distance or difference between the static level and the pumping level. When the drawdown for any particular capacity well and rate pump bowls is determined, the pumping level is known for that capacity. The pump bowls are located below the pumping level so that they will always be underwater. When the drawdown is fixed or remains steady, the well is then furnishing the same amount of water as is being pumped. Cone of depression as the water in a well is drawn down, the water near the well drains or flows into it. The water will drain further back from the top of the water table into the well as drawdown increases. Radius of influence the distance from the well to the edge of the cone of depression, the radius of a circle around the well from which water flows into the well. Annular space the space between the casing and the wall of the hole. Specific yield the geologist's method for determining the capacity of a given well and the production of a given water-bearing formation, it is expressed as gallons per minute per foot of drawdown.

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POTABLE WATER SOURCES

10.3 A CYCLE WITHOUT BEGINNING OR END To fully realize how water is made available, you must understand the hydrologic cycle (see Figure 10.1). The hydrologic cycle transports the earth's water from one location to another. And, as can be seen in Figure 10.1, it consists of precipitation, surface runoff, infiltration, percolation, and evapotranspiration. In the hydrologic cycle, water from streams, lakes and oceans evaporated by the sun, together with evaporation from the earth and transpiration from plants, furnishes the atmosphere with moisture. Masses of warm air laden with moisture are either forced to cooler upper regions or encounter cool air masses, where the masses condense and form clouds. This condensed moisture falls to earth in the form of rain, snow, and sleet. Part of the precipitation runs off to streams and lakes. Part enters the earth to supply vegetation and rises through the plants to transpire from the leaves, and part seeps or percolates deeply into the ground to supply wells, springs, and the baseflow (dry weather flow) of streams. The cycle constantly repeats itself; a cycle without end.

J Note: How long water that falls from the clouds takes to return to the atmosphere varies tremendously. After a short summer shower, most of the rainfall on land can evaporate into the atmosphere in only a matter of minutes. A drop of rain falling on the ocean may take as long as 37,000 years before it returns to atmosphere, and some water has been in the ground or caught in glaciers for millions of years. 10.4 SOURCES OF WATER Approximately 40 million cubic miles of water cover or reside within the earth. The oceans contain about 97 percent of all water on earth. The other 3 percent is freshwater: (1) snow and ice on the surface of earth contain about 2.25 percent of the water; (2) usable groundwater is approximately 0.3 percent; and (3) surface freshwater is less than 0.5 percent. In the U.S., for example, average rainfall is approximately 2.6 feet (a volume of 5,900 cubic kilometers). Of this amount, approximately 71 percent evaporates (about 4,200 cubic km), and 29 percent goes to stream flow (about 1,700 cubic km). Beneficial freshwater uses include manufacturing, food production, domestic and public needs, recreation, hydroelectric power production, and flood control. Stream flow withdrawn annually is about 7.5 percent (440 cubic km). Irrigation and industry use almost half of this amount (3.4 percent or 200 cubic km per year). Municipalities use only about 0.6 percent (35 cubic km per year) of this amount. Historically, in the U.S., water usage is increasing (as might be expected). For example, in 1900, 40 billion gallons of freshwater were used. In 1975, the total increased to 455 billion gallons. Projected use in 2000 is about 720 billion gallons. The primary sources of freshwater include the following: captured and stored rainfall in cisterns and water jars groundwater from springs, artesian wells, and drilled or dug wells surface water from lakes, rivers, and streams desalinized seawater or brackish groundwater reclaimed wastewater Current federal drinking water regulations actually define three distinct and separate sources of freshwater. They are surface water, groundwater, and groundwater under the direct influence of surface water (GUDISW). This last classification is the result of the Sugace Water Treatment Rule. The

Su$ace Water

129

definition of what conditions constitute GUDISW, while specific, are not obvious. This classification is discussed in detail later in this chapter.

10.5 SURFACE WATER With even a cursory review of a map of the world, we readily realize that surface waters are not uniformly distributed over the Earth's surface. In the U.S., for example, only about 4 percent of the land mass is covered by rivers, lakes, and streams. The volumes of these freshwater sources depend on geographic, landscape, and temporal variations, and on the impact of human activities. Surface water is that water that is open to the atmosphere and results from overlandflow (i.e., runofithat has not yet reached a definite stream channel). Put a different way, surface water is the result of surface runofi. For the most part, however, surface water (as used in the context of this Handbook) refers to water flowing in streams and rivers, as well as water stored in natural or artificial lakes; man-made impoundments such as lakes made by damming a stream or river; springs that are affected by (i.e., a change in level or quantity) precipitation that falls in the vicinity of the spring; shallow wells that are affected by (i.e., a change in level or quantity) precipitation; wells drilled next to or in a stream or river; rain catchments; andor muskeg and tundra ponds.

10.5.1 ADVANTAGES AND DISADVANTAGES OF SURFACE WATER Probably the biggest advantage of using a surface water supply as a water source is that these sources are readily located; finding surface water sources does not demand sophisticated equipment or training. Many surface water sources have been used for decades and even centuries (in the U.S., for example), and considerable data is available on the quantity and quality of the existing water supply. Surface water is also generally softer (not mineral-laden), which makes its treatment much simpler. The most significant disadvantage of using surface water as a water source is pollution. Surface waters are easily polluted (or contaminated) with microorganisms that cause waterborne diseases and chemicals that enter the river or stream from surface runoff and upstream discharges. Another problem with many surface water sources is turbidity, which fluctuates with the amount of precipitation. Increases in turbidity increase treatment cost and operator time. Surface water temperatures can be a problem because they fluctuate with ambient temperature, making consistent water quality production at a waterworks plant difficult. Drawing water from a surface water supply might also present problems; intake structures may clog or become damaged from winter ice, or the source may be so shallow that it completely freezes in the winter. Water rights cause problems, too-removing surface water from a stream, lake, or spring requires a legal right. Using surface water as a source means that the purveyor is obligated to meet the requirements of the Surface Water Treatment Rule (SWTR) and Interim Enhanced Surface Water Treatment rule. [Note: This rule only applies to large public water systems (PWS), PWS that serve more than 10,000 people. It tightened controls on DBPs and turbidity and regulates Cqptosporidium (see Section 10.7)].

10.5.2 SURFACE WATER HYDROLOGY To properly manage and operate water systems, a basic understanding of the movement of water and the things that affect water quality and quantity are important: in other words, hydrology. A discipline of applied science, hydrology includes several components, including the physical

130

POTABLE WATER SOURCES

configuration of the watershed, the geology, soils, vegetation, nutrients, energy, wildlife, and the water itself. J Key Point: The study of the properties of water and water distribution and behavior is called hydrology.

The area from which surface water flows is called a drainage basin or catchment area. With a surface water source, this drainage basin is most often called in nontechnical terms a watershed (when dealing with groundwater, we call this area a recharge area).

J Key Point: The area that directly influences the quantity and quality of surface water is called the drainage basin or watershed. When you trace on a map the course of a major river from its meager beginnings on its seaward path, that its flow becomes larger and larger is apparent. While every tributary brings a sudden increase, between tributaries, the river grows gradually from overland flow entering it directly (see Figure 10.2). Not only does the river grow; its whole watershed or drainage basin, basically the land it drains into, grows too, in the sense that it embraces an ever-larger area. The area of the watershed is commonly measured in square miles, sections, or acres. When taking water from a surface water source, knowing the size of the watershed is desirable. 10.5.3 RAW WATER STORAGE

Raw water (i.e., water that has not been treated) is stored for single or multiple uses, such as navigation, flood control, hydroelectric power, agriculture, water supply, pollution abatement, recreation, and flow augmentation. The primary reason for storing water is to meet peak demands, andjor to store water to meet demands when the flow of the source is below the demand. Raw water is stored in natural storage sites (such as lakes, muskeg, and tundra ponds) or in man-made storage areas such as dams. Man-made dams are either masonry or embankment dams. If embankment dams are used, they are typically constructed of local materials with an impermeable clay core. 10.5.4 SURFACE WATER INTAKES

Withdrawing water from a river, lake, or reservoir so that it may be conveyed to the first unit process of the waterworks requires an intake structure. Intakes have no standard design and range from a simple-pump suction pipe sticking out into the lake or stream to expensive structures costing many thousands of dollars. Typical intakes include submerged intakes, floating intakes, infiltration galleries, spring boxes, and roof catchments. Their primary functions are to supply the highest quality water from the source and to protect piping and pumps from, or clogging as a result of, wave action, ice formation, flooding, or floating and submerged debris. A poorly conceived or constructed intake can cause many problems. Failure of the intake could result in system failure. On a small stream, the most common intake structures used are small gravity dams placed across the stream or a submerged intake. In the gravity dam type, water behind the dam can be removed by a gravity line or pumps. In the submerged intake type, water is collected in a diversion and carried away by gravity or pumped from a caisson. Another common intake used on small and large streams is an end-suction centrifugal pump or submersible pump placed on a float. The float is secured to the bank, and the water is pumped to a storage area. Often, the intake structure placed in a stream is an infiltration gallery. The most common infiltration galleries are built by placing well screens or perforated pipe into the stream bed. The pipe is

Mouth of Watershed Figure 10.2 Typical watershed.

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POTABLE WATER SOURCES

covered with clean, graded gravel. When water passes through the gravel, coarse filtration removes a portion of the turbidity and organic material. The water collected by the perforated pipe then flows to a caisson placed next to the stream and is removed from the caisson by gravity or pumping. Intakes used in springs are normally implanted into the water-bearing strata, then covered with clean, washed rock and sealed, usually with clay. The outlet is piped into a spring box. In some locations, a primary source of water is rainwater. Rainwater is collected from the roof of buildings with a device called a roof catchment. After determining that a water source provides a suitable quality and quantity of raw water, choosing an intake location includes determining the following: (1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12)

Best quality water location Dangerous currents Sandbar formation Wave action Ice storm factors Flood factors Navigation channel avoidance Intake accessibility Power availability Floating or moving object damage factors Distance from pumping station Upstream uses that may affect water quality

10.5.5 SURFACE WATER SCREENS

Generally, screening devices are installed to protect intake pumps, valves, and piping. A coarse screen of vertical steel bars, with openings of 1 to 3 inches placed in a near-vertical position excludes large objects. It may be equipped with a trash rack rake to remove accumulated debris. Leaves, twigs, small fish, and other material passing through the bar rack are removed by a finer screen, one with 318-inch openings. Traveling screens consist of wire mesh trays that retain solids as the water passes through them. Drive chain and sprockets raise the trays into a head enclosure, where the debris is removed by water sprays. The screen travel pattern is intermittent and controlled by the amount of accumulated material. When considering what type of screen should be employed, the most important consideration is ensuring that they can be easily maintained. 10.5.6 SURFACE WATER QUALITY

Surface waters should be of adequate quality to support aquatic life and be aesthetically pleasing, and waters used as sources of supply should be treatable by conventional processes to provide potable supplies that can meet the drinking water standards. Many lakes, reservoirs, and rivers are maintained at a quality suitable for swimming, water skiing, and boating as well as for drinking water. Whether the surface water supply is taken from a river, stream, lake, spring, impoundment, reservoir, or dam, surface water quality varies widely,. especially in rivers, streams, and small lakes. These water bodies are not only susceptible to waste discharge contamination but also to "flash" contamination (contamination that can occur almost immediately and not necessarily over time). Lakes are subject to summerlwinter stratification (turnover) and to algal blooms. Pollution sources

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range from runoff (agricultural, residential, urban) to spills, municipal and industrial wastewater discharges, recreational users, as well as from natural occurrences. Surface water supplies are difficult to protect from contamination and must always be treated.

10.6 GROUNDWATER Part of the precipitation that falls on land infiltrates the surface, percolates downward through the soil under the force of gravity, and becomes groundwater. Groundwater, like surface water, is extremely important to the hydrologic cycle and to our water supplies. Almost half of the people in the U.S. drink public water from groundwater supplies. Overall, more water exists as groundwater than surface water in the U.S., including the water in the Great Lakes. But sometimes, pumping it to the surface is not economical, and in recent years, pollution of groundwater supplies from improper disposal has become a significant problem. We find groundwater in saturated layers called aquifers under the earth's surface. Three types of aquifers exist: unconfined, confined, and springs. Aquifers are made up of a combination of solid material such as rock and gravel and open spaces called pores. Regardless of the type of aquifer, the groundwater in the aquifer is in a constant state of motion. This motion is caused by gravity or by pumping. The actual amount of water in an aquifer depends upon the amount of space available between the various grains of material that make up the aquifer. The amount of space available is called porosity. The ease of movement through an aquifer is dependent upon how well the pores are connected. For example, clay can hold a lot of water and has high porosity, but the pores are not connected, so water moves through the clay with difficulty. The ability of an aquifer to allow water to infiltrate is called permeability. The aquifer that lies just under the earth's surface is called the zone of saturation, a unconfined aquifer (see Figure 10.3). The top of the zone of saturation is the water table. An unconfined aquifer is only contained on the bottom and is dependent on local precipitation for recharge. This type of aquifer is often called a water table aquifer. Unconfined aquifers are a primary source of shallow well water (see Figure 10.3). These wells are shallow (and not desirable as a public drinking water source). They are subject to local contamination from hazardous and toxic materials-fuel and oil, and septic tanks and agricultural runoff providing increased levels of nitrates and microorganisms. These wells may be classified as groundwater under the direct influence of surface water (GUDISW), and therefore require treatment for control of microorganisms. A confined aquifer is sandwiched between two impermeable layers that block the flow of water. The water in a confined aquifer is under hydrostatic pressure. It does not have a free water table (see Figure 10.4). Confined aquifers are called artesian aquifers. Wells drilled into artesian aquifers are called artesian wells and commonly yield large quantities of high quality water. An artesian well is any well where the water in the well casing would rise above the saturated strata. Wells in confined aquifers are normally referred to as deep wells and are not generally affected by local hydrological events. A confined aquifer is recharged by rain or snow in the mountains where the aquifer lies close to the surface of the earth. Because the recharge area is some distance from areas of possible contamination, the possibility of contamination is usually very low. However, once contaminated, confined aquifers may take centuries to recover. Groundwater naturally exits the earth's crust in areas called springs. The water in a spring can originate from a water table aquifer or from a confined aquifer. Only water from a confined aquifer spring is considered desirable for a public water system.

Figure 10.4 Confined aquifer.

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10.6.1 GROUNDWATER QUALITY

Groundwater (generally) possesses high chemical, bacteriological, and physical quality. When pumped from an aquifer composed of a mixture of sand and gravel, if not directly influenced by surface water, groundwater is often used without filtration. It can also be used without disinfection if it has a low coliform count. However, as we said, groundwater can become contaminated. When septic systems fail, saltwater intrudes, improper disposal of wastes occurs, improperly stockpiled chemicals leach, underground storage tanks leak, hazardous materials spill, fertilizers and pesticides are misapplied, and when mines are improperly abandoned, groundwater can become contaminated. To understand how an underground aquifer becomes contaminated, you must understand what occurs when pumping is taking place within the well. When groundwater is removed from its underground source (i.e., from the water-bearing stratum) via a well, water flows toward the center of the well. In a water table aquifer, this movement causes the water table to sag toward the well. This sag is called the cone of depression. The shape and size of the cone depends on the relationship between the pumping rate and the rate at which water can move toward the well. If the rate is high, the cone is shallow, and its growth stabilizes. The area that is included in the cone of depression is called the zone of influence, and any contamination in this zone will be drawn into the well.

10.7 GUDISW Water under the direct influence of surface water (GUDISW) is not classified as a groundwater supply. A supply designated as GUDISW must be treated under the state's surface water rules rather than the groundwater rules. The Sugace Water Treatment Rule of the Safe Drinking Water Act requires each site to determine which groundwater supplies are influenced by surface water (i.e., when surface water can infiltrate a groundwater supply and could contaminate it with Giardia, viruses, turbidity, and organic material from the surface water source). To determine whether a groundwater supply is under the direct influence of surface water, USEPA has developed procedures that focus on significant and relatively rapid shifts in water quality characteristics, including turbidity, temperature, and pH. When these shifts can be closely correlated with rainfall or other surface water conditions, or when certain indicator organisms associated with surface water are found, the source is said to be under the direct influence of surface water.

10.8 SURFACE WATER QUALITYITREATMENT REQUIREMENTS Public water systems (PWS) must comply with applicable federal and state regulations and must provide quantity and quality water supplies including proper treatment (wherelwhen required) and competentlqualified waterworks operators. The USEPA's regulatory requirements insist that all public water systems using any surface or groundwater under the direct influence of surface water must disinfect and may be required by the state to filter, unless the water source meets certain requirements and site-specific conditions. Treatment technique requirements are established in lieu of Maximum Contaminant Levels (MCLs) for Giardia, viruses, heterotrophic plate count bacteria, Legionella, and turbidity. Treatment must achieve at least 99.9 percent removal andor inactivation of Giardia larnblia cysts and 99.9 percent removal andor inactivation of viruses. Qualified operators (as determined by the state) must operate all systems. To avoid filtration, waterworks must satisfy the following criteria:

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Fecal coliform concentration must not exceed 201100 mL, or the total coliform concentration must not exceed 100/100 mL before disinfection in more than 10 percent of the measurements for the previous six months, calculated each month. Turbidity levels must be measured every four hours by grab samples or continuous monitoring. The turbidity level may not exceed 5 NTU. If the turbidity exceeds 5 NTU, the water supply system must install filtration, unless the state determines that the event is unusual or unpredictable, and the event does not occur more than twice in any one year or five times in any consecutive 10 years. With a choice of water sources to consider (if such a choice exists), the source must present minimal risks of contamination from wastewaters and contain a minimum of impurities that may be hazardous to health. Acute (immediate) health effects such as those presented by exposure to Giardia lamblia and chronic (those that take longer to effect health) effects must be guarded against. Maximum contaminant levels (MCLs) must be monitored to ensure that the maximum permissible level of contaminant in water is not exceeded. J Note: Primary MCL is based on health considerations. Secondary MCL is based on aesthetic considerations (taste, odor, and appearance).

The Public Water System must also provide water free of pathogens (disease-causing microorganisms: bacteria, protozoa, spores, viruses, etc.). Chemical quality must also be monitored to ensure prevention of inorganic and organic contamination. 10.8.1 RECENT AMENDMENTS TO SAFE DRINKING WATER ACT (1996)

In addition to the requirements listed above, in 1996, the USEPA finalized the Stage l Disinfectants1Disinfection By-products (DIDBP) and Interim Enhanced Surface Water Treatment rules, and implemented them in 1998. These amendments tighten controls on DBPs and turbidity and regulate Cryptosporidium. Highlights of these changes include the following: (1) Stage 1 DIDBP Rule

tightened the total trihalomethane standard to 0.080 mg/L set new DBP standards for five haloacetic acids (0.060 mg/L), chlorite (1.0 mg/L), and bromate (0.0 10 m g k ) established new standards for disinfectant residuals (4.0 mg/L for chlorine, 4.0 mg/L for chloramines, and 0.8 mg/L for chlorine dioxide) requires systems using surface water or groundwater directly influenced by surface water to implement enhanced coagulation or softening to remove DBP precursors unless systems meet alternative criteria applies to all community and nontransient-noncommunity systems that disinfect, including those serving fewer than 10,000 people

MCLGs. For maximum contaminant level goals (MCLGs), however, the USEPA opted to retain the chloroform MCLG at zero instead of loosening it to 0.3 mg/L as set forth in the Spring 1998 Notice of Data Availability. The EPA also loosened the chlorite MCLG from 0.08 mg/L to 0.8 mg/L, loosened the maximum residual disinfectant level goal for chlorine dioxide from 0.3 mg/L to 0.8 = mg/L, and set no MCLG for the DBP chloral hydrate (control of which will be covered by the other requirements).

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Chloroform. In dropping its plan to loosen the chloroform MCLG, USEPA has backed away (for now) from its first attempt to set a level higher than zero MCLG for a carcinogenic contaminant, opting for more time to allow the issue to be discussed by stakeholders and the Science Advisory Board, which is slated to produce a chloroform report by November 1999. USEPA outlined what it termed a "compelling" case for recognizing a safe (or threshold) exposure level for chloroform, one of the regulated trihalomethanes. (2) Interim Enhanced Surface Water Treatment (IESWT) Rule This treatment optimization rule, which only applies to large (those serving more than 10,000 people) public water systems that use surface water or groundwater directly influenced by surface water, is the first to directly regulate Cryptosporidium (crypto). The rule: sets a crypto MCLG of zero requires systems that filter to remove 99 percent (2 log) of crypto oocysts. adds crypto control to watershed protection requirements for systems operating under filtration waivers is particular to the genus Cryptosporidium, not to the Cryptosporidium pawum species Turbidity. The rule requires continuous turbidity monitoring of individual filters and tightens allowable turbidity limits for combined filter effluent, cutting the maximum from 5 ntu to 1 ntu and the average monthly limit from 0.5 ntu to 0.3 ntu. Benchmarking. Systems must determine within 15 months of promulgation whether they must establish a disinfection benchmark to ensure maintenance of microbial protection as systems comply with new DBP standards. Because the determination is based on whether the PWS exceeds annual average levels of THMs or haloacetic acids, systems that lack such data must begin collecting it within three months of promulgation to have a year's worth by the 15-month deadline. The rule also requires states to conduct periodic sanitary surveys of all surface water systems regardless of size, and covers all new treated-water reservoirs. (3) Regulatory Deadlines Large surface water systems (those serving over 10,000) must comply with the Stage 1 DIDBP and IESWT rules by December 2001. Smaller surface water systems and all groundwater systems must comply with the Stage 1 DIDBP Rule by December 2003.

10.9 PUBLIC WATER SYSTEM QUANTITY REQUIREMENTS Many factors affect the use of water, including climate, economic conditions, type of community (i.e., residential, commercial, industrial), integrity of the distribution system (waste pressurelleaks in the system), and water cost. In the U.S., the typical per capita usage is approximately 150 gallons per day (gpd) per person. Each residential connection requires approximately 400 gpd per connection. Keep in mind that firefighting requirements at a standard fire flow of 500 gpm will use in 1 minute what a family of five normally uses in 24 hours. Water pressure delivered to each service connection should (at a minimum) reach 20 psi under all flow conditions.

10.10 SUMMARY The two sources of potable water demand different levels of treatment, and thus, the processes to prepare the water for use and systems that carry the water from source to consumer differ. In Chapter 11, we discuss Well Systems.

Chapter Review Questions

10.11 CHAPTER REVIEW QUESTIONS 10-1 List three sources of drinking water.

10-2 Explain GUDISW.

10-3 What are two advantages of surface water sources?

10-4 What are two disadvantages of surface water sources?

10-5 Define hydrology :

10-6 The area that directly influences the quantity and quality of surface water is called:

10-7 The area inside the cone of depression is called the 10-8 The key factor that prevents an embankment dam from leaking is 10-9 A spring is an example of what type of water source?

10-10 Describe the function of the bar screen at a surface water intake.

CHAPTER 11

Well Systems

PUBLIC HEALTH PROTECTION IN COLONIAL VIRGINIA No man, woman. . . dare to wash any unclean linnen, . . . or throw out the water or suds of fowle cloathes . . . within the Pallizadoes, or withinforty foote of the same, . . . nor rench and make clean any vessel within 20 foote of the olde well. . . nor shall anyone aforesaid, within lesse than a quarter of one mile from the Pallizadoes, dare to doe the necessities of nature, since by these unmanly, slothfill, and loathsome immodesties, the whole fort may be cloaked, andpoisoned. . . . 7

11.l INTRODUCTION HE most common method for withdrawing groundwater is to penetrate the aquifer with a vertical well, then pump the water up to the surface. This chapter briefly discusses the sequence of events that occurs in developing a well supply, including well site requirements, type of wells, components of a well, evaluating a well, pumps, operating records, protecting a well from contamination, and well abandonment.

T

11.2 DEVELOPING A WELL SUPPLY

In the past, when someone wanted a well, they simply dug (or hired someone to dig) and hoped (gambled) that they would find water in a quantity suitable for their needs. Today, in most locations in the U.S., for example, developing a well supply usually involves a more complicated step-by-step process. The actual requirements for development of a well supply in the U.S. are specified by local, state, and federal requirements. The standard sequence for developing a well supply generally involves a seven-step process. This process includes the following: Step l :Application Depending on location, filling out and submitting an application (to the applicable authorities) to develop a well supply is standard procedure. Step 2: Well site approval Once the application has been made, local authorities check various local geological and other records to ensure that the siting of the proposed well coincides with mandated guidelines for approval. '~roclamation by Sir Thomas Dale, Deputy Governor for the Colony of Virginia, May 24, 1610 (Historical Tracts).

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Step 3: Well drilling The well is then drilled. Step 4: Preliminary engineering report After the well is drilled and the results documented, a preliminary engineering report is made on the suitability of the site to serve as a water source. This procedure involves performing a pump test to determine if the well can supply the required amount of water. The well is generally pumped for at least six hours at a rate equal to or greater than the desired yield. A stabilized drawdown should be obtained at that rate, and the original static level should be recovered within 24 hours after pumping stops. During this test period, samples are taken and tested for bacteriological and chemical quality. Step 5: Submission of documentsfor review and approval The application and test results are submitted to an authorized reviewing authority who determines if the well site meets approval criteria. Step 6: Constructionpermit If the site is approved, a construction permit is issued. Step 7: Operationpermit When the well is ready for use, an operation permit is issued.

11.3 WELL SITE REQUIREMENTS To protect the groundwater source and provide high-quality safe water, the waterworks industry has developed standards and specifications for wells. The following listing includes industry standard practices, as well as those items included in example State Department of Environmental Compliance regulations. J Note: Check with your local regulatory authorities to determine well site requirements.

minimum well lot requirements -50 feet from well to all property lines -all-weather access road provided -lot graded to divert surface runoff -recorded well plat and dedication document minimum well location requirements -at least 50 feet horizontal distance from any actual or potential sources of contamination involving sewage -at least 50 feet horizontal distance from any petroleum or chemical storage tank or pipeline or similar source of contamination, except where plastic type well casing is used, the separation distance must be at least 100 feet vulnerability assessment -wellhead area = 1,000 ft radius from the well -what is the general land use of the area (residential, industrial, livestock, crops, undeveloped, other)? -what are the geologic conditions (sinkholes, surface, subsurface)?

11.4 TYPES OF WELLS Water supply wells may be characterized as shallow or deep. In addition, wells are classified as follows: Class I-cased and grouted to 100 ft Class I1 A--cased to a minimum of 100 ft and grouted to 20 ft Class I1 B-cased and grouted to 50 ft

Types of Wells

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J During the well development process, mudhilt forced into the aquifer during the drilling process is removed, allowing the well to produce the best-quality water at the highest rate from the aquifer.

11.4.1 SHALLOW WELLS Shallow wells are those that are less than 100 ft deep. Such wells are not particularly desirable for municipal supplies since the aquifers they tap are llkely to fluctuate considerably in depth, making the yield somewhat uncertain. Municipal wells in such aquifers cause a reduction in the water table (or phreatic surface) that affects nearby private wells, which are more likely to utilize shallow strata. Such interference with private wells may result in damage suits against the community.

11.4.1.l Dug Wells Shallow wells may be dug, bored, or driven. Dug wells are the oldest type of well and date back many centuries; they are dug by hand or by a variety of unspecialized equipment. They range in size from approximately 4 to 15 feet in diameter and are usually about 20 to 40 feet deep. Such wells are usually lined or cased with concrete or brick. Dug wells are prone to failure from drought or heavy pumpage. They are vulnerable to contamination and are not acceptable as a public water supply in many locations.

11.4.1.2 Driven Wells Driven wells consist of a pipe casing terminating in a point slightly greater in diameter than the casing. The pointed well screen and the lengths of pipe attached to it are pounded down or driven in the same manner as a pile, usually with a drop hammer, to the water-bearing strata. Driven wells are usually 2 to 3 inches in diameter and are used only in unconsolidated materials. This type of shallow well is not acceptable as a public water supply.

11.4.1.3 Bored Wells Bored wells range from l to 36 inches in diameter and are constructed in unconsolidated materials. The boring is accomplished with augers (either hand or machine driven) that fill with soil and then are drawn to the surface to be emptied. The casing may be placed after the well is completed (in relatively cohesive materials), but must advance with the well in noncohesive strata. Bored wells are not acceptable as a public water supply.

11.4.2 DEEP WELLS Deep wells are the usual source of groundwater for municipalities. Deep wells tap thick and extensive aquifers that are not subject to rapid fluctuations in water (piezometric surface-the height to which water will rise in a tube penetrating a confined aquifer) level and that provide a large and uniform yield. Deep wells typically yield water of more constant quality than shallow wells, although the quality is not necessarily better. Deep wells are constructed by a variety of techniques; we discuss two of these techniques (jetting and drilling) below.

11 A.2.l Jetted Wells Jetted well construction commonly employs a jetting pipe with a cutting tool. This type of well cannot be constructed in clay, hardpan, or where boulders are present. Jetted wells are not acceptable as a public water supply.

WELL SYSTEMS

11.4.2.2 Drilled Wells Drilled wells are usually the only type of well allowed for use in most public water supply systems. Several different methods of drilling are available, all of which are capable of drilling wells of extreme depth and diameter. Drilled wells are constructed using a drilling rig that creates a hole into which the casing is placed. Screens are installed at one or more levels when water-bearing forrnations are encountered.

11.5 COMPONENTS OF A WELL The components that make up a well system include the well itself, the building and the pump, and related piping system. In this section, we focus on the components that make up the well itself. Many of these components are shown in Figure 11.1.

11.5.1 WELL CASING A well is a hole in the ground called the borehole. The hole is protected from collapse by placing a casing inside the borehole. The well casing prevents the walls of the hole from collapsing and prevents contaminants (either surface or subsurface) from entering the water source. The casing also provides a column of stored water and a housing for the pump mechanisms and pipes. Well casings constructed of steel or plastic materials are acceptable. The well casing must extend a minimum of 12 inches above grade.

