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United StatesEnvironmental ProtectionAgency

Center for EnvironmentalResearch InformationCincinnati, OH 45268

EPA/625/5-90/025April 1990

Technology Transfer

Environmental PollutionControl Alternatives:

Drinking Water Treatmentfor Small Communities

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Technology Transfer EPA/625/5-90/025

Environmental PollutionControl Alternatives:

Drinking Water Treatmentfor Small Communities

April 1990

LIBRARY IRCPO Box 93190, 2509 AD THE HAGUE

Tel.: +31 70 30 689 80Fax: +31 70 35 899 64

BARCODE: /£ ^<7ALO: 2S"0 Q Q j r^ j ^ Printed on Recycled Paper

This document has been reviewed by the U.S. EnvironmentalProtection Agency and approved for publication. Mention oftrade names or commercial products does not constituteendorsement or recommendation of their use.

AcknowledgementsAppreciation is expressed to thoseindividuals who assisted in providingtechnical direction and resourcematerials and reviewing drafts of thispublication:

John R. Trax, National Rural WaterAssociation, Washington, DC

Fred Reiff, Pan American HealthOrganization, Washington, DC

Deborah Brink and ElizabethKawczynski, American WaterworksAssociation Research Foundation,Denver, CO

John Dyksen, Department of WaterSupply, Ridgewood, New Jersey

U.S. Environmental Protection AgencyOffice of Drinking Water, Washington,DC:

Steven Clark

Peter L Cook

Jane Ephremides

Ken Hay

A.W. Marx

Marc J. Parrotta

Peter Shanaghan

U.S. Environmental Protection AgencyRisk Reduction EngineeringLaboratory, Cincinnati, OH:

Jon Bender

Walter Feige

Kim Fox

Benjamin Lykins, Jr.

Donald J. Reasoner

Thomas Sorg

Alan A. Stevens

James Westrick

U.S. Environmental Protection AgencyOffice of Technology Transfer andRegulatory Support, Washington, DC:

Ronnie Levin

Management of the preparation of thisdocument was provided by James E.Smith, Jr. of EPA's Center for Environ-mental Research Information. Techni-cal writing, editorial work, production,and design was provided by JenniferHelmick, Lynn Knight, SusanRichmond, and Karen Ellzey ofEastern Research Group, Inc.,Arlington, MA.

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Contents

Introduction 1

Chapter 1 Drinking Wator Treatment: An Overview 3

Why Do We Need Drinking Water Treatment? 3How Is Drinking Water Treated? 5

Chapter 2 New and Proposed Drinking WaterTreatment Regulations: An Overview 9

Compliance Schedules 10Maximum Contaminant Levels 10Monitoring 13Surface Water Treatment Requirements 17

Chapter 3 Solutions to Drinking Water TreatmentProblems: An Overview 19

Questions to Consider inChoosing Treatment Technologies 19Special Issues for Small Systems 23

Chapter 4 Filtration Technologies for Small Systems 29

Processes Preceding Filtration 29Choosing a Filtration Technology 30Slow Sand Filtration 30Diatomaceous Earth Filtration 33Package Plants 34Membrane Filtration (Ultrafiltration) 34Cartridge Filtration 35Innovative Filtration Technologies 36

Chapter 5 Disinfection 37

Chlorination 37Ozonation 41Ultraviolet (UV) Radiation 43Obtaining Effective Disinfection: CT Values 44Disinfection By-Products and Strategies for Their Control 44

Chapter 6 Treating Organic Contaminants InDrinking Water 47

Granular Activated Carbon (GAC) 47Aeration 49Emerging Technologies for Organics Removal 51

Chapter 7 Control and Removal ofInorganic Contaminants 53

Corrosion 53Treatment Technologies forRemoving Inorganic Contaminants 55

Chapter 8 Resources 61

Appendix A How to Take Bacteriological Samples 69

Appendix B Checklist: Some Factors AffectingWater Treatment System Performance 71

Appendix C Selecting a Consulting Engineer 73

Appendix D Chlorine Residual Monitoring 77

Appendix E CT Values 79

Appendix F Sample CT Calculation 81

vi

Introduction

Small drinking water systems face adifficult challenge: to provide a safe,sufficient supply of water at areasonable cost. Our growing aware-ness of the biological and chemicalcontaminants that can affect the safetyof drinking water has led to the needfor more frequent monitoring andreporting and, in some cases, addition-al or upgraded treatment by water sup-pliers.

This document provides informationfor small system owners, operators,managers, and local decision makers,such as town officials, regarding drink-ing water treatment requirements andthe treatment technologies suitable forsmall systems, h is not intended to bea comprehensive manual for watertreatment and protection of publicwater supplies from sources of con-tamination. Rather, it is designed togive an overview of the problems asmall system may face, treatment op-tions that are available to solvespecific problems, and resources thatcan provide further information andassistance.

Chapter 1 discusses why we needdrinking water treatment and gives anoverview of drinking water treatmentprocesses.

Chapter 2 provides a summary of ex-isting and new federal drinking waterregulations and explains how theseregulations affect small systems.

Chapter 3 provides an overview ofhow to select drinking water treatmenttechnologies and discusses specialmanagement issues for small systems.

Chapters 4 through 7 describe tech-nologies that can enable small sys-tems to meet federal drinking waterregulations covering filtration, disinfec-tion, removal of organic and inorganiccontaminants, and corrosion control.These chapters describe establishedtechnologies, which are commonlyused in the water treatment industry.They also describe several emergingtechnologies suitable for small sys-tems. These technologies have notbeen widely used, but have proveneffective on the pilot scale and areemerging as viable full-scale optionsfor treating water supplies.

Chapter 8 lists organizations, publica-tions, and other resources that can as-sist small systems in their efforts toprovide safe drinking water to con-sumers.

For the purpose of this document,small systems are defined as systemsthat serve 25 to 1,000 people, or thathave a flow of 9,500 to 380,000 liters(2,500 to 100,000 gallons) psr day.They include small community sys-tems as well as noncommunity sys-tems, such as campgrounds andrestaurants.

Chapter One

Drinking WaterTreatment:An Overview

Why Do W« Need Drinking Wat«rTreatment?

For thousands of years, people havetreated water intended for drinking toremove particles of solid matter, re-duce health risks, and improve aes-thetic qualities such as appearance,odor, color, and taste. As early as2000 B.C., medical lore of India ad-vised, "Impure water should be puri-fied by being boiled over a fire, orbeing heated in the sun, or by dip-ping a heated iron into it, or it maybe purified by filtration through sandand coarse gravel and then allowedto cool."

Early in the nineteenth century, scien-tists began to recognize that specificdiseases could be transmitted bywater. Since that discovery, treatmentto eliminate disease-causing microor-ganisms has dramatically reduced theincidence of waterborne diseases(diseases transmitted through water)such as typhoid, cholera, and hepa-titis in the United States. For example,in 1900,36 out of every 100,000people died each year from typhoidfever; today there are almost nocases of waterborne typhoid fever inthe United States.

Ancient medical lore of India ad-vised that impure water should bepurified by heating or filteringthrough sand and coarse gravel.

Although water treatment processeshave greatly improved the quality andsafety of drinking water in the UnitedStates, there are still over 89,000cases each year of waterbornediseases caused by microorganisms-bacteria, viruses, protozoa, helminths,and fungi (Figure 1-1).1 Water can be-come contaminated with these or-ganisms through surface runoff (water

FUNGI PROTOZOA(microscopic one-

celled animals)

VIRUSES

HELMINTHS(parasitic worms) BACTERIA

Figure 1-1. Disease-causing microorganisms that might be found inwater supplies.

'Source: EPA estimate. Federal Register, June 19,1989 (54 FR 27522).

that travels over the ground duringstorms), which often contains animalwastes; failures in septic or sewersystems; and sewage treatment planteffluents (outflow). Microbiological con-tamination occurs most often in sur-face water, but it can also occur inground water, usually due to improp-erly placed or sealed wells. Contamina-tion can also occur after water leavesthe treatment plant, through cross con-nection (connection between safedrinking water and a source of con-tamination), backflow in a water supplyline, or regrowth of microorganisms inthe distribution system.

Table 1 -1 lists some of the diseasescaused by microorganisms found inwater supplies. The protozoan Giardialamblia is now the most commonlyidentified organism associated withwaterborne disease in this country.This organism causes giardiasis,which usually involves diarrhea,nausea, and dehydration that can besevere and can in soma cases last formonths. Over 20,000 water-relatedcases of this disease have beenreported in the last 20 years,2 withprobably many more cases going un-reported. Another protozoan disease,cryptosporidiosis, is caused by Cryp-tosporidium, a cyst-forming organismsimilar to Giardia. Other commonwaterborne diseases include viralhepatitis, gastroenteritis, and legionel-losis (Legionnaires' Disease).

Chemical contaminants, both naturaland synthetic, might also be present inwater supplies. Contaminationproblems in ground water (used by 85percent of small systems) are frequent-ly chemical in nature. Common sour-ces of chemical contamination includeminerals dissolved from the rocks thatform the earth's crust; pesticides andherbicides used in agriculture; leakingunderground storage tanks; industrialeffluents; seepage from septic tanks,sewage treatment plants, and landfills;and any other improper disposal ofchemicals in or on the ground. Insome systems, the water quality can

WaterborneDisease

Gastroenteritis

Typhoid

Dysentery

Cholera

Infectious hepatitis

Amoebic dysentery

Giardiasis

Cryptosporidiosis

Table 1-1. Waterborne Diseases

CausativeOrganism

Rotavirus

Salmonella(bacterium)

EnteropathogenicE. Coli

Salmonellatyphosa(bacterium)

Shigella(bacterium)

Vibrio comma(bacterium)

Hepatitis A(virus)

Entamoebahistolytica(protozoan)

Giardia lamblia(protozoan)

Cryptosporidium(protozoan)

Source ofOrganismIn Water

Human feces

Animal orhuman feces

Human feces

Human feces

Human feces

Human feces

Human feces,shellfish grownin pollutedwaters

Human feces



Symptom

Acute diarrheaor vomiting

Acute diarrheaand vomiting

Acute diarrheaor vomiting

Inflamed intes-tine, enlargedspleen, hightemperature—sometimes fatal

Diarrhea — rarelyfatal

Vomiting, severediarrhea, rapiddehydration,mineral loss—high mortality

Yellowed skin,enlarged liver,abdominal pain —low mortality, lastsup to 4 months

Mild diarrhea,chronic dysentery

Diarrhea, cramps,nausea, andgeneralweakness—notfatal, lasts 1 weekto 30 weeks

Diarrhea, stomachpain—lasts anaverage of 5 days

Source*. Adapted from American Water Works Association, Introduction toWater Treatment: Principles and Practices of Water Supply Operations,Denver, CO, 1984.

promote corrosion of materials in thedistribution system, possibly introduc-ing lead and other materials into thedrinking water. The water treatmentprocess might also introducetrihalomethanes— chemicals formed

when chlorine reacts with naturalorganic materials and other chemicalcontaminants—into the drinking water.(It should be noted, however, thatwhile the potential for chlorinationby-product formation cannot be

! Source: Dave Ryan, "Water Treatment to Combat Illness," EPA Journal, December 1987.

neglected, adequate disinfection is ofparamount importance to protect thepublic from microbiological contamina-tion of drinking water.)

Drinking water can be treated forreasons other than to reduce healthrisks from microorganisms and chemi-cals. A system might treat water to im-prove its color, odor, or taste even if itis safe to drink. For example, somesystems remove iron and mangan-ese, which can stain laundry andplumbing fixtures. Some com-

munities add fluoride to drinking waterto improve dental health.

To protect the public from the healthrisks of drinking water contaminants,the U.S. Environmental ProtectionAgency (EPA) has issued regulationscovering the quality and treatment ofdrinking water. These regulations arediscussed in Chapter 2.

EPA has also issued guidance forprotecting public drinking water fromsources of contamination. Protecting

ground-water supplies from con-taminants reduces the extent of treat-ment needed to protect public health.The Wellhead Protection (WHP)Program for public water supplies isan example of a protection program.Publications on the WHP Program arelisted in Chapter 8, Resources.

How Is Drinking Water Treated?

Table 1 -2 shows the types and goalsof water treatment processes typicallyused by small systems (includingpreliminary treatment and main water

Table 1-2. Water Treatment Processes

Process/Step

Preliminary Treatment Processes'

Screening

Chemical pretreatment

Presedimentation

Microstraining

Main Treatment Processes

Chemical feed and rapid mix

Coagulation/flocculation

Sedimentation

Softening

Filtration

Disinfection

Adsorption using granularactivated carbon (GAC)

Aeration

Corrosion control

Reverse osmosis, electrodialysis

Ion exchange

Activated alumina

Oxidation filtration

"Generally used for treating surface

Purpose

Removes large debris (leaves, sticks, fish) that can foul or damageplant equipment

Conditions the water for removal of algae and other aquatic nuisances

Removes gravel, sand, silt, and other gritty material

Removes algae, aquatic plants, and small debris

Adds chemicals (coagulants, pH adjusters, etc.) to water

Converts nonsettleable to settleable particles

Removes settleable particles

Removes hardness-causing chemicals from water

Removes particles of solid matter which can include biologicalcontamination and turbidity

Kills disease-causing microorganisms

Removes radon and many organic chemicals suchas pesticides, solvents, and trihalomethanes.

Removes volatile organic chemicals (VOCs), radon, H2S, and otherdissolved gases; oxidizes iron and manganese

Prevents scaling and corrosion

Removes nearly all inorganic contaminants

Removes some inorganic contaminants, including hardness-causing chemicals

Removes some inorganic contaminants

Removes some inorganic contaminants (e.g., iron, manganese, radium)

water supplies.

Source: Adapted from American Water Works Association, Introduction to Water Treatment, Vol. 2, 1984.

Chemicals from leaking under-ground storaga tanks mightmigrate to ground water and/orsurface water.

treatment processes). This documentdiscusses the water treatment proces-ses designed to protect the consumerfrom waterborne disease. Chapter 3discusses how to select appropriateprocesses and technologies for a par-ticular water system, and Chapters 4through 7 discuss treatment tech-nologies in more detail.

Filtration

Filtration is the process of removingparticles of solid matter from water,usually by passing the water throughsand or other porous materials. Filtra-tion helps to control biological con-tamination and turbidity. (Turbidity is ameasure of the cloudiness of watercaused by the presence of suspendedmatter. Turbidity can shelter harmfulmicroorganisms and reduce disinfec-tion effectiveness.) Filtration tech-nologies commonly used in smallsystems include slow sand filtration,diatomaceous earth filtration, andpackage filtration systems. Filtration isdiscussed in Chapter 4.

Disinfection

Disinfection is a chemical and/or physi-cal process that kills disease-causingorganisms. For the past severaldecades, chlorine (as a solid, liquid, orgas) has been the disinfectant ofchoice in the United States because itis effective and inexpensive and canprovide a disinfectant residual in thedistribution system. However, undercertain circumstances, chlorination

Runoff from agricultural areas can introduce microDioiogical con-taminants, pesticides, and nitrates Into drinking water sources.

might produce potentially harmful by-products, such as trihalomethanes.Small systems can successfully useozone and ultraviolet radiation asprimary disinfectants, but chlorine oran appropriate substitute must also beused as a secondary disinfectant toprevent regrowth of microorganisms inthe distribution system. Disinfection isdiscussed in Chapter 5.

Treatment of Organic Contaminants

Many synthetic organic chemicals(SOCs), manmade compounds thatcontain carbon, have been detected inwater supplies in the United States.Some of these, such as the solventtrichloroethylene, are volatile organicchemicals (VOCs). VOCs easily be-come gases and can be inhaled inshowers or baths or while washingdishes. They can also be absorbedthrough the skin.

Water supplies become contaminatedby organic compounds from sourcessuch as improperly disposed wastes,leaking gasoline storage tanks, pes-ticide use, and industrial effluents.Technologies that can be used effec-tively by small systems to removethese contaminants include activatedcarbon and aeration. These tech-nologies are discussed in Chapter 6.

Treatment of InorganicContaminants

The inorganic contaminants in watersupplies consist mainly of naturally oc-curring elements in the ground, suchas arsenic, barium, fluoride, sulfate,radon, radium, and selenium. In-dustrial sources can contribute metal-lic substances to surface waters.Nitrate, an inorganic substance fre-quently found in ground-water sup-plies, is found predominantly inagricultural areas due to the applica-tion of fertilizers. High levels of totaldissolved solids (TDS) might, in someinstances, require removal to producea potable supply.

Inorganic chemicals might also bepresent in drinking water due to cor-rosion. Corrosion is the deterioration

or destruction of components of thewater distribution and plumbing sys-tems by chemical or physical action,resulting in the release of metal andnonmetal substances into the water.The metals of greatest health concernare lead and cadmium; zinc, copper,and iron are also by-products of cor-rosion. Asbestos can be released bycorrosion of asbestos-cement pipe.Corrosion reduces the useful life of thewater distribution and plumbing sys-tems. It can also promote microor-ganism growth, resulting in dis-agreeable tastes, odors, and slimes.

Treatment alternatives for inorganiccontaminants include removal tech-niques and corrosion controls.Removal technologies — coagulation/filtration, reverse osmosis, ion ex-change, and activated alumina — treatsource water that is contaminated withmetals or radioactive substances(such as radium). Aeration effectivelystrips radon gas from source waters.Corrosion controls reduce thepresence of corrosion by-productssuch as lead at the point of use (suchas the consumer's tap). Treatmenttechnologies for inorganic con-taminants are discussed in Chapter 7.

Chapter Two

New andProposedDrinking WaterRegulations:An Overview

In 1974, Congress passed the SafoDrinking Water Act (SDWA), setting upa regulatory program among local,state, and federal agencies to help en-sure the provision of safe drinkingwater in the United States.

Under the SDWA, the federal govern-ment develops national drinking waterregulations to protect public healthand welfare. The states are expectedto administer and enforce these regula-tions for public water systems (sys-tems that either have 15 or moreservice connections or regularly servean average of 25 or more people dailyfor at least 60 days each year). Publicwater systems must provide watertreatment, ensure proper drinkingwater quality through monitoring, andprovide public notification of con-tamination problems.

Congress significantly expanded andstrengthened the SDWA in 1986. The1986 amendments include provisionson the following:

• Maximum Contaminant Levels.The Safe Drinking Water Act re-quired EPA to set numerical stan-dards, referred to as MaximumContaminant Levels (MCLs), ortreatment technique requirementsfor contaminants in public watersupplies. The 1986 amendmentsestablished a strict schedule forEPA to set MCLs or treatment re-quirements for previously unregu-lated contaminants.

• monitoring. EPA must issueregulations requiring monitoring ofall regulated and certain unregu-lated contaminants, depending onthe number of people served by thesystem, the source of the watersupply, and the contaminants likelyto be found.

• Filtration. EPA must set criteriaunder which systems are obligated

to filter water from surface watersources. It must also develop pro-cedures for states to determinewhich systems have to filter.

• Disinfection. EPA must developrules requiring all public water sup-plies to disinfect their water.

• Use of lead materials. The use ofsolder or flux containing more than0.2 percent lead, or pipes and pipefittings containing more than 8 per-cent lead, is prohibited in publicwater supply systems. Publicnotification is required where thereis lead in construction materials ofthe public water supply system, orwhere the water is sufficiently cor-rosive to cause leaching of leadfrom the distribution system/lines.

• Wellhead protection. The 1986SDWA amendments require allstates to develop Wellhead Protec-tion Programs. These programs aredesigned to protect public watersupplies from sources of con-tamination.

The impact of these new regulationson small systems will generally con-cern some fundamental aspects ofwater treatment. Many systems will berequired to improve treatment forremoval of microorganisms (throughthe addition of filtration and/or disinfec-tion processes). Most small systemsdo not face contamination by organicand inorganic chemicals at levels ex-ceeding the MCLs, and therefore willnot need to install treatment forremoval of these chemicals.3 Smallsystems will be required to conductperiodic monitoring, however, to docu-ment whether chemical contaminantsare present in their water supplies.Future regulations covering radioac-tive substances (particularly radon)and disinfection by-products couldalso have a significant impact.

3 G. Wade Miller, John E. Cromwell, III, Frederick A. Marrocco. "The Role of theStates in Solving the Small System Dilemma," JAWWA, August 1988, pp 31-37.

The rest of this chapter explains themajor provisions of EPA's new andproposed drinking water regulations asthey apply to small systems. In addi-tion to the federal regulations dis-cussed here, the water supplier shouldcheck with the state agency respon-sible for drinking water (see Chapters,Resources) to find out about stateregulations that apply to drinking watertreatment facilities.

Compliance Schedules

Most of the regulations contain com-pliance schedules that affect large sys-tems initially and small water systems2 to 4 years later. This means thatsmall systems have additional time toplan for their specific compliancerequirements.

The SDWA recognizes that meetingdrinking water standards might place alarge burden on small systems. Thelaw therefore provides for variances,allowing small systems to meet a lessstringent standard if an organic or inor-ganic contaminant cannot be removeddue to the quality of the raw water orothsr good reasons, as long as theless stringent standard poses no un-reasonable health risk. A small systemmay also be granted a temporary ex-emption if economic conditionsprevent the system from makingnecessary corrections, provided no un-reasonable risk to public healthresults. No exemptions are allowed fordisinfection of surface supplies or thecoliform rule for all public watersupplies. Monitoring requirements mayalso be reduced in some cases if thepublic water supply has a programunder an EPA-approved stateWellhead Protection Program.

Maximum Contaminant Levels

A Maximum Contaminant Level, orMCL, is the highest allowable con-centration of a contaminant in drinkingwater. In developing drinking waterregulations, EPA establishes Maxi-mum Contaminant Level Goals

4 EPA determines the BAT based on high removal efficiency of contaminant concentration; general geographic applicability; servicelite; compatibility with other water treatment processes; and ability to achieve compliance at a reasonable cost.

Community, Nontransient Noncommunity,0

and Transient Noncommunity Systems

The drinking water regulations distinguish between community watersystems (CWS), nontransient noncommunity water systems (NNWS),and transient noncommunity water systems (TNWS).

• A community system is a public water system that serves at least15 service connections used by year-round residents, or regularlyserves at least 25 year-round residents. Community systems includemobile home courts and homeowner associations.

• A nontransient noncommunity system regularly serves at least 25of the same people over six months of the year. Examples areschools and factories.

• Transient noncommunity systems, such as restaurants, gas sta-tions, and campgrounds, serve intermittent users.

The regulations governing each of these systems are slightly different.This is because certain contaminants cause health problems only whenconsumed on a regular basis over a long period of time, and are there-fore of greater concern in systems that regularly serve the same peoplethan in those that serve transient users.

Only the MCLs for turbidity, nitrate, and bacteria apply to transient non-community systems. (The new surface water treatment requirements, ex-plained below in this chapter, will replace the currently MCL for turbidityfor TNWS). Most MCLs are set at levels designed to prevent health ef-fects caused by long-term consumption of drinking water from a system.However, the presence of nitrate, bacteria, and turbidity indicate thepotential of the water to cause illness even from short-term consump-tion, so MCLS for these contaminants apply to transient noncommunityas well as other systems.

(MCLGs), which are the maximumlevels of contaminants at which noknown or anticipated adverse health ef-fects will occur. MCLs are set as closeto the MCLG as is feasible. In settingan MCL, EPA takes into account thetechnical feasibility of control systemsfor the contaminant, the analyticaldetection limits, and the economic im-pact of regulating the contaminant. AnMCL is usually expressed in mil-ligrams per liter (mg/L), which isequivalent to parts per million (ppm)for water quality analysis.

The SDWA amendments direct EPA toestablish MCLs for 83 specific contami-nants and to develop a list of contami-nants every 3 years to be consideredfor regulation. The Agency must prom-ulgate at least 25 MCLs from each ofthese lists starting in 1991. EPA mayset treatment technology requirementsinstead of MCLs when it is difficult orexpensive for water suppliers to testfor specific contaminants.

Whenever EPA establishes an MCLfor a particular contaminant, theAgency must also identify the BestAvailable Technology (BAT)4 for

10

removing that contaminant. To complywith the MCL, public water systemsare required to use the BAT or an alter-native treatment technology deter-mined by the state to be at least aseffective as the BAT.

MCLs fur Volatils OrganicCompounds

EPA has issued final MCLs for 8volatile organic compounds. Theseare shown in Table 2-1. Nontransientnoncommunity water systems as wellas community systems must meetthese MCLs.

MCLs for Inorganic and SyntheticOrganic Compounds

The final MCL for fluoride has beenset at 4.0 mg/L (see Federal RegisterApril 2,1986 - 41 FR 11396).5 EPAhas proposed MCLs for lead and cop-per (Table 2-2), and for 8 other inor-ganic compounds and 30 syntheticorganic chemicals (Table 2-3). Table2-3 shows proposed MCLs along withmaximum allowable levels underregulations currently in effect.

MCLs for the inorganic chemicals andsynthetic organic chemicals in Table2-4 will be proposed in the near future.

MCLs for MicrobiologicalContaminants

EPA has set final MCLs for totalcoliforms (Table 2-5). Coliforms areusually present in water contaminatedwith human and animal feces and areoften associated with disease out-breaks. Although total coliforms in-clude microorganisms that do notusually cause disease themselves,their presence in drinking water mightmean that disease-causing organismsare also present. All public water sys-tems must meet the MCL for totalcoliforms; monitoring requirements arediscussed below.

Table 2-1. Volatile Organic Chemicals: Final MCLs (in mg/L)

Chemical

Trichloroethylene

Carbon tetrachloride

Vinyl chloride

1,2-Dichloroe thane

Benzene

para-Dichloro benzene

1,1 -Dichloroethylane

1,1,1-Trichloroethane

Source: Federal Register, July 8,

Final MCL

0.005

0.005

0.002

0.005

0.005

0.075

0.007

0.2

1987 (52 FR 25690).

For surface water (or ground waterunder the direct influence of surfacewater)6 EPA has set treatment require-ments instead of MCLs for Giardia,viruses, heterotrophic bacteria,Legbnella, and turbidity. These re-quirements are explained below underSurface Water Treatment Require-ments. EPA intends to issue disinfec-tion regulations for ground water,including regulations to control thelevel of viruses, Leghnella, andheterotrophic bacteria, at a later date.

MCLs for RadionuclideContaminants

New MCLs for radionuclides (radioac-tive elements) will be proposed in the

future. The anticipated MCL for radon,a naturally occurring radionuclide,might affect many small public watersupplies. Table 2-6 shows the currantMCLs for radiological contaminants.Note that only systems serving popula-tions greater than 100,000 people arerequired to meet MCLs for manmaderadionuclides.

MCLs for Disinfectants andDisinfection By-Products

In 1979, EPA established an MCL fortotal trihalomethanes—chloroform,bromoform, bromodichloromethane,and dibromochloromethane—of 0.1milligram per liter. This MCL appliesonly to systems serving populations

Table 2-2. Lead and Copper: Proposed MCLs

(Measured as water leaves the treatment plant or enters the distributionsystem)

LeadCopper

0.005 mg/L1.3 mg/L

Source; Federal Register, August 18, 1988 (53 FR 31571).

See Chapter 8, Resources, for information about the Federal Register.6 Any water beneath the surface of the ground with (i) significant occurrence of insects or other microorganisms, algae, or large-diameter pathogens such as Giardia lamblia, or (ii) significant and relatively rapid shifts in water characteristics such as turbidity,temperature, conductivity, or pH which closely correlate to climatological or surface water conditions. Direct influence must be deter-mined for individual sources in accordance with criteria established by the state.

11

Table 2-3. Proposed MCLs for Synthetic Organic Chemicals and Inorganic Chemicals

Contaminant

AcrylamideAlachlorAldicarb

Aldicarb sulfoxideAldicarb sulfoneAtrazine

CarbofuranChlordanecis-1,2-Dichloroethylene

Dibromochloropropane (DBCP)1,2-Dichloropropaneo-Dichlorobenzene

2,4-DEthylenedibromide (EDB)Epichlorphydrin

EthylbenzeneHeptachlorHeptachlor epoxide

LindaneMethoxychlorMon ochloroben zene

PCBs (as decachlorobiphenyl)PentachlorophenolStyrenec

Tetrachloroethylene 'Toluene2,4,5-TP (Silvex)

Toxaphenetrans-1,2-DichloroethyleneXylenes (total)

AsbestosBariumCadmium

ChromiumMercuryNitrate (as nitrogen)

Nitrite (as nitrogen)Selenium

"NPDWR • National Primary Drinking WaterbTT = Treatment Technique.CEPA proposes MCLs of 0.1 mg/L based on

classification."7 million fibers/liter (only fibers longer than

Source: Federal Register, May 22, 1989 (54

ExistingNPDWR" (mg/L)

—

—

E0.1

E0.0040.1

0.01

0.005

1.00.010

0.050.002

10.0

0.01

ProposedMCL(mg/L)

•nr*0.0020.0I

0.010.040,003

0.040.0020.07

0.00020.0050.6

0.070.00005TT"

0.70.00040.0002

0.00020.40.1

0.0050.20.005/0.1

0.0052.00.05

0.0050.1

10.0

7F/Ld

5.00.005

0.10.002

10.0

1.00.05

Regulations,

a group C carcinogen classification and 0.005 mg/L based on a B2

10 m).

FR 22064).

12

greater than 10,000 people. EPAplans to propose new rules for ground-water disinfection and for disinfectionby-products; small systems might beincluded in these new requirements.Disinfectants and disinfection by-products that might be included inthese rules are shown in Table 2-7.

Monitoring

New monitoring requirements forchemical contaminants under the1986 SDWA amendments could havea major impact on small systems.These new requirements are ex-plained below.

Volatile Organic ChemicalsAll systems must monitor for the regu-lated VOCs in Table 2-1 and the un-regulated VOCs in Table 2-8. Therequired monitoring is shown in Table2-9. Small systems serving fewer than3,300 people must complete initialmonitoring for these VOCs by Decem-ber 31, 1991. Nontransient noncom-munity systems, as well as communitysystems, must meet the requirementsfor VOCs.

FluorideMonitoring requirements for fluorideare shown in Table 2-10.

Other Inorganic and SyntheticOrganic ChemicalsEPA has proposed monitoring require-ments for 38 regulated chemicals and111 unregulated contaminants (inor-ganic and synthetic organic chemicals).In addition, EPA will propose monitor-ing requirements for chemicals inTable 2-4.

RadlonuclldeaCurrently, community systems mustmonitor for natural radiological chemi-cals every 4 years. EPA will be propos-ing new monitoring requirements forradionuclides, including radium-226,radium-228, uranium (natural), andradon.

Microbiological Contaminants

• Total conforms. In June 1989,EPA issued new monitoring require-

Table 2-4. Inorganic and Synthetic Organic Chemicalsto be Regulated

Arsenic"Méthylène chlorideAntimonyEndrinb

DalaponDiquatEndothallGlyphosateAndipates2,3,7,8-TCDD (Dioxin)Trichlorobenzene

"Current MCL is 0.05 mg/L."Current MCL is 0.0002 mg/L.

SulfateHexachlorocyclopentadieneNickelThalliumBerylliumCyanide1,1,2-TrichloroethaneVydateSimazinePAHsAtrazine

Source: U.S. Environmental Protection Agency, Fact Sheet. "Drinking WaterRegulations under 1986 Amendments to SDWA," February 1989.

Table 2-5. Maximum Contaminant Level for Total Conforms

• Compliance is based on presence/absence of total coliforms in sample, ratherthan on an estimate of coliform density.

• MCL for systems analyzing at least 40 samples/month: no more than 5.0 per-cent of the monthly samples may be total coliform-positive.

• MCL for systems analyzing fewer than 40 samples/month: no more than 1sample/month may be total coliform-positive.

• A public water system must demonstrate compliance with the MCL for totalcoliforms each month it is required to monitor.

• MCL violations must be reported to the state no later than the end of the nextbusiness day after the system learns of the violation.

Source: U.S. Environmental Protection Agency, Fact Sheet. "Drinking WaterRegulations under 1986 Amendments to SDWA," February 1989.

merits for total coliforms, effectiveDecember 31,1990. Tables 2-11and 2-12, respectively, show theminimum number of routine andrepeat samples required.

• Fecal coliforms/Eschar/cWa coll.The presence of fecal coliforms indrinking water is strong evidence ofrecent sewage contamination, andindicates that an urgent publichealth problem probably exists.Therefore, EPA requires that publicwater systems analyze eachsample that is positive for totalcoliforms to determine if it contains

fecal coliforms. Alternatively, thesystem may test for the bacteriumEscherichia coli instead of fecalcoliforms. The requirements formonitoring fecal coliforms and E.coli are effective December 31,1990.

Heterotrophic bacteria. Hetero-trophic bacteria can interfere withtotal coliform analysis. EffectiveDecember 31, 1990, public watersystems must follow specific proce-dures to minimize this interference.

13

Table 2-6. Maximum Contaminant Levels for Radiological Chemicals

Natural Radionuclides Manmade Radionuclides

CommunitySystems

NoncommunitySystems

GrossAlpha

15pCi/L

Stateoption

CombinedRadium226 &226

5 pCi/L

Stateoption

GrossBeta

50 pCi/Lb

Stateoption

Tritium

20,000 pCi/Lb

Stateoption

Strontium90

8 pCi/Lb

Stateoption

aPicocuries per liter (pCi/L) is a measure of the concentration of a radioactive substance. A level of 1 pCi/L means thatapproximately 2 atoms of the radionuclide per minute are disintegrating in every liter of water,

bApplies only to surface water systems serving populations greater than 100,000 people.

Source; Adapted from National Rural Water Association, Water System Decision Makers: An Introduction to Water SystemOperation and Maintenance, Duncan, OK, 1988.

Table 2-7. Disinfectants and Disinfectant By-Products

Disinfectants and Residuals

Chlorine, hypochlorous acid, and hypochlorite ionChlorine dioxide, chlorite, and chlorateChloramines and ammoniaOzone

Disinfectant By-Products

Trihalomethanes: chloroform, bromoform, bromodichloromethane, dibromochloromethaneHaloacetonitriles: bromochloroacetonitrile, dibromochloroacetonitrile, dichlorobromoacetonitrile, trichloroacetonitrileHaloacetic acids: mono-, di-, and tri-chloroacetic acids; mono- and dibromoacetic acidsHaloketones: 1,1-dichloropropanone and 1,1,1-tri-chloropropanoneOther: chloral hydrate, chloropicrin

Cyanogen chlorideChlorophenols (2-chlorophenol, 2,4-dichlorophenol, 2,4,6-trichlorophenol)N-organochloramines

MX[3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone)]

Ozone by-products

Source: U.S. Environmental Protection Agency, Fact Sheet. "Drinking Water Regulations under 1986 Amendments toSDWA," February 1989.

14

Table 2-8. Monitoring for Unregulated VOCs

Required for All Systems:

ChloroformBromodichloromethaneChlorodibromomethane

Bromoformtrans-1,2-DichloroethyleneChlorobenzene

m-DichlorobenzeneDichloromethanecis-1,2-Dichloroethylene

o-DichlorobenzeneDibromomethane1,1-Dichloropropane

TetrachloroethyleneToluenep-Xylene

o-Xylenem-Xylene1,1-Dichloroethane

Required for Vulnerable Systems* Only:

1 ^-Dibromo-S-chloropropane (DBCP)Ethylenedibromide (EDB)

At Each State's Discretion:

1,2,4-Trimethylbenzene1,2,4-Trichlorobenzene1,2,3-Trichlorobenzene

n-Propylbenzenen-ButylbenzeneNaphthalene

HexachlorobutadieneBromochloromethane

"A system's vulnerability to contamination is assessed by evaluating(e.g., pesticides), type of source, location of waste disposal facilitiestribution system.

I

1,2-Dichloropropane1,1,2,2-TetrachloroethaneEthylbenzene

1,3-DichloropropaneStyreneChloromethans

Bromomethane1,2,3-Trichloropropane1,1,1,2-Tetrachloroethane

Chloroethane1,1,2-Trichloroethane2,2-Dichloropropane

o-Chlorotoluenep-ChlorotolueneBromobenzene

1,3-DichloropropaneEthylene dibromide1,2-Dibromo-3-chloropropari8

1,3,5-Trimethylbenzenep-lsopropyltolueneIsopropylbenzene

tert-Butylbenzenesec-ButylbenzeneFluorotrichloromethane

Dichlorodifluoromethane

factors such as geological conditions, use patterns, historical monitoring record, and nature of the dis-

Source: Adapted from U.S. Environmental Protection Agency, Fact Sheet. "Drinking Water Regulations under 1986Amendments to SDWA," February 1989.

15

Table 2-9. Compliance Monitoring for Regulated and Unregulated Volatile Organic Chemicals

Initial monitoring: All community and nontransient noncommunity systems must monitor each source at leastonce within 4 years.

• Surface waters: four quarterly samples.

• Ground water: four quarterly samples; state can exempt systems from subsequent monitoring if noVOCs are detected in the first sample.

• Composite samples of up to five sources are allowed.

Repeat monitoring: varies from quarterly to once every 5 years. The frequency is based on whether VOCsare detected in the first round of monitoring and whether the system is vulnerable to contamination.

Source: Adapted from U.S. Environmental Protection Agency, Fact Sheet. "Drinking Water Regulations under 1986 Amend-ments to SDWA," February 1989.

• Sanitary surveys. Periodicsanitary surveys are required for allsystems that collect fewer than fivecoliform samples per month. (Asanitary survey is a comprehensivereview of a system's operations, in-cluding watershed control, the disin-fection system, raw water quality,and monitoring, to determinewhether operational requirementsare being met.) The schedule forconducting sanitary surveys isshown in Table 2-13.

Laboratory Analysis and SamplingRequirements

To meet the monitoring requirementsfor some contaminants, small systemswill need the services of a commerciallaboratory. For compliance monitoringpurposes, analyses must be per-formed in an EPA or state-approvedlaboratory. Contact the Safe DrinkingWater Hotline (see Chapter 8, Resour-ces) for assistance in locating a cer-tified drinking water laboratory in yourarea. (These laboratories must suc-cessfully analyze performance evalua-tion samples within limits set by EPA.)

To ensure proper sampling andanalysis7:

* Samples must be collected inproper containers and preserved asnecessary. Discuss sample collec-tion procedures for the contaminantwith the laboratory in advance.(See Appendix A for bacteriologicalsample collection procedures.)

* Sample chain of custody must bemaintained (to ensure that some-one is always accountable for thesample).