11.5.2 GROUT To protect the aquifer from contamination, the casing is sealed to the borehole near the surface and near the bottom where it passes into the impermeable layer with grout. This sealing process keeps the well from being polluted by surface water and seals out water from water-bearing strata that have undesirable water quality. Sealing also protects the casing from external corrosion and restrains unstable soil and rock formations. Grout consists of near cement that is pumped into the annular space (it is usually completed within 48 hours of well construction); it is pumped under continuous pressure starting at the bottom and progressing upward in one continuous operation.

11.5.3 WELL PAD The well pad provides a ground seal around the casing. The pad is constructed of reinforced concrete 6 feet X 6 feet (6 in thick) with the well head located in the middle. The well pad prevents contaminants from collecting around the well and seeping down into the ground along the casing.

11.5.4 SANITARY SEAL To prevent contamination of the well, a sanitary seal is placed at the top of the casing. The type of seal varies depending upon the type of pump used. The sanitary seal contains openings for power and control wires, pump support cables, a drawdown gauge, discharge piping, pump shaft, and air vent, while providing a tight seal around them.

Figure 11.1 Components of a well.

WELL SYSTEMS

11.5.5 WELL SCREEN

Screens can be installed at the intake point(s) on the end of a well casing or on the end of the inner casing on a gravel packed well. These screens perform two functions: (1) supporting the borehole, and (2) reducing the amount of sand that enters the casing and the pump. They are sized to allow the maximum amount of water while preventing the passage of sand/sediment/gravel. 11.5.6 CASING VENT

The well casing must have a vent to allow air into the casing as the water level drops. The vent terminates 18 inches above the floor with a return bend pointing downward. The opening of the vent must be screened with #24 mesh stainless steel to prevent entry of vermin and dust. 11.5.7 DROP PIPE

The drop pipe or riser is the line leading from the pump to the well head. It assures adequate support so that an aboveground pump does not move and so that a submersible pump is not lost down the well. This pipe is either steel or PVC. Steel is the most desirable. 115.8 MISCELLANEOUS WELL COMPONENTS

We briefly discuss additional well components in the following.

( 1 ) Gauge and air line measures water level of the well. (2) Check valve located immediately after the well, it prevents system water from returning to the well. It must be located above ground and be protected from freezing. ( 3 ) Flow meter required to monitor the total amount of water withdrawn from the well, including any water blown off. (4) Control switches controls for well pump operation. ( 5 ) BlowofS valved and located between the well and storage tank; used to flush the well of sediment or turbid or super-chlorinated water. ( 6 ) Sample taps (a) Raw water sample tap-located before any storage or treatment to permit sampling of the water directly from the well. (b) Entry point sample tap-located after treatment. (7) Control valves isolates the well for testing or maintenance or used to control water flow.

11.6 WELL EVALUATION After a well is developed, conducting a pump test determines if it can supply the required amount of water. The well is generally pumped for at least six hours (many states require a 48 hour yield and drawdown test) at a rate equal to or greater than the desired yield. Yield is the volume or quantity of water per unit of time discharged from a well (GPM, cubic feet/sec). Regulations usually require that a well produce a minimum of 0.5 gallons per minute per residential connection. Drawdown is the difference between the static water level (level of the water in the well when it has not been used for some time and has stabilized) and the pumping water level in a well.

Routine Operation and Recordkeeping Requirements

147

Drawdown is measured by using an airline and pressure gauge to monitor the water level during the 48 hours of pumping. The procedure calls for the air line to be suspended inside the casing down into the water. At the other end is the pressure gauge and a small pump. Air is pumped into the line (displacing the water) until the pressure stops increasing. The gauge's highest pressure reading is recorded. During the 48 hours of pumping, the yield and drawdown are monitored more frequently during the beginning of the testing period, because the most dramatic changes in flow and water level usually occur then. The original static level should be recovered within 24 hours after pumping stops. Testing is accomplished on a bacteriological sample for analysis by the MPN method every half hour during the last 10 hours of testing. The results are used to determine if chlorination is required or if chlorination alone will be sufficient to treat the water. Chemical, physical, and radiological samples are collected for analyses at the end of the test period to determine if treatment other than chlorination may be required. J Note: Recovery from the well should be monitored at the same frequency as during the yield and drawdown testing and for at least the first 8 hours, or until 90 percent of the observed drawdown is obtained. SpeciJic capacity (often called productivity index) is a test method for determining the relative adequacy of a well, and over a period of time, is a valuable tool in evaluating well production. Specific capacity is expressed as a measure of well yield per unit of drawdown (yield divided by drawdown). When conducting this test, if possible, always run the pump for the same length of time and at the same pump rate.

11.7 WELL PUMPS

Pumps are used to move the water out of the well and deliver it to the storage tankldistribution system. The type of pump chosen for use should provide optimum performance based on location and operating conditions, required capacity, and total head. Two types of pumps commonly installed in groundwater systems are lineshaft turbines and submersible turbines. Whichever type of pump is used, they are rated on the basis of pumping capacity expressed in gpm (e.g., 30 gpm), not on horsepower.

11.8 ROUTINE OPERATION AND RECORDKEEPING REQUIREMENTS 11.8.1 OPERATIONAL CHECKS

Ensuring the proper operation of a well requires close monitoring; wells should be visited regularly. During routine monitoring visits, check for any unusual sounds in the pump, line, or valves, and for any leaks. In addition, as a routine, cycle valves to ensure good working condition. Check motors to make sure they are not overheating. Check the well pump to guard against short-cycling. Collect a water sample for a visual check for sediment. Also, check chlorine residual and treatment equipment. Measure gallons on the installed meter for one minute to obtain pump rate in gpm (look for gradual trends or big changes). Check water level in the well at least monthly (maybe more often in summer or during periods of low rainfall). Finally, from meter readings, determine gallons used and compare with water consumed to determine possible distribution system leaks.

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11.8.2 RECORDKEEPING Records must be accurately and consistently maintained for water supply wells. This recordkeeping is absolutely imperative. The records (an important resource for troubleshooting) can be useful when problems develop or helpful in identifying potential problems. A properly operated and managed waterworks facility keeps the following records of well operation. Well Log The Well Log provides documentation of what materials were found in the borehole and at what depth. The well log includes the depths at which water was found, the casing length and type, the depth at which what type of soils were found, testing procedure, well development techniques, and well production. In general, the following items should be included in the Well Log. w e l l location -who drilled the well -when the well was completed -well class -total depth to bedrock -hole and casing size ---casing material and thickness -screen size and locations -grout depth and type -yield and drawdown (test results) -pump information (type, HP, capacity, intake depth, model #) -geology of the hole A record of yield and drawdown data should be maintained. Pump data should be collected and maintained. This data should include: p u m p brand and model number r a t e capacity - d a t e of installation -maintenance performed -date replaced -pressure reading or water level when the pump will cut on and off -pumping time (hours per day the pump is running) -output in gpm A record of water quality should be kept and maintained, including bacteriological, chemical and physical (inorganic, metals, nitratelnitrite, voc), and radiological reports. System-specific Monthly Operation Reports should be kept and maintained. These reports should contain information and data from meter readingsltotal gallons per daylmonth, chlorine residuals, amount and type of chemicals used, turbidity readings, physical parameters (pH, temperature), pumping rate, total population served, and total number of connections. A record of water level (static and dynamic levels) should be kept and maintained. A record of any changes in conditions (such as heavy rainfall, high consumption, leaks, and earthquakes) should be kept and maintained. A record of specific capacity should also be kept and maintained.

11.9 WELL MAINTENANCE Wells do not have an infinite life, and their output is likely to reduce with time as a result of hydrological andor mechanical factors.

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149

Protecting the well from possible contamination is an important consideration. If proper well location (based on knowledge of the local geological conditions and a vulnerability assessment of the area) was effected, potential problems can be minimized. During the initial assessment, ensuring that the well is not located in a sinkhole area is important. A determination of where unconsolidated or bedrock aquifers may be subject to contamination must be made. Several other important determinations must be made. Is the well located on a floodplain? Is it located next to a drainfield for septic systems or near a landfill? Are petroleudgasoline storage tanks nearby? Is pesticidelplastic manufacturing conducted near the well site? Along with proper well location, proper well design and construction prevent wells from acting as conduits for vertical migration of contaminants into the groundwater. Basically, the pollution potential of a well equals how well it was constructed. Contamination can occur during the drilling process, and an unsealed or unfinished well is an avenue for contamination. Any opening in the sanitary seal or break in the casing may cause contamination, as can reversal of water flow. In routine well maintenance operations, corroded casing or screens are sometimes withdrawn and replaced, but this is difficult and not always successful. Simply constructing a new well may be cheaper. 11.9.1 TROUBLESHOOTING WELL PROBLEMS

During operation, various problems may develop. For example, the well may pump sand or mud. When this occurs, the well screen may have collapsed or corroded, causing the screen's slot openings to become enlarged (allowing debris, sand and mud, to enter). If the well screen is not the problem, the pumping rate should be checked; the pumping rate may be too high. Let's take a look at a few other well problems, their probable causes, and the remediation required. Water is white-pump might be sucking air-reduce pump rate Water rushes backwards when pump shuts off--check valve, may be leaking Decrease in well yield --check static water level. A downward trend in static water level suggests that the aquifer is becoming depleted. This could be the result of the following: -local overdraft-well spacing too close -general overdraft-pumpage exceeds recharge -temporary decrease in recharge---dry cycles -permanent decrease in recharge-less flow in rivers --check specific capacity-if it has dropped 1 0 4 5 percent take steps to determine cause; may be a result of incrustation J Incrustation occurs when clogging, cementation, or stoppage of a well screen and waterbearing formation occurs. Incrustations on screens and adjacent aquifer materials result from chemical or biological reactions at the air-water interface in the well. The chief encrusting agent is calcium carbonate, which cements the gravel and sand grains together. Incrustation could also be a result of carbonates of magnesium, clays and silts, or iron bacteria. Treatment involves pulling the screen and removing incrusted material, replacing the screen, or treating the screen and water-bearing formation with acids. If severe, treatment may involve rehabilitating the well.

-pump rate is dropping, but water level is not-probable cause is pump impairment -impellers might be worn -may be a change in hydraulic head, against which the pump is working. Head may change as a result of corrosion in the pipelines, higher pressure setting, or maybe a new elevated tank

150

WELL SYSTEMS

11 .l0 WELL ABANDONMENT In the past, common practice was simply to abandon a well when it ran dry. Today, while dry or failing wells are still abandoned, we know that they must be abandoned with care. An abandoned well can become a convenient (and dangerous) receptacle for wastes, thus contaminating the aquifer. An improperly abandoned well could also become a haven for vermin, or worse, a hazard for children. A temporarily abandoned well must be sealed with a watertight cap or wellhead seal. The well must be maintained so that it does not become a source or channel of contamination during temporary abandonment. When a well is permanently abandoned, all casing and screen materials may be salvaged. The well should be checked from top to bottom to assure that no obstructions interfere with plugging1 sealing operations. Prior to plugging, the well should be thoroughly chlorinated. Bored wells should be completely filled with cement grout. If the well was constructed in an unconsolidated formation, it should be completely filled with cement grout or clay slurry introduced through a pipe that initially extends to the bottom of the well. As the pipe is raised, it should remain submerged in the top layers of grout as the well is filled. Wells constructed in consolidated rock or that penetrate zones of consolidated rock can be filled with sand or gravel opposite of zones of consolidated rock. The sand or gravel fill is terminated five feet below the top of the consolidated rock. The remainder of the well is filled with sand-cement grout.

11 .l1 SUMMARY Water utilities employ wellhead protection programs to prevent groundwater contamination, protecting the public water supply. Surface water supplies require protection as well, watershed protection, which we discuss in Chapter 12.

11 .l2 CHAPTER REVIEW QUESTIONS 11-1 When water is drawn out of a well, a

of

will develop.

11-2 How far should the well casing extend above the ground or well-house floor?

11-3 A well casing should be grouted for at least 10 feet, with the first 20 feet grouted with

11-4 Identify the items indicated in Figure 11.2.

Figure 11.2 Components of a well.

Chapter Review Questions

11-5 Explain incrustation.

CHAPTER 12

Watershed Protection

To waste, to destroy, our natural resources, to skin and exhaust the land instead of using it so as to increase its usefulness, will result in undermining in the days of our children the very prosperity which we ought by right to hand down to them amplified and de~eloped.~

12.1 INTRODUCTION ATER regulates population growth, influences world health and living conditions, and determines biodiversity. For thousands of years, people have tried to control the flow and quality of water. Water provided resources and a means of transportation for development in North America and placed limits on that development in some areas. Even today, the presence or absence of water is critical in determining how we can use land. Yet, despite this long experience in water use and water management, humans often fail to manage water well. Sound water management was pushed aside in rapid, never-ending economic development in many countries. Often, optimism about the applications of technology (e.g., dambuilding, wastewater treatment, or irrigation measures) exceeded concerns for, or even interest in, environmental shortcomings. Pollution was viewed as the inevitable consequence of development, the price that must be paid to achieve economic progress. Clearly, we now have reached the stage of our development when the need for management of water systems is apparent, beneficial, and absolutely imperative. Raw water quality is directly impacted by land use and activities in the watershed. Effective watershed management improves raw water quality, controls treatment costs, and provides additional health safeguards. Depending on goals, watershed management can be simple or complex. This chapter discusses the need for water management on a watershed basis and provides a brief overview of the range of techniques and approaches that can be used to investigate the biophysical, social, and economic forces affecting water and its use. Water utility directors are charged with providing potable water in a quantity and quality to meet the public's demand. They are also charged with providing effective management on a holistic basis of the entire water supply system; such management responsibility includes proper management of the area's watershed.

W

J Key Point: Integrated water management means putting all of the pieces together, including considering social, environmental, and technical aspects. '~heodoreRoosevelt, Message to Congress, December 3, 1907.

154

WATERSHED PROTECTION

12.2 WATER MANAGEMENT CURRENT ISSUES9 Remarkable consensus exists among experts (who come from countries around the globe) over the current issues confronted by waterworks managers and others. These issues include the following:

(1) Water Availability, Requirements, and Use protection of aquatic and wetland habitat management of extreme events (droughts, floods, etc.) excessive extractions from surface and groundwaters global climate change safe drinking water supply waterborne commerce (2) Water Quality coastal and ocean water quality lake and reservoir protection and restoration water quality protection, including effective enforcement of legislation management of point- and nonpoint-source pollution impacts on landlwaterlair relationships health risks (3) Water Management and Institutions coordination and consistency capturing a regional perspective respective roles of federal and statelprovincial agencies respective roles of projects and programs economic development philosophy that should guide planning financing and cost sharing information and education appropriate levels of regulation and deregulation water rights and permits infrastructure population growth water resources planning, including --consideration of the watershed as an integrated system -planning as a foundation for, not a reaction to, decision making --establishment of dynamic planning processes incorporating periodic review and redirection -sustainability of projects beyond construction and early operation -a more interactive interface between planners and the public -identification of sources of conflict as an integral part of planning -fairness, equity, and reciprocity between affected parties

12.3 WHAT IS A WATERSHED? A watershed is a protected, reserved area, usually distant from the treatment plant, where natural or artificial lakes are used for water storage, natural sedimentation, and seasonal pretreatment, with ' ~ d a ~ t efrom d W. Viessman, Jr. Water management issues for the nineties. WaterResources Bulletin 26(6): 883-891, 1991;A. S. Goodman. Integrated water resources planning. Natural Resources Forurn. 16(1): 65-70, 1992;J. E. Nickum, and K. W. Easter. Institutional arrangements for managing water conflicts in lake basins. Natural Resources Forum. 14(3): 210-220, 1990.

155

Watershed Protection and Regulations

or without disinfection. A watershed is also defined as a collecting area into which water drains. Watersheds are associated with surface water (usually fed by gravity) to distinguish them from groundwater (usually fed by pumping). J The USEPA's watershed protection approach: "integrated, holistic strategy for more effectively restoring and protecting aquatic ecosystems and protecting human health (e.g., drinking water supplies and fish consumption)."

12.4 WATER QUALITY IMPACT For a typical river system (and generally speaking), water quality is impacted by about 60 percent nonpoint pollution, 21 percent municipal discharge, 18 percent industrial discharge, and about 1 percent sewer overflows. Of the nonpoint pollution, about 67 percent is from agriculture, 18 percent urban, and 15 percent from other sources. Land use directly impacts water quality. The impact of land use on water quality is clearly evident in Table 12.1. J From the waterworks operator point of view, water quality issues for nutrient contamination can be summarized quite simply:

(1) Nutrients (2) Nutrients

+ algae = taste and odor problems + algae + macrophytes + decay = THM precursors

12.5 WATERSHED PROTECTION AND REGULATIONS

The Clean Water Act and Safe Drinking Water Act Reauthorization addresses source water protection. Implementation of regulatory compliance requirements (with guidance provided by the U.S. Department of Health) is left up to state and local health department officials to implement. Water protection regulations in force today not only provide guidance and regulation for watershed protection, they also provide additional benefits for those tasked with managing drinking water utilities. The typical drinking water utility (which provides safe drinking water to the consumer) has two choices in water pollution control: "Keep it out or take it out." The "keep it out" part pertains to watershed management, of course, otherwise, if the water supply contains contaminants, they must be removed by treatment, "take it out." Obviously, utility directors and waterworks managers are concerned with controlling treatment costs. An effective watershed management program can reduce treatment costs by reducing source water contamination. The "take it out" option is much more expensive and time consuming than keeping it out in the first place. TABLE 12.1.

Sediment Urban Agriculture Logging Industrial Septic Tanks Construction

Land Use Directly Impacts Water Quality. Nutrients

Viruses, Bacteria

THM

Fe, Mn

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X X

X

X

X

156

WATERSHED PROTECTION

Proper watershed management also works to maintain consumer confidence. If the consumer is aware that the water source from the area's watershed is of the highest quality, then logically, confidence in the quality of the water is high. High-quality water also works directly to reduce public health risks.

12.6 HOW TO DEVELOP A WATERSHED PROTECTION PLAN Watershed protection begins with planning. The watershed protection plan consists of several elements, which includes the need to: inventory and characterize water sources identify pollutant sources assess vulnerability of intake establish program goals develop protection strategies implement program monitor and evaluate program effectiveness

12.7 RESERVOIR MANAGEMENT PRACTICES To ensure an adequate and safe supply of drinking water for a municipality, watershed management includes proper reservoir management practices. These practices include proper lake aeration, harvesting, dredging, and use of algicide. Water quality improvements from lake aeration include reduced iron, manganese, phosphorus, ammonia, and sulfide content. Lake aeration also reduces cost of capital and operation for water supply treatment. Algicide treatment controls algae, which in turn reduces taste and odor problems. The drawback of using algicides is that they are successful for only a brief period.

12.8 WATERSHED MANAGEMENT PRACTICES Watershed management practices include land acquisition, land use controls, and best management practices (BMPs). Land accession refers to the purchase of watershed lands-those land areas that form the watershed for a particular locality. The advantage of ownership of lands included within a particular watershed are obvious; the owner (in this case, the local utility) has better control of land use, and thus can effect protective measures for ensuring a quality water supply. Land use controls (those measures deemed necessary to protect the watershed from contamination andlor destruction) vary from location to location. For example, land use controls may be designed to prohibit mining or other industrial activities from taking place within the watershed, for protection of the water supply. Best management practices (BMPs) for watershed management refer specifically to agriculture, logging, urban, and construction practices. The chief problem with best management practices is that they are nonstructural measures. They are often hard to implement because they require people to change the way they behave. In agricultural systems, best management practices may include measures such as conservation tillage and contour plowing, confined animal facility management (contain or use waste on-site and keep animals out of waterways), and appropriate pesticide and herbicide application practices (minimize use or use alternative chemicals).

Chapter Review Questions

157

Examples of logging BMPs include construction of streamside buffer zones to protect the water course. Logging plans should also incorporate water quality and habitat planning. Urban BMPs revolve around targeted categories such as reduction of impervious areas (reducing tarrnac, asphalt-covering and cement-covering to allow for precipitation infiltration), non-stormwater discharges, and proper disposal of residential chemicals. The primary types of BMPs used include public education programs, inspections and enforcement, structural controls (end-of-pipe solutions, which seek to treat or remove pollution that has already occurred) and preventive options, which are implemented to prevent or reduce the creation of waste within a process). Examples of construction BMPs include enforcement of stormwater pollution prevention plans and inspections. Types of construction BMPs include erosion and sediment control (i.e., minimize clearing, stage construction, and stabilize stockpiles and finished areas) and chemical control (i.e., proper storage, handling, application and covering, and isolation of materials).

12.9 SUMMARY The foundation for successfully implementing best management practices in watershed protection is public education and awareness-getting the consumer (whether agricultural, industrial, or household) directly concerned with their own responsibility toward keeping the water supply clean. After all, the watershed they help to protect provides their water. How that water arrives at the consumer's door (via the water distribution and storage system) is the subject addressed in Chapter 13.

12.10 CHAPTER REVIEW QUESTIONS 12-1 Define watershed.

12-2 Another name for watershed is 12-3 Explain "keep it out" or "take it out."

12-4 What is the purpose of algicide in reservoir management?

12-5 What is BMP?

12-6 What are BMPs in regard to agricultural systems? urban? construction?

CHAPTER 13

Distribution and Storage

Possibly the most neglected and certainly the least visible component of a water utility is its distribution system. . . . storage of potable waterfor drinking purposes is and has been a prerequisite to survival of man throughout history. Early man used only such containers as he could carry on his person and those were generally made of animal skins, or organs. Development of other forms of transportation, such as boats and ox carts, allowed man to handle greater quantities of water and to use more substantial containers such as barrels and clay pots. Even at this point, water was stored strictly for drinking purposes, since those places to which most travelers were headed, had no dependable source of supply. Loss of any portion of the stored water could jeopardize the lives of all the travelers. Most such travelers were merely looking for another piece of ground where adequate water existed to meet the needs of theirfamilies and their livestock. Today'spopulation densities are such that it is not generally possible to obtain sources of supply of great enough capacity to meet the short-termpeak demand needs of most municipalities. For this reason, it is necessary to provide storage facilities sufJicient to store water to meet these short-term peak demands and allow relatively constant pumping rates from the source(s) of supply, be itfrom sur$ace water treatmentfacilities, wells, or both.I0 13.1 DISTRIBUTION S the name implies, a water distribution system includes the network of pipes, valves, fire hydrants, meters, and other associated appurtenances used to distribute water to locations for consumer use. The distribution system is installed for two definite functions: (1) to deliver adequate quantities of water to customers, and (2) to deliver high quantities of water when needed for fire protection. In short, a water distribution system should be capable of meeting the demands placed on it at all times and at satisfactory pressures. The distribution system for small water systems may be as simple as a single-building plumbing system or as complex as an extensive system serving a small community. In our experience, many of the violations of the USEPA Drinking Water Standards and various state waterworks regulations are related to poor operation and maintenance of the water distribution system or to the presence of sanitary defects in the distribution system. When planning the construction or extension of a water distribution system, generally, a minimum of six (though more are possible) decisions must be made, including the following:

A

(1) Determination of water demands in various segments of the system (2) Design of the system to take fire protection, if planned, into account ''From J. P. Reames' The Distribution System (p. 334) and M. V. Lowry's Storage of Potable Water (p. 495),in C. K. Foster's (ed.). Manual of Water Utility Operations. Austin, Texas: Texas Water Utilities Association, 1988.

160

DISTRIBUTION AND STORAGE

(3) Determination of the elevation differences throughout the service area as they will affect static pressure; determination of whether pumping or additional storage is necessary (4) Assessment of advantages and disadvantages of piping materials; selection of most appropriate (5) Assessment of physical characteristics of soils, depth to rock and groundwater, frost penetration depth (6) Assessment of the water characteristics that may affect the choice of pipe and appurtenances Many considerations are of concern in the design of distribution systems: type of material used, size of mains, sizing and placement of storage reservoirs, inclusion of fire protection, location of valves, and many other equally important items. The primary consideration in designing, constructing, and operating a water distribution system is preserving water quality throughout. No component or activity in the distribution system should degrade the water quality below that existing at the source. Pressure. The system should be designed to supply adequate quantities of water at adequate pressure and operated to prevent conditions leading to the occurrence of pressures under 20 psi at any time. The system should never be operated in a way that will allow negative pressures to develop in the pipes. Cross-connections. Assuring that no connections occur between the water distribution system and any sewer, storm drain, ditch, or other source of water contamination is essential. We discuss crossconnection in more detail in Chapter 14. Looping. Looped water mains allow the water to circulate freely, entering specific segments of pipe from either end as necessary. In a looped (or gridded) system, a water main closed down for repair or maintenance affects a minimum number of consumers. A dead-end pipe can cause deterioration of water quality from stagnation, and all customers on the line may be affected by a problem at the feed end.

13.1.l PIPED DISTRIBUTION SYSTEM In the past, many types of materials have been used to convey water from one point to another. Wood and masonry were probably the first materials used, and the newest, synthetics like plastics, are now being used quite extensively. Pipe size is related to flow rate and length of run. At present, water mains used extensively are made of the following materials: Galvanized Not recommended for underground piping, subject to corrosion from soil and water. Copper Heavy types are used underground, lighter types are only used in building plumbing; copper materials are less sensitive to corrosion. Plastic Corrosion resistant; several types specifically meant for waterworks use (polyvinyl chloride, polyethylene, polybutylene), must meet standards of the National Sanitation Foundation (NSF). Cast iron/ductile iron Corrosion resistant; good hydraulic characteristics, durable; should be lined with cement mortar to avoid corrosion. Asbestos-cement (Transite) No longer manufactured, but a lot is still in use. Corrosion resistant; lightweight, easily cut, but easily broken. Lead Used in older systems, particularly as service lines. No longer approved; any system with lead piping should make immediate plans to replace it. Common practice in the past was to install water lines as needed. As the community grew, the water distribution system grew along with it. The result of this practice is that mains develop in

Distribution

161

a more or less haphazard manner. Eventually, the mains must be reinforced or replaced to access new service areas. Good practice plans waterworks facilities for a period of not less than 20 to 30 years, estimating the population that must be served at the end of that period of time. A definite plan for future extension is valuable, particularly if the plan is properly used and updated as needed. In planning water distribution systems, ensuring that pipes are looped to minimize dead ends and allow water to circulate is important, as is providing a fire hydrant or blowoff at all dead ends. Water lines must be separated from sewer lines. For parallel lines, horizontal separation of 10 feet is required (may be closer if bottom of water line is 18 inches or more above the top of the sewer). Pipes that cross the bottom of the water line must be 18 inches or more above the top of the sewer. A piped distribution system can vary from simple to extremely complicated. Most piped systems have the same basic components: pipes, valves, fire hydrants, meters, thrust blocks and anchors (to protect against pipe movement), service connections, and reservoirs.

13.1.l .l Valves A sufficient number of properly located valves is essential to the proper distribution system operation. Valves control water flow and backflow, adjust water pressures and levels, and isolate sections of distribution system for repair. Valve types include the following: Shut-ofsvalves Stop the flow of water (usually gate valves or butterfly valves; smaller lines may use globe valves) Check valves Permit water to flow in one direction only; used on pump discharges, between pressure zones (Note:not acceptable for backflow prevention). Flow control valves Provide uniform flow at varying pressures. Relief valves Allow water to escape from the system to relieve excessive pressure, or allow air to enter the system to relieve vacuum Float valves Respond to water levels to open or close a pipe Blowoff valves Provide a means to flush sediment from low points and dead ends in the distribution system Altitude valves Used to shut off flow of water into storage tank at a preset level to avoid overflow Air relief valves Used at high points to release entrapped air J Access to main line valves on piped systems is through a valve box. Valve boxes are made of cast iron, concrete, or PVC with a cast-iron lid. Valve pits must drain to the surface or to a seepage pit; there are no connections to sewers.

13.1.l .2 Fire Hydrants The primary function of a fire hydrant is to provide access to water for fire suppression. Fire hydrants can also be used for secondary functions such as access to water for construction, access to water for other utilities such as street cleaning and sewer cleaning, and as an access point for testing the distribution system's flow capabilities. They also provide flushing ports. Fire hydrants should be spaced to conform with requirements of the American Insurance Association. The hydrants should be inspected at least twice, and preferably four times, a year. Fire hydrant drain valves drain to dry wells, with no connection to sewers.

162

DISTRIBUTION AND STORAGE

1 3.1.l .3 Water Meters Because the operation of a public water supply is a business, the amount of product produced as well as how much of it is received by each customer (for customer billing) must be known for the business to operate efficiently. In short, water meters are used to monitor flow through various sections of distribution system to provide regulation, reimbursement, and maintenance information. Meter pits cannot drain to sewers.

13.1.2 SELECTION OF PIPE SIZES Selection of adequate pipe sizes ensures an adequate supply of water to consumers at satisfactory pressures. If the piping is undersized, large pressure losses reduce the delivery pressure, reduce the volume of water available to customers, and increase the potential for backflow. Various state waterworks regulations specify requirements for minimum pipe sizes. Generally (in many locations), 4-inch diameter is the minimum size allowable, although 3- and 2-inch may be appropriate for short dead-end lines. If fire protection is provided, the water lines must be at least 6 inches in diameter.