* Analysis must be performed withinspecified holding times (the periodof time between sample collectionand analysis).

* Approved analytical proceduresmust be used.

* Adequate quality assurance datamust be generated within thelaboratory.

A water system manager should ob-tain the following information from alaboratory he or she plans to use:

• References of similar work

• Copy of applicable accreditationsor certifications

• Information about availability andcost of sample containers, preser-vatives, and shipping containers

• Commitment or estimate of projectturnaround

• Definition of analytical methods,detection limits, and cost of analysis

• Type of quality assurance data thatwill be reported

• State-approved reporting forms, ifapplicable

• Fees

Table 2-10. Monitoring Requirements for Fluoride

Surface waters:

Ground waters:

Minimum repeat:

1 sample each year

1 sample every 3 years

1 sample every 10 years

Source: Federal Register, April 2, 1986 (41 FR 11396).

7 From Metcalf and Eddy, A Guide to Water Supply Management in the 1990s, Wakefield, MA, November 1989.

16

Table 2-11. Total Coliform Sampling Requirements According toPopulation Served

Population Served

Minimum Numberof Routine Samples

Per Month*

25 to 1,000b

1,001 to 2,500

2,501 to 3,300

aln lieu of the frequency specified in this table, a noncommunity water systemusing only ground water (except ground water under the direct influence of sur-face water) and serving 1,000 persons or fewer may monitor at a lesser fre-quency specified by the state (in writing) until a sanitary survey is conductedand the state reviews the results. Thereafter, such systems must monitor ineach calendar quarter during which the system provides water to the public, un-less the state determines (in writing) that some other frequency is more ap-propriate. Beginning June 29, 1994, such systems must monitor at least onceevery year.

A noncommunity water system using surface water, or ground water under thedirect influence of surface water, regardless of the number of persons served,must monitor at the same frequency as a like-sized community water system,i.e., the frequency specified in the table. A noncommunity water system usingground water (which is not under the direct influence of surface water) and serv-ing more than 1,000 persons during any month must monitor at the same fre-quency as a like-sized community water system, i.e., the frequency specified inthe table, except that the state may reduce the monitoring frequency (in writing)for any month the system serves 1,000 persons or fewer. However, in no casemay the state reduce the sampling frequency to less than once every year.

^Includes public water systems that have at least 15 service connections, butserve fewer than 25 persons.

Source: Federal Register, June 29, 1989 (54 FR 27545).

Table 2-12. Monitoring Requirements Following a Total Coliform-Positive Routine Sample

Number of RoutineSamples/Month

Number of RepeatSamples"

Number of RoutineSamples Next Month*

1 /month or fewer

2/month

3/month

5/month

5/month

5/month

a Number of repeat samples in the same month for each total coliform-positiveroutine sample.b Except where state has invalidated the original routine sample, or where thestate substitutes an onsite evaluation of the problem, or where the state waivesthe requirement on a case-by-case basis. See 40 CFR 141.21a (b) (5) for moredetails.


Typical costs of laboratory analyses

are shown in Table 2-14.

Contact your state drinking water

agency for additional information

about requirements for sample collec-

tion and analysis and reporting.

Surface Water TreatmentRequirements

EPA has set treatment requirements to

control microbiological contaminants

in public water systems using surface

water sources (and ground-water sour'

ces under the direct influence of sur-

face water). These requirements,

effective December 31, 1990, include

the following:

• Treatment must remove or inac-tivate at least 99.9 percent ofGiardia lamblia cysts and 99.99 per-cent of viruses.

• All systems must disinfect, and also

might be required to filter if certain

source water quality criteria and site-

specific criteria are not met.

• The regulations set criteria fordetermining if treatment, includingturbidity removal and disinfectionrequirements, is adequate for fil-tered systems.

• All systems must be operated byqualified operators as determinedby the states.

Systems using surface water must

make certain reports to the state

documenting compliance with treat-

ment and monitoring requirements.

Detailed guidance on surface watertreatment requirements is provided inEPA's Guidance Manual for Com-pliance with the Filtration and Disinfec-tion Requirements for Public WaterSystems Using Surface WaterSources.

17

Table 2-13. Sanitary Survey Frequency for Public Water Systems Collecting Fewer than Five Samples/Montha

System TypeInitial SurveyCompleted by

Frequency ofSubsequentSurveys

Community water system

Noncommunity water system

June 29, 1994

June 29, 1999

Every 5 years

Every 5 yearsb

"Annual onsite inspection of the system's watershed control program and reliability of disinfection practice is also required by40 CFR 141.71 (b) for systems using unfiltered surface water or ground water under the direct influence of surface water.The annual onsite inspection, however, is not equivalent to the sanitary survey. Thus, compliance with 40 CFR 141.71(b)alone does not constitute compliance with the sanitary survey requirements of this coliform rule (141.21a(d)), but a sanitarysurvey during a year can substitute for the annual onsite inspection for that year.

bFor a noncommunity water system that uses only protected and disinfected ground water, the sanitary survey may berepeated every 10 years, instead of every 5 years.


Table 2-14. Approximate Commer-cial Laboratory Costs Per SampleAnalysis ($1989)

Turbidity

Coliform Bacteria

Copper

Lead

Radium 226/228

8 VOCS (Table 2-10)

Table 2-8 Contaminants

$20

$20

$20

$20

$120

$200

$500

Source: Adapted from Metcalf andEddy, A Guide to Water SupplyManagement in the 1990s,Wakefield, MA, November 1989.

Systems using surface water are required to filter unless stringentcriteria are met.

18

Chapter Three

Solutions toDrinking WaterTreatmentProblems:An Overview

This chapter presents an overview ofthe technologies that a small systemshould consider for meeting its treat-ment needs. In addition, it discussesadministration and other issues thatcan be important for small systems,including financial and capital improve-ments, cooperative arrangements,operator capabilities, and selection ofa consulting engineer or equipmentvendor. Appendix B presents a check-list of factors that can affect watertreatment system performance. Whilethis list is not all-inclusive, it may helpa water system operator or managerin determining improvements that maybe needed.

The treatment needs of a water sys-tem are likely to differ depending onwhether the system uses a ground-water or surface water source. Com-mon surface water contaminantsinclude turbidity, microbiological con-taminants (Giardia, viruses, and bac-teria), and low levels of a largenumber of organic chemicals. Ground-water contaminants include naturallyoccurring inorganic contaminants(e.g., arsenic, fluoride, radium, radon)and nitrate, and a number of specificorganic chemicals (e.g., trichbro-ethylene) that sometimes occur in rela-tively high concentrations.8 Bacteriaand viruses can also contaminate rela-tively shallow ground water (for ax-ample, from sewage overflow orseepage into wells and springs, orfrom surface runoff). Giardia cysts areless likely to be found in ground water,but they have contaminated ground-water supplies where sewage or con-taminated surface water entered

improperly constructed or locatedwells. Corrosion control is a concernfor systems using both surface andground-water supplies.

Figure 3-1 presents an overview ofsteps that a small system can follow todetermine treatment needs. Tables 3-1and 3-2 present the contaminants like-ly to be found in surface water andground water, and the most suitabletreatment technologies for each.

The treatment options available tosmall systems for filtration, disinfec-tion, organic and inorganic con-taminant removal, and corrosioncontrol are also listed in Table 3-3.This table presents the major ad-vantages and disadvantages of eachtechnology. Costs are shown in Table3-4. Chapters 4 through 7 containmore detailed information about eachof these technologies, including theireffectiveness in removing specific con-taminants in water.

Questions to Consider InChoosing Treatment Technologies

When selecting among the differenttreatment options, the water systemmanager must consider a number offactors: regulatory requirements, char-acteristics of the raw water, configura-tion of any existing system, cost,operating requirements, availability ofnontreatment alternatives, com-patibility of the processes currentlybeing used or to be used, wastemanagement, and future needs of theservice area. Each of these factors isdiscussed below.

8 Thomas J. Sorg, "Process Selection for Small Drinking Water Supplies,"Proceedingsof the Twenty-Third Annual Public Water Supply Engineers Conference: New Direc-tions for Water Supply Design and Operation, University of Illinois, April 21-23,1981 •

9 Gunther F. Craun, "Review of the Causes of Waterborne Disease Outbreaks,"Surveillance and Investigation of Waterborne Disease Outbreaks, Health EffectsResearch Laboratory, U.S. Environmental Protection Agency, November 1989.

19

• • luililllllii

Steps to Determine Treatment Needs

ÜH|HP|

Collect sample of raw water (see Chapter 2, LaboratoryAnalysis and Sampling Requirements) lililí

mMÊmï

Illllliili¡¡Illll

Send sample to laboratory for analysis (microbiological, organic, andinorganic contaminants)

Compare contaminants and their levels to applicable standards(see Chapter 2, Maximum Contaminant Levels)

StandardsExceeded

¡¡¡lilil

Systems using surface water sour-ces must disinfect, and must filterunless stringent requirements aremet; systems using ground-watersources will have to meet futureground-water disinfection rules

(see Chapter 2)

llliillllilll

Compile list of"contaminants of concern"

(those that exceed maximumconcentration allowed by

regulations)

¡lili

illl:;:::^'iM;:

ïiiilWSi

Hill

If filtration and/ordisinfection must

be added orupgraded

Élit!

Identify and evaluatetreatment technologies avail-able to control contaminantsof concern (see Tables 3-1through 3-4 and Chapters 4

through 7)

fililí

¡lili

SíSSit;!;;:^^

!••!liïi;|ÎSI?piS

Contact vendors or consulting engineer for information abouttreatment technology selection, costs, and design (see Appendix C)

and/or contact organizations that assist small systems(see Chapter 8, Resources)

Figure 3-1. Steps to determine treatment needs.

20

Table 3-1. Common Problems and Suitable Treatment Technologies: Ground Water'

Micro-biological Fluoride Barium Nitrate Radium Radon Arsenic Selenium Orgánica

Chlorination •

Ozonation •

Ultraviolet

radiation •

Aeration • •

Ion exchange • • • • •

Activated alumina • • •

Coagulation/Filtration • •

Membranes(reverse osmosis • • • • • •and electrodialysis)Granular activatedcarbon (GAC) • •

Point-of-use/Point-of-entry systems Might be suitable for some very small systems to remove organic or inorganic contaminants.

Package Plants Package plants might be available to solve specific inorganic or organic contamination problems.

aln general, "•" indicates the principal function of the treatment technology listed. Many of these technologies,however, have secondary effects in addition to those shown here. (For example, ozone can remove some organic chemicalsas well as provide disinfection.)

What Are the Requirements forDrinking Water Supplied by theSystem?

Federal and state drinking waterregulations are the most important fac-tors to consider in developing a watersystem's treatment goals. The suppliermay also choose to consider con-sumer preferences and nonmandatoryguidelines developed by regulatoryagencies and professional organiza-tions, such as EPA's Secondary Maxi-mum Contaminant Levels (federallynonenforceable goals for controllingcontaminants that affect the aestheticqualities of drinking water), Health Ad-visories (guidance values developedby EPA to address immediate or emer-gency concerns associated with acci-dents, spills, or newly detecteddrinking water contamination situa-

tions), and American Water Works As-sociation water quality goals.

Are Nontreatment AlternativesAvailable?

Small water systems might not alwayshave the resources to install a com-plete treatment system to solve a con-tamination problem. In such situations,however, a small system might beable to find a new water source. Forexample, a well can be located in anarea distant from the source ofcontamination.

The development of a new well,however, is only part of the solution.The area around the well must bemanaged to protect it from future con-tamination. Establishing a wellhead

protection is an appropriate nontreat-ment alternative.

As another option, a small system canconsider cooperating with other sys-tems, such as by buying treated waterfrom a larger utility (see Multicom-munity Cooperative Arrangementsbelow).

What Are the Characteristics of theRaw Water?

To determine treatment needs, the sys-tem manager must know the quality ofthe source water—what biological andchemical contaminants are in thewater and at what concentrations theyare present. Knowledge of other watercharacteristics, such as pH, tempera-ture, alkalinity, and calcium and mag-nesium content is useful because of

21

Table 3-2. Common Problems and Suitable Treatment Technologies: Surface Water'1

Turbidity Microbiological Control Corrosion Control Organ les

Chlorination •

Ozonation •

Ultraviolet radiation •

Package plants^ • •

Slow sand filtration • •

Diatomaceousearth filtration • •

Ultrafiltration

(membrane filtration)0 • •

Cartridge filtration0 • •

Aeration •

Granular activated carbon (GAC) •

pH control •

Corrosion inhibitors •

Point-of-use/Point-of-entry systems'* • • •

aln general, "•" indicates the principal function of the treatment technology listed. Many of these technologies, however,have secondary effects in addition to those shown here. (For example, ozone can remove some organic chemicals aswell as provide disinfection.)

bWhile package plants are most widely used to remove turbidity, color, and microbiological contaminants, package plantsare also available that can remove organic and/or inorganic contaminants.

°Emerging technology.

dMight be suitable tor some very small systems that cannot install central treatment. Point-of-use/Point-of-entry systemsuse a variety of treatment processes, including reverse osmosis, ion exchange, and activated carbon.

their impact on aesthetics and the ef-ficiency of treatment processes.

What Is the Configuration of theExisting System?

The configuration of the existing sys-tem can be an important considerationin selecting a treatment option. For ex-ample, if a supplier is considering add-ing a new treatment technology, he orshe must know if the existing systemis compatible with or adaptable to the

new technology. In addition, an exist-ing system's ability to blend treatedwater with raw water can be important.A system might be able to economizewith an expensive technology by treat*ing only part of the total flow, and stillmeet regulatory requirements that limitthe concentration of a contaminant infinished water.

The method of water distribution andits composition (e.g., asbestos-cement

pipe, copper, polyvinyl chloride, gal-vanized, lead) can also be an impor-tant factor in selecting a treatmentoption. For example, corrosion wouldnot be a great concern in systemsusing polyvinyl chloride (PVC) pipes.The length of the distribution systemand how quickly water moves throughit can affect requirements for secon-dary disinfection (to prevent regrowthof microorganisms in the distributionsystem).

22

What Ara tha Costs of theTreatment Options?

The total costs of treatment include one-time capital costs and annual operatingand maintenance costs. Each treatmenttechnology has a different mix of capi-tal and operating and maintenancecosts. Technologies with high capitalcosts often have lower operating andmaintenance costs (and those with bwercapital costs often have higher operatingand maintenance costs). Thus, small sys-tems that cannot afford appropriate capi-tal equipment can become saddled withhigher operating and maintenance costs.

What Are the TreatmentTechnology's OperatingRequirements?

The most important operational con-sideration is the consistency of the rawwater. The less consistent the raw waterquality, the greater the need for monitor-ing, and the greater the operating com-plexity of most systems. Thus, a lessconsistent influent requires a higherlevel of operator training and attention,and might require greater instrumenta-tion, controls, and automation.

Other important operating considera-tions include:

• Energy requirements

• Chemical availability, consumptionrate, and storage

• Instrumentation and automation

• Preventive maintenance

• Noise

• Aesthetics

• Backup/redundant systems

• Requirements for a startup phasebefore full removal capacity isachieved

• Cleaning and backwashing require-ments

• Distribution system

• Staffing needs

• Operator training requirements

• Process monitoring requirements

How Compatible Are the ProcessesUsed?

To achieve overall treatment goals, allthe treatment processes must be com-patible. For example, a lower pH isdesirable for efficient chlorine disinfec-tion; however, lower pH increases cor-rosion in the water distribution system.Therefore, a system might maintain alower pH but use a corrosion inhibitor(described in Chapter 7) to minimizecorrosion (or the system might elevatethe pH before distribution). All the ele-ments of treatment should be chosenso that they interact as efficiently andeffectively as possible.

In addition, using one treatment tech-nology to meet more than oneregulatory requirement reduces costsand operating complexity. For ex-ample, a system might use reverse os-mosis (described in Chapter 7) whenboth organic and inorganic con-taminants are present in raw water.Ozone (described in Chapter 5) canremove organic chemicals as well asprovide primary disinfection. Packedtower aeration (described in Chapter6) can remove both volatile organicchemicals and radon in ground water.It also removes carbon dioxide, there-by raising the pH to a more desirablelevel for corrosion control. (Aeration,however, can increase dissolvedoxygen levels, which can contribute tocorrosion.)

What Waste Management IssuesAre Involved?

Waste management can be a significantissue for water treatment systems. Mosttreatment processes concentrate con-taminants into a residual stream (brineor sludge) that requires proper manage-ment. For example, removal of radonwith granular activated carbon canproduce a low-level radioactive waste.Water treatment systems must followfederal and state regulations coveringthe management of wastes. In somecases, this can significantly increase dis-posal costs for the treatment system.

What Are the Future Needs of theService Area?

The future of the service and supply areais another important factor in selecting atreatment technology. The supplier canevaluate future demands using popula-tion and economic forecasts of the ser-vice area. Present and potential watersupplies should also be examined todetermine their vulnerability to naturaland manmade contamination.

Special Issues for Small Systems

Financial/Capital ImprovementFinancing water system improvementscan be an obstacle for a small system.User charges must be high enough tocover the actual costs of water treat-ment, analytical work, and distribution.Because costs are spread over fewerpeople, rate increases have a greaterimpact on the individual customer thanthose for large systems.

Most small systems are also at a dis-advantage when they attempt to raisefunds in the local and national capitalmarkets, since their credit base,market recognition, and financing ex-pertise are usually limited. They mightbe able to obtain financial assistancethrough state and federal loan andgrant programs. Many states currentlyhave drinking water financial assis-tance programs. Some states assistsmall systems in gaining access tocapital through low-interest loans fromstate revolving loan funds, state bondpools, and state-funded bond in-surance.

Sources of federal grants and loansfor small systems include the FarmersHome Administration (FmHA) and aproposed federal grants program thatblends federal grant money with statebond money to provide low-interestloans to small water systems.

Other financing options for small sys-tems include federal revenue sharingand revenue bonds (for municipal sys-tems), loans through the United StatesSmall Business Administration (SBA),and use of tax exempt industrial

23

Table 3-3. Overview of Water Treatment Technologies

TreatmentRequirements

Filtration of surfacewater supplies tocontrol turbidityand microbialcontamination

Disinfection

Organic contaminationcontrol

TechnologicalOptions to MeetRegulatoryRequirements

Slow sand filtration

Package plant filtration

Ultrafiltration(Membrane filtration)

Cartridge filtration

Chlorine

Ozone

Ultraviolet radiation

Granular activated carbon

Packed column aeration

Diffused aeration

Multiple tray aeration

Higee aeration

Mechanical aeration

Catenary grid

Stage ofAcceptability

Established

Established

Emerging

Emerging

Established

Established

Established

Best AvailableTechnology (BAT)

Best AvailableTechnology (BAT)

Established

Established

Experimental

Experimental

Experimental

(continued on next page)

Comments

Operationally simple; lowoperating cost; requiresrelatively low turbidity sourcewater

Compact; variety of processcombinations available

Experimental, expensive

Experimental, expensive

Most widely used method;concerns about health effectsof by-products

Very effective but requires asecondary disinfectant, usuallysome form of chlorine

Simple, no established harmfulby-products, but requiressecondary disinfectant,usually some form of chlorine

Highly effective; potential wastedisposal issues; expensive

Highly effective for volatile com-pounds; potential air emissionsissues

Variable removal effectiveness

Variable removal effectiveness

Compact, high energy require-ments; potential air emissionsissues

Mostly for wastewater treatment;high energy requirements,easy to operate

Performance data scarce;potential air emissions issues

revenue bonds by a private contractorsupplying service to a municipality.