13.1.3 DISTRIBUTION SYSTEM DISINFECTION Probably the most commonly omitted or ignored waterworks operation is disinfecting new water pipe installations. Any time a new water pipe is installed or an existing one is opened to the air during repairs, it should be disinfected. Three techniques (as recommended by the American Water Works Association) are used for disinfecting water mains. Except for the tablet method, the pipe should be thoroughly flushed at 2.5 ftlsec water velocity; all valves and hydrants should be operated while the pipe is being flushed. Continuous Feed. Introduce potable water at a constant flow and add chlorine at a dose of 50 mg/L. Let the chlorinated water stand for 24 hours, after which the chlorine residual should be at least 10 mg/L. Operate all valves while the chlorinated water is in the pipe. Then, thoroughly flush the main and send a sample to the state laboratory for a bacteriological examination. If the water does not meet the accepted standard, the procedure must be repeated and efforts continued until the desired potable water is obtained. Slug Method. Introduce potable water at a constant flow and add chlorine to produce a "slug" of water with a 100 mg/L chlorine concentration long enough to assure that all parts of the pipe are exposed to a 100 mg/L concentration of chlorine for at least three hours. Check the chlorine residual along the pipe at least every 2,000 feet. Operate all valves while the chlorinated slug is passing. Tablet Method. Another convenient and effective way to disinfect mains, especially for small jobs, is to use calcium hypochlorite (HTH) tablets. This method cannot be used if the pipes have any nonpotable water or foreign matter in them or if the water temperature is less than 5°C (41"F). Place tablets in each pipe section and in all appurtenances and use enough tablets to provide a chlorine concentration of at least 25 mg/L. Attach the tablets to the crown of the pipe with an approved adhesive or crush or rub the tablets in all appurtenances. Fill the pipe with potable water at a fill velocity of less than 1 foot per second. Maintain contact with the chlorinated water for at least 24 hours. When the required contact time has passed, flush the pipes with potable water to remove the heavily chlorinated water. Flushing is complete when the chlorine residual in the pipe is approximately the same as that in the potable water used for the flush. Collect bacteriological samples along the pipe, not more than 2,000 feet apart. Do not place the line in service until negative bacteriological reports are received from the laboratory. If the tests show the presence of coliform bacteria, repeat the procedure.

Tank Maintenance and Inspection

163

13.1.4 WATER MAIN LEAKAGE Even properly installed water mains deteriorate over time. Practically all distribution systems have some leakage or a certain percentage of unaccounted-for water. Unaccounted-for water in excess of 15 percent is considered unacceptable, and any sudden increase in the percentage should signal the need for a search for leaks. Whenever a new main is installed, it should be completely tested for leakage. After covering the main, a test should be made with water under p ressure, usually at least 50 psi greater than normal operating pressure. In a new main, the leaks should be less than 25 gallons per 24 hours per mile of pipe per inch of nominal diameter for 12 foot lengths and 10 gallons for 16 foot lengths.

13.2 STORAGE Water storage facilities for water distribution systems are required primarily to provide for fluctuating demands of water usage (to provide a sufficient amount of water to average or equalize daily demands on the water supply system). In addition, other functions of water storage facilities include increasing operating convenience, leveling pumping requirements (to keep pumps from running 24 hours a day), decreasing power costs, providing water during power source or pump failure, providing large quantities of water to meet fire demands, providing surge relief (to reduce the surge associated with stopping and starting pumps), increasing detention time (to provide chlorine contact time and satisfy the desired CT values requirements), and blending water sources.

13.3 TYPES OF STORAGE Six basic types of storage facilities are commonly used; those built with all or most of the storage vessel below ground (reservoir or clear well), those built at ground level, those elevated above the ground (elevated tanks or standpipes), and hydropneumatic tanks (tanks that are pressurized with air). Clear wells. Used to store filtered water from a treatment plant. Also used as chlorine contact tanks (see Figure 13.1). Elevated tanks. Located above the service zone and used primarily to maintain an adequate and fairly uniform pressure to the service zone (see Figure 13.2). Standpipes. Standpipes are tanks that stand on the ground and have a height greater than their diameter (see Figure 13.3). Ground-level reservoirs. Located above service area to maintain the required pressures (see Figure 13.4). Hydropneumatic or pressure tanks. Usually used on small water systems such as with a well or booster pump. They are constructed of steel or fiberglass. These tanks are pressurized by a pump or a pump and air compressor. The tanks commonly contain 113 air and 213 water. The air is compressed when the tank is filled, acting like a big spring. When the pump shuts off, the air is used to push the water out of the tank (see Figure 13S ) . Surge tank. Not necessarily a storage facility, but often used to control water hammer or to regulate the flow of water (see Figure 13.6).

13.4 TANK MAINTENANCE AND INSPECTION The problems of and need for tank maintenance and inspection must be recognized by waterworks operators primarily for three reasons: (1) to verify the physical condition of the tank, (2) to verify that sanitary conditions are being maintained in the tank, and (3) to ensure proper maintenance and repair activities are performed to maintain the integrity of the tank system.

From Water Treatment Plant or Transmission System

Clear Well

Figure 13.1 Clear well.

Figure 13.2 Elevated storage tank.

To Distribution

Figure 13.4 Ground-level service storage reservoir.

Air Chamber

To Distribution System Figure 13.6 Surge tank.

DISTRIBUTION AND STORAGE

13.5 SUMMARY Water storage and distribution are essential parts of getting water to the consumer. Ensuring that the water arrives to the consumer in a safe and clean condition is part of the water operator's responsibility. In Chapter 14, we discuss the biggest potential risk of contamination in the distribution system-cross connection.

13.6 CHAPTER REVIEW QUESTIONS 13-1 What is the primary (or definite) function of a water distribution system?

13-2 List five types of materials that have been used to convey water.

13-3 The pressure in a water distribution system should never drop below

13-4 Describe the ways in which a new water main can be disinfected.

13-5 What is unaccounted-for water?

13-6 A hydropneumatic tank contains

% air.

psi.

CHAPTER 14

Cross Connection Control

The greatest potential hazard in distribution systems is associated with cross-connections to nonpotable waters. There are many connections between potable and nonpotable systemsevery toilet constitutes such a connection-but cross connections are those through which backflow can occul: Facilities which are particularly likely to have cross-connectionsthrough which dangerous materials can enter the distribution system include hospitals, metal plating and chemical plants, car washes, laundries, and dye works.l'

14.1 INTRODUCTION

of the primary functions of the waterworks operator is to ensure that water under his or her care is kept from being contaminated. Putting great effort into treating water for public consumption, then allowing it to become contaminated before it is used makes little sense. However, after having stated the obvious, we point out that water contamination is not always so obvious, and often prevention of contamination is beyond the waterworks operator's control. Most water practitioners agree that a public water distribution system can become contaminated in many obvious ways. However, the water supply can become contaminated in ways that are not so obvious (even if beyond the operator's control, these still present a double-edged sword). For example, consider the less publicized, but potentially as dangerous, cross-connection problems that occur at the customer's service connection.Potentially deleterious plumbing connections at schools, water treatment plants, wastewater treatment plants, and private facilities can allow water contaminated with sewage or chemicals to flow backwards into a water system. In small communities, possible sources of contamination that could flow into the water system are associated with swimming pools and wastewater treatment plants, including chemicals such as chlorine and fluoride and boiler chemicals. For large municipalities, millions of uncontrolled cross-connections could exist within customers' premises.

0

NE

J Key Term:A cross-connectionis any physical arrangement whereby a public water supply is connected, directly or indirectly, with a nonpotable or unapproved water supply or system.

J Key Point: The probability of cross-connectionproblems is not determined by the length of drinking water pipelines, but by the complexity of "other" water lines or nonpotable lines, such as airconditioned cooling systems, roof or intermediate water storage tanks feeding nonpotable lines, and complex hot and cool water lines. Anticorrosion chemicals used to treat cooling towers are the most likely to produce contamination from cross-connections. "From G. 1. Angele, Sr.'s Cross Connections and Backjlow Protection, 2nd ed., Denver: American Water Works Association, 1974.

170

CROSS-CONNECTION CONTROL

A health risk exists if drinking water systems connect directly or indirectly to contaminated sources. Should a person become ill due to backflow of contaminants through a service connection, the water purveyor could be liable. Keep in mind that purveyors commit an unlawful act when they install or maintain a service connection to a customer's water system with knowledge that crossconnections occur or could occur on the premises. Thus, though perhaps not obvious, and beyond the control of the purveyor, ultimately, the control of such cross-connections is the responsibility of the purveyor (the double-edged sword). During the last few decades, public health officials employed by the Health Authorities have developed a new field of specialization to prevent the occurrence of contaminated water supplies. This chapter provides reference to the contamination of potable water systems from uncontrolled cross-connections and presents information needed to implement an effective cross-connection control program.

14.2 CROSS-CONNECTION CONTROL

To understand cross-connection control, we must define the key terms used. As defined earlier, a cross-connection is a physical arrangement, link, or channel connecting a possible source of contamination with a potable water supply. A liquid is the most likely source of contamination (i.e., oil, plating acid, sewage, groundwater, or water that has left the control of the waterworks and whose quality is now questionable). The cross-connection can only cause a problem if a reversal of flow in the system occurs. This reversal or backwards flow (or simply, backflow) refers to the flow of undesirable material into a potable water supply. Backflow occurs when a pressure differential forces flow in the direction of the potable supply. J Backflows occur when two factors are present: (1) a physical link between the undesirable material and the potable supply, and (2) a driving force toward the potable supply.

In Chapter 9 (Basic Hydraulics), we pointed out that the movement of water is subject to the principles of hydraulics. Generally, the driving force that causes backflow is pressure, sometimes high pressures such as those provided by pumps but often merely atmospheric pressure. The term backpressure is generally applied to the reverse flow of a liquid caused by a pressure higher than atmospheric into a pressurized potable water supply. More specifically, backpressure exists any time the pressure in the contaminated source exceeds the pressure in the distribution system. Backpressure could happen as a result of a booster pump in a heating system or excessive pressures in a boiler that is improperly connected to the potable water supply (see Figure 14.1). Besides a backpressure condition, backflow can occur through backsiphonage. Backsiphonage occurs when the pressure in the system drops below atmospheric pressure (essentially forming a vacuum), and the water distribution system is connected to a nonpotable source open to the atmosphere. This could occur if the distribution system pressure were lowered as a result of a break or heavy use such as during a fire. 14.2.1 CROSS-CONNECTIONS In water piping systems, two basic types of cross-connections can be created: (1) a solid pipe with a valved connection (usually made to continuous or intermittent waste lines) and (2) a submerged inlet (commonly found on plumbing fixtures and in many temporary situations). In a water system, either type may be found, but submerged inlet cross-connections are often more difficult to find and correct than solid-piped connections.

Cross-Connection Control

Figure 14.1 Failure of the check valve would allow boiler feed water (with chemicals) to enter the drinking water system.

14.2.2 CROSS-CONNECTION PREVENTION

Cross-connection prevention is regulated by each state's drinking water regulations. In our experience, however, while regulations are easy enough to put on the books, ensuring compliance is much more difficult. Because inspection of facilities is difficult, time-consuming, and not always possible, compliance is not absolute. To solve this problem, the waterworks industry has taken a preventive approach to cross-connection control. Under this approach, facilities with a high potential of cross-connection or that handle highly hazardous materials are required to protect the water system. 14.2.2.1 Prevention Measures

The most effective method of avoiding backpressure backflow is total or complete separation of the two piping systems. If maintaining a physical connection between the systems is not necessary, mechanical devices called backflow preventers or backflow prevention devices (i.e., specialized valves that provide multiple levels of protection against backflow) can be used. 14.2.2.2 Backflow Prevention Devices

Several varieties of backflow prevention devices can be used to prevent backsiphonage and backpressure backflow. The devices used to prevent backflow from a potential cross-connection are as follows: air gaps atmospheric vacuum breakers pressure vacuum breakers double check valve assemblies reduced pressure backflow prevention device assemblies Generally, the selection of the proper device for a particular application depends on the degree of hazard posed by the cross-connection (e.g., a high-hazard facility would include a sewage treatment

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plant pumping station; a low level of hazard would be a situation where the odor and taste of the water might be affected, but no health risk could occur). Plumbing arrangements in the facility and the use of additional devices with the facility, piping size, location, and the need for periodical testing and maintenance are also considerations.

J To be acceptable for use in a public water supply system, the devices must be manufactured to the standards of the American Society of Sanitary Engineers (ASSE), the American Water Works Association (AWWA), or The Foundation for Cross-Connection Control and Hydraulic Research (University of Southern California).

14.2.2.2.1 Air Gaps The air gap is a nonmechanical backflow preventer that provides the greatest degree of protection against backpressure and backsiphonage. The air gap is easy to observe and inspect and is a positive way to protect the water supply from a chemical vat, for example. Generally, the air gap must be twice the inside diameter of the water supply pipe, but never less than one inch (see Figure 14.2). Air gaps can be used on high-hazard connections. The problem with air gaps is that, though extremely effective, they also interrupt the piping flow, eliminating the system pressure, which might be needed past the air gap. Air gaps are only practical at the ends of piping lines, where storage tanks are used, or where there is a provision for repressurizing the water with a pump. Air gaps should be frequently inspected to assure that they have not been compromised with pipe extensions or hoses.

14.2.2.2.2 Atmospheric Vacuum Breakers Atmospheric vacuum breakers are among the simplest and least expensive mechanical backflow preventers. They are used on low-degree hazard conditions such as lawn sprinkler systems, janitor sinks, and supply lines on low concentration chemical vats, such as chlorine and fluoride solutions. When they are installed properly, they can provide excellent protection against backsiphonage. Atmospheric vacuum breakers open when a backsiphonage occurs and allow air to be drawn into the line, preventing a backflow of the downstream solutions. However, they cannot be used to protect against backpressure. Construction usually consists of a plastic float that is free to travel on a shaft (see Figure 14.3). When water is flowing through it, the float seals against an atmospheric vent. Water pressure keeps the float in the upward position. When water pressure drops to zero, the float disc drops, venting the unit and opening the downstream piping to the air. This breaks the siphon in the piping.

J Note: A downstream valve cannot be installed on an atmospheric vacuum breaker. 14.2.2.2.3 Pressure Vacuum Breakers The pressure vacuum breaker also provides protection against backsiphonage and not against backpressure, but may also be used in situations where it is subjected to constant pressure, such as in locations with a downstream shutoff valve. Pressure vacuum breakers are used for the same functions as an atmospheric vacuum breaker, though there are differences between the two. For example, the pressure vacuum breaker has an internal spring that helps it open, valves allow the device to be tested, and a valve can be placed in the downstream line.

D = Diameter -W

4

Figure 14.2 Typical air gap.

Figure 14.3 Atmospheric vacuum breaker.

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CROSS-CONNECTION CONTROL

14.2.2.2.4 Double Check Valve Assemblies A double check valve assembly (DCVA) is composed of two independent, internally weighted check valves (springs), isolation valves on each side of the assembly, and test ports or cocks on the assembly that allow a tester to determine that the check valves are watertight. In low-hazard conditions, such as food processing steam kettles, apartment projects, and similar applications, the DCVA protects against backpressure or backsiphonage. 14.2.2.2.5 Reduced Pressure Device Reduced pressure devices are used for high-hazard conditions. They are essentially modified DCVAs with an atmospheric vent placed between the two check valves. The assembly also has an isolation valve on each end, as well as test ports to determine the proper operation of the assembly. The valve is designed so that the valve on the reduced pressure side (or zone) will open any time the pressure in the zone gets to within 2 psi of the supply pressure. If high pressure is applied to the reduced pressure zone through a fouled downstream check valve, the relief port opens, venting the backflowing liquid.

J Note: Because reduced pressure devices are generally installed in high-hazard locations where backflow is likely to cause injury, illness, or damage to the waterworks, they must be tested and inspected frequently (at least annually) to assure proper operation. 14.2.2.3 Testing Backflow Preventers

Those backflow preventers that can be tested (pressure vacuum breakers, double check valves assemblies, and reduced pressure backflow preventers) are equipped with shut-off gate valves and test cocks that allow them to be tested in-line. The devices must be tested once each year by a certified backflow prevention device tester. Air gaps are "tested" by visual inspection; atmospheric vacuum breakers can't be tested.

J CAUTION: Never install a bypass around a backflow preventer unless it is protected by the same type of device; such a bypass creates a new cross-connection.

14.3 CROSS-CONNECTION CONTROL PROGRAM

The Safe Drinking Water Act and various state waterworks regulations require all water purveyors to develop and enforce a cross-connection and backflow prevention program. In most states, this program must be approved by the Division of Water Supply Engineering before the waterworks can obtain an operation permit. The program must include the designation of an individual to be responsible for cross-connection inspection and to require at least annual inspections of backflow prevention devices. The individuals who conduct inspections and device maintenance, whether employed directly by the waterworks or by outside firms, should be certified as backflow preventer inspectors1 maintainers. Records should be kept on installing, inspecting, testing, and repairing backflow-prevention devices. Complete records are a waterworks entity's first line of defense against potential legal liability in case of public health problems resulting from a cross-connection.

Chapter Review Questions

175

14.4 SUMMARY Keeping water clean through the distribution system is essential. But first, before the water enters storage and distribution, it must be changed from its raw state to a potable state. We discuss the water treatment process in Chapter 15.

14.5 CHAPTER REVIEW QUESTIONS

14-1 What is the meaning of (a) backflow and (b) backsiphonage?

14-2 What is cross-connection?

14-3 Name the different devices used in backflow prevention and when each would be sufficient.

14-4 Cross-connection devices should be tested how often?

14-5 What would be the proper cross-connection control device for a sewage treatment plant?

CHAPTER 15

Water Treatment

Rising from ocean to sky, forming clouds, then raining back down to the earth, trickling and flowing in rivulets, in rivers, and even underground, water moves in a vast, immeasurable circle as broad as the earth and sky. As it washes and flows across the land, down mountainside and over city street, draining both farmland and your own backyard or neighborhood park, water bears with it the story of where it has been.12

15.1 INTRODUCTION N this chapter, we focus on the reasons for treatment, the basic theories associated with treatment processes, and on the unit processes that make up conventional treatment. Treatment systems are installed to remove those things that cause disease andor create nuisances. The basic goal of water treatment is to protect public health, with a broader goal to provide potable and palatable water. Water treatment works to provide water that is safe to drink and is pleasant in appearance, taste, and odor. In this text, we define water treatment as any unit process that changes the chemical, physical, or bacteriological quality of water with the purpose of making it safe for human consumption andor appealing to the consumer. Treatment also is used to protect the distribution system components from corrosion. Many water treatment processes are commonly used today. Treatment processes used depend upon the evaluation of the nature and quality of the particular water to be treated and the desired quality of the finished water. In water treatment unit processes employed to treat raw water, one thing is certain: as new USEPA regulations take effect, many more processes will come into use in the attempt to produce water that complies with all the regulations, despite source water conditions. Small water systems tend to use a smaller number of the wide array of unit treatment processes available, in part because they usually rely on groundwater as the source, and in part because small size makes many sophisticated processes impractical (i.e., too expensive to install, too expensive to operate, too sophisticated for limited operating staff). This chapter concentrates on those treatment unit processes usually found in conventional water treatment systems, and on corrosion control. We follow this format though entry-level certification as a water operator focuses primarily on small water systems, not necessarily on the conventional water treatment system. To perform their functions at the highest knowledge level possible, operators must understand the basic concepts and theories behind more complex water treatment systems. We provide the information needed for the entry-level operator and present information that lays the groundwork for

I

"From S. A. Lewis's Safe Drinking Water. San Francisco: The Sierra Book Club, 1996.

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Volumes I1 and I11 of this handbook series, which prepare water operators for certification at higher levels.

15.1.l PURPOSE OF WATER TREATMENT Again, the purpose of water treatment is to condition, modify, or remove undesirable impurities, to provide water that is safe, palatable, and acceptable to consumers. While this is the obvious reason for treating water, various regulations also require water treatment. Some regulations state that if the contaminants listed under the various regulations are found in excess of maximum contaminant levels (MCLs), the water must be treated to reduce the levels. If a well or spring source is surface influenced, treatment is required, regardless of the actual presence of contamination. Some impurities affect the aesthetic qualities of the water; if they exceed secondary MCLs established by USEPA and the state, the water may need to be treated.

15.1-2 REASONS FOR WATER TREATMENT If we assume that the water supply used to feed a small water supply system is groundwater (usually the case), a number of common groundwater problems may require water treatment. Keep in mind that water that must be treated for one of these problems will also exhibit several other problems. Among these problems are: bacteriological contamination hydrogen sulfide odors hard water corrosive water iron and manganese

15.1.3 STAGES OF WATER TREATMENT In Section 15.1, we stated that in this chapter we discuss the "conventional" model of water treatment. Figure 1.1 (see Chapter 1 and the various reiterations throughout this chapter) presents the "conventional" model water treatment process referred to in this text. Figure 1.1 clearly illustrates that water treatment is made up of various stages or unit processes combined to form one treatment system. Note that a given treatment facility may contain all of these unit processes or stages or any combination of them. One or more of these stages may be used to treat any one or more of the groundwater problems listed in Section 15.1.2. Also note that the model shown in Figure 1.1 does not necessarily apply to small water systems. In small water systems, water treatment may consist of nothing more than removal of water via pumping from a groundwater source to storage to distribution. In some small water supply operations, disinfection may be added because it is required (see Chapter 16). While the model shown in Figure 1.1 more than likely does not mimic the type of treatment process used in most small systems, we use it in this handbook for illustrative and instructive purposes, because higher level licensure requires you to learn these processes.

15.2 PRETREATMENT Simply stated, water pretreatment (also called preliminary treatment) is any physical, chemical, or mechanical process used before main water treatment processes. It can include screening, presedimentation, and chemical addition (see Figure 15.1). Pretreatment usually consists of oxidation or other treatment for the removal of tastes and odors, iron and manganese, trihalomethane precursors,

Pretreatment

Pretreatrnent Stage

Water

+ ,/,l Screening

I

Figure 15.1 Pretreatment.

or entrapped gases (like hydrogen sulfide). Treatment processes may include chlorine, potassium permanganate or ozone oxidation, activated carbon addition, aeration, and presedimentation. Pretreatment of surface water supplies accomplishes the removal of certain constituents and materials that interfere with or place an unnecessary burden on conventional water treatment facilities. Pretreatment processes include the fo1lowingl3: Removal of debris from water from rivers and reservoirs that would discharge or clog pumping equipment Destratification of reservoirs to prevent anaerobic decomposition that could result in reducing iron and manganese from the soil to a state that would be soluble in water. This can cause subsequent removal problems in the treatment plant. The production of hydrogen sulfide and other taste- and odor-producing compounds also results from stratification. Chemical treatment of reservoirs to control the growth of algae and other aquatic growths that could result in taste and odor problems Presedimentation to remove excessively heavy silt loads prior to the treatment processes Aeration to remove dissolved odor-causing gases such as hydrogen sulfide and other dissolved gases or volatile constituents, and to aid in the oxidation of iron and manganese, although manganese or high concentrations of iron are not removed in the detention provided in conventional aeration units Chemical oxidation of iron and manganese, sulfides, taste- and odor-producing compounds, and organic precursors that may produce trihalomethanes upon the addition of chlorine Adsorption for removal of tastes and odors J An important point to keep in mind is that in small systems, using groundwater as a source, pretreatment may be the only treatment process used. 15.2.1 PRETREATMENT GENERAL TREATMENT CONSIDERATIONS Pretreatment generally involves aeration or the addition of chemicals to oxidize contaminants that exist in the raw water. It may be incorporated as part of the total treatment process or may be located adjacent to the source before the water is sent to the treatment facility. ' ' ~ r o mW. J. O'Brien's & W. T. Ballard's Pretreatment of Surface Water Supplies in Manual of Water Utility Operations, 8th ed., C . K. Foster (ed.). Austin, Texas: Texas Water Utilities Association, 1988.

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15.2.1 .1 Aeration Aeration is commonly used to treat water that contains trapped gases (such as hydrogen sulfide) that can impart an unpleasant taste and odor to the water. Just allowing the water to rest in a vented tank will (sometimes) drive off much of the gas, but usually some form of forced aeration is needed. Aeration works well (about 85 percent of the sulfides may be removed) whenever the pH of the water is less than 6.5. Aeration may also be useful in oxidizing iron and manganese, oxidizing humic substances that might form trihalomethanes when chlorinated, eliminating other sources of taste and odor, or imparting oxygen to an oxygen-deficient water. J Note: Iron is a naturally occurring mineral found in many water supplies. When the concentration of iron exceeds 0.3 mg/L, red stains will occur on fixtures and clothing. This increases customer costs for cleaning and replacement of damaged fixtures and clothing.

Manganese, like iron, is a naturally occurring mineral found in many water supplies. When the concentration of manganese exceeds 0.05 m g k , black stains occur on fixtures and clothing. As with iron, this increases customer costs for cleaning and replacement of damaged fixtures and clothing. Iron and manganese are commonly found together in the same water supply. We discuss iron and manganese further in Section 15.2.3.

15.2.1.2 Chemical Addition When chemicals are used in the pretreatment process, they must be the proper ones, fed in the proper concentrations and introduced to the water at the proper locations. Determining the proper amount of chemical to be used is accomplished by testing. The operator must test the raw water periodically to determine if the chemical dosage should be adjusted. For surface supplies, this checking must be done more frequently than for groundwater (remember, surface water supplies are subject to change on short notice, while groundwaters generally remain stable). The operator must be aware of the potential for interactions between various chemicals and how to determine the optimum dosage (e.g., adding both chlorine and activated carbon at the same point will minimize the effectiveness of both processes, as the adsorptive power of the carbon will be used to remove the chlorine from the water). J Note: Sometimes using too much chemical can be worse than not using enough.

Prechlorination (distinguished from chlorination used in disinfection at the end of treatment) is often used as an oxidant to help with the removal of iron and manganese (see Section 15.2.3.2). However, currently, concern for systems that prechlorinate is prevalent because of the potential for the formation of total trihalomethanes (TTHMs), which form as a by-product of the reaction between chlorine and naturally occurring compounds in raw water.

J TTHMs such as chloroform are known or suspected to be carcinogenic and are limited by water and state regulations. The USEPA's TTHM standard does not apply to water systems that serve less than 10,000 people, but operators should be aware of the impact and causes of TTHMs. Chlorine dosage or application point may be changed to reduce problems from TTHMs.

Pretreatment

181

J To be effective, pretreatment chemicals must be thoroughly mixed with the water. Short-circuiting or slug flows of chemicals that do not come in contact with most of the water will not give proper treatment. All chemicals intended for use in drinking water must meet certain standards. Thus, when ordering water treatment chemicals, the operator must be assured that they meet all appropriate standards for drinking water use. Chemicals are normally fed with dry chemical feeders or solution (metering) pumps. Operators must be familiar with all of the adjustments needed to control the rate at which the chemical is fed to the water. Some feeders are manually controlled and must be adjusted by the operator when the raw water quality or the flow rate changes; other feeders are paced by a flow meter to adjust the chemical feed so it matches the water flow rate. 15.2.2 IRON AND MANGANESE REMOVAL

Iron and manganese are frequently found in groundwater and in some surface waters. They do not cause health-related problems but are objectionable because they may cause aesthetic problems. Severe aesthetic problems may cause consumers to avoid an otherwise safe water supply in favor of one of unknown or of questionable quality, or may cause them to incur unnecessary expense for bottled water. 15.2.2.1 Aesthetic Problems Caused by Iron and Manganese

We have already mentioned one problem attributable to the presence of iron and manganese in the water: color. Recall that iron may turn water reddish brown, while manganese can turn W ater black or very dark brown. Iron can also stain plumbing fixtures and laundry with brownish or reddish brown stains. Over time, laundry becomes gray and dull from iron and manganese. Other problems include turbidity, taste, bacterial growth, and economic concerns. Turbidity is associated with two problems related to water quality: water clarity and health-related problems. Turbidity (a condition in water caused by the presence of suspended matter, resulting in the scatter and absorption of light rays) causes soluble iron and manganese to precipitate or oxidize from soluble to insoluble forms, causing the water to become cloudy. Of greater concern is that turbidity is a health issue. While turbidity itself is not normally a health hazard, it indirectly creates a health hazard. Aesthetically, people avoid drinking turbid water and seek other drinking water sources. However, turbidity particles provide hiding places for microorganisms, reducing the possibility that they will be killed by a disinfectant such as chlorine. Turbidity also increases the amount of chlorine required (demand) while it reduces the amount of chlorine available to kill disease-causing (pathogenic) microorganisms. The presence of iron and manganese in water also causes taste problems. For example, beverages (especially heated beverages like tea and coffee) have a bitter taste when made with water with high iron and manganese levels. Bacterial growth is another problem related to the iron content of water. Iron bacteria are microorganisms that metabolize iron. When iron levels are high, iron bacteria flourish. Accumulations of iron bacteria reduce the hydraulic capacity of water distribution piping. Periodically, accumulations of decaying bacteria will slough off the pipe, imparting unpleasant taste and odor to the water. We mentioned earlier that economic concerns are linked to iron and manganese contamination of water. In addition to the aesthetic and economic concerns over consumer costs and increased chemical usage, iron and manganese problems affect a number of processing industries including textiles, dyes, and food processing, for example. Iron residue can cause buildups in pipes (tuberculation) that

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increase the pumping pressures required while they decrease the carrying capacity of the pipe. Pipes may become totally clogged. To avoid these problems, the USEPA and local health departments have set secondary MCLs for iron and manganese. While not enforceable (no penalties are incurred for exceeding these limits), water that exceeds secondary MCLs is generally not desirable and should be treated. J The secondary MCL for iron is 0.3 mg/L, and for manganese is 0.05 m g L

15.2.2.2 Iron and Manganese Removal Techniques

Chemical precipitation treatments for iron and manganese removal are called deferrization and demanganization. The usual process is aeration; dissolved oxygen is the chemical causing precipitation; chlorine or potassium permanganate may be required.

15.2.2.2.1 Precipitation Precipitation (or pH adjustment) of iron and manganese from water in their solid forms can be effected in treatment plants by adjusting the pH of the water by adding lime or other chemicals. Some of the precipitate will settle out with time, while the rest is easily removed by sand filters. This process requires the pH of the water to be in the range of 10-1 1. J While the precipitation or pH adjustment technique for treating water containing iron and man-

ganese is effective, note that the pH level must be adjusted higher (10-1 1 range) to cause the precipitation, which means that the pH level must then also be lowered (to the 8.5 range or a bit lower) to use the water for consumption.