Multlcommunity CooperativeArrangements (Reglonallzatlon)In some cases, a small communitycan share resources with other smallcommunities or a larger communitythrough a cooperative or a regional

water supply authority. Multicommunitycooperative arrangements can im-prove cost effectiveness, upgradewater quality, and result in more effi-cient operation and management.

A wide range of cooperative ap-proaches is available to the small sys-tem, including:

Centralizing functions. A group ofsmall systems working togethercan centralize functions such aspurchasing, maintenance,laboratory services, engineeringservices, and billing. Several smallsystems together might be able toafford resources, such as highly

24

Table 3-3. Overview of Water Treatment Technologies'1 (continued)

TreatmentRequirements

Inorganic contam-ination control

Corrosioncontrols

TechnologicalOptions to MeetRegulatoryRequirements

Membranes(Reverse osmosisand electrodiafysis)

Ion exchange

Activated alumina

Coagulation/Filtration

Aeration

Granular Activated Carbon

pH control

Corrosion inhibitors

aA variety of package plants are available that can perform onetaminant control, etc.).

Source: U.S. EnvironmentalTechnologies (or Upgrading

Stage ofAcceptability

Established

Established

Established

Established

Established

Established

Established

Establishedand emerging

Comments

Highly effective; expensive;potential waste disposal issues



May be difficult for verysmall systems

Preferred technology for radonremoval

Highly effective for radonremoval; potential wastedisposal issues

Potential to conflict with othertreatments

Variable effectivenessdepending on type of inhibitor

or several treatment functions (i.e., filtration, organic con-

Protection Agency, Office of Drinking Water and Center for Environmental Research Information,Existing or Designing New Drinking Water Treatment Facilities, March 1990. EPA 625/4-89-023.

skilled personnel, on a part-timebasis.

• Physically interconnecting exist-ing systems. Two or more smallsystems can be connected, or asmall system can join a larger sys-tem, to achieve the economies ofscale available to large systems.This approach might not befeasible in some situations,however, such as in locationswhere supplies are isolated fromeach other by long distances orrugged terrain. It is also importantto weigh potential disadvantagessuch as loss of local autonomy,complexities of ensuring equity ineach community, and loss of cost

effectiveness when distributionlines become too long.

Creating a satellite utility. A satel-lite utility taps into the resources ofan existing larger facility withoutbeing physically connected to, orowned by, the larger facility.Resources provided by the largerutility can include technical, opera-tional, or managerial assistance;wholesale treated water; or opera-tion and maintenance responsibility.

Creating water districts. Waterdistricts are formed by county offi-cials and provide for the publicownership of the utilities. Theutilities in a district combine resour-

ces and/or physically connect sys-tems, so that one or two facilitiessupply water for the entire district.By forming a water district, privatelyowned systems become eligible forpublic grants and loans.

• Creating county or state utilities.A county or state government cancreate a board to construct, main-tain, and operate a water supplywithin its district. Constructionand/or upgrading of facilities maybe financed through bonds orproperty assessments.

Operator Capabilities

The level of understanding and techni-cal ability of small systems operators

25

Table 3-4. Estimated Costs of Drinking Water Treatment Technologies for a 100,000 GPD Planta ($1989)

Technology

Package Plant Filtration

Coagulation/Filtration with tube settlers

Pressure depth clarifier/Pressure filter

Pressure depth clarifier/Pressure filter with GAG adsorber

Other Filtration

Diatomaceous earth vacuum filter

Diatomaceous earth pressure filter

Slow sand filter: covered

Slow sand filter: uncovered

Inorganic Contaminant Control

High pressure reverse osmosis

Low pressure reverse osmosis

Cation exchange

Anion exchange

Activated alumina

Organic Contaminant Control

GAC in pressurevessel

Packed tower aerator

CapitalCost

$176,000

$206,000

$246,000

$103,000

$106,000

$580,000

$335,000

$275,000

$275,000

$151,000

$115,000

$104,000

$175,000

$45,100


Annual O&M

$11,000

$10,400

$16,300

$11,100

$10,600

$ 7,700

$7,100

$41,300

$29,800

$ 8,500

$10,300

$14,600

$14,400( 6-mo carbon

$ 9,800(12-mo carbon

$ 2,900

Total Cost" Per1,000 Gallons

$1.73

$1.90

$2.47

$1.27

$1.26

$4.15

$2.55

$4.03

$3.40

$1.44

$1.46

$1.47

$1.92replacement)

$1.67replacement)

$0.45

is crucial to the success of the SafeDrinking Water Act (SDWA). Theoperator's basic knowledge, skills, andtraining might include the following10:

• Sufficient training to protect publichealth

Knowledge of all aspects of the dis-tribution system (including main-tenance)

Knowledge of the source watersupply (including pump operation)

Skill to maintain drinking waterquality (including water treatmentwhere necessary, plus state andfederally required samplingroutines)

10 From National Rural Water Association, Water System Decision Makers: An Introduction to Water System Operation and Main-tenance, Duncan, OK, 1988.

26

Table 3-4. Estimated Costs of Drinking Water Treatment Technologies for a 100,000 GPD Plant8 (continued)

TechnologyCapitalCost Annual O&M

Total Cost" Per1,000 Gallons

Disinfection

Gas feed chlorination

Hypochlorite solution

Pellet feed chlorinators

Ultraviolet light6 (57,600 GPD)

Ozonation-high pressure0

$ 10,465

$ 4,080

$ 1,670

$ 25,990

$ 39,270

$ 3,520

$ 5,558

$4,010

$ 2,090

$ 5,074

$0.26

$0.33

$0.23

$0.49

$0.53

Gallons x 3.785 = liters.Sources: G.S. Logsdon, T.J. Sorg, and RM. Clark, Cost and Capability of Technologies for Small Systems, Drinking WaterResearch Division, Risk Reduction Engineering Laboratory, EPA, Cincinnati, OH, May 1989.

R.C. Gumerman et al.. Estimation of Small System Water Treatment Costs, Final Report, Culp/Wesner/Culp, Santa Ana,CA, November 1984.

U.S. Environmental Protection Agency, Office of Drinking Water, Microorganism Removal for Small Water Systems,Washington, DC, June 1983. EPA 570/9-83-012.

"Construction costs generally include manufactured equipment, concrete, steel, labor, pipes and valves, electrical equipmentand instrumentation, housing, site evacuation, some other site work, general contractor's overhead and profit, engineeringcosts, financial and administrative costs, and interest costs during construction. Construction costs do not include landcosts, legal fees, interface piping, roads, and certain other site work. O&M costs generally include annual energy, labor, andchemical costs. Construction costs can vary depending on specific data characteristics. O&M costs can vary, up to plus orminus 100 percent for some technologies, depending on such variables as feed water characteristics, flow rate, and chemi-cal dosage requirements.

bCosts include capital costs annualized at 10 percent interest over 20 years plus annual O&M costs. Average flow assumedat 50 percent of design flow.

cCosts for ultraviolet and ozone disinfection reflect those for primary disinfection only. A secondary disinfectant is necessaryto maintain a residual in the distribution system. The costs of secondary disinfection are not included in the table.

• Knowledge of sources of con-tamination and methods used tomanage these sources.

• Knowledge and understanding ofenergy sources

• Understanding of emergency proce-dures

• Knowledge of state and federalregulations

• Recordkeeping skills

• A willingness to participate in con-tinuing education programs

Without a properly trained operator,system operation and water quality willsuffer. The small system might havedifficulty attracting skilled staff be-

cause of economic constraints. In addi-tion, many small system operatorshave multiple duties, such as maintain-ing the grounds or performing other re-lated public works duties, and mightnot have the opportunity to specializeand develop expertise in drinkingwater treatment.

Operator capability can also limit thetechnology options available to asmall system: a technology that workswell in a large city might require moreoperator training than the small sys-tem can obtain.

Small systems might be able to obtainqualified plant operators by contract-ing the services of personnel from alarger neighboring utility, governmentagency, service company, or consult-

ing firm. Small systems can also usethe National Rural Water Associationfor technical assistance (see Chapter8, Resources).

A "circuit rider" approach, in which ser-vice is provided to several systemsthat cannot individually afford a trainedoperator, can also be used. The circuitrider attends to a number of treatmentsystems, and his or her salary isshared among them. The circuit ridercan directly operate the plants orprovide technical assistance to in-dividual plant operators through on-the-job training and supervision.

Another source of training is the treat-ment equipment manufacturer. Whentreatment equipment is purchased,vendors should supply startup assis-

27

tance and training, as well as detailed office to determine whether POU/POEoperation and maintenance manuals. devices are appropriate.

Additional training rosources for smallsystems are listed in Chapter 8.

Selecting a Consulting Engineer/Equipment Vendor

In some cases, a small communitymight need to use the services of aconsulting engineer or equipment ven-dor to design a treatment system.Consultants should have proven ex-perience in solving problems for smallsystems. Appendix B provides someguidelines for selecting a consultant.

Using a Polnt-of-Use/Polnt-of-Entry(POU/POE) System

A number of point-of-use (POU) andpoint-of-entry (POE) systems are avail-able from a large number of manufac-turers. Types of systems include thoseusing reverse osmosis, activatedalumina, and ion exchange. In certainsituations, POU/POE devices can be acost-effective solution when a verysmall community cannot afford centraltreatment for a contaminant, such asan organic chemical or fluoride. For ex-ample, with state approval, severalsmall communities (25 to 200 people)in Arizona installed home systemsusing activated alumina to removefluoride. A manufacturing/engineeringcompany on contract with one com-munity provides and maintains all thesystems.11

In addition to home devices, somevery small systems (such as trailerparks) might be able to install a treat-ment system at the point of entry andblend resulting treated waters withwater not treated with the POE device.

A public water supplier must monitorand ensure the quality of water treat-ment, whether it provides central treat-ment or decentralized treatmentthrough POU/POE devices. The sup-plier should check with the state drink-ing water agency or regional EPA

11 Thomas Sorg, "Process Selection for Small Drinking Water Supplies," Proceedings of the Twenty-Third Annual Public WaterSupply Engineers' Conference: New Directions for Supply Design and Operation, University of Illinois, April 21-23, 1981.

28

Chapter Four

FiltrationTechnologiesfor SmallSystems

Filtration is the process of removingsuspended solids from water as thewater passes through a porous bed ofmaterials. Natural filtration removesmost suspended matter from groundwater as the water passes throughporous layers of soil into aquifers(water-bearing layers under theground). Surface waters, however, aresubject to runoff and other sources ofcontamination, so these waters mustbe filtered by a constructed treatmentsystem.

The solids removed during filtration in-clude soil and other particulate matterfrom the raw water, oxidized metals,and microorganisms. Filtration can beused to remove many microorgan-isms, some of which might be resis-tant to disinfection. Filtration alsoprevents suspended material(measured as turbidity) from interfer-ing with later treatment processes,including disinfection. Filtration com-bined with disinfection provides a"double barrier" against waterbornedisease caused by microorganisms.

The filtration process usually works bya combination of physical and chemi-cal processes. Mechanical strainingremoves some particles by trapping

them between the grains of the filtermedium (such as sand). A more impor-tant process is adhesion, by whichsuspended particles stick to the sur-face of filter grains or previouslydeposited material. Figure 4-1illustrates these two removalmechanisms. Biological processes arealso important in slow sand filters.These filters form a fitter skin contain-ing microorganisms that trap andbreak down algae, bacteria, and otherorganic matter before the waterreaches the filter medium itself.

Processes Preceding Filtration

Even when treating low turbidity water,filtration is preceded by some form ofpretreatment. Several processes mayprecede filtration (Figure 4-2):

• Chemical feed and rapid mix.Chemicals may be added to thewater to improve the treatmentprocesses that occur later. Thesechemicals may include pH ad-justers and coagulants. (Coag-ulants are chemicals, such asalum, that neutralize positive ornegative charges on small par-ticles, allowing them to sticktogether and form larger, more easi-ly removed particles.) A variety of

A. Mechanical B. AdsorptionRAW WATER RAW WATER

Large particles become lodged and cannot Particles stick to the media and cannotcontinue downward through the media continue downward through the media.

Figura 4-1. Filtration primarily depends on physical and chemicalmechanisms to remove particles from water. (Reprinted from Introductionto Water Treatment, Vol. 2, by permission. Copyright 1984, American WaterWorks Association.)

29

Pimp hhk»

HoMkig link

Figure 4-2. Several processes can precede filtration to improve treatment processes that occur later.

devices, such as baffles, hydraulicjumps, static mixers, impellers, andin-line jet sprays can be used tomix the water and distribute thechemicals evenly.

Flocculation. In this process,which follows rapid mixing, thechemically treated water is sent intoa basin where the suspended par-ticles can collide and form heavierparticles called floe. Gentle agita-tion and appropriate detentiontimes (the length of time waterremains in the basin) facilitate thisprocess-Sedimentation. Following floccula-tion, a sedimentation step may beused. During sedimentation, thevelocity of the water is decreasedso that the suspended material (in-cluding flocculated particles) cansettle out of the water stream bygravity. Once settled, the particlescombine to form a sludge that islater removed from the clarified su-pernatant water.

Filtration processes can include onlyone of these pretreatment proceduresor all of them.

Choosing a Filtration Technology

Conventional filtration, which includescoagulation with the addition of chemi-cals, rapid mixing, flocculation andsedimentation, and granular mediafiltration, is the most versatile systemfor treating raw water that is variable inquality. However, a conventional filtra-tion plant is usually neither appropriatenor economically feasible for verysmall systems. Package plants areone available cost-effective alternativewhen automatic chemical feed controlsystems simplify operation.

Other filtration technologies that canbe more suitable for small systems areslow sand filtration and diatomaceousearth filtration. Membrane filtration andcartridge filtration are two emergingtechnologies that are suitable for smallsystems. Table 4-1 presents the ad-vantages and disadvantages of thesetechnologies. Table 4-2 shows the

removal capacities (percentages thatare effectively removed) of Giardiacysts and viruses for these four tech-nologies. Filtration technologies forsmall systems are described in moredetail below.

Slow Sand Filtration

Slow sand filtration, first used in theUnited States in 1872, is the oldesttype of municipal water filtration. Aslow sand filter consists of a layer offine sand supported by a layer ofgraded gravel. Slow sand filtrationdoes not require extensive active con-trol by an operator. This can be impor-tant for a small system in which anoperator has several responsibilities.

Slow sand filters require a very low ap-plication or filtration rate (.022 cubicmeters per hour per square centimeter[0.015 to 0.15 gallons per minute persquare foot of bed area], dependingon the gradation of the filter media andthe quality of the raw water). Theremoval action includes a biologicalprocess in addition to physical and

30

Table 4-1. Advantages and Disadvantages of Filtration Technologies

Filtration Technology

Slow sand

Diatomaceous earth

Membrane

Cartridge

Advantages

Operational simplicity and reliabilityLow costAbility to achieve greater than 99.9percent Giardia cyst removal

Compact size

Simplicity ot operation

Excellent cyst and turbidity removal

Extremely compact

Automated

Easy to operate and maintain

IDisadvantages

Not suitable for water with high turbidityMaintenance needs of filter surfaces

Most suitable for raw water with lowbacterial counts and low turbidity(less than 10 NTU)

Requires coagulant and filter aids

for effective virus removal

Potential difficulty in maintainingcomplete and uniform thickness ofdiatomaceous earth on filter septum

Little information available toestablish design criteria oroperating parameters

Most suitable for raw water withless than 1 NTU; usually must bepreceded by high levels ofpre treatment

Easily clogged with colloids andalgae

Short filter runs

Concerns about membrane failure

Complex repairs of automatedcontrols

High percent of water lost inbackflushing

Little information available toestablish design criteria andoperating parameters

Can be quickly clogged by algae and

colloids

Requires low turbidity influent

Can require relatively largeoperating budget

31

Table 4-2. Removal Capacities of Four Filter Options

Filtration Options

Slow sandDiatomaceous earthMembraneCartridge

"Aided by coagulation.''With filter aid.

Source: U.S. EnvironmentalTechnologiBs for Upgrading

AchievableGlardla CystLevels(percent Removal)

99.9999.99a

100>99

AchievableVirusLevels

99.999999.95"Very lowLittle data available

Protection Agency, Office of Drinking Water and Center for Environmental Research Information,Existing or Designing New Drinking Water Treatment Facilities, March 1990. EPA 625/4-89-023.

chemical ones. A sticky mat ofsuspended biological matter, called a"schmutzdecke," forms on the sandsurface, where particles are trappedand organic matter is biologicallydegraded. Water applied to slow sandfilters is usually not prechlorinated,since the chlorine destroys theorganisms in the schmutzdecke thathelp remove microbiological, organic,and other contaminants. (Sometimeswater is prechlorinated and thendechlorinated before slow sandfiltration.)

Water with high turbidity can quicklyclog the fine sand in these filters.Water is generally applied to slowsand filters without any pretreatmentwhen it has turbidity levels lower than10 NTU (nephelometric turbidity units).The upper turbidity limit for slow sandfilters is between 20 and 50 NTU.When slow sand filters are used withsurface waters having widely varyingturbidity levels, they can be precededby infiltration galleries or roughing fil-ters, such as upflow gravel filters, toreduce turbidity.

RAWWATERINLET

FILTERED -WATER SUPPLYFOR BACKFILLING

— SCHMUTZOECKE

SCUM OUTLET

i TO DRAIN

I VENTILATION

FILTEREDI WATER

TO DRAIN

Figure 4-3. Slow sand filter. (Source: International Reference Centre forCommunity Water Supply and Sanitation, Technology of Small Water SupplySystems in Developing Countries, WHO Collaborating Centre, The Hague,The Netherlands, 1982.)

Because of the absence of coagulation,slow sand filtration is limited to certaintypes of raw water quality. Stow sand fil-ters do not provide very good removal oforganic chemicals, dissolved inorganicsubstances such as heavy metals, andtrihalomethane precursors (chemicalcompounds, formed when natural or-ganic substances dissolve in water, thatmight form THMs when mixed withchbrine). Also, waters with very fineclays are not easily treated using sandfilters. High algae blooms will result inshort filter runs.

A slow sand filter must be cleanedwhen the fine sand becomes clogged(as measured by the head loss). Thelength of time between cleanings canrange from several weeks to a year,depending on the raw water quality.Cleaning is performed by scraping offthe top layer of the filter bed. A "ripen-ing period" of 1 to 2 days is requiredfor scraped sand to produce a function-ing biological filter. The filtered waterquality is poor during this time, and thefiltered water must be wasted. Ex-tended cleaning periods require redun-dant or standby systems. In somesmall slow sand filters, geotextile filtermaterial is placed in layers over thesurface. A layer of filter cloth can beremoved periodically so that the uppersand layer requires less frequent re-placement.

32

In climates subject to below-freezingtemperatures, slow sand systemsusually must be housed. Unhoused fil-ters in harsh climates develop an icelayer that prevents cleaning. Thus,uncovered slow sand filters willoperate effectively only if turbiditylevels of the influent (water flowing in)are low enough for the filter to operatethrough the winter months withoutcleaning. In warm climates, a coverover the slow sand filter may beneeded to reduce algae growth withinthe filter. Figure 4-3 shows a typicalslow sand system.

In addition to maintenance, slow sandfilters require:

• Daily inspection

• Control valve adjustment

• Daily turbidity monitoring

Slow sand filters can achieve 91 to99.99 percent removal of viruses andgreater than 99.9 percent removal ofGiardia cysts.

Package slow sand filters, constructedfrom lightweight materials andtransported for local installation, havebeen used successfully in small ruralcommunities in developingcountries.12 These might be ap-propriate where community size isless than 1,000 people and conven-tional construction of a slow sand filterwould be too slow or inconvenient.

Diatomaceous Earth Filtration

Diatomaceous earth (DE) filtration,widely used for filtering swimming poolwaters, has also been used success-fully to remove turbidity and Giardiacysts from drinking water. Advantagesof DE filters include compact size,simplicity of operation, and excellentturbidity removal. They are mostsuited for water systems with low tur-bidity (less than 10 NTU) and low bac-terial counts.

Filtrate

Clear liquid line

Preeoaltank

Ra* / •—>—©-water » f « rFmersource ^—' , - - J

Bodyleedtank

Backwashline

Filler

Body leedpump

Septum

Backwash^/drain line

Precoatdrainline

- To drain

pump

Figure 4-4. Typical pressure diatomaceous earth filtration system.

DE filters (Figure 4-4) use a very thinlayer of diatomaceous earth as a filtermaterial (3.2 to 6.4 mm [1/8 to 1/4 in.])which is coated on a porous septum orfilter element. An appropriate grade ofdiatomaceous earth should be used.(Grades vary from fine to coarse, withfine grades removing smaller particlesizes but producing shorter filter runs).The septum is placed in a pressurevessel or operated under a vacuum inan open vessel. Additional diatoma-ceous earth ("body feed") is alsoadded to the influent water during thefiltration process to prolong the filterrun. Higher body feed doses areneeded for higher concentrations ofsuspended solids in the raw water.When the filter becomes plugged, it isbackwashed and agitated so that thediatomaceous earth falls off the sep-tum and is flushed from the filter tank.

Operation and maintenance ofdiatomaceous earth filters require:

• Preparing slurries of filter body feedand precoat diatomaceous earth.

• Adjusting body feed dosages for ef-fective turbidity removal.

• Periodic backwashing, every 1 to 4days, depending on raw waterquality.

• Disposing of spent filter cake.

• Periodically inspecting the filter sep-tum for cleanliness and damage.

• Verifying the effluent quality.

• Maintaining pumps, mixers,feeders, valves, and piping neededfor precoat and body feed opera-tions.

DE filters can effectively removeGiardia cysts, algae, and asbestos,and the fine grades of diatomaceousearth can remove bacteria. These fil-ters require, however, that the waterbe pretreated with coagulating chemi-cals and special filter aids to effective-ly remove viruses.

Plain diatomaceous earth treatment(without the use of a coagulant) doesnot provide good removal of very fineparticles. DE filters also are notcapable of removing dissolved sub-stances, including color-causingmaterials. Excessive suspended mat-ter and algae in the raw water cancause short filter runs.

12 B.J. Lloyd, M. Pardon, D. Wheeler, Rural Water Treatment Package Plant: Final Report for the U.K. Overseas DevelopmentAdministration, July 1986. DelAgua, P.O. Box 92, Guildford, GU2STO, England.

33

Figure 4-5. A package filtration system In Meredith, New Hampshire.

Package Plants

Package plants (Figure 4-5) are treat-ment units that are assembled in a fac-tory, skid mounted, and transported tothe treatment site or that are trans-ported as component units to the siteand then assembled. They are mostwidely used to treat surface watersupplies for removal of turbidity, color,and coliform organisms with filtrationprocesses, but package plants thatcan remove inorganic and/or organiccontaminants are also available. Pack-age plants are often used to treatsmall community water supplies, aswell as supplies in recreational areas,state parks, construction sites, skiareas, military installations, and otherareas not served by municipal supplies.

Package plants can vary widely intheir design criteria and operating andmaintenance requirements. The mostimportant factor to consider in select-ing a package plant is the nature ofthe influent, including characteristicssuch as temperature, turbidity, andcolor levels. Pilot tests (tests thatevaluate treatment processes andoperations on a small scale to obtainperformance criteria) might be neces-sary before a final system can beselected. The package treatment

equipment manufacturer can often per-form these tests.

Package plants can be (and usuallyare) designed to minimize the amountof day-to-day attention required tooperate the equipment. Their opera-tion and maintenance are simplified byautomated devices such as effluent tur-bidimeters connected to chemical feedcontrols and other operating para-meters, such as backwashing. Chemi-cal feed controls are especiallyimportant for plants without full-timeoperators or with variable influent char-acteristics. Even with these automateddevices, however, the operator needsto be properly trained and well ac-quainted with the process and controlsystem.

Figure 4-6 depicts a package plant.The three basic types of packagewater treatment systems are:

• Conventional package plants.These contain the conventionalprocesses of coagulation, floccula-tion, sedimentation, and filtration.

• Tube-type clarifier packageplants. These use tube settlers toreduce settling detention time (theaverage length of time waterremains in the tank or chamber).

• Adsorption clarifier packageplants. These use a contact "bed"with plastic bead media (an adsorp-tion clarifier) to replace the floccula-tion and sedimentation basin,thereby combining these two stepsinto one. A mixed media filter (a fil-ter with a coarse-to-fine gradationof filter media or several types of fil-ter media) completes the treatment.

Package plants can effectively removeturbidity and bacteria from surfacewater of fairly consistent quality,provided that they are run by com-petent operators and are properlymaintained. Package plants also canbe designed to remove dissolved sub-stances from the raw water, includingcolor-causing substances andtrihalomethane precursors. However,when the turbidity of the raw watervaries a great deal, these plants re-quire a high level of operational skilland operator attention.

Membrana Filtration (Ultraflltration)

Membrane filtration, also known asultrafiltrat ion, uses hollow fibermembranes to remove solids fromwater. It can be an attractive option forsmall systems because of its smallsize and automated operation, and itdoes not require coagulation as apretreatment step.

Many membrane systems aredesigned as skid-mounted units.Figure 4-7 shows an example of thistype of membrane system.

Membrane filtration systems canremove bacteria, Giardia, and someviruses. They are most suitable forpolishing water that has already beentreated by other methods, or for drink-ing water supplies with turbidity of lessthan 1 NTU. Fouling of the fibers is themajor problem preventing widespreadapplication of this technology.

Traditional membrane filters work byfeeding water to the inside of the fibermembrane, with the filtrate (filteredwater) emerging on the outside of themembrane. State-of-the-art membrane

34

SERVICE ACCESS PLATFORMWITH HANDRAIL AND 4" KICKPLATETYPICAL STANDARD

AXIAL FLOW TYPEVARIABLE SPEEDFLOCCULATORS TWOSTASE EACH TRAIN

TUBE SETTLERS 60"PVC TYPICAL STANDAEACH TRAIN -

DIE FORMED TANKSTRuCTURALS

SLUDGE DRAW OFF TOWASTE EACH TRAIN

LAUNDER WITH ADJUSTABLEWElftS EACH TRAIN

SETTLED SOLIDS TROUGHSWITH COLLECTORS ANDMANIFOLDS

ROTARY SURFACEAOITATOR EACH FILTER

NON-CORRODING FILTERUNDERDRAW SYSTEM

WASHWATER COLLECTION TROUGHWITH ADJUSTABLE WEIRSEACH TRAIN

SURFACE AGITATOR INLETCONNECTION EACH TRAIN

WASHWATER OUTLET TO WASTEEACH TRAIN

FILTERED WATER OUTLET ANDBACKWASH WATER INLET

FILTER MEDIAEACH TRAIN

Figure 4-6. Package plant system for surface water treatment. (Courtesy of Smith and Loveless, Inc.)

filters pass influent to either the insideor outside of the membrane. The hoi-bw fiber membranes are contained ina pressure vessel or cartridge. Thecontaminants collect on the end of thehollow fiber and are discharged towaste by a reversal of water flow.Uhrafiltration membranes exclude par-ticles larger than 0.2 microns.

The membrane filter system must becleaned to clear the hollow fibers. Thisis done by backflushing and chemicalcleaning or by air pressure. Somemanufacturers have developed self-cleaning systems to extend the timebetween chemical cleanings.

One major concern about membranefilters is the potential for membranefailure. The failure of a membraneshould trigger an operational shut-down or an alarm to the operator.

A diagram of a sample membrane sys-tem is shown in Figure 4-8.

Cartridge Filtration

Cartridge filters consist of ceramic orpolypropylene filter elements that arepacked into pressurized housings.

They use a physical process forfiltration—straining the water throughporous media. Cartridge filtration sys-tems require raw water with lowturbidity.

Cartridge filters are easy to operateand maintain, making them suitablefor small systems with low turbidity in-fluent. Skilled personnel are notneeded; personnel are needed onlyfor daily operation and general main-tenance (cleaning and cartridge re-

Non-CoTOtlva Piping-Syiiom

Chwnlcal R.slsUnt

Clean In Placa -System

MteropnicaaaorControl» for RadialP U I H , CIP System,

d Mb

Stain lm-StMl SkidMountad

Stalnlaaa StnlCMtrifugal Pumpa

PreNltnttkm and PnMnutment SytltmWhen Required

Figure 4-7. Typical skid-mounted membrane filtration assembly.

35

placement). Ceramic filters may becleaned and used for repeated filtercycles. Polypropylene cartridges be-come fouled relatively quickly andmust bs replaced with new units. Al-though these filter systems are opera-tionally simple, they are not automatedand can require relatively large operat-ing budgets.

Cartridge filtration systems sometimesuse "roughing filters" as pretreatmentto remove large solids. Prechlorinationis recommended to prevent the growthof microorganisms on the filters.(However, this should be avoided if theraw water contains organic substan-ces that can contribute to formation oftrihalomethanes.) Except for a disinfec-tant, no other chemicals need to beadded.

Little information is available concern-ing the effectiveness of cartridge filtersfor virus removal.

Innovative Filtration Technologies

Several other simple low-cost filtrationmethods might be appropriate forsome small systems. For example, asystem developed by 3M Companyusing disposable filter bags made ofpolypropylene fibers (Figure 4-9) canremove Giardia cysts from drinkingwater supplies. Small systems inseveral states have successfully usedthese filters with disinfection for treat-ment of water from surface sources.

FILTEREDWATER

RAW WATER

CLARIFIEDRECYCLE

DISCHARGE

- HOLLOW FIBERMEMBRANES

MEMBRANE CLEANINGSOLUTION TO

CHEMICALCOAGULANT

AIR INLET FORBACKWASHING

-BACKFLUSHWASTEWATER

BACKFLUSH CLARIFIER

SLUDGE

Figure 4-8. Flow sheet of membrane filtration system.

Figure 4-9. Simple filter bag system removes particles ranging from 1to 4 microns. (Courtesy of 3M Filtration Products)

36

Chapter Five

Disinfection Disinfection is the treatment processused to destroy disease-causing or-ganisms in a water supply. Primarydisinfection refers to the part of thetreatment process that provides thenecessary ¡nactivation of Giardiacysts, bacteria, and viruses in sourcewater. Secondary disinfection refers tomaintenance of a disinfectant residualwhich prevents the regrowth ofmicroorganisms in the water distribu-tion system. Systems must disinfectsurface water according to the require-ments of the Surface Water Treat-ment Rule (see Chapter 2).

Chlorination (the addition of chlorine)is the most common method of disin-fecting drinking water. Other disinfec-tants that small systems might want toconsider are ozone and ultraviolet(UV) radiation. Table 5-1 summarizesthe advantages and disadvantages ofthese three disinfectants. Thepreferred application point for each dis-infectant is shown in Table 5-2.

Chlorination

When chlorination is performed proper-ly, it is a safe, effective, and practicalway to destroy disease-causing or-ganisms. It also provides a stableresidual (disinfectant remaining in thewater) to prevent regrowth in the dis-tribution system. However, under cer-tain conditions, chlorine can combinewith remaining organic materials in thewater to produce potentially harmfulby-products such as trihalomethanes.(See Disinfection By-Products andStrategies for Their Control below.)

Complex chemical reactions occurwhen chlorine is added to water, butthese reactions are not always ob-vious. For example, a chlorine taste orodor in finished water is sometimesthe result of too little chlorine ratherthan too much, ft is important foroperators to understand basic chlorina-tion chemistry and the factors affectingchlorination efficiency. These topicsare covered thoroughly in many water

supply textbooks. (See Chapter 8,Resources.)

Disinfection Terminology

When chlorine is fed into water, itreacts with any substances that exerta "chlorine demand." Chlorinedemand is a measure of the amount ofchlorine that will combine with im-purities and therefore will not be avail-able to act as a disinfectant. Impuritiesthat increase chlorine demand includenatural organic materials, sulfides, fer-rous iron, and nitrites.

Chlorine can also combine with am-monia or other nitrogen compounds toform chlorine compounds that havesome disinfectant properties. Thesecompounds are called combined avail-able chlorine residual. ("Available"means available to act as a disinfec-tant.)

The uncombined chlorine that remainsin the water after any combinedresidual is formed is called free avail-able chlorine residual. Free chlorine isa much more effective disinfectantthan combined chlorine.

Free chlorine is not available for disin-fection unless the chlorine demand ofthe raw water is satisfied. Whenchlorine dosage exceeds the "break-point"—the point at which chlorinedemand is satisfied—additionalchlorine will result in a free availablechlorine residual. The chlorine dosageneeded to produce a free residualvaries with the quality of the watersource.

Factors Affecting ChlorinationEfficiency

Five factors are important to success-ful chlorination: concentration of freechlorine, contact time, temperature,pH, and turbidity levels.

The effectiveness of chlorination isdirectly related to the concentration offree available chlorine and the contacttime. Contact time is the length of time

37

Table 5-1. Advantages and Disadvantages of Three Disinfectants

Disinfectant

Chlorine

Ozone

Ultravioletradiation

Advantages

Very effective; has a proven historyof protection against waterbornedisease. Widely used. Variety ofpossible application points.Inexpensive. Appropriate as bothprimary and secondary disinfectant.Operators can easily test for chlorineresidual throughout the water system.

Very effective. Minimal harmfulby-products identified to date.

Very effective for viruses andbacteria. Readily available.No known harmful residuals.Simple operation and maintenancefor high quality waters.

Disadvantages

Potential for harmfulby-products undercertain conditions

Relatively high cost. More complexoperations because it must begenerated on site.Requires a secondary disinfectant.

Inappropriate for surface waterRequires a secondary disinfectant.

Source: Adapted from U.S. Environmental Protection Agency, Office of Drinking Water and Center for Environmental ResearchInformation, Technologies for Upgrading Existing or Designing New Drinking Water Treatment Facilities, March 1990.EPA 625/4-89-023.

the organisms are in physical contactwith the chlorine. If the chlorine con-centration is decreased, then the con-tact time must be increased.

The lower the pH, the more effectivethe disinfection. The pH also affectscorrosivity and formation of disinfec-tion by-products. The effects of pHshould be considered along with disin-fection effectiveness.

The higher the temperature, the fasterthe disinfection rate. The treatmentsystem operator usually cannot controlthe temperature, but then must in-crease the contact time or dose atlower temperatures.

Chlorine (or any disinfectant) is effec-tive only if it comes into contact withthe organisms to be killed. High tur-bidity levels can prevent good contactand protect the organisms. Turbidityshould be reduced where necessarythrough coagulation, sedimentation

and filtration, or other treatmentmethods.

Chlorinatlon Chemicals

Chlorine is available as a liquid(sodium hypochlorite), a solid (calciumhypochlorite), or a gas. Small systemsmost commonly use sodiumhypochlorite or calcium hypochlorite,because they are simpler to use andhave less extensive safety require-ments than gaseous chlorine. Thechoice of a chlorination system—liq-uid, solid, or gas—depends on a num-ber of site-specific factors, including:

• Availability and cost of the chlorinesource chemical

• Capital cost of the chlorination sys-tem

• Operation and maintenance costsof the equipment

• Location of the facility

• Availability of electricity at the treat-ment site

• Operator skills

• Safety considerations

Disinfection with SodiumHypochlorite Solution

Sodium hypochlorite (chlorine in liquidform) is available through chemicaland swimming pool equipment sup-pliers, usually in concentrations of 5 to15 percent chlorine. It is easier tohandle than gaseous chlorine or cal-cium hypochlorite. Sodiumhypochlorite is very corrosive,however, and should be handled andstored with care and kept away fromequipment that can be damaged bycorrosion.

A basic liquid chlorination system orhypochlorinator (Figure 5-1) includestwo metering pumps (one serving as astandby), a solution tank, a diffuser (toinject the solution into water), and

38

Table 5-2. Desired Points of Disinfectant Application3

Disinfectant Point of Application

Chlorine

Ozone

Ultraviolet radiation

Towards the end of the water treatment process so that water is as clarified(organic free) as possible, thereby minimizing THM formation and providingsecondary disinfection.

Prior to the rapid mixing step in all treatment processes. In addition,sufficient time for biodégradation of the oxidation products of the ozonationof organic compounds is recommended prior to secondary disinfection.

Towards the end of the water treatment process to minimize the presence of othercontaminants that interfere with this disinfectant and to minimize operatingproblems.

aln general, disinfectant dosages will be lessened by placing the point of application towards the end of the water treatmentprocess because of the lower levels of contaminants there to interfere with efficient disinfection. However, water plants withshort detention times in dear wells and with nearby first customers might be required to move their point of disinfectionupstream to attain the appropriate CT value (see page 44) under the Surface Water Treatment Rule.

Source: U.S. Environmental Protection Agency, Office of Drinking Water and Center for Environmental Research Information,Technologies for Upgrading Existing or Designing New Drinking Water Treatment Facilities, March 1990. EPA 625/4-89-023.

tubing. Hypochlorinators, used withchlorine in either liquid or solid form,are discussed in more detail underHypochlorination Equipment below.

Sodium hypochlorite solutions losetheir disinfecting power duringstorage, and should be stored in acool, dry, dark area. No more than a1 -month supply should be purchasedat one time, to prevent loss of avail-able chlorine.

Sodium hypochlorite solution is morecostly per pound of available chlorinethan chlorine gas. It also does not con-tain the high concentration of chlorineavailable from chlorine gas. However,the handling and storage costs arelower than for chlorine in its gaseousform.

Disinfection with Solid CalciumHypochlorite

Calcium hypochlorite is a white solidthat can be purchased in granular,powdered, or tablet form. It contains65 percent available chlorine and iseasily dissolved in water. The chemi-cal is available in 1-, 2-, 4-, and 16-kg

(2-, 5-, 8-, and 35-pound) cans and360-kg (800-pound) drums.

When packaged, calcium hypochloriteis very stable, so that a year's supplycan be bought at one time. However, it

is hygroscopic (readily absorbs mois-ture) and reacts slowly with moisturein the air to form chlorine gas. There-fore, shipping containers must beemptied completely or carefullyreseated.

-sw*.

SOURCE OFSUPPLY

Figure 5-1. Simple liquid ch lor ¡nation disinfection system for ground-watersupplies. Source water Is pumped to a service reservoir into which achlorine solution is dosed. (Source: International Reference Centre for Com-munity Water Supply and Sanitation, Technology of Small Water Supply Systemsin Developing Countries, WHO Collaborating Centre, The Hague, The Nether-lands, 1981.)