1% X T . Z Oxidation One of the most common methods of removing iron and manganese is through the process of oxidation (another chemical process), usually followed by settling and filtration. These minerals can be oxidized by air, chlorine, or potassium permanganate. Each oxidant has advantages and disadvantages, and each operates slightly differently. We discuss each oxidant in turn. ( l ) Air To be effective as an oxidant, the air must come in contact with as much of the water as possible. Aeration is often accomplished by bubbling diffused air through the water, by spraying the water up into the air, or by trickling the water over rocks, boards, or plastic packing materials in an aeration tower. The more finely divided the drops of water, the more oxygen comes in contact with the water and the dissolved iron and manganese. We also discuss aeration in Section 15.2.3.2.5. (2) Chlorine This is one of the most popular oxidants for iron and manganese control because it is also widely used as a disinfectant; iron and manganese control by prechlorination can be as simple as adding a new chlorine feed point in a facility already using chlorine. It also provides a pre-disinfecting step that can help control bacterial growth through the rest of the treatment system. The downside to chlorine use, however, is that when chlorine reacts with the organic materials found in surface water and some groundwaters, it forms TTHMs. This process also requires that the pH of the water be in the range of 6.5 to 7; because many groundwaters are more acidic than this, pH adjustment with lime, soda ash, or caustic soda may be necessary when oxidizing with chlorine. (3) Potassium permanganate This is the best oxidizing chemical to use for manganese control removal. An extremely strong oxidant, it has the additional benefit of producing manganese

Pretreatment

183

dioxide during the oxidation reaction. Manganese dioxide acts as an adsorbent for soluble manganese ions. This attraction for soluble manganese provides removal to extremely low levels. The oxidized compounds form precipitates that are removed by a filter. Note that sufficient time should be allowed from the addition of the oxidant to the filtration step. Otherwise, the oxidation process will be completed after filtration, creating insoluble iron and manganese precipitates in the distribution system.

15.2.2.2.3 Ion Exchange While the ion exchange process is used mostly to soften hard waters (see Section 15.2.4.2.l), it will also remove soluble iron and manganese. The water passes through a bed of resin that adsorbs undesirable ions from the water, replacing them with less troublesome ions. When the resin has given up all its donor ions, it is regenerated with a strong salt brine (sodium chloride); the sodium ions from the brine replace the adsorbed ions and restore the ion exchange capabilities. 1XXXZ'.4 Sequestering

Sequestering or stabilization may be used when the water contains mainly low concentrations of iron, and the volumes needed are relatively small. This process does not actually remove the iron or manganese from the water but complexes (binds it chemically) it with other ions in a soluble form that is not likely to come out of solution (i.e., not likely oxidized).

15.2.2.2.5 Aeration The primary physical process uses air to oxidize the iron and manganese. The water is either pumped up into the air or allowed to fall over an aeration device. The air oxidizes the iron and manganese, that is then removed by use of a filter. The addition of lime to raise the pH is often added to the process. While this is called a physical process, removal is accomplished by chemical oxidation. 15.2.2.2.6 Potassium Permanganate Oxidation and Manganese Greensand

The continuous regeneration potassium greensand filter process is another commonly used filtration technique for iron and manganese control. Manganese greensand is a mineral (gluconite) that has been treated with alternating solutions of manganous chloride and potassium permanganate. The result is a sand-like (zeolite) material coated with a layer of manganese dioxide-an adsorbent for soluble iron and manganese. Manganese greensand has the ability to capture (adsorb) soluble iron and manganese that may have escaped oxidation, as well as the capability of physically filtering out the particles of oxidized iron and manganese. Manganese greensand filters are generally set up as pressure filters, totally enclosed tanks containing the greensand. The process of adsorbing soluble iron and manganese "uses up" the greensand by converting the manganese dioxide coating to manganic oxide, which does not have the adsorption property. The greensand can be regenerated in much the same way as ion exchange resins, by washing the sand with potassium permanganate.

15.2.3 HARDNESS TREATMENT Hardness in water is caused by the presence of certain positively charged metallic ions in solution in the water. The most common of these hardness-causing ions are calcium and magnesium; others include iron, strontium, and barium.

184

WATER TREATMENT TABLE 15.1.

I

Classification of Hardness. mg/L CaCO,

Classification

I

0-75 75- 150 150-300 Over 300

Soft Moderately hard Hard Very hard

As a general rule, groundwaters are harder than surface waters, so hardness is frequently of concern to the small water system operator. This hardness is derived from contact with soil and rock formations such as limestone. Although rainwater itself will not dissolve many solids, the natural carbon dioxide in the soil enters the water and forms carbonic acid (HCO), which is capable of dissolving minerals. Where soil is thick (contributing more carbon dioxide to the water) and limestone is present, hardness is likely to be a problem. The total amount of hardness in water is expressed as the sum of its calcium carbonate (CaCO,) and its magnesium hardness. However, for practical purposes, hardness is expressed as calcium carbonate. This means that regardless of the amount of the various components that make up hardness, they can be related to a specific amount of calcium carbonate (e.g., hardness is expressed as mg/L as CaC0,-milligrams per liter as calcium carbonate). J Note: The two types of water hardness are temporary hardness and permanent hardness. Temporary hardness is also known as carbonate hardness (hardness that can be removed by boiling); permanent hardness is also known as noncarbonate hardness (hardness that cannot be removed by boiling).

Hardness is of concern in domestic water consumption because hard water increases soap consumption, leaves a soapy scum in the sink or tub, can cause water heater electrodes to bum out quickly, can cause discoloration of plumbing fixtures and utensils, and is perceived as a less desirable water. In industrial water use, hardness is a concern because it can cause boiler scale and damage to industrial equipment. The objection of customers to hardness is often dependent on the amount of hardness they are used to. People familiar with water with a hardness of 20 mg/L might think that a hardness of 100 mg/L is too much. On the other hand, a person who has been using water with a hardness of 200 mg/L might think that 100 mg/L was very soft. Table 15.1 lists the classifications of hardness.

15.2.3.1 Hardness Calculation Recall that hardness is expressed as mg/L as CaC0,. The mg/L of Ca and Mg must be converted to mg/L as CaC0, before they can be added. The hardness (in m g L as CaC03) for any given metallic ion is calculated using the formula: J W

Hardness (mg/L as CaCO,) = M (mgk) X eq. wt. of M W here

M = metal ion concentration in mg/L eq. wt. = equivalent weight - gram molecular weight valence

Pretreatment

Example 15.1 Problem:

A water supply has a concentration of Ca" = 100 m g L and Mg" = 50 mgL. What is the total hardness? J Note: Calcium has a molecular weight of 40, and its valence (charge) is +2. Therefore, the equivalent weight of calcium is 4012 = 20. Magnesium's molecular weight is 24, and it also has a charge of +2, so its equivalent weight is 2412 = 12.

Solution: Hardness ( m g L as CaCO,) =

Since the total hardness is 458 mg/L as CaC0, (well over 300 mg/L as CaCO,), the water is very hard. 15.2.3.2 Treatment Methods

Two common methods are used to reduce hardness: ion exchange and cation exchange.

15.2.3.2.1 Ion Exchange Process The ion exchange process is the most frequently used process for softening water. Accomplished by charging a resin with sodium ions, the resin exchanges the sodium ions for calcium andor magnesium ions. Naturally occurring and synthetic cation exchange resins are available. Natural exchange resins include such substances as aluminum silicate, zeolite clays [zeolites are hydrous silicates found naturally in the cavities of lavas (greensand); glauconite zeolites; or synthetic, porous zeolites], humus, and certain types of sediments. These resins are placed in a pressure vessel. A salt brine is flushed through the resins. The sodium ions in the salt brine attach to the resin. The resin is now said to be charged. Once charged, water is passed through the resin and the resin exchanges the sodium ions attached to the resin for calcium and magnesium ions, thus removing them from the water. The zeolite clays are most common because they are quite durable, can tolerate extreme ranges in pH, and are chemically stable. They have relatively limited exchange capacities, however, so they should be used only for water with a moderate total hardness. One of the results is that the water may be more corrosive than before. Another concern is that addition of sodium ions to the water may increase the health risk of those with high blood pressure.

15.2.3.2.2 Cation Exchange Process The cation exchange process takes place with little or no intervention from the treatment plant operator. Water containing hardness-causing cations (Ca", MgU, Fe+,) is passed through a bed of

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cation exchange resin. The water coming through the bed contains a hardness near zero, although it will have an elevated sodium content. (The sodium content is not likely to be high enough to be noticeable, but it could be high enough to pose problems to people on highly restricted salt-free diets.) The total lack of hardness in the finished water is likely to make it very corrosive, so normal practice bypasses a portion of the water around the softening process. The treated and untreated waters are blended to produce an effluent with a total hardness around 50 to 75 mg/L as CaCO,.

15.3 COAGULATION From Figure 15.2, we see that following screening and the other pretreatment processes, the next unit process in a conventional water treatment system is a mixer where the first chemicals are added in what is known as coagulation. The exception to this situation occurs in small systems using groundwater, when chlorine or other taste and odor control measures are introduced at the intake and are the extent of treatment. Materials present in raw water may vary in size, concentration, and type. Dispersed substances in the water may be classified as suspended, colloidal, or solution. Suspended particles may vary in mass and size and are dependent on the flow of water. High flows and velocities can carry larger material. As velocities decrease, the suspended particles settle according to size and mass. Other material may be in solution, for example, salt dissolves in water. Matter in the colloidal state does not dissolve, but the particles are so small they will not settle out of the water. Color (as in tea-colored swamp waters) is mainly due to colloids or extremely fine particles of matter in suspension. Colloidal and solute particles in water are electrically charged. Because most of the charges are alike (negative) and repel each other, the particles stay dispersed and remain in the colloidal or soluble state. Suspended matter will settle without treatment, if the water is still enough to allow it to settle. The rate of settling of particles can be determined, as this settling follows certain laws of physics. However, much of the suspended matter may be so slow in settling that the normal settling processes become impractical, and if colloidal particles and particles in solution are present, settling will not occur. Therefore, sedimentation alone is usually an impractical way to obtain clear water in most locations, and another method of increasing the settling rate must be used: coagulation. The term coagulation refers to the series of chemical and mechanical operations by which coagulants are applied and made effective. These operations are comprised of two distinct phases: Pretreatment Stage

Addition of Coagulant

W Water + Screening

Figure 15.2 Coagulation.

Coagulation

187

(1) rapid mixing to disperse coagulant chemicals by violent agitation into the water being treated and (2) flocculation (see Section 15.4) to agglomerate small particles into well-defined floe by gentle agitation for a much longer time.14 J Chemicals used as coagulants are expected to be safe for drinhng water when used according to standards. l5

The coagulant must be added to the raw water and perfectly distributed into the liquid; such uniformity of chemical treatment is reached through rapid agitation or mixing (see Figure 15.2). Coagulation results from adding salts of iron or aluminum to the water. Common coagulants (salts) are as follows: alum-aluminum sulfate sodium aluminate ferric sulfate ferrous sulfate ferric chloride polymers Coagulation is the reaction between one of these salts and water. The simplest coagulation process occurs between alum and water. Alum or aluminum sulfate is made by a chemical reaction of bauxite ore and sulfuric acid. The normal strength of liquid alum is adjusted to 8.3 percent, while the strength of dry alum is 17 percent. When alum is placed in water, a chemical reaction occurs that produces positively charged aluminum ions. The overall result is the reduction of electrical charges and the formation of a sticky substance-the formation offloc, which when properly formed, will settle. These two destabilizing factors are the major contributions that coagulation makes to the removal of turbidity, color, and microorganisms. Liquid alum is preferred in water treatment because it has several advantages over other coagulants, including the following: (1) (2) (3) (4) (5) (6) (7) (8)

Ease of handling Lower costs Less labor required to unload, store and convey Elimination of dissolving operations Less storage space required Greater accuracy in measurement and control provided Elimination of the nuisance and unpleasantness of handling dry alum Easier maintenance

The formation of floc is the first step of coagulation; for greatest efficiency, rapid, intimate mixing of the raw water and the coagulant must occur. After mixing, the water should be slowly stirred so that the very small, newly formed particles can attract and enmesh colloidal particles, holding them together to form larger floc. This slow mixing is the second stage of the process (flocculation), covered in Section 15.4. 14Fromcommittee report, "Coagulation as an Integrated Water Treatment Process, J. Am. Water WorksAssoc. 8 1(11)72-78, 1989. "AWWA Standards (Coagulation-No. 42402 to 42407), AWWA, Denver, Colorado.

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Figure 15.3 Jar test.

A number of factors influence the coagulation process-pH, turbidity, temperature, alkalinity, and the use of polymers. The degree to which these factors influence coagulation depends upon the coagulant use. The raw water conditions, optimum pH for coagulation, and other factors must be considered before deciding which chemical is to be fed and at what levels. To determine the correct chemical dosage, a Jar Test or Coagulation Test is performed. Jar tests (widely used for many years by the water treatment industry) simulate full-scale coagulation and flocculation processes to determine optimum chemical dosages. The test conditions are intended to reflect the normal operation of a chemical treatment facility. The test can be used to: select the most effective chemical select the optimum dosage determine the value of a flocculant aid and the proper dose The testing procedure requires a series of samples to be placed in testing jars (see Figure 15.3) and mixed at 100 rpm. Varying amounts of the process chemical or specified amounts of several flocculants are added (one volume/sample container). The mix is continued for one minute. Next, the mixing is slowed to 30 rpms to provide gentle agitation, then the floc is allowed to settle. The flocculation period and settling process is observed carefully to determine the floc strength, settleability, and clarity of the supernatant liquor (defined: the water that remains above the settled floc). Additionally, the supernatant can be tested to determine the efficiency of the chemical addition for removal of TSS, BOD,, and phosphorus. The equipment required for the jar test includes a six-position variable speed paddle mixer (see Figure 15.3), six two-quart widemouthed jars, an interval timer, and assorted glassware, pipettes, graduates, and so forth.

Jar Testing Procedure (1) Place an appropriate volume of wastewater sample in each of the jars (250-1,000 mL samples may be used, depending upon the size of the equipment being used). Start mixers and set for 100 rpms.

Flocculation

189

Add previously selected amounts of the chemical being evaluated. (Initial tests may use wide variations in chemical volumes to determine the approximate range. This is then narrowed in subsequent tests). Continue mixing for 1 minute. Reduce the mixer speed to a gentle agitation (30 rpm), and continue mixing for 20 minutes. Again, time and mixer speed may be varied to reflect the facility. J During this time, observe the floc formation-how tion (floc strength).

well the floc holds together during the agita-

Turn off the mixer and allow solids to settle for 20-30 minutes. Observe the settling characteristics, the clarity of the supernatant, the settleability of the solids, the flocculation of the solids, and the compactability of the solids. Perform phosphate tests to determine removals. Select the dose that provided the best treatment based upon the observations made during the analysis. J After initial ranges andor chemical selections are completed, repeat the test using a smaller range of doses to optimize performance.

15.4 FLOCCULATION

As we see in Figure 15.4, flocculation follows coagulation in the conventional water treatment process. Flocculation is the physical process of slowly mixing the coagulated water to increase the probability of particle collision. Through experience, we see that effective mixing reduces the required amount of chemicals and greatly improves the sedimentation process, which results in longer filter runs and higher quality finished water. Flocculation's goal is to form a uniform, feather-like material similar to snowflakes-a dense, tenacious floc that entraps the fine, suspended, and colloidal particles and carries them down rapidly in the settling basin. Proper flocculation requires from 15 to 45 minutes. The time is based on water chemistry, water temperature, and mixing intensity. Temperature is the key component in determining the amount of time required for floc formation. To increase the speed of floc formation and the strength and weight of the floc, polymers are often added. Pretreatment Stage

Addition of Coagulant

Figure 15.4 Flocculation.

WATER TREATMENT

Pretreatment Stage

Addition of Coagulant

Screening

i

Figure 15.5 Sedimentation.

15.5 SEDIMENTATION

After the raw water and chemicals have been mixed and the floc formed, the water containing the floc (because it has a higher specific gravity than water) flows to the sedimentation or settling basin (see Figure 15S). In conventional treatment plants, the amount of detention time required for settling can vary from 2 to 6 hours. Detention time should be based on the total filter capacity when the filters are passing 2 gpm per square foot of superficial sand area. For plants with higher filter rates, the detention time is based on a filter rate of 3 to 4 gpm per square foot of sand area. The time requirement is dependent on the weight of the floc, the temperature of the water, and how quiescent (still) the basin. A number of conditions affect sedimentation: (1) uniformity of flow of water through the basin; (2) stratification of water due to difference in temperature between water entering and water already in the basin; (3) release of gases that may collect in small bubbles on suspended solids, causing them to rise and float as scum rather than settle as sludge; (4) disintegration of previously formed floc; and (5) size and density of the floc.

Filtration [usually preceded by coagulation, flocculation, and sedimentation (see Figure 15.6)] is not often used for small water systems, although recent regulatory requirements under USEPA's Interim Enhanced Surface Water Treatment rules may make including filter systems necessary. Pretreatment Stage

Addition of Coagulant

Screening

I Sludge Processing Figure 15.6 Filtration.

Filtration

15.6.1 FILTRATIONTHEORY Water filtration is a physical process of separating suspended and colloidal particles from water by passing the water through a granular material. The process of filtration involves straining, settling, and adsorption. As floc passes into the filter, the spaces between the filter grains become clogged, reducing this opening and increasing removal. Some material is removed merely because it settles on a media grain. One of the most important processes is adsorption of the floc onto the surface of individual filter grains. This helps to collect the floc and reduces the size of the openings between the filter media grains. In addition to removing silt and sediment, floc, algae, insect larvae, and any other large elements, filtration also contributes to the removal of bacteria and protozoans such as Giardia lamblia and Cryptosporidium. Some filtration processes are also used for iron and manganese removal.

15.6.2 TYPES OF FILTER TECHNOLOGIES The Surface Water Treatment Rule (SWTR) specifies four filtration technologies, although SWTR also allows the use of alternate filtration technologies, e.g., cartridge filters. These include slow sand filtratiodrapid sand filtration, pressure filtration, diatomaceous earth filtration, and direct filtration. Of these, all but rapid sand filtration are commonly employed in small water systems that use filtration. Each type of filtration system has advantages and disadvantages. Regardless of the type of filter, however, filtration involves the processes of straining (where particles are captured in the small spaces between filter media grains), sedimentation (where the particles land on top of the grains and stay there), and adsorption (where a chemical attraction occurs between the particles and the surface of the media grains).

15.6.2.1 Slow Sand Filters The first slow sand filter was installed in London in 1829 and was used widely throughout Europe, though not in the U.S. By 1900, rapid sand filtration began taking over as the dominant filtration technology, and a few slow sand filters are in operation today. However, with the advent of the Safe Drinking Water Act and its regulations (especially the Surface Water Treatment Rule) and the recognition of the problems associated with Giardia lamblia and Cryptosporidium in surface water, the water industry is reexamining slow sand filters. Because of low technology requirements, their popularity is expected to increase among small systems, although large land requirements may prevent many state water systems from using this type of equipment. On the plus side, slow sand filtration is well suited for small water systems. It is a proven, effective filtration process with relatively low construction costs and low operating costs (it does not require constant operator attention). It is quite effective for water systems as large as 5,000 people, beyond that, surface area requirements and manual labor required to recondition the filters make rapid sand filters more effective. The filtration rate is generally in the range of 45 to 150 gallons per day per square foot. Components making up a slow sand filter include the following: a covered structure to hold the filter media an underdrain system graded rock that is placed around and just above the underdrain the filter media, consisting of 30 to 55 inches of sand with a grain size of 0.25 to 0.35 mm inlet and outlet piping to convey the water to and from the filter, and the means to drain filtered water to waste

192

WATER TREATMENT

Slow sand filters are operated by flooding the area above the top of the sand layer with water to a depth of 3 to 5 feet and allowing it to trickle down through the sand. An overflow device prevents excessive water depth. The filter must have provisions for filling it from the bottom up, and it must be equipped with a loss-of-head gauge, a rate-of-flow control device (such as a weir, orifice, or butterfly valve), a weir or effluent pipe that assures that the water level cannot drop below the sand surface, and filtered waste sample taps. When the filter is first placed in service, the head loss through the media caused by the resistance of the sand is about 0.2 feet (i.e., a layer of water 0.2 feet deep on top of the filter will provide enough pressure to push the water downward through the filter). As the filter operates, the media becomes clogged with the material being filtered out of the water, and the head loss increases. When it reaches about 4 to 5 feet, the filter needs to be cleaned. For efficient operation of a slow sand filter, the water being filtered should have a turbidity averaging less than 5 TU, with a maximum of 30 TU. Slow sand filters are not backwashed the way conventional filtration units are. The top 1 to 2 inches of material must be removed on a periodic basis to keep the filter operating. r

15.6.2.2 Rapid Sand Filters

Rapid sand filters are similar in some ways to slow sand filters. The major difference in the principle of operation is the speed or rate at which water passes through the media. In operation, water passes downward through a sand bed that removes the suspended particles. The suspended particles consist of the coagulated matter remaining in the water after sedimentation, as well as a small amount of uncoagulated suspended matter. The success of rapid sand filtration depends on the construction and operation of the filter bed. Some significant differences exist in construction, control, and operation between slow sand filters and rapid sand filters. The higher filtration rate also reduces the land area needed to filter the same quantity of water. The rapid sand filter structure and equipment includes the following: structure to house media filter media gravel media support layer underdrain system valves and piping system filter backwash system waste disposal system The filter mediais usually 2 to 3 feet deep, supported by approximately 1 foot of gravel. The media may be fine sand or a combination of sand, anthracite coal, and coal (dual- or multimedia filter). Water is applied to a rapid sand filter at a rate of 1.5 to 2 gallons per minute per square foot of filter media surface (1.5-2 gprn/ft2).When the rate is between 4 and 6 gprn/ft2,the filter is referred to as a high-rate filter; at filtration rates over 6 gprn/ft2, the filter is called ultra-high-rate. These rates compare to the slow sand filtration rate of 45 to 150 gallons per day per square foot. High-rate and ultra-high-rate filters must meet additional conditions to assure proper operation. Generally, raw water turbidity is not that high. However, even if raw water turbidity values exceed 1,000 TU, properly operated rapid sand filters can produce filtered water with a turbidity of well under 0.5 TU. The time the filter is in operation between cleanings (filter runs) usually lasts from 12 to 72 hours, depending on the quality of the raw water; the end of the run is indicated by the head loss approaching 6 to 8 feet. Filter breakthrough (when filtered material is pulled through the filter into the effluent) can occur if the head loss becomes too great. Operation with head loss too high can

Filtration

193

also cause air binding (which blocks part of the filter with air bubbles), increasing the flow rate through the remaining filter area. Rapid sand filters have the advantage of lower land requirement, and they have other advantages, too. For example, rapid sand filters cost less, are less labor-intensive to clean, and offer higher efficiency with highly turbid waters. On the downside, operation and maintenance costs of rapid sand filters are much higher because of the increased complexity of the filter controls and backwashing system. In backwashing a rapid sand filter, cleaning the filter is accomplished by passing treated water backwards (upward) through the filter media and agitating the top of the media. The need for backwashing is determined by a combination of filter run time (i.e., the length of time since the last backwashing), effluent turbidity, and head loss through the filter. Depending on the raw water quality, the run time varies from one filtration plant to another (and may even vary from one filter to another in the same plant). J Backwashing usually requires 3 to 7 percent of the water produced by the plant. 15.6.2.3 Pressure Filter Systems

When raw water is pumped or piped from the source to a gravity filter, the head (pressure) is lost as the water enters the floc basin. When this occurs, pumping the water from the plant clearwell to the reservoir is usually necessary. One way to reduce pumping is to place the plant components into pressure vessels, thus maintaining the head. This type of arrangement is called a pressure filter system. Pressure filters are also quite popular for iron and manganese removal and for filtration of water from wells. They may be placed directly in the pipeline from the well or pump with little head loss. Most pressure filters operate at a rate of about 3 gpm/ft2. Operationally the same, and consisting of components similar to those of a rapid sand filter, the main difference between a rapid sand filtration system and a pressure filtration system is that the entire pressure filter is contained within a pressure vessel. These units are often highly automated and are usually purchased as self-contained units with all necessary piping, controls, and equipment contained in a single unit. They are backwashed in much the same manner as the rapid sand filter. The major advantage of the pressure filter is its low initial cost. They are usually prefabricated, with standardized designs. A major disadvantage is that the operator is unable to observe the filter in the pressure filter and so is unable to determine the condition of the media. Unless the unit has an automatic shutdown feature on high effluent turbidity, driving filtered material through the filter is possible. 15.6.2.4 Diatomaceous Earth Filters

Diatomaceous earth is a white material made from the skeletal remains of diatoms. The skeletons are microscopic, and in most cases, porous. There are different grades of diatomaceous earth, and the grade is selected based on filtration requirements. These diatoms are mixed in a water slurry and fed onto a fine screen called a septum, usually of stainless steel, nylon, or plastic. The slurry is fed at a rate of 0.2 lb per square foot of filter area. The diatoms collect in a pre-coat over the septum, forming an extremely fine screen. Diatoms are fed continuously with the raw water, causing the buildup of a filter cake approximately 118 to 115 inch thick. The openings are so small that the fine particles that cause turbidity are trapped on the screen. Coating the septum with diatoms gives it the ability to filter out very small microscopic material. The fine screen and the buildup of filtered particles cause a high head loss through the filter. When the head loss reaches a maximum level (30 psi on a pressure-type filter or 15 inches of mercury on a vacuum-type filter), the filter cake must be removed by backwashing.

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WATER TREATMENT

A slurry of diatoms is fed with raw water during filtration in a process called bodyfeed. The body feed prevents premature clogging of the septum cake. These diatoms are caught on the septum, increasing the headloss and preventing the cake from clogging too rapidly by the particles being filtered. While the body feed increases headloss, headloss increases are more gradual than if body feed were not used. Although diatomaceous earth filters are relatively low in cost to construct, they have high operating costs and can give frequent operating problems if not properly operated and maintained. They can be used to filter raw surface waters or surface-influenced groundwaters with low turbidity (<5 NTU), low coliform concentrations (no more than 50 coliforms/100 mL), and may also be used for iron and manganese removal following oxidation. Filtration rates are between 1.0 and 1.5 gpm/ft2. 15.6.2.5 Direct Filtration

The term direct filtration refers to a treatment scheme that omits the flocculation and sedimentation steps prior to filtration. Coagulant chemicals are added, and the water is passed directly onto the filter. All solids removal takes place on the filter, which can lead to much shorter filter runs, more frequent backwashing, and a greater percentage of finished water used for backwashing. The lack of a flocculation process and sedimentation basin reduces construction cost but increases the requirement for skilled operators and high quality instrumentation. Direct filtration must be used only where the water flow rate and raw water quality are fairly consistent and where the incoming turbidity is low. 15.6.2.6 Alternate Filters

A cartridgefilter system can be employed as an alternate filtering system to reduce turbidity and remove Giardia. A cartridge filter is made of a synthetic media contained in a plastic or metal housing. These systems are normally installed in a series of three or four filters. Each filter contains a media that is successively smaller than the previous filter. The media sizes typically range from 50p to 5p or less. The filter arrangement is dependent on the quality of the water, the capability of the filter, and the quantity of water needed. The USEPA and state agencies have established criteria for the selection and use of cartridge filters. Generally, cartridge filter systems are regulated in the same manner as other filtration systems. 15.6.3 COMMON FILTER PROBLEMS

Two common types of filter problems occur: those caused by filter runs that are too long (infrequent backwash), and those caused by inefficient backwash (cleaning). Too long a filter run can cause breakthrough (the pushing of debris removed from the water through the media and into the effluent) and air binding (the trapping of air and other dissolved gases in the filter media). Breakthrough occurs when the headloss across a filter becomes high enough to push the debris collected in the filter through the media and into the finished water. This may cause Giardia and viruses to be pushed into the finished water. Air binding occurs when the rate at which water exits the bottom of the filter exceeds the rate at which the water penetrates the top of the filter. When this happens, a void and partial vacuum occurs inside the filter media. The vacuum causes gases to escape from the water and fill the void. When the filter is backwashed, the release of these gases may cause a violent upheaval in the media and destroy the layering of the media bed, gravel, or underdrain. Two solutions to the problems are as follows: (1) check the filtration rates to assure they are within the design specifications and (2) remove the top 1 inch of media and replace with new media.

Corrosion Control

195

This keeps the top of the media from collecting the floc and sealing the entrance into the filter media. Another common filtration problem is associated with poor backwashing practices: the formation of mud balls that get trapped in the filter media. In severe cases, mud balls can completely clog a filter. Poor agitation of the surface of the filter can form a crust on the top of the filter; the crust later cracks under the water pressure, causing uneven distribution of water through the filter media. Filter cracking can be corrected by removing the top 1 inch of the filter media, increasing the backwash rate, or checking the effectiveness of the surface wash (if installed). Backwashing at too high a rate can cause the filter media to wash out of the filter over the effluent troughs and may damage the filter underdrain system. Two possible solutions are as follows: (1) check the backwash rate to be sure that it meets the design criteria, and (2) check the surface wash (if installed) for proper operation.