39

Calcium hypochlorite is dissolved inwater in a mixing tank. The resultingsolution is stored in and fed from astock solution vessel made ofcorrosion-resistant materials, such asplastic, ceramic, glass, or rubber-linedsteel.

The equipment used to mix the solu-tion and inject it into the water is thesame as that for liquid chlorine. Solu-tions of 1 or 2 percent availablechlorine can be delivered by adiaphragm-type, chemical feed/meter-ing pump.

Calcium hypochlorite is a corrosivamaterial with a strong odor, and re-quires proper handling. It must be keptaway from organic materials such aswood, cloth, and petroleum products.Reactions between calcium hypo-chlorite and organic material cangenerate enough heat to cause a fireor explosion.

Hypochlorination Equipment13

Hypochlorinators, used with chlorine ineither liquid or solid form, pump or in-ject a chlorine solution into the water.When they are properly maintained,hypochlorinators provide a reliablemethod for applying chlorine to disin-fect water.

Types of hypochlorinators include posi-tive displacement feeders, aspiratorfeeds, suction feeders, and tablethypochlorinators.

Positiva displacement feeders. Acommon type of positive displacementhypochlorinator uses a piston ordiaphragm pump to inject the solution.This type of equipment, which is adjus-table during operation, can bedesigned to give reliable and accuratefeed rates. When electricity is avail-able, the stopping and starting of thehypochlorinator can be synchronizedwith the pumping unit. A hypo-chlorinator of this kind can be usedwith any water system; however, it is

especially desirable in systems wherewater pressure is low and fluctuating.

Aspirator feeders. The aspiratorfeeder operates on a simple hydraulicprinciple that uses the vacuum createdwhen water flows either through a ven-turi tube or perpendicular to a nozzle.The vacuum created draws thechlorine solution from a container intothe chlorinator unit where it is mixedwith water passing through the unit,and the solution is then injected into thewater system. In most cases, the waterinlet line to the chlorinator is connectedto receive water from the discharge sideof the water pump, with the chlorine solu-tion being injected back into the suctionside of the same pump. The chlorinatoroperates only when the pump is operat-ing. Solution flow rate is regulated bymeans of a control valve, though pres-sure variations may cause changes inthe feed rate.

Suction feeders. One type of suctionfeeder consists of a single line thatruns from the chlorine solution con-tainer through the chlorinator unit andconnects to the suction side of thepump. The chlorine solution is pulledfrom the container through suctioncreated by the operating water pump.

Another type of suction feeder operateson the siphon principle, with the chlorinesolution being introduced directly into awell. This type also consists of a singleline, but the line terminates in the wellbelow the water surface instead of the in-fluent side of the water pump. When thepump is operating, the chlorinator is ac-tivated so that a valve is opened and thechlorine solution is passed into the well.

In each of these units, the solutionflow rate is regulated by means of acontrol valve and the chlorinatorsoperate only when the pump is operat-ing. The pump circuit should be con-nected to a liquid level control so thatthe water supply pump operation is in-

terrupted when the chlorine solution isexhausted.

Tablet hypochlorinators. The tablethypochlorinating unit consists of a spe-cial pot feeder containing calciumhypochlorite tablets. Accurately con-trolled by means of a flow meter, smalljets of feed water are injected into thelower portion of the tablet bed. Theslow dissolution of the tablets providesa continuous source of fresh hypo-chlorite solution. The hypochlorinatingunit controls the chlorine solution. Thistype of chlorinator is often used whenelectricity is not available, but requiresadequate maintenance for efficientoperation. It can operate where thewater pressure is low.

Disinfection with Chlorine Gas

Chlorine is a toxic, yellow-green gas atstandard temperatures and pressures.It is supplied as a liquid in high-strength, high-pressure steel cylin-ders, and immediately vaporizes whenreleased. Small water systems canpurchase the quantities they needfrom chemical or swimming pool sup-pliers.

Gas chlorinators used in small sys-tems are often cylinder-mounted orwall-mounted systems. Figure 5-2shows a gas chlorinator. Daily opera-tion of a gas chlorinator consists ofregulating the feed rate, starting andstopping the chlorinator, and changingthe chlorine cylinders.

Chlorine gas, if accidentally releasedinto the air, irritates the eyes, nasalmembranes, and respiratory tract. It islethal at concentrations as low as 0.1percent air by volume. Therefore,systems using chlorine gas must haveseveral major pieces of safetyequipment:

• Chlorine gas detectors to provideearly warning of leaks

• Self-contained breathing apparatusfor the operator

13 From U.S. Environmental Protection Agency, Office of Drinking Water, Manual of Individual Water Supply Systems, October 1982.EPA-570/9-82/004.

40

• A power ventilation system forrooms in which chlorine is housed

• Emergency repair kits

Chlorination Monitoring

Whenever chlorine is used for disinfec-tion, the chlorine residual should bemonitored at least daily. Samplesshould be taken at various locationsthroughout the water distribution sys-tem, including the farthest points ofthe system. Most small systems use aquick and simple test called the DPDcolorimetric test, available as a kitfrom companies specializing in water-testing equipment and materials(Figure 5-3). Table 5-3 lists some com-panies that supply chlorine residualtest kits. Appendix D describes how totake a sample for chlorine residualanalysis.

Ozonation

Ozone (O3) is widely used as aprimary disinfectant in other parts of

the world, but is relatively new to theUnited States as a drinking water disin-fectant. A toxic gas formed when aircontaining oxygen flows between twoelectrodes, ozone is a powerful disin-

fectant, requiring shorter contact timethan chlorine for disinfection.

Ozone gas is unstable and must begenerated on site. In addition, it has a

Two-stage ozone system. (Courtesy of Carus Chemical Company)

Figure 5-2. Typical deep well gas chlorination system. (Courtesy of Fischer & Porter, Inc.)

41

Table 5-3. Some Suppliers of Chlorine Residual Test Kits

Capital Controls Co. Box 211, Colmar, PA 18195(215) 822-2901 (800) 523-2553

Fischer and Porter Co., County Line Rd., Warminster, PA 18974(215) 674-6000 (800) 421 -3411

Hach Co., Box 389, Loveland, CO 80537(303) 669-3050 (800) 227-4224

Hydro Instruments, Inc., Box 615, Quakertown, PA(215)538-1367

Wallace & Tiernan, 25 Main St., Belleville, NJ 07109(201)759-8000

Figure 5-3. Test kit analyzes free and total chlorine. (Courtesy of HachCompany)

low solubility in water, so efficient con-tact with the water is essential.A secondary disinfectant, usuallychlorine, is required because ozonedoes not maintain an adequateresidual in water.

Pure oxygen or ambient (freely circulat-ing) air can be used in ozone produc-tion. Pure oxygen delivers higherconcentrations of ozone. Packagedozone generator systems using

oxygen to produce the ozone are avail-able for small systems.

Air feed systems used for ozonationare classified by tow, medium, or highoperating pressure. (High pressuresystems typically are used in small-tomedium-sized applications.) Thesesystems vary in their maintenance re-quirements, capital costs, and operat-ing costs. The air feed systems arenecessary to dry the air (lower its dewpoint) to increase the amount of ozone

produced and to prevent fouling andcorrosion of equipment.

Ozone used for water treatment isusually generated using a corona dis-charge cell consisting of twoelectrodes separated by a dischargegap and a dielectric plate (Figure 5-4).The dried air (or pure oxygen) flowsbetween the electrodes and is con-verted to ozone. Several types ofozone generators are commerciallyavailable: horizontal tube, verticaltube, and plate generators. Thesesystems are available with varyingoperating frequencies and voltages.An ozone contactor is used to dissolvethe ozone in water. Ozone can begenerated under positive or negativepressure, depending on the needs ofthe contactor to be used.

As with chlorine, the ozone demand ofthe water must be satisfied before anozone residual is available for disinfec-tion. This can be accomplished byusing two ozone contacting chambers(Figure 5-5). The ozone delivered tothe first chamber satisfies the ozonedemand of the water, and the secondchamber maintains the disinfectingresidual.

Because ozone is toxic, the ozone inexhaust gases from the contactormust be recycled or removed anddestroyed before venting. Figure 5-6depicts a complete treatment systemthat includes ozone disinfection.

The capital costs of ozonation sys-tems are relatively high and operationand maintenance are relatively com-plex. Electricity Is a major part ofoperating costs, representing 26 to 43percent of total operating and main-tenance costs for small plants. Opera-tion and maintenance for ozonationsystems include periodic repair andreplacement of equipment parts, peri-odic generator cleaning, annual main-tenance of the contacting chambers,maintenance of the air preparationsystem, and day-to-day operation ofthe generating equipment (averaging1/2 hour per day).

42

Monitoring the Ozonatlon SystemOperation

Proper monitors should be suppliedwith the ozonation system, including:

• Gas pressure and temperaturemonitors in the air preparationsystem

• Continuous monitors to determinemoisture content of the dried gasfed to the ozone generator

• Generator coolant monitors

• Flow rate, temperature, and pres-sure monitors, and ozone con-centration monitor for the gasdischarged from the ozone gener-ator to determine the ozone produc-tion rate

• Power input monitor for the ozonegenerator

• Ozone residual monitor

The ozone residual should bemeasured at a minimum of two pointsin the contactors). Ozone residualmonitoring can be performed using amanual chemical analyzer (by atrained laboratory technician) or an in-line instrument that continuouslysamples the water.

Ultraviolet Radiation (UV)

Ultraviolet radiation effectively killsbacteria and viruses. As with ozone, asecondary disinfectant must be usedin addition to ultraviolet radiation toprevent regrowth of microorganisms inthe water distribution system. UVradiation can be attractive as aprimary disinfectant for a small systembecause:

• It is readily available.

• It produces no known toxicresiduals.

• Required contact times are short.

• The equipment is easy to operateand maintain.

Ultraviolet radiation, however, doesnot inactivate Giardia cysts, and can-not be used to treat water containing

XJ,ELECTRODE

DIELECTRIC

02-DISCHARGE

GAP

HEAT

Figure 5-4. Typical ozone generating configuration for a corona dischargecell.

. . / .»• « Í ¡î

•'ÍVH"

FLOW METER (TYPICAL)

VALVE (TYPICAL)

Figure 5-5. Two-compartment ozone contactor with porous diffusera.

those organisms. Therefore, it isrecommended only for ground waternot directly influenced by surfacewater, in which there is no risk ofGiardia cyst contamination. (Futureground-water disinfection rules will es-tablish whether and how UV may beused.) UV radiation is unsuitable forwater with high levels of suspendedsolids, turbidity, color, or soluble or-

ganic matter. These materials canreact with or absorb the UV radiation,reducing the disinfection performance.

UV radiation is generated by a speciallamp (Figure 5-7). When ultravioletradiation penetrates the cell wall of anorganism, it destroys the cell's geneticmaterial and the cell dies.

43

The effectiveness of UV radiation disin-fection depends on the energy doseabsorbed by the organism, measuredas the product of the lamp's intensity(the rate at which photons aredelivered to the target) and the time ofexposure. If the energy dosage is nothigh enough, the organism's geneticmaterial might only be damaged in-stead of destroyed. To provide a safetyfactor, the dosage should be higherthan needed to meet disinfection re-quirements. For example, if disinfec-tion criteria require a 99.99 percentreduction of viruses, the UV systemshould be designed to provide a99.999 percent reduction.

Substances in the raw water exert aUV demand similar to chlorinedemand. The UV demand of the wateraffects the exposure time and intensityof the radiation needed for properdisinfection.

The most important operating factorfor ultraviolet radiation disinfection isthe cleanliness of surfaces throughwhich the radiation must travel.Surface fouling can result in inade-quate performance, so a strict main-tenance schedule should be followed.Another important operating factor isthe timely replacement of the UVlamps, because they bse their outputintensity and this loss is not readily ap-parent. A sensor should be used at alltimes to ensure the desired dose.

Obtaining Effective Disinfection:CT Values

To ensure proper disinfection, the disin-fectant must be in contact with the tar-get organisms for a sufficient amountof time. CTvaluBS describe thedegree of disinfection that can be ob-tained as a product of the disinfectantresidual concentration, C, (in mg/L)

and the contact time, T (in minutes).EPA's Guidance Manual for Com-pliance with the Filtration and Disinfec-tion Requirements for Public WaterSystems Using Surface Water Sour-ces provides CT values for achievingvarious levels of inactivation of Giardiaand viruses. Appendix E presents CTvalues for chlorine and ozone atseveral water temperatures and waterpH levels for inactivating Giardia andviruses, and Appendix F provides anexample of a CT calculation for asmall system.

Disinfection By-Products andStrategies for Their Control

Adding a disinfectant to water mightresult in the production of harmful by-products.

Chlorine, for example, can mix withthe natural organic compounds inwater to form trihalomethanes (THMs).

AIR PREPARATION OXIDATION

FLOCCULATION

FILTRATION

ixed Bed Filter

SECONDARY DISINFECTION STORAGE

Hydrozon Qxidator

Process Air Dryer

am

fii—n

mLAir

mm

3=

CompressionUnit

Rocculant

DISTRIBUTION

WELL

Figure 5-6. Schematic of system that provides primary disinfection with ozone, filtration, secondary disinfection,and excess ozone gas destruction. (Courtesy of Carus Chemical Company)

44

COINLET

DUAL ACTIONWIPER SEGMENT

GERMICIDALLAMP IN QUARTZSLEEVE

TRANSFORMER HOUSINGAND JUNCTION BOX

Figure 5-7. Ultraviolet disinfection unit. (Courtesy of Atlantic UltravioletCorporation)

used alone. For these reasons, it is im-portant to know what compounds arein the raw water before choosingozone as a disinfectant. Researchersare continuing to study ozonation by-products and their potential healtheffects.

Ultraviolet radiation might producesome by-products from organic com-pounds, but by-products of UV radia-tion have not yet been identified.

One THM—chloroform—is asuspected carcinogen. Other commontrihalomethanes are similar tochloroform and may cause cancer.

The formation of chlorination by-products depends on several factors,including:

• Temperature and pH of the water

• Chlorine dosage

• Concentration and types of organicmaterials in the water

• Contact time for free chlorine

Several strategies for minimizing harm-ful chlorination by-products can beused by small systems:

• Reducing the concentration of or-ganic materials before addingchlorine. Common water clarifica-tion techniques, such as coagula-tion, sedimentation, and filtration,can effectively remove many or-ganic materials. Activated carbon(described in Chapter 6) might beneeded to remove organicmaterials at higher concentrationsor those not removed by othertechniques.

• Réévalua ting the amount ofchlorine used. The same degreeof disinfection might be possiblewith lower chlorine dosages.

* Changing the point in treatmentwhere chlorine Is added. Ifchlorine is presently added beforetreatment (chemical feed, coagula-tion, sedimentation, and filtration),it can instead be added after filtra-tion, or just before filtration andafter chemical treatment.

• Using alternative disinfectionmethods. A system with a high con-centration of chlorination by-products in the treated water mightconsider alternative disinfectionmethods. However, ozonation andultraviolet radiation, the alternativemethods most practical for smallsystems, cannot be used as disin-fectants by themselves. Both re-quire a secondary disinfectant(usually chlorine) to maintain aresidual in the distribution system.

Ozonation might also result in the for-mation of some harmful by-products.Ozone can produce toxic by-productsfrom a few synthetic organic com-pounds, such as the pesticide hep-tachlor. If ozone is added to watercontaining bromide ions, it can formbrominated organic compounds suchas bromine-containing trihalo-methanes. Also, studies have shownthat the addition of ozone followed bychlorine or chloramines can result inhigher levels of certain by-productsthan when these disinfectants are

45

Chapter Six

Treating OrganicContaminantsin DrinkingWater

Soma small drinking water systemsface contamination of raw water bynatural or synthetic organic substan-ces. Sources of these substancesinclude leaking undergroundgasoline/storage tanks, runoff ofherbicides or pesticides, or improperlydisposed of chemical wastes. Naturalorganic materials might also bepresent in water.

The technologies most suitable for or-ganic contaminant removal in smallsystems are granular activated carbon(GAC) and aeration. Several emerg-ing technologies using aeration mayalso be suitable for small systems.

Table 6-1 presents operational condi-tions for the organics treatment tech-nologies most suitable for smallsystems. Table 6-2 presents removaleffectiveness data for organic con-taminants by granular activated car-bon, packed column aeration, and

diffused aeration. Information aboutorganics removal effectiveness is notyet available for the other technologiesdescribed in this chapter.

Granular Activated Carbon (GAC)

Granular activated carbon (GAC)removes many organic contaminantsfrom water supplies. Congress hasdesignated GAC as the Best AvailableTechnology (BAT) for synthetic organicchemical removal.

Activated carbon is carbon that hasbeen exposed to very high tempera-ture, creating a vast network of inter-nal pores (Figure 6-1). It removescontaminants through adsorption, aprocess in which dissolved con-taminants adhere to the porous sur-face of the carbon particles. Becauseactivated carbon is very porous, it hasa large internal surface area; 1 gramof activated carbon has a surface areaequivalent to a football field. One

Table 6-1. Operational Conditions for Organic Treatments

Technology

Granular activatedcarbon (GAC)

Packed columnaeration (PCA)

Diffused aeration

Multiple trayaeration

Mechanical aeration

Catenary grid

Higee aeration

Level ofOperationalSkillRequired

Medium

Low

Low

Low

Low

Low

Low

Level ofMaintenanceRequired

Low

Low

Low

Low

Low

Low

Medium

EnergyRequirements

Low

Varies

Varies

Low

Low

High

High

Source: U.S. Environmental Protection Agency, Office of Drinking Water andCenter for Environmental Research Information, Technologies for UpgradingExisting or Designing New Drinking Water Treatment Facilities, March 1990.EPA 625/4-89-023.

47

Table 6-2. Treatment Technology Removal Effectiveness Reported for Organic Contaminants (Percent)8

Contaminant

AcrylamideAlachlorAldicarbBenzeneCarbofuranCarbon tetrachlorideChlordaneChlorobenzene2,4-D1,2-Dichloroethane1,2-DichloropropaneDibromochloropropaneDichlorobenzeneo-Dichlorobenzenep-Dichlorobenzene1,1 -Dichloroethylenec/s-1,2-Dichloroethylenefrans-1,2-DichloroethyleneEpichlorohydrinEthylbenzeneEthylene dibromideHeptachlorHeptachlor epoxideHigh molecuiar weight

hydrocarbons (gasoline,dyes, amines, humics)

LindarteMethoxychlorMonochlorobenzen©Natural organic materialPCBsPhenol and chlorophenolsPentachlorophenolStyreneTetrachloroethyleneTrichloroethyleneTricholoroethsne1,1,1-Trichloroe thaneToluene2,4,5-TPToxapheneVinyl chlorideXylenes

Granular ActivatedCarbon (GAC)

NA0-49NA70-10070-10070-10070-10070-10070-10070-10070-10070-10070-10070-10070-10070-10070-10070-100NA70-10070-10070-100NAW

70-10070-100NAP70-100W70-100NA70-10070-10070-10070-10070-10070-10070-10070-10070-100

Packed ColumnAeration (PCA)

1-2970-1000-2970-1000-2970-1000-2970-10070-10070-10070-10030-69NA70-10070-10070-10070-10070-1000-2970-10070-10070-100NANA

0-29NANANA70-100NA0NANA70-100NA70-10070-100NA70-10070-10070-100

DiffusedAeration

NANANANA11-20NANANANA42-7712-79NANA14-72NA9732-8537-96NA24-89NANANANA

NANA14-85NANANANANA73-9553-95NA58-9022-89NANANA18-89

"Additional treatment information is available in EPA Office of Drinking Water Health Advisories for specific contaminants.

W = well removed. P = poorly removed.

Note: Little or no specific performance data were available for:1. Multiple Tray Aeration2. Catenary Aeration

3. Higee Aeration4. Mechanical Aeration

NA = not available.

Source: U.S. Environmental Protection Agency, Office of Drinking Water and Center for Environmental ResearchInformation, Technologies for Upgrading Existing or Designing New Drinking Water Treatment Facilities, March 1990.EPA 625/4-89-023.

48

pound of activated carbon can adsorbover 112 pound of carbon tetrachloride.

GAC has an affinity for high molecularweight compounds. It is not effectivein removing vinyl chloride, a highlyvolatile substance, from water. Table6-3 lists organics that are readily orpoorly adsorbed by activated carbon.

GAC can be used as a replacementfor existing media (such as sand) in aconventional filter or it can be used ina separate contactor (a vertical steelpressure vessel used to hold the ac-tivated carbon bed).

GAC contactors require monitoring toensure that they work effectively. AGAC monitoring system shouldinclude:

* Laboratory analysis of treatedwater to ensure that the system isremoving organic contaminants

* Monitoring of headloss (the amountof energy used by water in movingfrom one point to another) throughthe contactors to ensure that back-flushing (reversing the flow toremove trapped material) is per-formed at appropriate times

• Bacteria monitoring of thecontactor's effluent (since bacteriacan grow rapidly within the ac-tivated carbon bed)

• Turbidity monitoring of thecontactor's effluent (to determine ifsuspended material is passingthrough GAC bed)

After a period of a few months or afew years, depending on the con-centration of contaminants, the sur-face of the pores in the GAC can nolonger adsorb contaminants. Thecarbon must then be replaced.

Several operational and maintenancefactors affect the performance of GACContaminants in the water can occupyGAC adsorption sites, whether theyare targeted for removal or not. Also,adsorbed contaminants can bereplaced by other contaminants with

Figure 6-1. Representation ofinternal carbon structure. (Reprintedfrom Introductbn to Water Treatment,Vol. 2, by permission. Copyright 1984,American Water Works Association.)

which GAC has a greater affinity.Therefore, the presence of other con-taminants might interfere with theremoval of the contaminants ofconcern.

A significant drop in the contaminantlevel in influent water will cause aGAC filter to desorb, or slough off, ad-sorbed contaminants, because GAC isan equilibrium process. As a result,raw water with frequently changingcontaminant levels can result intreated water of unpredictable quality.

Bacterial growth on the carbon isanother potential problem. Excessivebacterial growth may cause cloggingand higher bacterial counts in thetreated water. This means that bac-terial levels in the treated water mustbe closely monitored and the final dis-infection process must be carefullycontrolled.

GAC is available in different grades ofeffectiveness. Low-cost carbon re-quires a lower initial capital outlay, butmust be replaced more often, resultingin higher operating costs.

Aeration

Aeration, also known as air stripping,mixes air with water to volatilize

Table 6-3. Readily and Poorly Adsorbed Organics

Readily Adsorbed Organics

* Aromatic solvents (benzene, toluene, nitrobenzenes)

* Chlorinated aromatios (PCBs, chlorobenzenes, chloronaphthalene)

* Phenol and chlorophenols

* Polynuclear aromatics (acenapthene, benzopyrenes)

* Pesticides and herbicides (DDT, aldrin, chlordane, heptachlor)

* Chlorinated aliphatics (carbon tetrachloride, chloroalkyl ethers)

* High molecular weight hydrocarbons (dyes, gasoline, amines, humics)

Poorly Adsorbed Organics

* Alcohols

• Low molecular weight ketones, acids, and aldehydes

* Sugars and starches

• Very high molecular weight or colloidal organics

* Low molecular weight aliphatics


49

To Almosphín?

Figure 6-2. Packed tower aeration system.

AERATION BASIN-

MIXING PATTERNS-

COMPRESSED AIR PIPING

-DOWNCOMER PIPE

-DIFFUSERS

-MANIFOLD

Figure 6-3. Diffuser aeration system. (Reprinted from Introduction to WaterTreatment, Vol. 2, by permission. Copyright 1984, American Water WorksAssociation.)

Aeration, also known as air stripping,mixes air with water to volatilizecontaminants (turn them to vapor).The volatilized contaminants are eitherreleased directly to the atmosphere orare treated and then released. Aera-tion is used to remove volatile organicchemicals and can also remove radon(see Chapter 7).

A small system might be able to use asimple aerator constructed from rela-tively common materials instead of a

specially designed aerator system.Examples of simple aerators include:

• A system that cascades thewater or passes it through aslotted container

• A system that runs water over acorrugated surface

• An airlift pump that introducesoxygen as water is drawn froma well

Other aeration systems that might besuitable for small systems include

packed column aeration, diffusedaeration, and multiple tray aeration.Emerging technologies that use aera-tion for organics removal includemechanical aeration, catenary grid,and Higee aeration.

Packed Column Aeration

Packed column aeration (PCA) orpacked tower aeration (PTA) is awaterfall aeration process which dropswater over a medium within a tower tomix the water with air. The medium isdesigned to break the water into tinydroplets, and maximize its contact withtiny air bubbles for removal of the con-taminant. Air is also blown in from un-derneath the medium to enhance thisprocess. Figure 6-2 shows a PCAsystem.

Systems using PCA may needpretreatment to remove iron, solids,and biological growth to prevent clog-ging of the packing material. Posttreat-ment (such as the use of a corrosioninhibitor) may also be needed toreduce corrosive properties in waterdue to increased dissolved oxygenfrom the aeration process.

Packed columns usually operate auto-matically, and need only daily visits toensure that the equipment is runningsatisfactorily. Maintenance require-ments include servicing pump andblower motors and replacing air filterson the blower, if necessary.

PCA exhaust gas may require treat-ment to meet air emissions regula-tions, which can significantlyincrease the costs of this technology.

Diffused Aeration

In a diffused aeration system, a dif-fuser bubbles air through a contactchamber for aeration (Figure 6-3).The main advantage of diffused aera-tion systems is that they can becreated from existing structures, suchas storage tanks. However, they areless effective than packed columnaeration, and usually are used only insystems with adaptable existingstructures.

50

Multiple Tray Aeration

Multiple tray aeration directs waterthrough a series of trays made ofslats, perforations, or wire mesh(Figure 6-4). A blower introduces airfrom underneath the trays.

Multiple tray aeration units have lesssurface area than do PCA units. Thistype of aeration is not as effective asPCA, and can experience cloggingfrom iron and manganese, biologicalgrowth, and corrosion problems.Multiple tray aeration units are readilyavailable from package plant manufac-turers.

Emerging Technologies forOrganics Removal

Mechanical Aeration

Mechanical aeration uses mechanicalstirring mechanisms to mix air with thewater (Figure 6-5). These systemscan effectively remove volatile organicchemicals (VOCs).

Mechanical aeration units need largeamounts of space because theydemand long detention times for effec-tive treatment. As a result, they oftenrequire open-air designs, which canfreeze in cold climates. These unitsalso can have high energy require-ments. However, mechanical aerationsystems are easy to operate, and areless susceptible to clogging frombiological growth than PCA systems.

Catenary Grid

Catenary grid systems are a variationof the packed column aerationprocess. The catenary grid directswater through a series of wire screensmounted within the column. Thescreens mix the air and water in thesame way as packing materials inPCA systems. Figure 6-6 shows acatenary grid unit.

These systems can effectively removevolatile organic chemicals. There is lit-tle information available about the ef-fectiveness of catenary grid systemsfor other organic compounds, but theyprobably would not remove these com-

pounds effectively. They have higherenergy requirements than PCA sys-tems, but their more compact designlowers their capital cost relative toPCA.

Hlgee Aeration

Higee aeration is another variation ofthe PCA process. These systemspump water into the center of a spin-ning disc of packing material, wherethe water mixes with air (Figure 6-7).

Higee units require less packingmaterial than PCA units to achieve thesame removal efficiencies. Becauseof their compact size, they can beused in limited spaces and heights.Current Higee systems are best suitedfor temporary applications of less than1 year with capacities up to 380 liters(100 gallons) per minute.

INLET

CHAMREBfilH

- OUTLET

... BATTLES

Am STACKS

Figure 6-4. Schematic of awood slat tray aerator

red-

Snr;«c« fctntor

t—|ComprM3ûr

TurblntSp«r8tr

'S' *"" -

( " '

r V ; . . ' . « l . , y . J . '

Figure 6-5. Schematic of mechanical aeration process.

51

- Raw Watf

1>*aied Water /to Dram —'

Figure 6-6. Catenary grid system.

EXHAUST AIR

BLOWER

GROUND WATER HIGEE

FILTERPRODUCT

WATER

PUMP

Figure 6-7. Schematic of Higee system.

52

Chapter Seven

Control andRemoval ofInorganicContaminants

Water systems control or remove inor-ganic contaminants using two differentstrategies:

1. Preventing Inorganic contamina-tion of finished water. Corrosioncontrols prevent or minimize thepresence of corrosion products(such as lead and copper) at theconsumer's tap.

2. Removing Inorganiccontaminants from raw water.Removal technologies treat sourcewater that is contaminated with me-tals or radioactive substances(radionuclides).

Inorganic contaminants presentlyregulated under the Safe DrinkingWater Act (SDWA) include lead,radium, nitrate, arsenic, selenium,barium, fluoride, cadmium, chromium,mercury, and silver.

This chapter describes several tech-nologies for inorganic contaminantremoval (reverse osmosis, ion ex-change, activated alumina, aeration,and granular activated carbon). Con-ventional treatment (coagulation/filtration) can also remove inorganiccontaminants and is discussed in thischapter.

Corrosion

Corrosion is the deterioration of a sub-stance by chemical action. Lead, cad-mium, zinc, copper, and iron might befound in water when metals in waterdistribution systems corrode. Drinkingwater contaminated with certain me-tals (such as lead and cadmium) canharm human health.

Corrosion also reduces the useful lifeof water distribution systems, and canpromote microorganism growth, result-ing in disagreeable tastes, odors,slimes, and further corrosion. Often acustomer complaint is the first indica-tion of a corrosion problem, and at thisstage corrosion may be extensive.

Table 7-1 shows typical customer com-plaints and their causes.

Controlling Lead Laveis InDrinking Water

Because it is widespread and highlytoxic, lead is the corrosion product ofgreatest concern. Table 7-2 shows therisk factors that can indicate potential-ly high lead levels at the tap. Leadlevels in drinking water are managedindirectly through corrosion controls.Lead is not typically found in sourcewater, but rather at the consumer's tapas a result of the corrosion of theplumbing or distribution system. The1986 amendments to the Safe Drink-ing Water Act ban the use of leadsolders, fluxes, and pipes in the instal-lation or repair of any public water sys-tem or in any plumbing systemproviding water for human consump-tion. In the past, solder used in plumb-ing has been 50 percent tin and 50percent lead. Using lead-free solders,such as silver-tin and antimony-tinsolders is a key factor in lead cor-rosion control. Replacement of leadpipes can also be an effective strategyfor reducing lead in drinking water.

The current Maximum ContaminantLevel (MCL) for lead applies to waterdelivered by the supplier. New leadregulations might include an MCL forwater at the consumer's tap.

If tests for corrosion by-products findunacceptably high levels of lead, im-mediate steps should be taken to mini-mize consumers' exposure until along-term corrosion control plan is im-plemented. Some short-termmeasures the consumer can takeinclude:

• Running the water for about 1minute before each use

• Using home treatment processes inextreme cases

• Using bottled water

53

Table 7-1. Typical Customer Water Quality Complaints That Might Be Due to Corrosion

Customer Complaint

Red water or reddish-brown stainingof fixtures and laundry

Bluish stains on fixtures

Black water

Foul taste and/or odors

Loss of pressure

Lack of hot water

Short service life of householdplumbing

Possible Causa

Corrosion of iron pipes or presence of natural iron in raw water

Corrosion of copper lines

Sulfide corrosion of copper or iron lines or precipitations of naturalmanganese

By-products from microbial activity

Excessive scaling, tubercle buildup from pitting corrosion, leak in systemfrom pitting or other type of corrosion

Buildup of mineral deposits in hot water system (can be reduced by settingthermostats to under 60"C [140'F])

Rapid deterioration of pipes frompitting or other types of corrosion

Source: U.S. Environmental Protection Agency, Office of Drinking Water, Corrosion Manual for Internal Corrosion of Water Dis-tribution Systems, April 1984. EPA 570/9-84-001.

Table 7-2. Risk Factors Indicating Potentially High Lead Levels at the Tap

" Components of the water distribution system or structure's plumbing are made of lead, or lead-containingmaterial such as brass, and/or the structure's plumbing has solder containing lead.

And one or more of the following apply:

* The structure is less than 5 years old.

' The tap water is soft and/or acidic.

* The water stays in the plumbing for 6 or more hours.

* The structure's electrical system is grounded to the plumbing system.

Source: Adapted from U.S. Environmental Protection Agency, Office of Drinking Water and Center for Environmental ResearchInformation, Technologies for Upgrading Existing or Designing New Drinking Water Treatment Facilities, March 1990. EPA625/4-89-023.

Techniques for ControllingCorrosion

Solutions to corrosion problems in-

clude modifying the water quality

(especially pH and alkalinity), and add-

ing corrosion inhibitors to form protec-

tive coatings over metal. It should also

be noted that corrosion in a

homeowner's plumbing can be related

to conditions in the home (such as

pipes that are too small or the use of

dissimilar metals in joining pipes and

valves) rather than to the quality of

water from the distribution system.

Modifying water quality. Table 7-3shows some of the characteristics ofwater that affect its corrosivity. Allwater is corrosive to some degree, butwater that is acidic (less than 7.0 pH)is likely to corrode metal more quickly.

54

Table 7-3. Chemical Factors Influencing Corrosion and Corrosion Control |

Factor

PH

Alkalinity

Dissolved oxygen (DO)

Chlorine residual

Total dissolved solids(TDS)

Hardness (Ca and Mg)

Chloride, sulfate

Hydrogen sulfide

Silicate, phosphates

Natural color, organic matter

Iron, zinc, or manganese

Effect

Low pH may increase corrosion rate; high pH may protect pipesand decrease corrosion rates

May help form protective calcium carbonate (CaCO3) coating,helps control pH changes, reduces corrosion

Increases rate of many corrosion reactions

Increases metallic corrosion

High TDS increases conductivity and corrosion rate

Ca may precipitate as CaCOs and thus provide protectionand reduce corrosion rates

High levels increase corrosion of iron, copper, and galvanized steel

Increases corrosion rates

May form protective films

May decrease corrosion

May react with compounds on interior of asbestos-cement pipeto form protective coating

Source: U.S. Environmental Protection Agency, Office of Drinking Water, Corrosion Manual for Internal Corrosion of Water Dis-tribution Systems, April 1984. EPA 570/9-84-001.

Adjusting pH and alkalinity is the mostcommon corrosion control method, be-cause it is simple and inexpensive.(pH ¡s a measure of the concentrationof hydrogen ions present in water;alkalinity is a measure of water'sability to neutralize acids.) Generally,an increase in pH and alkalinity candecrease corrosion rates and helpform a protective layer of scale on cor-rodible pipe material. Chemicals com-monly used for pH and alkalinityadjustment are lime, caustic soda,soda ash, and sodium bicarbonate. Ad-justing pH to control corrosion,however, might conflict with ideal pHconditions for disinfection and controlof disinfection by-products. Drinkingwater suppliers should carefullychoose the treatment methods so that

both disinfection and corrosion controlare effective.

Avoiding high dissolved oxygen levelsdecreases water's corrosive activity.Removing oxygen from water is notpractical because of cost. However,treatment systems might be able tominimize the dissolved oxygen levelsby minimizing air/water contact.

Corrosion inhibitors. Corrosion in-hibitors reduce corrosion by formingprotective coatings on pipes. The mostcommon corrosion inhibitors are inor-ganic phosphates, sodium silicates,and mixtures of phosphates and sili-cates. These chemicals have provensuccessful in reducing corrosion inmany systems.

Treatment Technologies forRemoving Inorganic Contaminants

Inorganic contamination of raw watersupplies can come from a wide varietyof sources. Naturally occurring inor-ganics, such as fluoride, arsenic,selenium, and radium, are commonlyfound in ground-water sources. Syn-thetic contaminants are usually foundin surface water supplies. Nitrates andnitrites are a problem in agriculturalareas and areas without sanitarysewer systems, and have been foundat relatively high levels in both surfacewater and ground water.

No single treatment is perfectly suitedfor all inorganic contaminants. Table7-4 shows the removal effectivenessof six inorganic treatment processes

55

Table 7-4. Most Probable Applications of Water Treatment Processes for Inorganic Contaminant Removal

TreatmentProcess

Conventionalcoagulation

Cation exchange

Anion exchange

Activated alumina

Granular activatedcarbon

Reverse osmosis andelectrodialysis

Principal Application forWater Treatment

Clarification of surface waters

Removal of hardnessfrom ground water

Removal of nitrate fromground water

Removal of fluoride fromground water

Removal of taste, odors,and organics

Desalting of sea wateror brackish ground water

aHigh—greater than 80 percent; moderate—20 to 80 percent

Ag = SilverAs = ArsenicBa = BariumCd = CadmiumCr = ChromiumF = Fluoride

Source; Adapted from Thomas J. Sorg and Gary S. Logsdon

Inorganic ContaminantTreatment CapabilityEffectlvenessa

High

CdCrl l lCrVIAsVAgPb

BaRaCdPbCrll l

NO3CrVISe

FAsSe

Hg(i)Hg(O)

AsVBaCrPbCdSeAgFRaHg

Moderate

AsmSe IVHg (O)Hg O)

Cd

NO3

As III

Low

BaFN03RaSe VI

AsSeNO3FCrVI

BaRaCdPbCrll l

BaRaCd

AgBaRaCrll lFNO3

low—less than 20 percent.

Hg =NO3 =Pb =Ra =Se =

MercuryNitrateLoadRadiumSelenium

Treatment Technology to Meet the

Most Probable Applicationfor Inorganic Removal

Removal of Cd, Cr, As, Ag, orPb from surface waters

Removal of Ba or Ra fromground water

Removal of NOa fromground water

Removal of F, As, or Se fromground water

Removal of Hg from surface orground water

Removal of all inorganicsfrom ground water

Interim PrimaryDrinking Water Regulations for Inorganics: Part 5," Journal of the American Wator Works Association, July 1980.

56

and their most probable application forinorganic removal. Processes suitablefor small systems include:

• Coagulation/filtration

• Membranes (reverse osmosis andelect rodialysls)

• Ion exchange

• Activated alumina

Table 7-5 presents advantages anddisadvantages of these processes.Coagulation/filtration is generally toooperationally complex for very smallsystems (serving 500 people orfewer). Reverse osmosis, ion ex-change, and activated alumina aresimpler operations and may be betteralternatives for these systems, unlessthe contaminant of concern cannot beremoved by these processes, or un-less the costs or maintenance require-ments are prohibitive. Each of theseprocesses is described below. Aera-tion and granular activated carbon,commonly used to remove radon fromwater supplies, are also discussedbelow.