15.7 CORROSION CONTROL Any discussion related to water treatment is incomplete without including disinfection, fluoridation, and corrosion control. We discuss disinfection and fluoridation in subsequent chapters, but for now, we focus on another important element of water treatment-corrosion control. The number one nuisance in water systems is corrosion. When you consider that waters typically have low natural pH, are high in dissolved oxygen, low in total dissolved solids, low alkalinity, and have low hardness, that they are aggressively corrosive should come as no surprise. Corrosion is the oxidation of unprotected metal surfaces. In water distribution systems, it is a highly complex chemical and electrochemical process that can cause metal pipes and tankage to be corroded by the water. The metal ions corrode from the metal surfaces (iron, copper, lead, aluminum, and others) and dissolve into the water, where they can cause problems of staining and (in some cases) adverse health implications. Other problems caused by corrosion include reduced pipeline capacity, increased pumping costs, low flows and pressures in parts of the distribution system, and leakage of storage tanks, building plumbing, and distribution pipes. Along with being a nuisance in the water system, corrosion can also have severe economic consequences as well. Aggressive and corrosive waters increase the cost to the customer, both directly and indirectly. The customer's water heaters and faucets deteriorate faster than normal, increasing customer cost. The cost resulting from the deterioration of the water distribution is shared by all customers. Another problem with corrosion in water systems has caught the full attention of the USEPA: corrosive waters can produce adverse health implications. The USEPA has issued several regulations that address corrosivity, primarily on how it affects the lead and copper content of the water. A new set of regulations was issued in 1991 to further tighten the requirements for lead and copper control, requiring further "non-corrosivity" of finished water. A number of systems with naturally corrosive water will be forced to treat that water to avoid violating the lead and copper regulations. For the water operator, some obvious symptoms indicate that a water system has a corrosion problem. These include the following: red or black water occurrences blue-green stains in porcelain fixtures (sinks, toilets) pitting on insides of pipes significant increases in pumping pressures or decreases in water delivery Factors that can determine whether corrosion occurs or that can affect the rate at which it occurs include such physical characteristics as pipe materials; velocity and direction of water flow; junctures of dissimilar metals (e.g., brass and iron); the uniformity of scaling or deposits in the pipeline;

196

WATER TREATMENT

the presence of surface defects in the pipe; and the chemical composition of the water, including temperature, dissolved oxygen and dissolved carbon dioxide concentrations, dissolved solids concentrations, pH, alkalinity, and calcium carbonate content. The most acceptable means of determining if water is corrosive is through the use of a calculation process called the Langlier Saturation Index. This index considers pH, total dissolved solids, temperature, calcium hardness, and alkalinity. The Langlier Index is calculated using the following formula: L1 = pH - pH, where pH, is the pH at which an equilibrium exists between alkalinity and carbon dioxide. The formula for calculating pH, is beyond the scope of this Handbook, but you should know that a positive value derived indicates supersaturation; a negative value indicates potential corrosivity. J The LI is not a foolproof measure of the corrosivity of the water, so you should be aware that you must know more about it if your facility uses it to test for corrosivity in the water system.

Corrosion can be controlled using several techniques, either singly or in combination. Some experimentation is usually necessary to determine the optimum corrosion control program. use non-metallic materials, such as PVC piping use corrosion-resistant materials install cathodic protection, in which an electrical charge is imposed on the pipeline or storage tank to counter the electrical flow that takes place naturally use chemical corrosion inhibitors such as polyphosphates adjust the pH upward maintain an optimum combination of pH, calcium carbonate concentration, and alkalinity in the water to deposit a film on the insides of pipes feed lines soda ash or caustic soda to deposit a film on the insides of pipes

15.8 ROLE OF THE WATERWORKS OPERATOR

Water treatment protocols and procedures are important, however, without proper implementation, they are nothing more than hollow words occupying space on paper. This is where the waterworks operator comes in. To successfully treat water requires the skill and vigilance of a trained, conscientious waterworks operator. The role of the waterworks operator can be succinctly stated: Waterworks operators provide water that complies with state Waterworks Regulations, water that is safe to drink and ample in quantity and pressure without interruption. Waterworks operators must know their facilities. Waterworks operators must be familiar with bacteriology, chemistry, and hydraulics. Waterworks operators must stay abreast of technological change and stay current with water supply information. In operating a waterworks facility, waterworks operator duties include: maintaining distribution system collecting or analyzing water samples

Chapter Review Questions

operating chemical feed equipment keeping records operating treatment unit processes performing sanitary surveys of the water supply watershed operating a cross-connection control program

15.9 SUMMARY

Whether a small system or a large one, regulations require that all surface water or groundwater under the influence of surface water must undergo the next step in the treatment process-disinfection. We discuss this essential step in Chapter 16.

15.10 CHAPTER REVIEW QUESTIONS

15-1 Explain coagulation.

15-2 What are the advantages of using liquid alum?

15-3 What is a jar test used for?

15-4 The most common method of reducing hardness in a small system is:

15-5 Two chemicals that can be used to remove or reduce iron and manganese are:

15-6 The amount of chlorine used in a reaction is called:

15-7 Water that is safe to drink is called:

15-8 Define palatable W ater.

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WATER TREATMENT

15-9 Filters are cleaned by:

15-10 Aggressive water can cause iron and copper in household plumbing to be:

15-11 Particles that are less than l micron in size are called:

15-12 The primary reason for treating water is:

15-13 The quantity of a chemical added to water is called:

15-14 The time that water is kept in the sedimentation basin is called:

15-15 Disease-causing microorganisms are called:

15-16 The primary components of hardness are:

15-17 When polymers are added just before or in the flash mix, they are called:

15-18 Poor backwash can result in:

15-19 Infrequent backwash can result in:

15-20 In a conventional water treatment system, unit processes discussed in this chapter include (arranged in order) :

15-21 Coagulation is a

process.

Chapter Review Questions

15-22 Alum is fed at which process unit in a typical water filtration unit?

15-23 A physical process used to reduce iron and manganese that can also be used to reduce odors and taste is:

15-24 Chemicals that can be used to keep iron or manganese in solution are called:

15-25 The units of measure of turbidity are:

15-26 The difference between the pressure above a filter and the pressure below the filter is called:

CHAPTER 16

Disinfection

As general requirements, USEPA (1989) states that all public water systems, using any su$ace water or groundwater under the direct influence of sugace watel; must disinfect . . . disinfection must achieve at least a 99.9 and 99.99 percent inactivation of Giardia cysts and viruses, respectively. This must be demonstrated by the system meeting "CT" values in the rule ("CT" is the product of residual concentration (mg/Z)and contact time (minutes) measured at peak ho~rlyflow).'~

16.1 INTRODUCTION chemical or physical process used to control waterborne pathogenic organisms and prevent waterbome disease is called disinfection. The goal in proper disinfection in a water system is to destroy all disease-causing organisms. Disinfection should not be confused with sterilization. Sterilization is the complete killing of all living organisms. Waterworks operators disinfect by destroying organisms that might be dangerous, they do not attempt to sterilize water. In water treatment, disinfection is almost always accomplished by adding chlorine or chlorine compounds after all other treatment steps (see Figure 16.1), although in the U.S. ultraviolet (UV) light and ozone processes may be encountered. The effectiveness of disinfection in a drinking water system is measured by testing for the presence or absence of coliform bacteria.

T

HE

J Note that the examination of routine bacteriological samples cannot be regarded as providing complete information concerning water quality. Always consider bacteriological results in the light of information available concerning the sanitary conditions surrounding the sample location and sanitary survey data of the waterworks, including the source.

Colifomz bacteria found in water are generally not pathogenic, though they are good indicators of contamination. Their presence indicates the possibility of contamination, and their absence indicates the possibility that the water is potable-if the source is adequate, the waterworks history is good, and an acceptable chlorine residual is present. Desired characteristics of a disinfectant include the following: It must be able to deactivate or destroy any type or number of disease-causing microorganisms that may be in a water supply, in reasonable time, within expected temperature ranges, and despite changes in the character of the water (pH, for example). "%SEPA,Surface Water TreatmenfRule, 1989.

201

DISINFECTION Addition of

Water _) // Supply // Screening

)

Mixing Tank

---) Flocculation

Settling Tank

Basin

I

Processing

-)

I

To Storage and Distribution

Sand Filter

Disinfection

Figure 16.1 Disinfection.

It must be nontoxic. It must not add unpleasant taste or odor to the water. It must be readily available at a reasonable cost and be safe and easy to handle, transport, store, and apply. * It must be quick and easy to determine the concentration of the disinfectant in the treated water. It should persist within the disinfected water at a high enough concentration to provide residual protection through the distribution system. Disinfection is effective in reducing waterborne diseases because most pathogenic organisms are more sensitive to disinfection than are nonpathogens. However, disinfection is only as effective as the care used in controlling the process and assuring that all of the water supply is continually treated with the amount of disinfectant required to produce safe water. The methods of disinfection are as follows: (1) Heat possibly the first method of disinfection. Disinfection is accomplished by boiling water for 5 to 10 minutes. Good, obviously, only for household quantities of water when bacteriological quality is questionable. (2) Ultraviolet (UV) light while a practical method of treating large quantities, adsorption of UV light is very rapid, so the use of this method is limited to nonturbid waters close to the light source. (3) Metal ions silver, copper, mercury ( 4 ) Alkalis and acids (5) pH adjustment to under 3.0 or over 11.0 (6) Oxidizing agents bromine, ozone, potassium permanganate, and chlorine The vast majority of water systems in the U.S. use chlorine for disinfection. Along with meeting the desired characteristics listed above, chlorine has the added advantage of a long history of useit is fairly well understood. Although some small water systems may use other disinfectants, we concentrate on chlorine.

16.2 CHLORINATION Chlorine is the most commonly used substance for disinfection of water in the U.S. The addition of chlorine or chlorine compounds to water is called chlorination. Chlorination is considered to be the single most important process for preventing the spread of waterborne disease.

203

Chlorination

Chlorine deactivates microorganisms through several mechanisms, assuring that it can destroy most biological contaminants: It causes damage to the cell wall. It alters the permeability of the cell (the ability to pass water in and out through the cell wall). It alters the cell protoplasm. It inhibits the enzyme activity of the cell so it is unable to use its food to produce energy. It inhibits cell reproduction. Chlorine is available in a number of different forms: (1) as pure elemental gaseous chlorine (a greenish-yellow gas possessing a pungent and irritating odor that is heavier than air, nonflammable, and nonexplosive), when released to the atmosphere, this form is toxic and corrosive; (2) as solid calcium hypochlorite (in tablets or granules); or (3) as a liquid sodium hypochlorite solution (in various strengths). The selection of one form of chlorine over the others for a given water system depends on the amount of water to be treated, configuration of the water system, the local availability of the chemicals, and the skill of the operator. One of the major advantages of using chlorine is the effective residual that it produces. A residual indicates that disinfection is completed, and the system has an acceptable bacteriological quality. Maintaining a residual in the distribution system provides another line of defense against pathogenic organisms that could enter the distribution system and helps to prevent regrowth of those microorganisms that were injured but not killed during the initial disinfection stage. 16.2.1 CHLORINE TERMS

Often, new waterworks operators have difficulties understanding the terms used to describe the various reactions and processes used in chlorination. Common terms used in chlorination include the following: Chlorine reaction regardless of the form of chlorine used for disinfection, the reaction in water is basically the same. The same amount of disinfection can be expected, provided the same amount of available chlorine is added to the water. The standard term for the concentration of chlorine in water is milligrams per liter (mg/L) or parts per million (ppm); these terms indicate the same quantity. Chlorine dose the amount of chlorine added to the system. It can be determined by adding the desired residual for the finished water to the chlorine demand of the untreated water. Dosage can be either milligrams per liter (mg/L) or pounds per day. The most common is mg/L. Chlorine demand the amount of chlorine used by iron, manganese, turbidity, algae, and microorganisms in the water. Because the reaction between chlorine and microorganisms is not instantaneous, demand is relative to time. For instance, the demand 5 minutes after applying chlorine will be less than the demand after 20 minutes. Demand, like dosage is expressed in mg/L. The chlorine demand is as follows: Cl2demand = Cl2dose-Cl2 residual

(16.1)

Chlorine residual the amount of chlorine (determined by testing) remaining after the demand is satisfied. Residual, like demand, is based on time. The longer the time after dosage, the lower the residual will be, until all of the demand has been satisfied. Residual, like dosage and demand, is expressed in mg/L. The presence of a free residual of at least

204

DISINFECTION

0.2-0.4 ppm usually provides a high degree of assurance that the disinfection of the water is complete. Combined residual is the result of combining free chlorine with nitrogen compounds. Combined residuals are also called chloramines. Total chlorine residual'is the mathematical combination of free and combined residuals. Total residual can be determined directly with standard chlorine residual test kits (see Section 16.2.7). Chlorine contact time one of the key items in predicting the effectiveness of chlorine on microorganisms. It is the interval (usually only a few minutes) between the time when chlorine is added to the water and the time the water passes by the sampling point, contact time is the "T" in CT. CT is calculated based on the free chlorine residual prior to the first customer, times the contact time in minutes. CT = Concentration X Contact Time = mg/L X minutes

(1 6.2)

A certain minimum time period is required for the disinfecting action to be completed. The contact time is usually a fixed condition determined by the rate of flow of the water and the distance from the chlorination point to the first consumer connection. Ideally, the contact time should not be less than 30 minutes, but even more time is needed at lower chlorine doses, in cold weather, or under other conditions. Pilot studies have shown that specific CT values are necessary for the inactivation of viruses and Giardia. The required CT value will vary depending on pH, temperature, and the organisms to be killed. Charts and formulas are available to make this determination. USEPA has set a CT value of three log (CTgg,,)inactivation to assure the water is free of Giardia. State drinking water regulations include charts giving this value for different pH and temperature combinations. Filtration, in combination with disinfection, must provide a 3 log removal/inactivation of Giardia. Charts in the USEPA Surface Water Treatment Rule Guidance manual list the required CT values for various filter systems. Under the 1996 Interim Enhanced Surface Water Treatment (IESWT) rules, the USEPA requires systems that filter to remove 99 percent (2 log) of Cryptosporidium oocysts. To be assured that the water is free of viruses, a combination of filtration and disinfection to provide a 4 log removal of viruses has been judged the best for drinking water safety-99.99 percent removal. Viruses are inactivated (killed) more easily than cysts or oocysts. 16.2.2 CHLORINE CHEMISTRY

The reactions of chlorine with water and the impurities that might be in the water are quite complex, but a basic understanding of these reactions can aid the operator in keeping the disinfection process operating at its highest efficiency. When dissolved in pure water, chlorine reacts with the H+ions and the OH- radicals in the water. Two of the products of this reaction (the actual disinfecting agents) are hypochlorous acid, HOCl, and the hypochlorite radical, OC1-. If microorganisms are present in the water, the HOCl and the OC1- penetrate the microbe cells and react with certain enzymes. This reaction disrupts the organisms' metabolism and kills them. The chemical equation for hypochlorous acid is as follows: Cl2 (chlorine)

+

H20 (Water)

HOCl (hypochlorous acid)

+

HCl (hydrochloric acid)

(16.3)

J Note: The symbol * indicates that the reactions are reversible.

Hypochlorous acid (HOCl) is a weak acid but a strong oxidizing and germicidal agent. Hydrochloric acid (HC1) in the above equation is a strong acid and retains more of the properties of chlo-

205

Chlorination

rine. HCl tends to lower the pH of water, especially in swimming pools where the water is recirculated and continually chlorinated. The total hypochlorous acid and hypochlorite ions in water constitute the free available chlorine. Hypochlorites act in a manner similar to HC1 when added to water, since hypochlorous acid is formed. When chlorine is first added to water containing some impurities, the chlorine immediately reacts with the dissolved inorganic or organic substances and is then unavailable for disinfection. The amount of chlorine used in this initial reaction is the chlorine demand of the water. If dissolved ammonia (NH3)is present in the water, the chlorine will react with it to form compounds called chloramines. Only after the chlorine demand is satisfied and the reaction with all the dissolved ammonia is complete is the chlorine actually available in the form of HOCl and OC1-.The equation for the reaction of hypochlorous acid (HOCl) and ammonia (NH,) is as follows: HOCl (hypoclorous acid)

+

NH3 (ammonia)

H

NHzCl (monochloramine)

+

H20 (water)

(16.4)

J Key Point: The chlorine as hypochlorous acid and hypochlorite ions remaining in the water after the above reactions are complete is known as free available chlorine, and it is a very active disinfectant. 16.2.2.1 Breakpoint Chlorination

To produce a free chlorine residual, enough chlorine must be added to the water to produce what is referred to as breakpoint chlorination [i.e., the point at which near complete oxidation of nitrogen compounds is reached; any residual beyond breakpoint is mostly free chlorine (see Figure 16.2)]. When chlorine is added to natural waters, the chlorine begins combining with and oxidizing the chemicals in the water before it begins disinfecting. Although residual chlorine will be detectable in the water, the chlorine will be in the combined form with a weak disinfecting power. As we see in Figure 16.2, adding more chlorine to the water at this point actually decreases the chlorine residual as the additional chlorine destroys the combined chlorine compounds. At this stage, water may have a strong swimming pool or medicinal taste and odor. To avoid this taste and odor, add still more chlorine to produce a free residual chlorine. Free chlorine has the highest disinfecting power. The point at which most of the combined chlorine compounds have been destroyed and the free chlorine starts to form is the breakpoint. The chlorine breakpoint of water can only be determined by experimentation. This simple experiment requires 20 1,000-rnL breakers and a solution of chlorine. Place the raw water in the beakers and dose with progressively larger amounts of chlorine. For instance, you might start with zero in the first beaker, then 0.5 mg/L, and 1.0 mg/L, and so on. After a period of time, say 20 minutes, test each beaker for total chlorine residual and plot the results.

16.2.2.1.1 Breakpoint Chlorination Curve Refer to Figure 16.2 for the following explanation. When the curve starts, no residual exists, even though there was a dosage. This is called the initial demand and is the result of the chlorine being used by microorganisms and interfering agents. After the initial demand, the curve slopes upward. This part of the curve is produced by chlorine combining to form chloramines. All of the residual measured on this part of the curve is combined residual. At some point, the curve begins to drop back toward zero. This portion of the curve results from a reduction in combined residual, which occurs because enough chlorine has been added to destroy (oxidize) the nitrogen compounds used to form combined residuals.

DISINFECTION

Figure 16.2 Breakpoint chlorination curve.

The breakpoint is the point where the downward slope of the curve breaks upward. At this point, all of the nitrogen compounds that could be destroyed have been destroyed. After breakpoint, the curve starts upward again, usually at a 45" angle. Only on this part of the curve can free residuals be found. Notice that the breakpoint is not zero. The distance that the breakpoint is above zero is a measure of the remaining combined residual in the water. This combined residual exists because some of the nitrogen compound will not have been oxidized by chlorine. If irreducible combined residual is more than 15 percent of the total residual, chlorine odor and taste complaints will be high. 16.2.3 GAS CHLORINATION

Gas chlorine is provided in 100 lb, 150 lb or 1 ton containers. Chlorine is placed in the container as a liquid. The liquid boils at room temperature, reducing to a gas and building pressure in the cylinder. At room temperature of 70°F7a chlorine cylinder will have a pressure of 85 psi; cylinders should be maintained in an upright position and chained to the wall. To prevent a chlorine cylinder from rupturing in a fire, the cylinder valves are equipped with special fusible plugs that melt between 158 and 164°F. Chlorine gas is 99.9 percent chlorine. A gas chlorinator meters the gas flow and mixes it with water, which is then injected as a water solution of pure chlorine. As the compressed liquid chlorine is withdrawn from the cylinder, it expands as a gas, withdrawing heat from the cylinder. Care must be taken not to withdraw the chlorine at too fast a rate: if the operator attempts to withdraw more than about 40 pounds of chlorine per day from a 150 pound cylinder, it will freeze up. J All chlorine gas feed equipment sold today is vacuum operated. This safety feature ensures that if a break occurs in one of the components in the chlorinator, the vacuum will be lost, and the chlorinator will shut down without allowing gas to escape.

Chlorine gas is a highly toxic lung irritant, and special facilities are required for storing and housing it. Chlorine gas will expand to 500 times its original compressed liquid volume at room temperature (one gallon of liquid chlorine will expand to about 67 ft3). Its advantage as a drinking water

Chlorination

207

disinfectant is the convenience afforded by a relatively large quantity of chlorine available for continuous operation for several days or weeks without the need for mixing chemicals. Where water flow rates are highly variable, the chlorination rate can be synchronized with the flow. Chlorine gas has a very strong, characteristic odor that can be detected by most people at concentrations as low as 3.5 ppm. Highly corrosive in moist air, it is extremely toxic and irritating in concentrated form. Its toxicity ranges from throat irritation at 15 ppm to rapid death at 1,000 ppm. Although chlorine does not burn, it supports combustion, so open flames should never be used around chlorination equipment. While changing chlorine cylinders, an accidental release of chlorine may occasionally occur. To handle this type of release, an approved (NIOSH-approved) Self-contained Breathing Apparatus (SCBA) must be worn. Special emergency repair kits are available from the Chlorine Institute for use by emergency response teams to deal with chlorine leaks. Because chlorine gas is 2.5 times heavier than air, exhaust and inlet air ducts should be installed at floor level. A leak of chlorine gas can be found by using the fumes from a strong ammonia solution. A white cloud develops when ammonia and chlorine combine. 16.2.4 HYPOCHLORINATION

Hypochlorites are produced by combining chlorine with calcium or sodium. Calcium hypochlorites are sold in powder or tablet forms and can contain chlorine concentrations up to 67 percent. Sodium hypochlorite is a liquid (bleach, for example) and is found in concentrations up to 16 percent. Chlorine concentrations of household bleach range from 4.75 percent to 5.25 percent. Most small system operators find using these liquid or dry chlorine compounds more convenient and safer than chlorine gas. The compounds are mixed with water and fed into the water with inexpensive solution feed pumps. These pumps are designed to operate against high system pressures, but can also be used to inject chlorine solutions into tanks, though injecting chlorine into the suction side of a pump is not recommended as the chlorine may corrode the pump impeller. Calcium hypochlorite can be purchased as tablets or granules, with approximately 65 percent available chlorine (10 pounds of calcium hypochlorite granules contain only 6.5 pounds of chlorine). Normally, 6.5 pounds of calcium hypochlorite will produce a concentration of 50 mg/L chlorine in 10,000 gallons of water. Calcium hypochlorite can bum (at 350°F) if combined with oil or grease. When mixing calcium hypochlorite, operators must wear chemical safety goggles, a cartridge breathing apparatus, and rubberized gloves. Always place the powder in the water. Placing the water into the dry powder could cause an explosion. Sodium hypochlorite is supplied as a clear, greenish-yellow liquid in strengths from 5.25 percent to 16 percent available chlorine. Often referred to as "bleach," it is, in fact, used for bleaching. As we stated earlier, common household bleach is a solution of sodium hypochlorite containing 5.25 percent available chlorine. The amount of sodium hypochlorite needed to produce a 50 mg/L chlorine concentration in 10,000 gallons of water can be calculated using the solutions equation:

where:

C = the solution concentration in mg/L or % V = the solution volume in the liters, gal., qts., etc. 1.O% = 10,000 mg/L In this example, C, and V, are associated with the sodium hypochlorite and C2 and V, are associated with the 10,000 gallons of water with a 50 mg/L chlorine concentration. Therefore:

208

DISINFECTION

Vl = unknown volume of sodium hypochlorite C2= 50 mg/L V, = 10,000 gallons (52,500 mg/L)(V1)= (50 mg/L)(10,000 gal) mgL) (10,000 gal) v*= (5052,500 mgL Vl = 9.52 gal of sodium hypochlorite Sodium hypochlorite solutions are introduced to the water in the same manner as calcium hypochlorite solutions. The purchased stock "bleach" is usually diluted with water to produce a feed solution that is pumped into the water system. Hypochlorites must be stored properly to maintain their strengths. Calcium hypochlorite must be stored in airtight containers in cool, dry, dark locations. Sodium hypochlorite degrades relatively quickly even when properly stored, it can lose more than half of its strength in 3 to 6 months. Operators should purchase hypochlorites in small quantities to assure they are used while still strong. Old chemicals should be discarded safely. A chemical metering pump's pumping rate is usually manually adjusted by varying the length of the piston or diaphragm stroke. Once the stroke is set, the hypochlorinator feeds accurately at that rate. However, chlorine measurements must be made occasionally at the beginning and end of the well pump cycle to assure correct dosage. A metering device may be used to vary the hypochlorinator feed rate, synchronized with the water flow rate. Where a well pump is used, the hypochlorinator is connected electrically with the pump's on-off controls to assure that chlorine solution is not fed into the pipe when the well is not pumping.

16.2.5 DETERMINING CHLORINE DOSAGE Proper disinfection requires calculation of the amount of chlorine that must be added to the water to produce the required dosage. The type of calculation used depends on the form of chlorine being used. The basic chlorination calculation used is the same one used for all chemical addition calculations-the pounds formula.The pounds formula is Pounds = mg/L X 8.34 X MG

where: pounds = pounds of available chlorine required m g L = desired concentration in milligrams per liter 8.24 = conversion factor MG = millions of gallons of water to be treated

(16.6)

Chlorination

Example 16.1 Problem: Calculate the number of pounds of gaseous chlorine needed to treat 250,000 gallons of water with 1.2 mg/L of chlorine.

Solution: Pounds = 1.2 mg/L X 8.34 X 0.25 MG = 2.5 lb J Hypochlorites contain less than 100 percent available chlorine. Thus, we must use more hypochlorite to get the same number of pounds of chlorine into the water.

Let's take the same problem in Example 16.1, but substitute calcium hypochlorite with 65 percent available chlorine: 2.5 lb of available chlorine is still needed, but more than 2.5 pounds of calcium hypochlorite is needed to provide that much chlorine. Determine how much of the chemical is needed by dividing the pounds of chlorine needed by the decimal form of the percent available chlorine. Since 65 percent is the same as 0.65, we need to add 2.5 lb = 3.85 lb Ca (OCl), 0.65 available chlorine to get that much chlorine. In practice, since most hypochlorites are fed as solutions, we often need to know how much chlorine solution we need to feed. In addition, the practical problems faced in day-to-day operation are never so clearly stated as the practice problems we work. For example, small water systems do not usually deal with water flow in million gallons per day. Real-world problems usually require a lot of intermediate calculations to get everything ready to plug into the pounds formula.

Example 16.2 Problem: We have raw water with a chlorine demand of 2.2 mg/L. We need a final residual of l .O mg/L at the entrance to the distribution system. We can use sodium hypochlorite or calcium hypochlorite granules as the source of chlorine. If well output is 65 gallons per minute (gpm) and the chemical feed pump can inject 100 milliliters per minute (rnL1min) at the 50 percent setting, (1) What is the required strength of the chlorine solution we will feed? (2) What volume of 5.20 percent sodium hypochlorite will be needed to produce one gallon of the chlorine feed solution? (3) How many pounds of 65 percent calcium hypochlorite will be needed to mix each gallon of solution?

DISINFECTION

Well pump +++ Treated Water

?' Chlorination Metering Pump

C2

=

unknown

Figure 16.3 Chlorination system problem.

Solution: (1) Step 1: Determine the amount of chlorine to be added to the water (the chlorine dose). The dose is defined as the chlorine demand of the water, plus the desired residual, or in this case: dose = demand + residual = 2.2 mg/L+ 1.0 mg/L = 3.2 mg/L To obtain a 1.0 mg/L residual when the water enters the distribution system, we must add 3.2 mg/L of chlorine to the water. (2) Step 2: Determine the strength of the chlorine feed solution that would add 3.2 mg/L of chlorine to 65 gallons/minute of water when fed at a rate of 100 W m i n u t e . To make this calculation, consider the diagram of this chlorination system in Figure 16.3. The well pump below is producing water at a flow rate (Ql) of 65 gpm, with a chlorine concentration (C1)of 0.0 m g L . The metering pump will add 100 W m i n (Q2) of chlorine solution, but we do not know its concentration (C2) yet. The finished water will have been dosed with a chlorine concentration of 3.2 mg/L (C,) and will enter the distribution system at a rate (Q,) of 65 gallons + 100 mL per minute, with a free residual chlorine concentration of l .O mg/L after the chlorine contact time. (3) Step 3: We must now convert the metering pump flow (100 mL/min) to gpm SO we can calculate Q,. To do this, we use standard conversion factors, 100 mL min

X

1L 1,000 mL

X

1 gal - 0.026 gaVmin 3.785 L -

So, now we know that Q, is 0.026 gpm and that Q, is 65 gpm + 0.026 gpm = 65.026 gpm. (4) Step 4: We must now use what is known as the standard mass balance equation. The mass balance equation says that the flow rate times the concentration of the output is equal to the flow rate times the concentration of each of the inputs added together, or in equation form,

Substituting the numbers given and those we have calculated so far gives us (65 gpm X 0.0 mg/L) + (0.026 gpm X m g L ) = [(65 + 0.026) gpm X 3.2 rng/L]

Chlorination

This is the answer to the first part of the question, the required strength of the chlorine feed solution. Since a 1 percent solution is equal to 10,000 m g L , a solution strength of 8,004 mglL is approximately a 0.80 percent solution. To determine the required volume of bleach per gallon to produce this 0.80% solution, we go back to the pounds formula: Pounds = mg/L X 8.34 X MG = 8,004 mg/L X 8.34 X 0.000001 MG = 0.067 lb chlorinelgal solution J Note: Remember to convert gallons to MG

Recalling that the bleach, like water, weighs 8.34 lblgal and contains approximately 5.20 percent (0.0520) available chlorine, 1 gal bleach = 8.34-

lb gal

X

0.0520

= 0.43 lb available chlorine per gallon of bleach

If one gallon of bleach contains 0.43 lb of available chlorine, how many gallons of bleach do we need to provide the 0.067 lb of chlorine we need for each gallon of chlorine feed solution? To determine the gallons of bleach needed, we use the simple ratio equation: l gallon - X gallons 0.443 lbC12 - 0.067 1bC12

X=

1 gal X 0.067 lb 0.43 lb

= 0.16 gal bleach per gal solution

Or, to determine the required volume of bleach per gallon to produce this 0.80% solution, we use the solutions equation and calculate it this way:

c,v, = c2v2 Cl = 0.80% V, = 1.0 gal C2= 5.20% V2= unknown 0.80% solution X l .0 gal = 5.20% solution X gal

X=

0.80% X 1.0 gal 5.20%

= 0.15 gal bleach per gal solution

DISINFECTION

To summarize, one gallon of household bleach: contains 5.20% or 52,000 mg/L available chlorine 0.85 gal water 0.15 gal available chlorine weighs 8.34 lb 0.43 available chlorine The third part of the problem requires that we determine the pounds of calcium hypochlorite needed for each gallon of feed solution. We know that we need 0.066 lb of chlorine for each gallon of solution and that HTH contains 65 percent available chlorine; that is, l .O lb of HTH contains 0.65 lb of available chlorine. Using the ratio equation,

X lb HTH 1 lb HTH 0.65 lb Clz = 0.067 lb Clz

= 0.1 lb HTH per gal solution

16.2.6 FACTORS AFFECTING CHLORINATION

Disinfection by chlorination is a rather straightforward process, but several factors or interferences can affect the ability of chlorine to perform its main function: disinfection. Turbidity is one such interference. As we described earlier, turbidity is a general term that describes particles suspended in the water. A water with a high turbidity appears cloudy. Turbidity interferes with disinfection when microorganisms "hide" from the chlorine within the particles of turbidity. This problem is especially severe when turbidity comes from organic particles, such as those from sewage effluent. To overcome this, the length of time the water is exposed to the chlorine or the chlorine dose must be increased, although highly turbid waters may still shield some microorganisms from the disinfectant. The USEPA took this type of problem into consideration in its Surface Water Treatment Rule and the 1996Amendments (the Interim Enhanced Surface Water Treatment) (IESWT) rule that tightens controls on DBPs and turbidity and regulates Cryptosporidium. The rule requires continuous turbidity monitoring of individual filters and tightens allowable turbidity limits for combined filter effluent, cutting the maximum from 5 ntu to 1 ntu and the average monthly limit from 0.5 ntu to 0.3 ntu. J Note: Recall that the IESWT rule applies to large (those serving more than 10,000 people) public water systems that use surface water or groundwater directly influenced by surface water and is the first to directly regulate Cryptosporidium.

Temperature affects the solubility of chlorine, the rate at which disinfecting ions are produced, and the proportion of highly effective forms of chlorine that will be present in the water. More importantly, however, temperature affects the rate at which the chlorine reacts with the microorganisms themselves. As water temperature decreases, the rate at which the chlorine can pass through the microorganisms' cell walls decreases, making the chlorine less effective as a disinfectant.

Chapter Review Questions

213

Along with the presence of turbidity-causing agents such as suspended solids and organic matter, chemical compounds in the water may influence chlorination: high alkalinity, nitrates, manganese, iron, and hydrogen sulfide. 16.2.7 MEASURING CHLORINE RESIDUAL

During normal operations, waterworks operators perform many operating checks on unit process operations. One of the most important and most frequent operating checks an operator performs is the chlorine residual test. This test must be performed whenever a distribution sample is collected for microbiological analysis and should be done frequently where the treatment facility discharges to the water distribution system to ensure that the disinfection system is working properly. In testing for chlorine residual, several methods are available. The most common and most convenient is the DPD Color Comparator Method. This method uses a small portable test kit with prepared chemicals that produce a color reaction indicating the presence of chlorine. By comparing the color produced by the reaction with a standard, we can determine the approximate chlorine residual concentration of the sample. DPD color comparator chlorine residual test kits are available from the manufacturers of chlorination equipment. J Note: The color comparator method is acceptable for most groundwater systems and for chlorine residual measurements in the distribution system. However, keep in mind that the methods used to take chlorine residual measurements for controlling the disinfection process in surface water systems and some groundwater systems where adequate disinfection is essential must be approved by standard methods.

16.3 SUMMARY

Disinfection is critical to providing the public with clean, safe water. However, at every stage of the water treatment process, so that we are able to provide the consumer with potable water, we must move that water. Pumping systems, the machinery essential for that task, are covered in Chapter 17.

16.4 CHAPTER REVIEW QUESTIONS

16-1 Define sterilization:

16-2 Define disinfection:

16-3 Name two methods commonly used to disinfect drinking water other than chlorination.

16-4 Name the two types of hypochlorites used to disinfect water:

214

DISINFECTION

16-5 When is free chlorine obtained in the chlorination process?

16-6 The best pH range for disinfection is between

and

16-7 Describe what is meant by CT.

16-8 A chlorine leak can be detected by:

16-9 A chlorine demand test will show the:

16-10 The part of the chlorine cylinder designed to melt at approximately 158°F to prevent the cylinder from exploding in the event of fire is the:

16-11 What are chloramines?

16-12 Where should exhaust ducts and air inlet ducts be installed in chlorination rooms?

CHAPTER 17

Pumping Systems

Pumps are the usual source of energy necessaryfor the transportation of water from one location to another through various sizes and types of pipe. The only exception may be where the source of energy is supplied entirely by gravity. Modem waterworks operators must therefore be familiar with pumps, pump characteristics,pump operation and maintenance.17

17.1 INTRODUCTION

the chapter opening points out, waterworks rely extensively on pumps. Pumps provide the energy needed to move water from the aquifer to the surface of the ground, to move it through the treatment unit processes, to put it into a storage tank, to provide system pressure, and to feed chemicals. In short, pumping equipment forms an essential part of the transportation and distribution facilities for water. In fact, pumps may be the most important type of mechanical equipment in any water system, and almost every water system has at least one pump. This chapter briefly covers the subject of pumps and chemical feeders.

A

S

17.2 PUMPS

Essentially, a pump is a mechanical device designed to impart energy to a liquid such as water. The differences among the various types of pumps primarily concern the manner in which mechanical energy is transferred to the water. Some use the centrifugal force of a rotating impeller to pressurize water, while some use the concept of positive displacement to push the water down the pipe. J The elevation of any pump above the source of supply should not exceed 22 feet. J A pump is a device that puts energy into the water. This energy can be expressed in two ways: an increase in psi or an increase in flow. J Valves should be closed slowly to avoid water hammer. J A water seal on a pump serves two basic purposes: to lubricate and to keep materials from entering the packing assembly. 17.2.1 CENTRIFUGAL PUMPS

Centrifugal pumps are popular because of their simplicity, compactness, low cost, and ability to operate under a wide variety of conditions. Most well pumps and high-volume water pumps are "A. E. Hunt and C. M. Miller's Pumps and Measurement of Pumps in Manual of Wclter Utility Operations, 8th ed., C. K. Foster (ed). Austin, Texas: Texas Water Utilities Association, p. 372, 1988.

PUMPING SYSTEMS

t

Discharge

Nozzle

Figure 17.1 Cross-sectional diagram showing the features of a centrifugal pump.

centrifugal pumps. Centrifugal describes a pump that consists of a set of rotating vanes called an impeller, attached to a shaft that rotates in an enclosed housing or casing, with inlet and outlet piping connections (see Figure 17.1). The impeller driven at a high speed throws water into the volute, which channels it though the nozzle to the discharge piping. The rotating impeller transfers energy to the liquid from centrifugal force, but note that water is not pushed out the discharge. Instead, the impeller actually slips through the water in the casing, and this is why a centrifugal pump can be operated for short periods of time with the discharge valve completely closed. J In a centrifugal pump, internal leakage is prevented by wear rings. J Note: A centrifugal pump is the only type of pump that can be operated against a closed valve.

The impeller used for pumping drinking water consists of a number of curved vanes. The vanes curve backwards from the direction of rotation so the impeller can slide through the water. The vanes may be connected to a single shroud (in which case it is called a semi-open impeller) or may be totally enclosed between two shrouds (closed impeller). The closed impeller is the most efficient but can only be used on water with very low solids content. 17.2.1.l Types of Centrifugal Pumps Centrifugal pumps can be divided into one of three classifications based on configuration. The three are end suction centrifugal, split case, and vertical turbines.

l 7 . 2 . l . l . l End Suction Centrifugal Pump The end suction centrifugal pump is the most common centrifugal pump, frequently used in water plants, booster pump stations, and sewage lift stations. They are easy to recognize because the suction and discharge ports are usually at 90' angles to each other (see Figure 17.2). The water enters

Pumps

Figure 17.2 End-suction centrifugal pump.

the end of the pump parallel to the pump shaft. It leaves perpendicular to the shaft. Although many configurations are available, depending on manufacturer, end suction pumps all have the same operating characteristics. End suction pumps may be mounted horizontally or vertically. The motor may be connected to the pump by a shaft, or it may be close-coupled, with the pump impeller mounted directly on the pump shaft as in Figure 17.2. If the pump impeller needs to be serviced, the entire end of the pump casing must be removed and the impeller pulled off the shaft. 17.2.1.1.2 Split Case Pumps Split case pumps are unique. The case has a row of bolts that allow half of the case to be removed, providing access to the entire rotating assembly for inspection or removal. They are recognized by the piping arrangement: the inlet and outlet ports are parallel but on opposite sides of the pump (see Figure 17.3). Water enters the pump perpendicular to the drive shaft, turns 90" into the impeller, and leaves perpendicular to the shaft. Split case pumps are joined to the motor by a shaft. When removing the impeller is necessary, the top of the case is taken off, and the impeller and shaft lift out of the bottom of the case. These pumps are normally found as fire service pumps and circulation pumps in medium to large communities. 17.2.1.1.3 Vertical Turbine Pumps The vertical turbine type centrifugal pump is one of the most common configurations used in a water system (see Figure 17.4). Usually, several impellers (or stages) run on a vertical shaft with a pipe column that carries the water to the surface. The impellers are often located in deep wells, with the electric motors set vertically above the well, and joined by a flexible shaft. The multiple stages add more and more energy to the water, often necessary in a deep well. A common variation of the vertical turbine that is often used for small- and moderate-capacity wells is the submersible pump. A submersible pump is a vertical turbine pump with the motor close

PUMPING SYSTEMS

Figure 17.3 Split case centrifugal pump.

coupled to it and placed in a watertight enclosure; the pump and motor are connected to the surface with a flexible discharge pipe and electrical connections. This type of pump is extremely reliable and provides a neat, clean wellhead that can eliminate the need for a large structure around the well. However, if either the pump or motor needs to be repaired or replaced, the entire pump must be removed from the well. This often requires a crane and other specialized equipment. 17.2.2 POSITIVE DISPLACEMENT PUMPS

Positive displacement pumps force or displace water through the pumping mechanism. Most have a reciprocating element that draws water into the pump chamber on one stroke and pushes it out on the other. Positive displacement pump types include piston pumps, diaphragm pumps, and peristaltic pumps, which are the focus of our discussion. Positive displacement pumps are generally appropriate for small flow rates at high or very high discharge pressures, especially where carefully regulating the rate of flow is important. In the water supply industry, positive displacement pumps are most often found as chemical feed pumps. Remember that positive displacement pumps cannot be operated against a closed discharge valve. As the name indicates, something must be displaced with each stroke of the pump. Closing the discharge valve can rupture the discharge pipe, the pump head, the valve, or some other component. 17.2.2.1 Piston Pump

The piston pump is one type of positive displacement pump. This pump works just like the piston in an automobile engine. On the intake stroke, the intake valve opens, filling the cylinder with liquid. As the piston reverses direction, the intake valve is pushed closed and the discharge valve is pushed open; the liquid is pushed into the discharge pipe. With the next reversal of the piston, the discharge valve is pulled closed and the intake valve is pulled open, and the cycle repeats. A piston pump is usually equipped with an electric motor and a gear and cam system that drives a plunger connected to the piston. Just like an automobile engine piston, the piston must have packing rings to prevent leakage and must be lubricated to reduce friction. Because the piston is in contact

Figure 17.4 Vertical turbine pump.

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with the liquid being pumped, only good grade lubricants can be used on machines that pump materials to be added to drinking water. The valves must be replaced periodically as well.

17.2.2.2 Diaphragm Pump A diaphragm pump is composed of a chamber used to contain the fluid; a diaphragm operated by electric or mechanical means; and two valve assemblies, a suction and a discharge valve assembly. A diaphragm pump is a variation of the piston pump. In the diaphragm pump, the plunger is isolated from the liquid being pumped by a rubber or synthetic diaphragm. As the diaphragm moves back and forth by the plunger action, liquid is pulled into and pushed out of the pump. This arrangement provides better protection against leakage of the liquid being pumped and allows the use of lubricants that otherwise would not be permitted. Care must be taken to assure that diaphragms are replaced before they rupture. Diaphragm pumps are appropriate for discharge pressures up to about 125 psi but do not work well if they must lift liquids more than about 4 feet. Diaphragm pumps are frequently used for chemical feed pumps. By adjusting the frequency of the plunger motion and the length of the stroke, extremely accurate flow rates can be metered. The pump may be driven hydraulically by an electric motor or by an electronic driver in which the plunger is operated by a solenoid. Electronically driven metering pumps are extremely reliable (few moving parts) and inexpensive.

17.2.2.3 Peristaltic Pumps Peristaltic pumps (sometimes called tubing pumps) use a series of rollers to compress plastic tubing to move the liquid through the tubing. A rotary gear turns the rollers at a constant speed to meter the flow. The flow rate is adjusted by changing the speed at which the roller-gear rotates (to push the waves faster) or by changing the size of the tubing (so each wave moves more liquid). As long as the right type of tubing is used, peristaltic pumps can operate at discharge pressures up to 100 psi. The tubing must be resistant to deterioration from the chemical being pumped. The principal item of maintenance is the periodic replacement of the tubing in the pump head. This type of pump has no check valves or diaphragms.

17.3 PUMP MAINTENANCE Pumps are generally reliable, but they must be properly maintained to ensure this reliability. They must be lubricated and adjusted periodically. An important, but routinely neglected, task is adjustment of the packing gland. A packing gland shaft seal requires a constant drip of water to maintain the seal, cool the shaft, and flush debris out of the packing. Over time, the drip will increase; this signals the need to tighten the packing gland. Eventually, the packing gland will reach its limit of travel, at which point the packing must be replaced. Many pumps have mechanical seals instead of packing; these seals are not supposed to leak or drip. Lubrication is important, but equally important is not to over-lubricate. Using the right kind of lubricant is also important. For well pumps, only food-grade lubricants can be used on components that can contaminate the water. Excessive noise and vibration (especially of centrifugal pumps) indicates potential problems. If the pump room is dirty, pump and electric motor operation may be impaired; dirt will get into lubricants and shorten the life of the bearings. Keep in mind that pumps, like all rotating machinery, are inherently dangerous. In addition,

221

Chapter Review Questions

because most pumps are powered by electricity, electrical components such as wiring and controls must be adequately protected to prevent injury. Before working on any pump, be sure to lockouthagout the electric power source so no one can start the pump and so that automatic controls cannot kick in. If lockout/tagout is not possible, disconnect the electric power.

17.4 SUMMARY Pumps provide the muscle to move water from source to process to consumer in water operations. Feeder systems provide the means to ensure safe, accurate, and reliable chemical additions to the water. We discuss fluoride, a common drinking water additive, in Chapter 18.

17.5 CHAPTER REVIEW QUESTIONS 17-1 A water seal on a pump serves two purposes, which are:

17-2 In a centrifugal pump, internal leakage is prevented by:

17-3 A valve that allows water to flow in one direction only is a

valve.

17-4 The pressure at which a pump must operate is measured in terms of:

17-5 The energy placed into the water by a pump can be expressed as an increase in and an increase in 17-6 Why should valves be closed slowly?

17-7 The elevation of any pump above the source of supply should not exceed 17-8 What type of pump cannot be operated against a closed discharge valve?

feet.

CHAPTER 18

Fluoridation

The incidence of dental caries relative to the concentration offluoride in drinking water is well established. Low levels offluoride result in increasing incidence of caries, while excessivefluoride results in mottled tooth enamel. At the optimum concentrationfor the local climate, consumers realize maximum reduction in tooth decay with no aesthetically signzjicant dental jluorosis. Medical studies have also indicated thatfluoride benefits older persons by reducing the prevalence of osteoporosis and hardening of the arteries. Most public water supplies add fluoride to achieve an optimum level as a public health measure.I8

18.1 INTRODUCTION ECENTLY, various reports have surfaced professing that water fluoridation is not the safe public health measure we have been led to believe. Skeptics raise concerns over uncontrolled dosage, accumulation in the body over time, and effects beyond the teeth (brain as well as bones), saying that these issues have not been resolved for fluoride. These same skeptics justify their opinions by stating that, for the health of all citizens, ensuring that all the facts be considered is important, not just those that are politically expedient. Most modem medical authorities take issue with the skeptics7view about the efficacy versus the risk of fluoridating water supplies. Most authorities hold that a moderate quantity of fluoride ions (F-) in drinking water contributes to good dental health. Fluoride is seldom found in appreciable quantities in surface waters and appears in groundwater in only a few geographical regions. Fluoride is sometimes found in a few types of igneous or sedimentary rocks. Fluoride is toxic to humans in large quantities. It is also toxic to some animals. Based on human experience, fluoride, used in small concentrations (about l .O mg/L in drinking water), can be beneficial. Indeed, real-world, factual, documented experience shows that the addition of fluoride to drinking water reduces tooth decay among children between ages 10-15 by approximately 67 percent. It also helps to prevent root tip decay in people whose gums have begun to recede. Fluoridated water may also be beneficial for preventing bone fractures in individuals susceptible to osteoporosis. Experience and documented evidence also indicate that when the concentrations of fluorides in untreated natural water supplies are excessive, alternate water supplies must be used or treatment to reduce the fluoride concentration must be applied. Otherwise, excessive fluoride content in drinking water can cause mottled or discolored teeth, a condition called dentalfluorosis.

R

" ~ r o m~ r t h u rR. , A. J., Hanging on the Lifeline, Water and Environment International, 5(41) International Trade Publications, Surrey, England: pp. 12-13, 35-36,1996.

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Notwithstanding the opinions of several quasi-scientific studies, conducted by so-called "experts," the jury is in on the benefits of fluoridating drinking water supplies. The jury (i.e., the American Dental Association, the American Cancer Society, the Royal College of Physicians, the American Heart Association, and the American Medical Association) has given its endorsement to the procedure as safe and effective. The only adverse condition in a population that consumed fluoridated water might be some instances of mottled teeth. In this chapter, we briefly discuss fluoridation concepts of interest and importance to the entrylevel waterworks operator.

18.2 FLUORIDE ADDITION Waterworks operators whose public water supply does not contain enough fluoride to prevent tooth decay may be directed to adjust the fluoride content of the water. This relatively inexpensive process consists of adding the proper amount of the source chemical using a suitable chemical feeder. Waterworks operators who are already adding chemicals such as lime or chlorine to the water find the addition of fluoride very similar. The amount of chemical to be fed depends upon the amount of fluoride desired in the finished water, the amount already naturally present, and the fluoride source selected. The optimum concentration of fluoride ions (F-) in the finished water is generally designated as 1.0 mg/L or 1.0 parts per million (1 ppm). When fluoridation is practiced, enough fluoride-containing chemical is added to the water to maintain the fluoride content as close to 1.0 mg/L as possible.

J Note: Fluoride levels in water should not exceed 4.0 mg/L. To gain an appreciation for the proper dosage or addition of fluoride chemicals, consider that if the water supply contains only a trace of natural fluoride, and sodium silicofluoride is used, 14 pounds of this material must be added to each million gallons of water to have 1.0 mg/L. If hydrofluosilicic acid is used, then approximately 46 pounds (4.5 gallons) provide 1.0 mg/L fluoride in a million gallons of water. The exact amount of either chemical required varies according to the percent purity of the commercial product used and the natural content of the water supply. We mentioned two of the compounds used to fluoridate water-sodium silicofluoride and hydrofluosilicic acid. There is another compound that is also used: sodium fluoride. At one time, many veteran waterworks operators considered hydrofluosilicic acid too much of a safety hazard and too costly. Experience, however, has proven that hydrofluosilicic acid is actually less hazardous than once thought, compared with powdered silicofluoride. Sodium silicofluoride is available as a powder of approximately 98 percent purity containing 60 percent fluoride. Sodium silicofluoride is only partially soluble (0.75 percent at 75OF, less than 1 percent). Therefore, it is fed practicably only by dry feed machines, which feed the chemical at rates that give sodium silicofluoride a practicable solubility of about 0.2 percent. Water must be added to the solution vessel in sufficient amounts to dissolve all of the chemical fed, approximately 60 gallons per pound of chemical. The solution vessel size should be sufficient to provide a detention time of about 5 minutes and should be made of stainless steel or some other corrosion-resistant material, because the solution is quite corrosive. Piping is normally plastic or rubber. Hydrofluosilicic acid is usually available in 23 percent strength and contains approximately 18 percent fluoride. The price varies considerably depending on location source and the quantities ordered. This acid is fed by a displacement pump or chemical metering pump, either with or without dilution of the acid. Sodium fluoride is the most commonly used compound and is available in purity of 90 to 98 percent NaF. It is soluble in concentration of up to 4 percent. Some states require that the chemical,

Chapter Review Questions

225

which is white, be tinted blue to distinguish it from other water treatment chemicals. Saturated solutions of NaF are easily fed in the proportions necessary to obtain the concentration desired in water. The water used to make the solution may need to be softened. Fluoride chemical feeders may be broadly divided into two types: (1) solution feeders, where a measured volume of accurately prepared fluoride solution is delivered during a specified period; and (2) dry feeders, where a predetermined quantity of the solid material is fed during a given time interval. In addition to selecting one of the types of fluoride compounds and a feeder system, deciding where it should be applied is also necessary. Fluorides may be applied to the water at any point between the raw water intake check valve and the clearwell storing the treated water, or may be added to the effluent line. When fed prior to filtration, approximately 10 percent of the chemical adheres to floc and is lost, so feeding it to the filter effluent is more economical. The point of application should be selected based on conditions at each separate water supply. Well supplies, in many cases, require no treatment other than chlorination, and the water is pumped directly into the system. In such a system, fluoride must be fed at each well. The installation should be designed to allow fluoride feed at well pump operation. The main precaution required in feeding fluoride into a well supply is to provide sufficient mixing to be sure the water will have a consistently optimum fluoride content prior to reaching the first consumer outlet. Controlling the fluoride level in the water supply is, obviously, the most important part of the fluoride treatment process. If the fluoride level is not kept at optimum, consumers lose the full benefit, and if levels stay too high for an extended period of time, consumers might experience mild mottling of the teeth. To maintain proper fluoride dosage, records are kept of how much chemical is fed each day, how much water is treated each day, and the results of the tests for fluoride. Fluoridation requires an operator with certain qualifications. If local operators do not have these qualifications, and the community wants fluoridation, they must gain the necessary knowledge and lab skill required.

18.3 SUMMARY

Fluoridation is the last process step for water before delivery to the customer, though it is not the end of what entry-level operators need to learn, or the end of their responsibilities. We cover an issue that affects everything operators do on the job-safety-in Chapter 19.

18.4 CHAPTER REVIEW QUESTIONS

18-1 Does fluoride occur naturally in water?

18-2 Name three chemical compounds commonly used for fluoridation.

18-3 Why is having more than 4.0 mg/L fluoride in a public water supply undesirable?

CHAPTER 19

Safety

Though often ignored (until someone is injured, or worse), safety is as much apart of operating a waterworks as is adjusting thefeed rate of a metering pump. Safety is part of every action the operator takes. Everyone connected with a waterworks-the owner, administrators, operators, laborers, the administrative assistants, or plant clerk-has a responsibilityfor safety. When we speak of safety, we usually refer to the protection of the waterworks employeesfrom disease, injury, or death. Howevel; in the real world of waterworks operations, we must not and cannotforget the safety of the general public, as well-our customers. Last, but definitely not insignificantly,we must operate our waterworks in such a manner so as to protect our environment. Any behavior or action that comprises the safety of the workel; the public, andor the environment is not an option. The bottom line: waterworks are inherently dangerous work sites, and accidents on site may have further repercussions in the areas outside the plant. Our only defense? Safe work practices-ones that go beyond the writtenform.

HILE a waterworks may not seem like a hazardous work location, plenty of hazards await the uninformed, misinformed, or careless operator. The fact is, over the years, several statistical reports on accident rates have provided evidence that the waterlwastewater treatment industry is an extremely unsafe occupational field. Treatment plant personnel experience extremely high injury rates. The high injury rate occurs for several reasons. Chief among them is that all of the major classifications of hazards exist at waterlwastewater treatment facilities, with the exception, in most cases, of radioactivity. These classifications include the following:

W

oxygen deficiency (less than 19.5 percent oxygen) physical hazards toxic gases and vapors infections fire explosions electrocution I 9 ~ u c of h this information was adapted from F. R. Spellman and N. E. Whiting's Safety Engineering: Concepts and Applications. Rockville, Maryland: Government Institutes, 1999.

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SAFETY

Obviously, though, many industries have many of the same types of hazards in their workplaces. If this is the case, and it is, then why are those industry rates lower than waterlwastewater treatment facility injury rates? In this chapter, we answer this question. More importantly, we discuss a paradigm (a model or prototype) that has been used successfully to decrease the rate of on-the-job injuries in the water and wastewater professions.

19.2 SAFETY PRECAUTIONS Safe work practices for waterlwastewater operators have evolved over time around certain standard safety precautions, which usually include: compliance with plant safety policy compliance with plant safety rules using required safety equipment compliance with state and federal safety regulations investigation of accidents correction of identified safety hazards use of adequate personal hygiene implementation of an aggressive safety program Some argue that instituting the above safety precautions is all that is required to ensure the safety and health of workers in waterlwastewater operations. Few reasonable people would want to discredit the validity of and need for such precautions. However, stating that implementing a list of safety precautions will ensure the safety and health of "any" worker is ludicrous. Simply, safety involves more than that from management and workers. Any facility can institute safe work practices and written safety programs, rules, guidelines, etc. Instituting them is easy. However, if these procedures and practices do not have the full and strong support of top management, in essence, that facility has no safety policy or program. Under such conditions, written safe work practices, safety programs, rules, guidelines, etc., are nothing but empty words. They can provide little or no relevance in effecting workplace practices or protection for workers. In short, an organization's safety program begins with, or ends without, top management support. Upper management support and written safety programs and practices are a good beginning, but other elements are needed for an effective safety program in any organization. Worker training is an absolute necessity. Management support and written safety practices are worthless unless workers are informed of management's safety policy and written safety practices and are taught to implement them effectively. Remember, too, that safety training must be documented. Providing extensive, expensive time-consuming training is a futile effort if this training is not properly recorded. Enforcement is another important ingredient in the mix that makes up an effective safety program. Written rules and guidelines must be followed to be effective. Ensuring that they are followed is the responsibility of every supervisor and worker. Worker input is important in any safety program. Common sense dictates that those who work with or around hazards probably have a better feel or sense for the needed safety precautions (or rules) to protect themselves than would someone unfamiliar with the hazard. One thing is certain, putting together any program on paper then forcing it upon organizational members without their input has little chance of success. Another major element of any organizational safety program is compliance with the regulators; namely, compliance with OSHA. The items mentioned to this point (management support, written

OSHA-Required Safety Programs for Waterworks

229

safe work practices, training, enforcement, and worker input) are all important. However, all of these elements must be blended with one of the main ingredients that drives safety programs: regulatory compliance. Typically, in many water and wastewater treatment plants, specific OSHA Standards are applicable. Typical OSHA Standards that apply include the following: hazard communication confined space entry lockout/tagout respiratory protection hearing conservation laboratory safety machine guarding Personal Protective Equipment (PPE) electrical safety excavation safety fire safety hazardous materials emergency response bloodborne pathogens We discuss each of these OSHA-required programs in the following sections.

19.3 OSHA-REQUIRED SAFETY PROGRAMS FOR WATERWORKS J Note: Keep in mind that the guidance provided in the following sections discusses the "minimal" compliance requirements. Each plant must evaluate its own particular compliance requirements, whether the requirements be local, state, or federal, then ensure implementation. J Note: Written programs are the cornerstone of compliance with OSHA standards and are always requested by OSHA inspectors for review, to ensure compliance.

19.3.1 HAZARD COMMUNICATION OSHA's Hazard Communication Standard (a.k.a. HAZCOM or Employees' Right To Know Standard), 29 CFR l9lO.1200, is the most frequently cited OSHA violation, and the only standard that applies equally to all industries. HazCom requires that employers alert (communicate to) workers to the existence of potentially dangerous substances in the workplace. HazCom also mandates that employers provide their employees with the proper means and methods to protect themselves against hazards. With respect to communicating chemical hazards to employees, HazCom requires each employer to do the following:

(1) Make Material Safety Data Sheets (MSDS) available to all employees, designated representatives, contractors, visitors, and OSHA. (2) Instruct employees to label all portable containers containing hazardous substances not intended for their immediate use. (3) Train each employee about the main features of the standard: labels, MSDS, the written program, list of hazardous materials, and required training, and inform each employee of how to

SAFETY

recognize, understand, and protect themselves from hazards they will encounter in the workplace.

19.3.2 CONFINED SPACE ENTRY PROGRAM Whether the confined space is a manhole, chemical storage tank, pumping station wet well, or other process vault or vessel, confined space entry and water treatment are intertwined. Along with the requirement to develop a written confined space program, employers are required under OSHA's Confined Space Entry Standard (29 CFR 1910.146) to do the following: (1) Identify and properly label all workplace confined spaces. (2) Train confined space entrants, attendants, and "competent" persons on all aspects of safe confined space entry (document the training). (3) Train and station a qualified rescue team at each entry location whenever required. (4) Ensure that someone qualified and trained in CPWFirst Aid is readily available anytime confined space entry is effected. (5) Provide approved safety equipment to ensure safe confined space entry (air monitoring, etc.).

19.3.3 LOCKOUTITAGOUT PROGRAM Maintenance and servicing of plant machinery often require that existing safeguarding be removed or disengaged to provide access to machine parts and controls. During these operations, isolation and deenergization of the equipment by the person or persons performing the work is required to protect the worker(s) from unexpected start-up of the machine or release of energy. This is called Lockout/Tagout and is covered under OSHA's 29 CFR 1910.147 Standard. Lockout, which involves placement of a lockout device on an energy isolating device, is the most effective means to protect maintenance personnel. Energy isolating devices are mechanical devices that physically prevent the transmission or release of energy. Examples include manually operated electric circuit breakers, disconnect switches, and line valves. Tagout, which involves placement of a warning tag on or near the energy isolating device, can be adequate to protect personnel if all tagout procedures are understood and followed by all employees. Along with a written lockout/tagout program, employers are required to do the following: (1) Develop energy control procedures (in writing). (2) Provide to employees the protective materials and hardware required to properly effect lockout/ tagout. (3) Ensure that lockout/tagout devices are used only for energy control. (4) Ensure that lockout/tagout devices are substantial enough to prevent removal without excessive force or unusual techniques. (5) Ensure that lockout/tagout devices identify the specific employee applying the device. (6) Conduct periodic inspections of the energy control procedures at least annually. (7) Ensure that all employees are trained on recognition of applicable hazardous energy sources, the type and magnitude of the energy available in the workplace, and the methods and means necessary to control and isolate energy (document training).

19.3.4 RESPIRATORY PROTECTION PROGRAM Water workers may need protection from airborne contaminants that present health hazards. Proper protection from airborne contaminants is the responsibility of the employer. When airborne

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hazards cannot be eliminated by other methods of control, proper selection and use of respiratory protection is part of that responsibility. Remember that respiratory protection is more than simply distributing respirators to workers who are exposed to airborne hazards. Effective protection of workers demands that a well-planned program be implemented, including medical evaluation, evaluation of the airborne hazard, proper selection of respirators, fit testing, regular maintenance, and employee training. In the past, employers supplied respirators to workers without first establishing a comprehensive respirator program, relying on the excuse that the respirators are not really required because contaminant concentrations in the work environment do not exceed permissible exposure limits (PELs). This practice is strictly prohibited by OSHA regulations. At any rate, the practice of issuing workers with respirators implies that a hazard exists. In addition to a written program, the employer is required to do the following: (l) (2) (3) (4) (5) (6) (7) (8) (9) (10)

Evaluate the workplace for respiratory hazards. Select respirators based on the hazards present. Determine the types of respirators to be used. Provide instructions, training, and fit testing of the user. Provide instructions on how to clean and disinfect respirators. Provide proper storage for respirators. Maintain and inspect respirators. Evaluate the Respiratory Protection Program on a periodic basis. Ensure that workers who are required to don respirators are medically fit to do so. Ensure that only approved and certified respirators are used in the workplace.

19.3.5 HEARING CONSERVATION PROGRAM

While many of the unit processes in water treatment are fairly quiet, other treatment processes require machinery. Machines make noise and can be a safety and health hazard. Noise-induced hearing loss has long been recognized as a serious workplace problem by safety and health professionals and OSHA. Hearing loss can be temporary or permanent, depending on the noise level and length of exposure. Hearing protection is required for cases in which engineering or administrative controls are not effective in reducing employee exposures below permissible levels. The OSHA Occupational Noise Exposure Standard (29 CFR 1910.95) was implemented to protect workers from noise-induced hearing loss in the workplace. Along with having a written Hearing Conservation Program, under the standard, the employer is required to do the following: (l) Identify any areas or production processes that may overexpose an employee or employees to noise (i.e., conduct a workplace noise level survey and document the results, and make the results of the survey available to employees). (2) Obtain personal noise dosimetry measurements for employees assigned to these areas. (3) Conduct initial and annual audiometric testing of employees exposed to noise levels 85 DBA and above. (4) Maintain records for each employee assigned to work in high noise areas (i.e., record of exposure to high noise levels and records of workers' hearing acuity). (5) Provide hearing protection (at no cost to workers). (6) Provide and document training on hearing conservation, hearing protection, and other related issues. (7) Post warning signsllabels in high noise areas.

232

SAFETY

19.3.6 LABORATORY SAFETY Most water treatment plants have their own laboratories. Whether the laboratory is a smallor large-scale operation, or somewhere in between, the lab must still comply with OSHA's Laboratory Standard (29 CFR 1910.1450). Remember, no matter what the size of the laboratory, safety plays a key role in maintaining worker well-being and compliance with applicable Health, Safety and Environmental Standards. Along with a written Lab Safety Program or Chemical Hygiene Plan (CHP), the employer is required to do the following: (1) Provide the same kinds of safety programs for lab workers that are provided for all workers (2) In addition, a water laboratory that handles hazardous chemicals must have a written Chemical Hygiene Program (CHP). The written CHP must include the following: a. Procedures for minimizing chemical exposure b. Procedures for determining hazards c. Ventilation requirements d. Assigned responsibilities for safety and health of all lab personnel e. Basic safety rules and procedures f: Spill response plan g. Training h. Environmental monitoring i. Procedures for disposal of wastes j. Broken glass disposal procedure k. Personal protective equipment must be provided to lab workers at no cost to the workers l. Medical surveillance program for those lab workers exposed to hazards m. MSDS n. Labeling procedures

19.3.7 MACHINE GUARDING While machines allow more efficient, productive work, water workers must use them with great caution. OSHA has put forth several regulations that apply to the use of machinery and machine guarding. These rules can be found in 29 CFR 1910.211-.247. Along with written machine guarding procedures, the employer must do the following:

(1) Provide employee training on the hazards related to machines. (2) Institute a program whereby all machineslmachinery are routinely inspected to ensure that guards are in place andlor in good working condition. (3) Institute a lockout/tagout program that will ensure that when machines are put out of commission for any reason, they present no hazard to workers. (4) Ensure that employees wear appropriate clothing when operating or working around hazardous machines. Loose, oversized clothing can easily catch on machine parts. Employees should wear chemical-resistant clothing and shoes if the machine creates an exposure potential to lubricating oils or other substances. Employees with long hair may need to wear hats or hairnets if the long hair represents a hazard from the proximity of moving machinery in regard to. 19.3.8 PERSONAL PROTECTIVE EQUIPMENT (PPE) The primary objective of the waterlwastewater safety program is worker protection. Plant management holds the responsibility for carrying out this objective. Under OSHA's PPE Standard, 29 CFR 1910.132-1 38, part of this responsibility includes protecting workers from exposure to haz-

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233

ardous materials and hazardous situations that arise in the plant. The most effective way for plant management to try to eliminate these hazardous exposures is through changes in workplace design or engineering controls. Hazards should a1ways be "engineered out of existence," when possible. When hazardous workplace exposures cannot be controlled by these measures, personal protective equipment (PPE) becomes necessary. When looking at hazardous workplace exposures, keep in mind that OSHA regulations consider PPE the last alternative in worker protection because it does not eliminate the hazards. PPE only provides a barrier between the worker and the hazard. If PPE must be used as a control alternative, a positive attitude and strong commitment by management are required. In short, engineer out the hazard first, guard against the hazard second, and when neither of the preceding is possible, educate the workers about the hazard, and when no other recourse is available, provide appropriate PPE. Along with a written PPE safety program, the employer is required to do the following: (1) Make an assessment of the workplace to determine what hazards are present and what type of PPE is required to protect workers from the hazards. (2) Select proper type of PPE based on the hazards. (3) Implement an effective and thorough training program. (4) Familiarize workers with correct use and maintenance of PPE. (5) Enforce the use of PPE. 19.3.9 ELECTRICAL SAFETY

Water operators could not easily perform their assigned duties without the aid of electricity and electrical devices and machinery. Electricity has become such an integral part of our lives in the workplace and at home that we tend to take its power for granted, but here is a sobering fact. The Bureau of Labor Statistics (BLS) reported that during 1994, more than 300 of work-related deaths resulted from electrocution. Electrical accidents in water treatment plants can, for the most part, be avoided if safe electrical equipment and work practices are incorporated into the plant's safety program. Along with abiding by the requirements of OSHA's 29 CFR 1910.301-.399 (Electrical Safety Requirements), the employer must develop a written Electrical Safety Program that includes the following elements: (1) Workers must be trained on safe work practices for working with and/or around electrical equipment. (2) Workers must be made aware of the hazards involved with electricity. (3) Appropriate lockout/tagout procedures must be used anytime electrical machinery/equipment is to be worked on. (4) Electrical hazards must be appropriately marked or labeled (e.g., Danger: High Voltage). (5) Only approved electrical equipment should be used in the workplace. 19.3.10 EXCAVATION SAFETY

Water workers are frequently required to excavate to repair broken collection or interceptor system piping. OSHA regulations pertaining to excavation work (trenching and shoring) can be found in 29 CFR 1926.650-.652. An effective excavation safety program begins with knowing the hazards; workers must know the hazards they face during these operations and how to safeguard themselves from the hazards. Excavation work literally allows no room for error.

234

SAFETY

Along with developing a written excavation safety program, the employer should do the following: (1) Train all workers involved in excavation work on the proper procedures to use in excavating. (2) Contact utility companies before digging begins, to ensure that underground installations are found. (3) Assign a "competent" person to supervise the excavation.

J Note: OSHA defines the "competent" person as someone trained and capable of identifying existing and predictable conditions that are unsanitary, hazardous, or dangerous to workers. This person is responsible for performing the soil classification analysis; they have the authority to take prompt corrective measures to eliminate any hazards; they may be responsible for coordination and direction of emergency response; and they must inspect the excavation and adjacent areas at least once a day for signs of possible cave-ins, failures of protective systems and equipment, hazardous atmospheres, or other hazardous conditions. (4) Have emergency response procedures in place and emergency rescue equipment ready, in case an accident occurs.

19.3.11 FIRE SAFETY Fire can occur in any workplace. For plants handling large quantities of flammable materials, fire safety is the single most important safety concern. For others, fire still usually represents an extreme hazard, given the potential for economic damage and human tragedy. Clearly, fire safety is very important-important enough for OSHA to have mandated two separate fire protection standards: 29 CFR 1910.38 and .157. Along with a written fire prevention safety program, the employer must do the following: (1) Train all employees on the hazards of fires, fire chemistry, the causes of fires, proper use and storage of flammable materials, and types of portable fire extinguishers and how to use them properly. (2) Develop a fire prevention control program. (3) Conduct periodic plant inspections to ensure that fire hazards are removed or are properly controlled.

19.3.12 HAZARDOUS MATERIALS EMERGENCY RESPONSE If the water treatment plant uses or produces hazardous materials on the plant site, OSHA, under its 29 CFR 1910.120 Standard, requires the facility to develop an Emergency Response Plan for Chemical Emergencies. Under this Standard, the employer must do the following: (1) Develop a written emergency response plan for chemical, fire, and medical emergencies. (2) If plant employees are required to respond aggressively to chemical spills, fires, or provide emergency medical assistance (first aid/CPR), they must be fully trained to do so. (3) If employees are required to respond to chemical spills, fires, or medical emergencies by calling 911 or other emergency phone numbers, they must be trained on how to do this. (4) Whatever choice the employer makes for emergency response, the plan must be coordinated with local emergency responders (i.e., fire department, local HazMat Team, etc.).

Specific Hazards Related to Waterworks Operation

235

19.3.13 BLOODBORNE PATHOGENS Although the Center for Disease Control (CDC) has determined that HIV and other bloodborne pathogens are not waterborne diseases, the CDC warns that persons who provide emergency First AidKPR could become contaminated. For example, if a worker finds another worker or other person unconscious and not breathing, the worker could become contaminated with a bloodborne pathogen disease if the worker renders CPR to the victim without proper personal protection. If a worker attempts to aid another worker or other person who is bleeding, again, the worker could become contaminated with a bloodborne pathogen disease. Rendering any kind of first aid assistance whereby the rescuer canlcould be exposed to another person's body fluids must be done with care and caution and with proper personal protection. To protect employees from bloodborne pathogens (HIV and Hepatitis B), the employer must do the following: (1) Train all employees on the hazards of bloodborne pathogens. (2) Equip all company first aid kits with rescue barrier masks to prevent mouth to mouth contact, with latex protective gloves to prevent contact with body fluids, and with eye protection and a biohazard bag for disposal of cleanup materials. (3) Afford the exposed employee medical attention, including immunizations for self-protection at no cost to the employee as mandated by 29 CFR 1910.1030. 19.4 SPECIFIC HAZARDS RELATEDTO WATERWORKS OPERATION

We stated in the chapter opening that waterworks are inherently dangerous. We base this statement on two known facts: (1) statistics show that waterworks operators are injured on the job at a higher frequency than those in most other professions, and (2) waterworks operators, while exposed to the same workplace hazards as many other workers, are also exposed to chemical hazards, chemicals that by their very nature are hazardous, especially when handled incorrectly or unsafely. 19.4.1 HANDLING CHEMICALS

Written safe work practices that cover the correct procedures used when handling chemicals are critical to protecting the waterworks operator (and the public and the environment, as well). Many chemicals are used in a waterworks operation. Even simple well systems, for example, may use a chiorine compound (sodium hypochlorite or calcium hypochlorite) and perhaps fluoride; more complicated facilities will use gaseous elemental chlorine, lime, alum, powdered activated carbon, caustic, ammonia, hydrofluosilicic acid, as well as other chemicals. The various chemicals fall into some large groups. Each group has different characteristics and requires different precautions on the part of the operator. Each operator must know how to store chemicals, which chemicals will burn, how to put out chemical fires, how to feed the chemicals into the water, and how to mix chemical solutions. The waterworks operator must know which chemicals must be kept dry, which ones must be kept cool, which ones must be kept away from others; which ones form dust, which ones can burn the skin; which ones are toxic and in what concentrations, and the first aid or antidote to use. Remember, any exposure to water treatment chemicals can be dangerous. Any time a chemical spills on the body or splashes into the face, or when a chemical is ingested, professional help must be sought immediately. Some general precautions apply to all chemicals used in water treatment:

236

SAFETY

Use Personal Protective Equipment (PPE) Goggles, gloves, aprons, full-faceshields, boots, and other protective equipment are required when handling many chemicals. The PPE should be stored near the chemical handling area and should not be worn elsewhere in the facility. Do not work alone Whenever handling chemicals, the two-person rule should be in effect; someone else should be close by who knows what is going on to provide help if needed. Know the chemicals Know the dangers of each chemical and what to do if something goes wrong. Keep important safety information handy (material safety data sheet-MSDS) so it can be reviewed frequently. Do not smoke, eat, or drink around chemicals Chemical fumes and dust can get into food or be drawn in when inhaled. Many chemicals are flammable, meaning they will burn. Smoking must be strictly prohibited in chemical areas. Practice good housekeeping Clean up chemical spills immediately, and dispose of spilled material properly. Spilled chemicals pose chemical hazards and also present slip hazards. 19.4.1 .l Acids A number of different acids are used in water treatment, although most small waterworks will not keep these chemicals around. Some acids are relatively weak (such as acetic acid), while others are extremely strong (hydrofluosilicic acid, nitric acid, sulfuric acid). If acid spills on someone, the clothing should be immediately removed, and the person should get under a deluge shower as quickly as possible. Most acids will burn the skin very quickly. If the waterworks uses strong acids, special emergency showerleyewash stations must be set up within 100 feet or within 10 seconds reach of any employee exposed to corrosive chemicals. J Note: Keep in mind that within 100 feet andor 10 seconds means that a person who has a face full of sulfuric acid or other corrosive acid should be able to reach the emergency showerleyewash easily, without interference (doors, bulkheads, etc.).

Some of the acids commonly found at a waterworks facility include the following: acetic acid hydrofluosilicic acid hydrochloric acid nitric acid sulfuric acid Many acids give off irritating or even suffocating vapors. Work areas where acids are used should be well-ventilated. Rubber gloves, rubber aprons, and splash-proof goggles or full-face shields are required. One important way to handle acid spills is by neutralization, by applying a base such as sodium bicarbonate or lime to the acid. However, this must be done carefully (and by trained personnel only) to avoid a dangerous reaction. Whenever an acid spill occurs, the work center supervisor and local fire department should be notified immediately. 19.4.1.2 Bases

Bases used in waterworks operations are normally used to raise the pH of the water, although hypochlorite disinfection compounds are also bases. Some are very toxic and some will cause severe skin burns. When bases come in contact with acids, an explosive reaction can occur, although dilute acids can be used to neutralize bases that have been spilled.

Specific Hazards Related to Waterworks Operation

237

Many of the precautions mentioned for acids apply to bases as well. Use PPE and avoid breathing the vapors of the bases-some of them can be suffocating, while others can irritate the lungs. Some of the bases used in waterworks operations include the following: ammonia calcium hydroxide (hydrated lime) calcium oxide (caustic) sodium hydroxide (caustic) calcium hypochlorite (HTH) sodium carbonate (soda ash)

19.4.1.3 Gases Several gases are commonly used in waterworks operations, although the primary one is chlorine. Most water treatment gases are sold in compressed (liquified) form in steel cylinders. Compressed gases expand rapidly, in some cases almost explosively, if the tank ruptures. The expansion process requires heat, which means that rapidly expanding gases can freeze the cylinder and tubing in the gas feed system. Most gases used in waterworks operations are heavier than air, which means that they will accumulate near the floor (e.g., chlorine). Ventilation equipment in gas feeding and storage areas should pull from near the floor. When entering a room in which gases have escaped, an approved selfcontained breathing apparatus (SCBA) must be worn; not just a canister-type gas mask (an air purifying mask should not be worn; an air supplying-type mask is required). Gas cylinders must be handled with care. Do not drop them or bang them together. Never store incompatible gases adjacent to each other (e.g., oxygen and acetylene should be separated by 20 feet or by a wall at least 5 feet high). Empty cylinders should be stored separately from full cylinders. Never lift a cylinder by the neck, and always use lifting clamps or cradles instead of ropes, cables or chains. Cylinders must be stored so they cannot fall over, using safety chains or clamps for stability. Keep the protective caps on all cylinders not in use. Storage areas should be kept cool (chlorine storage rooms should be kept well below 140°F). Never use an open flame on a gas cylinder or on any pipe carrying a gas. Keep gas cylinder repair kits handy for any gas cylinders stored at the facility. Never attempt to repair a gas leak alone. Any time a room must be entered that contains an escaped gas, another person must stand by as an observer, and this observer must be trained on rescue and first aid procedures. J Note: Under OSHA's HAZWOPER Regulation (29 CFR l9lO.l2O), only trained and fully qualified emergency responders are allowed to aggressively attack a leaking chlorine cylinder (that is, any leaking chlorine cylinder with the potential to cause harm because of the level of toxic gases released or that has exceeded the threshold level of release, more than 10 lbs of chlorine).

No matter how minor a gas leak is, never enter a room containing escaped gas without proper respiratory protection. If you are caught in an area with a gas leak, do not panic, but leave the area immediately. Do not breathe or cough, and keep your head high until well away from leak. Call for help as soon as you reach safety.

19.4.1.4 Salts Many chemical salts are used in waterworks operations, although small systems do not use many of these. The characteristics of salts vary greatly; check the material safety data sheet (MSDS) for any chemicals used at the facility.

238

SAFETY

Among the chemical salts used in waterworks facilities are: aluminum sulfate (alum) ferric chloride ferric sulfate fluoride compounds sodium hexametap hosphate copper sulfate potassium permanganate Salts must be kept away from all acids and bases. When handling dry chemicals in bulk, they should be kept in a fire-safe area. Keep lids on containers and follow the instructions on the container. Avoid breathing the dust of salts when emptying bags or containers of salts into feed hoppers or solution tanks. Wear proper clothing including chemical goggles or face shield, rubber gloves, rubber boots, rubber apron, and a proper chemical (air-purifying) respirator. Concentrated solutions of many salts are slippery, and spills must be cleaned immediately. Many salts are slightly acidic or basic and should be neutralized before being washed down floor drains. 19.4.1.5 Powders

Powdered activated carbon is the most dangerous powder that operators are likely to contact at a waterworks. Powdered activated carbon (or PAC) is very dusty, which causes uncomfortable working conditions and can damage equipment, but it is not corrosive and will not attack the human body. The primary danger of PAC is the threat of fire. Carbon fires produce intense heat but bum with no visible smoke or flame, so they are often difficult to locate in a storage room or bin. PAC fires are also very difficult to put out. PAC must be stored in a clean, dry, fireproof location. Keep it away from all other chemicals. Never allow smoking or an open flame in the vicinity of PAC. Keep large carbon dioxide fire extinguishers near PAC storage and feed locations. Store bags of PAC in single rows no higher than 4 feet. Keep access aisles clear to prevent damage to the bags. All electrical equipment in carbon storage and feed areas must be explosion-proof. Keep equipment clean and dry. Never use a stream of water on burning PAC because it will cause particles of burning carbon to fly. Use only carbon dioxide fire extinguishers or fire-fighting foam. A carbon fire will burn without atmospheric oxygen, so firefighters must wear SCBA to avoid suffocation. 19.5 STORAGETANK SAFETY Many ground storage tanks and all elevated storage tanks have ladders for gaining access to the top of the tank. The ladder should be equipped with an appropriate locking device to keep unauthorized people from climbing the tank and a safety cage (if more than 20 feet in height) to protect those who are authorized to climb the tank. Never enter a water tank, whether empty or full, without taking proper precautions (which means adhering to the organization's Confined Space Entry Program). In addition, elevated storage tanks have a drop pipe at the bottom; this must be adequately guarded. Use safety lines and harnesses, scaffolding, nets, and other safety equipment when entering storage tanks. Some of the more horrific tales related to waterworks-related deaths involve those that have occurred in water storage tanks.

Chapter Review Questions

19.6 SAFETY INSPECTIONS Written safety programs and their implementation are important. Ensuring their effectiveness is even more important. Periodically, the plant should be inspected by the safety officer or some other designated person to ensure that safe work practices are followed, that safety rules and policies are abided by, and that the material condition of the plant site is good. Whenever safety inspections are conducted, some type of procedure whereby discovered discrepancies are corrected must be in place. The written report of the safety inspection must be placed in the hands of those plant officials responsible for ensuring safety compliance. After a reasonable length of time, any discrepancies that were discovered during the inspection should be re-checked to verify that they have been corrected. If they have not been corrected, action must be taken to ensure that they are corrected. A copy of all safety inspections must be kept on file. This is important for OSHA compliance.

19.7 ACCIDENT INVESTIGATIONS No matter how good the plant's safety program, accidents do and will occur. When they occur, finding the causal factors is essential. Once identified, these causal factors must be corrected as soon as possible. The results of accident investigations (i.e., the causal factors) are usually a good source of lessons learned. These lessons must be passed on to all employees to avoid recurrence.

19.8 SUMMARY While water operators face on-the-job risks, safe work practices, followed properly, consistently, and most importantly, thoughtfully, protect workers from job-site hazards. The key to your personal safety, though, is treating safety precautions with the respect they deserve. Familiarity with a job makes the hazards that job presents easy to ignore. For your own safety, don't fall into the trap of taking your skill or your safety for granted.

19.9 CHAPTER REVIEW QUESTIONS 19-1 What essential element is needed to begin an effective safety program?

19-2 Arrange the following steps in hazard control in the proper sequence: (1) guard the hazard, (2) engineer the hazard out if possible, (3) educate personnel.

19-3 What is the most important feature of a maintenance department's safety program?

19-4 What is the primary reason for accident investigation?

240

SAFETY

19-5 What systems do lockout/tagout programs apply to?

19-6 At the scene of an incident, which concerns should be given the highest priority?

CHAPTER 20

Final Exam

20.1 INTRODUCTION

ow that you have read each lesson and have completed the chapter review questions, you may test your overall knowledge of the waterworks fundamentals covered in this volume of the Handbook by completing the following review examination. For the questions you have difficulty answering or that you answer incorrectly, review the pertinent sections containing the applicable subject matter. Successful review and completion of all of the requirements specified in this edition of the handbook should prepare you for the entry-level certification examinations and should set the stage (along with completion of Handbooks 2 and 3) for subsequent successful completion of higher-level certification examinations. For those operators preparing for the higher level licensing exams (the actual entry-level class or grade depends on the state in which you seek licensure), review and completion of the requirements in Volumes 2 and 3 of the handbook (intermediate and advanced levels) is highly recommended. Unlike the actual state licensure examinations, which contain an assortment of different types of questions (i.e., multiple choice, true or false, essay, completion questions, etc.), the final review examination presented in each handbook requires a written completion answer to each question. We have formatted the examinations this way because in our experience, writing out the "correct" answer provides better information retention. As a student studying for an exam, view only the correct answers, not several different choices (many of which are incorrect). That can create confusion when you need to generate the correct answer yourself and lead you to select the wrong answer on the actual licensure examination. You will notice that several mathematical operations are presented in the final review examination. These questions are included, of course, because on actual licensure exams, you must be able to perform basic mathematicai operations. Without such knowledge and ability, obtaining a successful score to qualify for licensure is much more difficult (if not impossible). When you complete the final review exam, check your answers with those given in Appendix B. The formulae sheet in Appendix C should be used while completing this exam. Good luck!

N

20.2 REVIEW EXAM

20-1 Give two reasons for treating water.

20-2 The amount of water required to cover 1 acre 1 foot deep is expressed as:

242

FINAL EXAM

20-3 The process of bubbling air through a solution is called:

20-4 The oxygen used in meeting the metabolic needs of aerobic microorganisms in water rich in organic matter is known as:

20-5 An equation used for computing the quantity of water flowing through process media is:

20-6 The difference between the static level and the pumping level is known as:

20-7 Water that has been used for showering, clothes washing, and faucet use is called:

20-8 The force exerted on a unit area is called:

20-9 The gradual downward flow of water from the surface into soil material is known as:

20-10 An imaginary surface that coincides with the hydrostatic pressure level of water in an aquifer is called:

20- 11 An agency or person that supplies potable water is called a:

20-12 The appearance or disappearance of water at the ground surface is known as:

20-1 3 All water that occurs below the ground surface is called:

20-14 A solution of known strength or concentration (used in titration) is called:

Final Exam

243

20-15 The change of a substance from a liquid or solid state to the gaseous state is known as:

20- 16 The area of land that contributes surface runoff to a given point in a drainage system is called:

20-17 Name two types of disease transmission:

20- 18 Define total coliform:

20- 19 Define fecal colifonn:

20-20 What is the primary function of a public water supply?

20-21 Water cycles from the atmosphere to the earth and back to the atmosphere. What is this natural water cycle called?

20-22 The three states of matter are:

20-23 A compound is the combination of two or more 20-24 A charged atom is called an 20-25 A solid that is less than l micron in size is called a:

20-26 Define turbidity:

20-27 Two categories of water color are:

244

FINAL EXAM

20-28 A compound derived from minerals is called:

20-29 A compound derived from former living matter is called:

20-30 Define alkalinity :

20-3 1 Name two compounds that cause water hardness:

20-32 A device that permits flow of a fluid in a pipe in one direction only is known as a

20-33 A disadvantage of drawing water supply from a large lake is:

20-34 Write a formal equation that correctly shows the relationship between gauge pressure and absolute pressure:

20-35 The term "runoff" refers to:

20-36 Rate of flow of water through a water treatment plant is usually referred to in terms of:

20-37 Leaves are removed from the water entering the waterworks or aqueduct by:

20-38 The term "watercourse" refers to:

20-39 The first precaution a worker should take before entering a confined space is to:

245

Final Exam

20-40 When dealing with a leaking chlorine cylinder, you must remember that chlorine gas is:

20-41 The three major groups of microorganisms that cause disease in water are:

20-42 Are coliform bacteria pathogenic?

20-43 When a protozoan is in a resting phase, it is called a:

20-44 Name two pathogenic protozoans:

20-45 For a virus to live, it must have a:

20-46 Which is easier to destroy with chlorine, bacteria or viruses?

20-47 One cubic foot of water weighs?

20-48 One gallon of water weighs?

28-49 A flow of 1. cubic foot per second is equivalent to 20-50 Headloss is the result of:

20-5 1 What units are used to measure energy in pumping?

20-52 What are representative samples?

gPm.

246

FINAL EXAM

20-53 Water samples containing residual chlorine are generally dechlorinated by the addition of:

20-54 An incubating temperature of group.

"C is used for tests conducted on the coliform

20-55 A presumptive test is negative if gas is not produced within:

20-56 When are primary fermentation tubes used?

20-57 Define a composite number:

Final Exam

20-72 A water system has three wells with the following capacities: 110 gpm, 115 gpm, 95 gpm. What are the mean and medium pump capacities?

20-73 If we need 8 pounds of chemical to treat 1,200 gallons of water, how many pounds of chemical will we need to treat 15,000 gallons?

20-74 A 60-foot high water tank has 40 feet of water in it. How full is the tank in terms of the percentage of its capacity?

20-75 Convert 60 psi to feet of head.

20-76 Convert 16 psi to feet.

20-77 Convert 0.186 MGD to gpm.

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FINAL EXAM

20-78 Find the flow in cfs in a 6-inch line, if the velocity is 2 feet per second.

20-79 Find the flow in gpm when the flow is 0.65 cfs.

20-80 The reservoir for a community is 120,000 gallons. The well will produce 40 gpm. What is the detention time in the reservoir in hours?

20-81 What is the surface area of a circular tank with a 30 foot diameter?

20-82 Find the volume of a fuel tank 6 feet in diameter and 15 feet long.

20-83 Convert 80 gallons to pounds.

20-84 The sedimentation basin of a waterworks contains 8,240 gallons. What is the detention time if the flow is 150 gpm?

20-85 Water that is clear, without color or turbidity and tastes and smells good is said to be:

20-86 What is the maximum fluoride content of drinking water?

20-87 The first chemical process in water treatment is called:

20-88 Turbidity is measured in:

20-89 The quantity of chemical added to the water is called the:

Final Exam

20-90 The device used to determine proper chemical dosage of a coagulant is called:

20-91 The amount of free chlorine residual is directly related to the added.

of

20-92 The length of time water is kept in a basin is known as:

20-93 The process of cleaning a filter by pumping water up through the filter media is called:

20-94 In a small community, what is the most common method used to remove hardness?

20-95 A sedimentation tank is 40 feet by 12 feet. What is the area of the water surface in the tank?

20-96 What is the name of the agent used to keep iron and manganese in solution?

20-97 Define sterilization.

20-98 The best pH range for disinfection is between

and

20-99 What is meant by CT?

20- 100 Neutrality on the pH scale is:

20-101 A combination of two or more elements is a:

20-102 What type of substance produces hydroxide ions (OH-) in water?

250

FINAL EXAM

20- 103 Volts are the units of electrical 20-104 Opposition to current flow in an electrical circuit is known as what?

20-105 The three particles of an atom are:

20-106 An electrical circuit has a power source of 12 volts and a total circuit resistance of 120 ohms. What is the total amperage in the circuit?

20- 107 A column of water 65 feet high exerts how much pressure?

20-108 A column of water 2.3 1 feet high will exert 1.0 psi. To produce a pressure of 65 psi requires a water column high. 20-109 Find the height of water in a tank if the pressure at the bottom of the tank is 12 psi.

20-110 A pipe 12 inches in diameter has water flowing through it at 6 feet per second. What is the discharge in (a) cfs, (b) gpm, (c) MGD?

20- 111 Describe TDH.

20- 112 Describe head.

20-1 13 The three sources of drinking water are:

20-1 14 What are two advantages of surface water sources?

20-1 15 How far should the well casing extend above the ground or well-house floor?

Final Exam

251

20-1 16 Clogging, cementation, or stoppage of a well screen and water-bearing formation resulting from chemical or biological reactions at the air-water interface in the well is known as:

20-117 A collecting area is also known as:

20- 118 What is the purpose of adding copper sulfate to a reservoir?

20-1 19 The pressure in a water distribution system should never drop below:

20- 120 What is a cross-connection?

20-121 How often should cross-connection devices be tested?

20- 122 Disease-causing microorganisms are called:

20- 123 Infrequent filter backwashing can result in:

20-124 What is the difference between the pressure above a filter and the pressure below a filter called?

20- 125 Compounds formed or resulting from contact between dissolved ammonia and chlorine in water are called:

20-126 What is the significant fact related to ventilation of a chlorine storage area?

20-127 What is the function of the MSDS?

252

FINAL EXAM

20-128 What is the maximum distance between an emergency eyewashhhower station and a chemical handling point?

20-129 How tall or long must a fixed ladder be before a safety cage is required?

20- 130 What will occur if the discharge valve for a positive displacement pump is closed?

20- 131 To prevent water hammer:

20- 132 Excessive fluoride in drinking water can cause:

20-133 The first corrective action taken to correct a safety hazard is to:

20- 134 Convert 450 gpm to MGD.

20-135 Calculate the volume of a basin 20 feet wide, 70 feet long, and 12 feet deep.

20-136 A circular clarifier has a diameter of 30 feet. What is the surface area of the clarifier?

20-137 The flow rate at a waterworks is 6.5 mgd, which is 70 percent of the plant's capacity. What is the capacity of the plant?

20-138 A sedimentation tank has a capacity of 70,000 gal. If the flow to the clarifier is 21,000 gph, what is the detention time?

Final Exam

253

20- 139 When the pump is not in operation, the water level in a well is 41 feet below ground surface. The water level drops to 55 feet when the pump is in operation. What is the drawdown in feet?

20-140 Convert a gauge pressure of 15 feet to pounds per square inch gauge.

APPENDIX A

Answers to Chapter Review Questions

Chapter l :

Chapter 2:

2-1 To protect water resources; to properly operate a waterworks; to protect public health; to comply with applicable regulations Chapter 3:

3- 1 Location where microbial disease lives and multiplies; the diseased individual or animallthe microbe

APPENDIX A

3-2 3-3 3-4 3-5 3-6 3-7 3-8

Directhndirect No; must have a host Bacteria Skin rash, flu-like problems, severe gas and abdominal pains NO Coliforrn bacteria from feces, soil, or other origins Coliform bacteria or from warm-blooded animals

Chapter 4: Bacteria, viruses, protozoa No During rainstorms No Binary fission Spheres, rods, spirals Typhoid, cholera, gastroenteritis Amoebic dy sentery-Giardiasis Cyst Host Plug screens, machinery; cause taste and odor problems Chapter 5: Samples collected from designated sampling points (e.g., dead-end pipes, main lines, branch lines, loops, various water sources, storage tanks, pressure zones and other distribution configurations) Early in the day, if the first sample is unsatisfactory, the operator still has time in the day to resample Possible sewage contamination with pathogenic microorganisms present 1 hr; 170°C 121"C; 15 minutes Sodium thiosulfate 0"-10°C Wide mouth, ground and stoppered 37°C 6 .O In water analysis, the number and kind of bacteria in the water are determined by bacteriological examination 48 hours Tryptone glucose extract agar 10 Presumptive test Chapter 6:

Answers to Chapter Review Questions

363 619 213 518 9/14 1 5/12 1/28 625/1,000 = 518 314 = 0.75 451100 and 0.45 0.0625 Median = 7; mean = 8.33 1 X 107 250 gal X 3.78 Llgal = 945 liters A = L x W=9ftx30ft=270ft2 Radius = diameter X 2 25 X 2 = 12.5 ft A = n2= n (12.5)2= n(12.5 X 12.5) = 490.9 ft2 V=LxW =25x60x8 = 12,000 ft3 Radius = 2312 = 17.5 ft Area = n2= (3.14) X 17.5 X 17.5 = 962 ft2 Volume = area X h = 962 ft2X l 0 ft = 9,620 ft3 = 9,620 ft3X 7.48 = 7 1,957.8 gallons Radius = 812 = 4 inches 4 inches = 4/l 2 = 113 ft Area = n2= ~ ( 1 1 3=) ~ ( . 3 3 3= ) ~0.348 ft2 Q = V X A = 4 ft/min X 0.348 ft2= 1.39 ft3/min 1.39 ft3/min X 7.48 = 10.4 gaVmin 10.4 gaVmin X 60 = 624 gal/hr DT = 200 gaM0.4 gallm = 19.2 minutes V=Lxn2 V = 12 ft X n(2.5 ft)2 V= 12 ft X n (6.25 ft2) V= 235.6 ft3 d = 2412 = 12.5 inches V=Hxn2 V= 44 inches X n (12.5)2 V= 44 in X 3.14 X 156.3 in2= 21,605.4 in3 731100 = 0.73, add to 1 = 1 + 0.73 = 1.73 1.73 X 14,000 gal = 24,220 gal 50 gaVl X 8.34 lblgal = 417 lbs 4 lbsll X 16 oz/lb = 64 oz 135 ft3/l X 62.4 lbs/ft3= 8,424 lbs 40 ft/l X 0.433 ~ s i /ftl = 17.3 D S ~

258

6-30 6-31

6-32

APPENDIX A

1.S cfsll X 448 gprnll cfs = 672 gpm A=$ A = n (0.208 ft)2 A = n X 0.043 ft2 A =O.l4 ft2 Q = VA Q = 1.3 ft/sec X 0.14 ft2 Q = 0.18 cfs DT= 6,575 gall160 gallrnin = 41 minutes

Chapter 7: Na H2SO4 7 Base Changes Solid, liquid, gas Element Compound Periodic Solvent; solute An atom or group of atoms that carries a positive or negative electrical charge as a result of having lost or gained one or more electrons Colloid Turbidity Result of dissolved chemicals Toxicity Organic 0 to l 4 Measure of water's ability to neutralize an acid Calcium and magnesium Base

Chapter 8: Hertz Volts Amp Ohm E, I, R Proton, neutron, electron Three power leads versus two power leads Horsepower Watts A device that uses a core wrapped with magnetic wire. When an electrical power source is applied to the wire, an electrical field is generated and the wire-core assembly becomes an electromagnet.

Answers to Chapter Review Quesfions

Chapter 9: e 62.4; 7.48 600 X 7.48 = 4,488 gallons 8.34 448 Static head Friction The position of the impeller eye in relationship to the water. In suction lift, the water is below the eye. In suction head, the water is above the eye. .433 X 80' = 34.6 psi Composed of static head, velocity head, and headloss 14 psUO.433 psi/ft = 32.3 ft 823 ft3X 7.48 gal/ft3= 6,156 gallons Static head, ft = 210 ft - 120 ft = 90 ft. The equivalent distance water must be lifted to move from the supply tank or inlet to the discharge. Head can be divided into three components: static head, velocity head, and friction head.

Chapter 10: Surface water, groundwater, GUDISW Groundwater under the direct influence of surface water Easily located; softer than groundwater Easily polluted; turbidity or temperature fluctuations The study of the properties of water and its distribution and behavior Watershed or drainage basin Zone of influence Impermeable core GUDISW Prevent large material from entering the intake

Chapter 11: 11- 1 Cone, depression 11-2 12" 11-3 Concrete 11-4 a. casing vent b. sanitary well seal c. well pad d. topsoil e. water table f. water bearing sand g. casing h. cement grout formation seal i. drop pipe j. clay

APPENDIX A

k. submersible pump 1. pump motor m. drive shoe n. water bearing sand O. screen Clogging, cementation, or stoppage of a well screen and water-bearing formation, resulting from chemical or biological reactions at the air-water interface in the well

Chapter 12: A protected reserve area, usually distinct from the treatment plant, where natural or artificial lakes are used for water storage, natural sedimentation, and seasonal pretreatment with or without disinfection. Collection area into which water drains Either of two choices in water utility management-keep it out of watershed, take it out during treatment Control algae and in turn decrease taste and odor problems Best management practices Agriculture-conservative tilling and contour plowing; confined animal facility management; appropriate pesticide and herbicide application protection; urban-reduction of impervious areas; non-stormwater discharges; proper disposal of residential chemicals; construction-erosion and sediment control; minimize clearing; stage construction; stabilize stockpiles; chemical control

Chapter 13: 13-1 (1) To deliver adequate quantities of water; (2) to deliver high quantities of water when needed for fire protection 13-2 Wood, plastic, ACM pipe, cast iron, lead, copper, galvanized 13-3 20 13-4 Continuous feed-chlorine added at 50 mg/L with potable water at constant flow; slug method-potable water at constant flow, and chlorine added to produce a slug of water with 100 mg/L chlorine; tablet method-HTH tablets used in new distribution system line 13-5 Leakage of a certain percent of water not accounted for 13-6 113 0f33%

Chapter 14: (a) Reversal of flow in the system; (b) occurs when the pressure in the system drops below atmospheric pressure and the water distribution system is connected to a nonpotable source that is open to the atmosphere Any physical arrangement whereby a public water supply is connected, directly or indirectly, with a nonpotable or unapproved water supply or system Air gaps-high hazard control Atmospheric vacuum breakers-low degree of hazard connection Pressure vacuum breakers-backsiphonage protection only Double check valve assemblies-low hazard connection

261

Answers to Chapter Review Questions

Reduced pressure backflow prevention device assemblies-high 14-4 Annually 14-5 Air gap or reduced pressure device

hazard connections

Chapter 15: The destabilization and initial aggregation of colloidal and finely divided suspended matter by the addition of floc-forming chemical Ease of handling; lower costs; less labor required; dissolving operations are eliminated; less storage space; greater accuracy of measurement and control; nuisance and unpleasantness of handling dry alum eliminated; easily maintained Determine optimal chemical dosage Ion exchange Potassium permanganatelchlorine Demand Potable Water that is clear, without color or turbidity that tastes and smells good Backwashing Increased Colloidal Protect public health Dosage Settling time Pathogenic Calcium/magnesium Flocculation aids Mudballs and filter cracking Breakthrough and air binding Coagulation, flocculation, sedimentation, filtration Chemical Coagulation Aeration Sequestering agent NTU Headloss

Chapter 16: Total kill of microorganisms Control of pathogenic microorganisms, but not kill-off of all microorganisms Ozone, UV, bromine, iodine Calcium and sodium hypochlorite At breakpoint 5.5 to 7.5 Chlorine residual X the contact time Ammonia solution mist Amount of chlorine required to give a desired residual after a given time Fusible plug

262

APPENDIX A

16-11 Found as a result of contact between dissolved ammonia and chlorine in water 16-12 At floor level

Chapter 17: It lubricates and keeps materials from entering the packing assembly Wear rings Check psi Flow; psi To prevent water hammer 22 feet Positive displacement pump

Chapter 18: 18-1 Yes, depending on geographical location 18-2 Sodium fluoride, sodium silicofluoride, and hydrofluosilicic acid 18-3 Causes mottled teeth enamel

Chapter 19: 19-1 19-2 19-3 19-4 19-5 19-6

Management support 2,1,3 Written and enforced lockout/tagout program Correct the condition that caused the accident Lockout/tagout programs apply to any kind of machine start-up or release of energy Protecting emergency response personnel

APPENDIX B

Answers to Final Review Examination: Chapter 20

To protect public health; to improve the water's aesthetic qualities ac-ft. Aeration BOD Darcy7sLaw Drawdown Graywater Pressure Infiltration Piezometric surface Purveyor Seepage Subsurface water Titrant Vaporization Watershed Directfindirect Coliform bacteria from feces, soil, or other origin. Coliform from bacteria or warm-blooded animals To protect public health Hydrologic cycle Solid, liquid, gas Elements Ion Colloidal The property of water that causes light to be scattered and absorbed True and apparent Inorganic Organic The buffering capacity of water that tends to retard the change in pH by an acid Magnesium and calcium Check valve Nearby cities may dump sewage into the lake. Absolute pressure = gauge pressure + atmospheric pressure Amount of rainfall that flows from ground surface into the stream and reservoir mgd Screening Pipelines, aqueducts, or natural or artificial streams

APPENDIX B

Test the air in the confined space Heavier than air Bacteria, viruses, protozoa No Cyst Giardia lamblia and Cryptosporidium Host Bacteria 62.4 lbs 8.34 lbs 448 Friction Horsepower (HP) Samples collected from designated sampling points Sodium thiosulfate 37" 48 hours For presumptive test A number that has a factor other than itself and l (e.g., 4,6, 8,9, and 12) 26 200 50 1 55/72 9 7/12 1 1/12 1/3 1 3/26 2/9 5/14 6/25 3 113 16.6 0.3942 Mean: 102 gpm; median: 110 gpm 8 lb/1,200 = X lb/15,000 = (8)(15,000)/1,200 = 100 lb chemical 40160 = 0.667 or 67% 60 psi/l X 1 ftl0.433 psi = 138.6 ft 16 psi/l X 1 ft10.433 psi = 37 ft

A = n2 = n(0.25 ft)2 = n X 0.0625 ft2 = 0.196 ft2 Q = VA = 2 ft/sec X 0.196 ft2 = 0.392 cfs 0.65 cfsll X 448/cfs = 291 gpm 120,000 3,000 min = 50 hrs = 3,000 minutes or 20-80 40 gal/min 60 midhr

Answers to Final Review Examination: Chapter 20

gal = 55 minutes 150 gallmin Palatable 4.0 mgL Coagulation NTUs Dosage Jar Test Amount (dose), chlorine Detention time Backwashing Ion exchange A = LW = 4Oftx12ft = 480 ft2 Sequestering agent Total kill 5.5 to 7.5 CT = the chlorine residual X the contact time 7 .O Compound Base Pressure Ohm, resistance, or impedance Proton, neutron, electron E = I x R 12 volts = ? X 120 ohms I = E/R I = 121120 I = 0.1 amps 65 ft X 0.433 psilft = 28.1 psi 65 psi X 2.31 ftlpsi = 150 ft 12 psi = 27.7 ft ft = 0.433 psilft 87240

A = n X D214 = n X r2 A = n214 = 3.14 (1 ft)2/3 = 0.333 ft2 (a) Q = V X A = 6 ft/sec X 0.333 ft2 = 1.9 ft3/secor cfs (b) 1.9 cfs X 449 gprnkfs = 853 gpm 1.9 cfs = 1. B mgd ft = 1S 5 cfslmgd

266

APPENDIX B

Composed of static head, velocity head, and headloss The equivalent distance water must be lifted to move from the supply or inlet to the discharge. Surface water, ground water, GUDISW Easily located; generally softer than groundwater 12 inches Incrustation Watershed Control algae and in turn decrease taste and odor problems 20 psi Any physical arrangement whereby a public water supply is connected (directly or indirectly) with a nonpotable or unapproved water supply or system. Annually Pathogenic Breakthrough and air binding Headloss Chloramines Ventilation ducts must be mounted close to floor level Protect workers when handling hazardous materials 100 ft 20 ft Damage or destroy pump Close valves slowly Mottled tooth enamel Engineer it out 450 gpm X 60 min = 27,000 galhr 7,000 gph X 24 hrs = 648,000 gaYday = 0.65 mgd V = L x W x D = 20ft X 70ft X 12ft = 16,800 cu ft Area of circle = (0.785)(D)2 = (0.785) (30 ft)(30 ft) = 707 ft2 surface area 20- 137

70% = 6.5mgd X mgd

X = 9.3 mgd Vol of tank 20-138 X = flowrate

X =

70,000 gal 21,000 gph

= 3.33 hrs

X

100

Answers to Final Review Examination: Chapter 20

30-140

= 14ft 1 psig = 2.31 ft head

15 ft = 6.5 psig 2.31 ft/psig

APPENDIX C

Commonly Used Formulae/Equivalents in Waterworks Operations

FORMULAE (1) Area a. Rectangular tank A = length X width = L X W b. Circular tank (area of water surface in the tank) A = n X r20r A=D2/4 (n=3.1416) c. Circular tank (area of the sides of the tank) A = circumference X height = n X D X H (2) Volume Rectangular tank V = L x W x H Circular tank (with flat top and bottom) V = n X r 2 X H o r n X D2/4 X H Spherical tank V = 413 X n X r 3 Conical tank total gallonslday V = 113 X nSSR = x r 2 x H ft2surface area of tank (3) Flow gal (gpd) = gal (gph) X 1,440 min day min day gal (gpd) -

gal hr

hr day

= - (gph) X 24 -

day Flow in a pipe Q=AxV ft3 Q = flow sec

1-(

A = cross-sectional area of pipe (ft2) B = velocity of water (ft/sec) (4) Dose

270

APPENDIX C

mg/L =

lb (MG = million gallons) MG X 8.34 (5) Surface settling rate (SSR) total gallonslday SSR = ft2 surface area of tank (6) Filtration rate (from drop test) ft2W. S area X ft drop X 7.48 FR in Er =n ft3 min. of test X ft2filter area ft2

EQUIVALENTS Area:

foot = 12 inches yard = 36 inches = 3 feet square foot (ft2)= 144 square inches (in2) square yard (yd2)= 9 ft2 acre = 43,560 ft2

Volume:

cubic foot (ft3)= 1,728 cubic inches (in3) cubic yard (yd3)= 27 ft3 ft3of water = 7.48 gallons gallon (gal) = 3.785 liters (L) = 3785 (mL) liter (L) = 1,000 mL

Weight:

pound (lb) = 16 ounces (oz) = 453.6 grams = 7,000 grains kilogram (kg) = 1,000 gm gm = 1,000 milligrams (mg) = 15.43 gr gal of water weighs 8.34 lb ft3of water weighs 62.4 lb

Time:

day (d) = 24 hours (hr) = 1,440 minutes = 86,400 seconds

Flow:

million gallons per day (MGD) = 694 gallminute (gpm) MGD = 1.545 cubic feet per sec (ft3/secor cfs) cfs = 448.8 gallmin or gpm

Dosage:

grain per gallon (gpg) = 17.1 parts per million (ppm) gpg = 143 pounds per million gallons milligramslliter (mglL) = l ppm = 8.34 lbslmil gallons ppm = 1 pound in 1 million pounds

Pressure:

pound per square inch (psi) = 2.3 1 ft of water (head) ft of head = 0.433 psi

Power:

horsepower (hp) = 550 ft-poundslsec = 33,000 ft-lblmin hp = 746 watts (W) kilowatt (kw) = 1,000 W = 0.746 hp

Appendix C

Usage:

Average water usage: 100 gallons/capita/day (gpcd) Average persons per single family residence: 3.7 Equivalent residential connection (ERC): 400 gaVday

Index

absolute pressure, 116 absorb, 3 acceptors, 101 accident investigation, 239 acid, 95,236-237 acid rain, 3 acre-feet, 3 adsorption, 3 aeration, 3, 180, 183 agent, 21 air, 180 air binding, 192, 194 air gap, 172 algae, 39 algae bloom, 3 alkalinity, 96-97 alternating current (AC), 100, 105 ambient, 4 ampere, 100, 102 anaerobic bacteria, 35 anion, 88 annular space, 126 apparent color, 93 aquifer, 4, 126 area, 72-74 of circle, 73 of circular tank, 76 of rectangle, 73 artesian water, 4 asbestos-cement (Transite), 160 atom, 87, 101 atmospheric vacuum breaker, 172 averages, 65-67 backflow preventer, 171 back-pressure, 170 backsiphonage, 170 backwashing, 193 bacteria, 33-36 bacterial growth, 181 bacteriology, 4 1-5 1 bases, 95,237 benchmarkmg, l38 binary fission, 33

biochemical oxygen demand (BOD), 4 biota, 4 bloodborne pathogens, 235 blowoff, 146 body feed, 194 boiling point, 4 bored wells, 143 breakpoint chlorination, 205 breakthrough, 192, 194 caisson, l26 calcium hypochlorite, 207 cartridge filter, 194 casing vent, 146 cast ironlductile iron, 160 cation, 88 cation exchange process, 185 cell, 33 centrifugal force, 101 centrifugal pumps, 2 15-2 18 certification/licensure, 14 check valve, 146 chemical change, 89 chemical reaction, 89 chemistry, 87 chloramines, 205 chlorine, l82 chlorine contact time, 204 chlorine demand, 203 chlorine dosage, 208-212 chlorine dose, 203 chlorine reaction, 203 chlorine residual, 203-204 chlorine residual test, 2 13 chlorination, 202-2 13 cholera, 23-26 cilia, 36 clear wells, 163 closed circuit, 103 coagulation, 186-1 89 coliform bacteria, 201 colloidal, 88,93 color, 94 common factor, 54

Index composite number, 54 compound, 87 conductor, 100-1 01 cone of depression, 126 confined aquifer, 126 confined space program, 230 confirmed test, 48-50 connate water, 4 consumptive use, 4 contamination, 4, 126 continuous feed, l62 conversions, 69-72 temperature, 70-72 converter, 105 copper, 160 corrosion, 195 cross-connection, 160 cross-connection control, 170-1 74 Cryptosporidium, 11-12,26, 129,137-1 38,204, 212 cycle, 100 cysts, 36 Darcy's Law, 4 decimals, 60-62 deep wells, 143 deferrization, 182 degrees, 105 demanganization, 182 dental fluorosis, 223 detention time, 80-82 diaphragm pump, 220 diatomaceous earth, 193 diffusion, 4 direct current, 100, 105 direct filtration, 194 discharge, 117 disinfection, 35,201-213 dissolved oxygen, 41,94 dissolved solids, 4, 88 distribution and storage, 159-1 64 distribution system disinfection, 162 domestic consumption, 4 donors, 101 double check valve assembly, 174 drainage basin, 126, 130 drawdown, 4,126, 146 drilled wells, 144 drinking water standards, 4 driven wells, 143 drop pipe, 146 dug wells, 143 dynamic pressure, 118

E. coli, 27 effluent, 4 electrical attraction, 101 electrical safety, 233 electricity, 99-1 09

electromagnet, 10 6 107 electromagnetism, 100 electromotive force, 102 electrons, 100-1 0 1 elements, 87,89 energy, 4 elevated tanks, 163 entry, 22 equivalent length of pipe, 120 erosion, 5 eucaryotic, 32 eutrophication, 5, 39 evaporation, 5 excavation, 233 factor, 54 facultativebacteria, 35 fecaI coliform, 27,51 field capacity, 5 filtration, 5,190-1 94 fire hydrants, 161 fire safety, 234 flight, 22 flocculption, l89 flow, 78,80,115 flow meter, 146 fluoridation, 223-225 force, 111 fractions, 55-60 free available chlorine, 205 frequency, 100,105 galvanized, 160 gases, 87,237 gauge and air line, 146 Giardia lamblia, 20,26,36, 136,204 graywater, 5 ground-level reservoir, 163 groundwater, 5, 125 groundwater hydrology, 5 groundwater recharge, 5 groundwater runoff, 5 grout, 144 GUDISW, 136 hardness, 97, 183-184 handling chemicals, 235-236 hazard communication, 229 hazardous materials emergency response, 234 head, 76-78, 111,114 headloss, 111, 119 hearing conservation, 23 1 heavy metals, 5 hertz, 100 high-rate filter, 192 holding panel, 5 horsepower, 100 host, 21 hydrologic cycle, 5, 128

Index hydrology, 5, 125, 129 hydraulics, 111-1 22 hydraulic grade line, 121 hydraulic gradient, 5 hydraulic head, 5 hypochlorite radical, 204 hypochlorination, 207-208 impedance, 103 impeller, 2 16 impermeable, 126 impoundment, 5 incrustation, 149 indicator organism, 27 inertia, 111 infiltration, 5 inorganic matter, 95 insulation, 100-1 01 integer, 54 ion, 88 ion exchange, 183 ion exchange process, 185 ionization, 88, 91 iron and manganese removal, 181 jar testing procedure, 188-1 89 jetted weIIs, 143 laboratory safety, 232 Langlier Saturation Index, l96 law of continuity, 118 leaching, 5 lead, 160 liquids, 87 lockout/tagout, 230 looping, 160 machine guarding, 232 manganese greensand, 183 Mary Mallon (aka, Typhoid Mary), 23 mass, 89 matter, 87, 88-89 membrane filter method, 50-5 1 metals, 94 microbiology, 3 1-39 mixture, 87 molecule, 88,90 most probable number, 50 mud balls, 192 multiple barrier concept, 27-28 multiple fermentation tube method, 48 nonpoint source contamination, 6 neutron, 100-101 nucleus, 101 ohm, 100 Ohm's Law, 102- 103 oocysts, 204

open circuit, 103 operator, 14 organic matter, 94 overland flow, 125 overland flow runoff, 129 parts per million (ppm), 6 parasitic diseases, 26 pathogen, 22 percent, 68-69 percolation, 6 permeable, 125 Periodic Table, The, 90 peristaltic pump, 220 personal protective equipment, 232-233 pH, 6 9 6 phase, 100,105-1 06 photosynthesis, 6 physical change, 89 piezometric surface, 6 piston pump, 218-220 plastic, 160 plate count, 48 point source pollution, 6 pollution, 6 porosity, 6, 126 positive displacement pumps, 218-221 potable water, 6, 125-138 potassium permanganate, 182-1 83 power, 64, 100 precipitate, 88 precipitation, 6, 126, 182 presumptive test, 48-49 pressure, 76-78,111, 114,160 pressure filter system, 193 pressure tanks, 163 pressure vacuum breakers, 172 pretreatment, l78 primary MCL, 137 procaryotic, 32 proton, 100-101 protozoa, 36-38 pump maintenance, 220-221 pumps, 2 15-22 1 purging level, 126 purveyor, 6 radical, 85 radius of influence, l26 radon, 6 rapid sand filter, 192-195 ratio, 67-68 raw water, 126, 130 recharge, 6, 126, 130 reduced pressure devices, 174 reservoir, 6,22 resistance, 100, 102 respiratory protection, 230-23 1 responsible charge, 14

Index river basin, 6 rounding numbers, 63 Safe Drinking Water Act (SDWA), 11-1 2, 174 safety, 225-237 safety inspections, 239 salts, 95,236-237 sample taps, 146 sanitary seal, 144 saturated, 92 saturated solution, 98 saturation, zone of, 6 sediment, 6 sedimentation, 190 secondary MCL, 137 seepage, 6 septic tank, 6 sequestering, 181 shallow wells, 143 significant figures, 63 sine wave, 100, 105 single-phase power, 100 slow sand filter, 191-192 slug method, l62 sodium hypochlorite, 207 soil moisture, 7 solid, 87-88,93 solute, 88,91 solution, 9 1 solvent, 88,91 specific capacity, 147 specific heat, 7 specific yield, l26 split case pumps, 217 spring, 126 standpipes, 163 static, 111 static head, 120 static level, 126 sterilization, 199 Stevin's Law, 115- 116 straining, 189 stream, 7 tablet method, 162 taste problems, 18 1 thermal pollution, 7 thrce-phase power, 100 titrators, 7 total dissolved solids, 7

total dynamic head, 111, 121 total solids, 88 total suspended solids, 7 total trihalomethanes (TI'HMs), 180-1 81 toxicity, 7 transformer, 107 transmission, 22 transpiration, 8 trophozoites, 36 true color, 93 turbidity, 88,93, 129, 138, 181,212 ultra-high-rate filter, 192 unconfined aquifer, 126 vaIves, 161 vaporization, 8 velocity, 111 velocity head, 111, 121 vertical turbine pumps, 217-21 8 viruses, 26, 38 VOCs, 8 volume, 74-76 of circular tank, 75 of rectangular tank, 74-75 water chemistry, 87-97 water cycle, 8 water meters, 162 water quality, 8 water quality standard, 8 water rights, 126, 129 water sampling, 42 for fecal coliform, 47-48 procedure, 45-46 water supply, 8 water table, 126 waterborne disease, 8, 19-28 watershed, 8, 126, 130, 154-155 watershed protection, 153-157 watt, 100 well abandonment, 150 well casing, 144 well pad, 144 well screen, l46 well systems, 141-150 yield, 146 zone of aeration, 8