Coagulation (described in Chapter 4)is traditionally used to control turbidity,hardness, taste, and odors, but is alsoeffective in removing some inorganiccontaminants.

Coagulation using aluminum or ironsalts is effective in removing mostmetal ions or colloidally dispersedcompounds (finely divided substancesthat do not settle out of water for avery long period of time). It is ineffec-tive in removing nitrate, nitrite, radium,and barium. Table 7-6 presents poten-tial removal efficiencies usingaluminum and iron salts as coag-ulants. Coagulation to remove inor-ganics is more expensive thancoagulation to remove turbidity be-cause higher dosages of coagulantare needed.

Table 7-5. Advantages and Disadvantages of InorganicContaminant Removal Processes


Advantages

• Low cost for high volume• Reliable process well suited to automatic control

Disadvantages

• Not readily applied to small or intermittent flows• High-water-content sludge disposal• Very low contaminant levels may require two-stage precipitation• Requires highly trained operators

Membranes (Reverse Osmosis and Electrod la lysis)

Advantages

• Removes nearly all contaminant ions and most dissolved non-ions• Relatively insensitive to flow and total dissolved solids level• Low effluent concentration possible• In reverse osmosis, bacteria and particles are also removed• Automation allows for less operator attention

Disadvantages

' High capital and operating costs' High level of pretreatment required in some cases' Membranes are prone to fouling (RO). Electrodes require replace-

ment (ED).

Ion Exchange

Advantages

' Relatively insensitive to flow variations• Essentially zero level of effluent contamination possible• Large variety of specific resins available

Disadvantages

• Potential for unacceptable levels (peaks) of contamination in effluent' Waste requires careful disposal• Usually not feasible at high levels of total dissolved solids• Pretreatment required for most surface waters

Activated Alumina

Advantages

• Insensitive to flow and total dissolved solids background• Low effluent contaminant level possible• Highly selective for fluoride and arsenic

Disadvantages

• Strong acid and base are required for regeneration• Medium tends to dissolve, producing fine particles' Adsorption is slow• Waste requires careful disposal


57

Table 7-6. Removal Efficiency Potential of Alum Versus FerricChloride

InorganicContaminant

Ag (pH < 8.0)

Ag (pH = 8.0)

AsV

As V (pH < 7.5)

As V (pH = 7.5)

Cd (pH > B.0)

Cd (pH > 8.5)

Cr (III)

Cr III (pH = 10.5)

CrVI (using Fell)

Hg

Pb

Ag = SilverAs = ArsenicCd = CadmiumCr = ChromiumHg = MercuryPb = Lead

Removal

AlumCoagulant

90%

-

-

90%

-

-

70%

90%

-

-

70%

90%

Efficiency

IronCoagulant

-

70%

90%

-

90%

-

-

-

90%

90%

-

-

Source: U.S. Environmental Protection Agency, Office of Drinking Waterand Center for Environmental Research Information, Technologies forUpgrading Existing or Designing New Drinking Water Treatment Facilities,March 1990. EPA 625/4-89-023.

Reverse Osmosis andElectrodla lysis

Reverse osmosis removes con-taminants from water using a semiper-meable membrane that permits onlywater, and not dissolved ions (such assodium and chloride), to pass throughits pores (Figure 7-1). Contaminatedwater is subjected to a high pressurethat forces pure water through themembrane, leaving contaminants be-hind in a brine solution. Membranesare available with a variety of poresizes and characteristics.

Reverse osmosis can effectivelyremove nearly all inorganic con-taminants from water. It removes over70 percent of arsenic(lll), arsenic(IV),barium, cadmium, chromium(lll),chromium(Vl), fluoride, lead, mercury,nitrite, selenium(IV), selenium(VI), andsilver. Properly operated units will at-tain 96 percent removal rates.Reverse osmosis can also effectivelyremove radium, natural organic sub-stances, pesticides, and microbiologi-cal contaminants.

Reverse osmosis systems are com-pact, simple to operate, and have mini-mal labor requirements, making themsuitable for small systems. They arealso suitable for systems with a highdegree of seasonal fluctuation in waterdemand.

One disadvantage of reverse osmosisis its high capital and operating costs.For systems of less than 3.8 millionliters per day (1 million gallons per day[MGD]), operating costs range from $3to $6 per 3,800 liters (thousand gal-lons) of treated water. Capital costsrange from $1 to $2 per 3.8 liters (gal-lon) of capacity, depending on thelevel of pretreatment required. Manag-ing the wastewater (brine solution) isalso a potential problem for systemsusing reverse o?r.,osis.

Electrodialysis is a process that alsouses membranes. In this process,however, direct electrical current isused to attract ions to one side of thetreatment chamber. Electrodialysis sys-tems include a source of pressurizedwater, a direct current power supply,and a pair of selective membranes.Multistage units, in which membranepairs are "stacked" in the treatmentvessel, can increase the removal ef-ficiency. Electrodialysis is very effec-tive in removing fluoride and nitrate,and can also remove barium, cad-mium, and selenium.

ton Exchange

Ion exchange units (Figure 7-2) can beused to remove any ionic (charged)substance from water, but are usuallyused to remove hardness and nitratefrom ground water. Inorganic substan-ces are removed by adsorption ontoan exchange medium, usually a syn-thetic resin. One ion is exchanged foranother on the surface of the medium,which is regenerated with the ex-changeable ion before treatmentoperations. Ion exchange waste ishighly concentrated and requirescareful disposal.

The ¡on exchange process, likereverse osmosis, can be used withfluctuating flow rates. Pretreatment

58

with filtration might be needed if the in-fluent has a high level of suspendedsolids. Ion exchange units are alsosensitive to the presence of competingions. For example, influent with highlevels of hardness will compete withother cations (positive ions) for spaceon the exchange medium, and the ex-change medium must be regeneratedmore frequently.

Ion exchangers often use sodiumchloride to regenerate the exchangemedium because of the chemical's lowcost. However, this might result in ahigh sodium residual in the finishedwater. High sodium residual might beunacceptable for individuals with salt-restricted diets. This problem can beavoided by using other régénérantmaterials, such as potassium chloride.

Ion exchange effectively removesmore than 90 percent of barium, cad-mium, chromium (III), silver, radium,nitrites, selenium, arsenic (V),chromium (VI), and nitrate. Ion ex-change is usually the best choicefor small systems to removeradionuclides.

Activated Alumina

Activated alumina systems are il-lustrated in Figure 7-3. Activatedalumina is a commercially available¡on exchange medium, primarily usedto remove fluoride from ground water.The activated alumina medium isregenerated using a strong sodiumhydroxide solution. Because this in-creases the pH level of the water, sul-furie acid must be added to the waterafter it leaves the exchange unit.

Activated alumina removes over 90percent of arsenic (V), fluoride, andselenium (IV), and 70 percent ofselenium (VI). It also effectivelyremoves iron. K is not effective inremoving barium, cadmium, andradium.

While activated alumina effectivelyremoves several contaminants, it canbe hazardous because of the stronglyacidic and basic solutions used.Another disadvantage of activated

Cflurtfliy of Vlilliparo Çarcoraiian

FflOCÊSS FLOW THPOIJGH 5PIHAL-W0UND REVERSÉ 0$MCSt$ U

1 1o • • ,-,

L—.— ~-~

r "°"FlWr

1 - 0

^^——,j

HOLLOW -FIBER RFVERSE OSMOSIS UNIT

r^ F*

Figure 7-1. Two types of reverse osmosis membranes.

Figure 7-2. Ion exchange treatment system.

59

TREATMENT ANDDOWNFLOW RINSE

BACKWASH -*NDUPrLOW RINSE

UPFLOWREGENERATION

DOWNFLOWREGENERATION

Figure 7-3. Activated alumina systems: Operating mode flow schematics.

alumina is the long contact time re-quired (5 minutes, compared to 2 to 3minutes for ¡on exchange). Finally, ac-tivated alumina's costs are higher thanthose for ion exchange. Wastemanagement might also increasecosts because of high concentrationsof aluminum and other contaminantsin the waste stream, as well as highpH.

Technologies for Radon Removal:Aeration and Granular ActivatedCarbon

Several low-cost/low-technology aera-tion techniques can effectively lowerthe concentration of radon in drinking

water. (Radon is a naturally occurringradioactive gas that contaminatesground water in some geographicalareas.) These techniques includeopen air storage with no mixing, a flow-through reservoir system with influentcontrol devices, and a flow-throughreservoir with bubble aeration. Initialstudies found that minimal aerationapplied during 30 hours of storage canachieve more than 95 percent radonremoval.14

Another relatively low-cost aerationtechnique is a multistaged diffusedbubble aeration system manufacturedby Lowry Engineering, Inc. of Unity,

Maine. This process is applied in abox-shaped, low profile vessel madeof high density polyethylene. It isdesigned to remove volatile organicchemicals as well as radon. Packedtower aeration also is commonly usedto remove radon. The size of the pack-ed tower required for radon removalgenerally is much less than for or-ganics removal.

Granular activated carbon (GAC) canalso effectively remove radon fromwater. There are, however, concernsabout worker safety and disposal ofcarbon that is contaminated withradon.15

Aeration and GAC are discussed ingreater detail in Chapter 6, TreatingOrganic Contaminants in DrinkingWater.

14 N.E. Kinner, CE. Lessard, G.S. Schell, and K.R. Fox. "Low-Cost/Low-Technology Aeration Techniques for Removing Radon from Drink-ing Water," Environmental Research Brief, U.S. Environmental Protection Agency, Office of Research and Development, September 1987.EPA/600/M-87/031.

15 N.E. Kinner, CE. Lessard, and G.S. Schell, Radon Removal from Small Community Water Supplies Using Granular Activated Carbonand Low Technology/Low Cost Techniques, U.S. Environmental Protection Agency Cooperative Research Agreement CR-81-2602-01-0.

60

Chapter Eight

Resources Safe Drinking Water Hotline

1-800-426-47911-202-382-5533

This hotline, run by the U.S. Environ-mental Protection Agency, providesinformation on drinking water regula-tions, policies, and documents to thepublic, state and local government,public water systems, and, consultants.The Safe Drinking Water Hotline'shours are 8:30 am. to 4:30 p.m. East-ern Standard Time, Monday throughFriday excluding holidays.

U.S. Environmental ProtectionAgency Regional Offices

Regional offices of the U.S. Environ-mental Protection Agency are listed inTable 8-1.

State Drinking Water Agencies

State agencies responstole for publicwater supervision are listed in Table 8-2.

Organizations Assisting SmallSystems

American Water Work» Association(AWWA) Small Systams Program

This program provides information,training, and technical assistance tosmall systems, in coordination withstate regulatory agencies and otherorganizations assisting small systems.Contact the AWWA at 6666 W. QuincyAvenue, Denver, CO 80235 (303-794-7711 ) for the name of a contact for thesmall systems program in your area.

National Rural Watar Association(NRWA)

This organization provides trainingand technical assistance to small sys-tems. Contact the NRWA office at P.O.Box 1428, Duncan, OK 73534 (405-252-0629) for national information andthe name of your local contact.

Rural Community AaslatancaProgram (RCAP)

This program consists of six regionalagencies formed to develop the

capacity of rural community officials tosolve local water problems. It providesonsite technical assistance, training,and publications, and works to im-prove federal and state governmentresponsiveness to the needs of ruralcommunities. Table 8-3 lists the sixRCAP regional agencies.

Farmers Home Administration(FmHA)

The Farmers Home Administrationprovides grants and loans for ruralwater systems and communities withpopulations less than 25,000. ContactFmHA at USDA/FmHA, 14th and Inde-pendence Avenue SW, Washington,DC 20250 (202-447-4323).

Publications

General

American Water Works Association.Basic Management Principles forSmall Water Systems. Denver, Co,1982.

American Water Works Association.Design and Construction of SmallWater Systems—A Guide forManagers. 1984.

American Water Works Association.Introduction to Water Treatment Den-ver, CO, 1984.

Concern, Inc. Drinking Water: A Com-munity Action Guide. Washington, DC(1794 Columbia Road, NW, Washing-ton, DC 20009), December 1986.

National Rural Water Association.Water System Decision Makers: AnIntroduction to Water System Opera-tion and Maintenance. Duncan, OK,1988.

Opflow. A monthly publication of theAmerican Water Works Associationfocusing on the "nuts and bolts" con-cerns of treatment plant operators.

61

Table 8-1. EPA Regional Offices

EPA Headquarters

401 M Street, SWWashington, DC 20460202-382-5043

EPA Region 1

JFK Federal BuildingBoston, MA 02203617-565-3424

Connecticut, Massachusetts,Maine, New Hampshire,Rhode Island, Vermont

EPA Region 2

26 Federal PlazaNew York, NY 10278212-264-2515

New Jersey, New York,Puerto Rico, Virgin Islands

EPA Region 3

841 Chestnut StreetPhiladelphia, PA 19107215-597-9370

Delaware, Maryland, Pennsylvania,Virginia, West Virginia,District of Columbia

EPA Region 4

345 Courtland Street, NEAtlanta, GA 30365404-347-3004

Alabama, Florida, Georgia,

Kentucky, Mississippi,North Carolina, South Carolina,Tennessee

EPA Region 5

230 South Dearborn StreetChicago, IL 60604312-353-2000

Illinois, Indiana, Ohio, MichiganMinnesota, Wisconsin

EPA Region 6

1445 Ross AvenueDallas, TX 75202214-655-2200

Arkansas, Louisiana, New Mexico,Oklahoma, Texas

EPA Region 7

726 Minnesota AvenueKansas City, KS 66101913-236-2803

Iowa, Kansas, Missouri, Nebraska

EPA Region 8

One Denver Place999 18th Street, Suite 1300Denver, CO 80202303-293-1692

Colorado, Montana, North Dakota,South Dakota, Utah, Wyoming

EPA Region 9

215 Fremont StreetSan Francisco, CA 94105415-974-8083

Arizona, California, Hawaii, Nevada,American Samoa, Guam,Trust Territories of the Pacific

EPA Region 10

1200 Sixth AvenueSeattle, WA 98101206-442-1465

Alaska, Idaho, Oregon, Washington

62

Table 8-2. State Drinking Water Agencies

Region 1

Connecticut Department of Health ServicesWater Supplies Section150 Washington StreetHartford, CT 06106203-566-1251

Division of Water SupplyDepartment of Environmental ProtectionOne Winter Street, 9th FloorBoston, MA 02108617-292-5529

Drinking Water ProgramDivision of Health EngineeringMaine Department of Human ServicesState House (STA10)Augusta, ME 04333207-289-3826

Water Supply Engineering BureauDepartment of Environmental ServicesP.O. Box 95, Haren DriveConcord, NH 03302-0095603-271-3503

Division of Drinking Water QualityRhode Island Department of Health75 Davis Street, Cannon BuildingProvidence, Rl 02908401-277-6867

Water Supply ProgramVermont Department of Health60 Main StreetP.O. Box 70Burlington, VT 05402802-863-7220

Region II

Bureau of Safe Drinking WaterDivision of Water ResourcesNew Jersey Department ofEnvironmental ProtectionP.O. Box CN-029Trenton, NJ 06825609-984-7945

(continued on

I

Bureau of Public Water Supply ProtectionNew York State Department of Health2 University PlaceWestern Avenue, Room 406Albany, NY 12203-3313518-458-6731

Water Supply Supervision ProgramPuerto Rico Department of Health

P.O. Box 70184San Juan, PR 00936809-766-1616

Planning and Natural ResourcesGovernment of Virgin IslandsNifky Center, Suite 231St. Thomas, Virgin Islands 00802

Region III

Office of Sanitary EngineeringDelaware Division of Public HealthCooper BuildingP. O. Box 637Dover, DE 19903302-736-4731

Water Supply ProgramMaryland Department of the EnvironmentPoint Breeze Building 40, Room 8L2500 Broening HighwayDundalk, MD 27224301-631-3702

Water Hygiene BranchDepartment of Consumer and Regulatory Affairs5010 Overlook Avenue, SWWashington, DC 20032202-767-7370

Division of Water SuppliesPennsylvania Department of Environmental

ResourcesD O R<-iv O1K7".\J. DOX £O0 i

Harrisburg, PA 17105-2357717-787-9035

next page)

63

I Table 8-2. State Drinking Water Agencies (continued) 1

Evironmental Engineering DivisionOffice of Environmental Health ServicesState Department of HealthCapital Complex Building 3, Room 5501900 Kanawha Blvd., EastCharleston, WV 25305304-348-2981

Division of Water Supply EngineeringVirginia Department of HealthJames Madison Building109 Governor StreetRichmond, VA 23219804-786-1766

Region IV

Water Supply BranchDepartment of Environmental Management1751 Congressional W.L Dickinson DriveMontgomery, AL 36130205-271 -7773

Drinking Water SectionDepartment of Environmental RegulationTwin Towers Office Building2600 Blair Stone RoadTallahassee, FL 32399-2400904-487-1779

Drinking Water ProgramGeorgia Environmental Protection DivisionFloyd Towers East, Room 1066205 Butler Street, S.E.Atlanta, GA 30334404-656-5660

Drinking Water BranchDivision of WaterDepartment of Environmental Protection18 Reilly Road, Frankfort Office ParkFrankfort, KY 40601502-564-3410

Division of Water SupplyStats Board of HealthP.O. Box 1700Jackson, MS 39215-1700601-354-6616/490-4211

Public Water Supply SectionDivision of Environmental HealthDepartment of Environment, Health andNatural ResourcesP.O. Box 27687Raleigh, NC 27611-7687919-733-2321

Bureau of Drinking Water ProtectDepartment of Health andEnvironmental Control2600 Bull StreetColumbia, SC 29201803-734-5310

Division of Water SupplyTennessee Department of Health

and Environment150 Ninth Avenue, NorthTerra Building, 1st FloorNashville, TN 37219-5404615-741-6636

Region VDivision of Public Water SuppliesIllinois Environmental Protection Agency2200 Churchill RoadP.O. Box 19276Springfield, IL 62794-9276217-785-8653

Public Water Supply SectionOffice of Water ManagementIndiana Department of Environmental Manage-ment105 South MeridianP.O. Box 6015Indianapolis, IN 46206317-633-0174

Division of Water SupplyMichigan Department of Public HealthP.O. Box 30195Lansing, Ml 48909517-335-8318

Minnesota Department of HealthSection of Water Supply and Well ManagementDivision of Environmental Health925 S.E. Delaware StreetP.O. Box 59040Minneapolis, MN 55459-0040612-627-5170


64

Table 8-2. State Drinking Water Agencies (continued)

Division of Public Drinking WaterOhio Environmental Protection Agency1800 WaterMark DriveP.O. Box 1049Columbus, OH 43266-0149614-644-2752

Bureau of Water SupplyDepartment of Natural ResourcesP.O. Box 7921Madison, Wl 53707608-267-7651

Region VI

Division of EngineeringArkansas Department of Health4815 West Markham Street - Mail Slot 37Little Rock, AR 72205-3867501-661-2000

Office of Public HealthLouisiana Department of Health and HospitalsP.O. Box 60630New Orleans, LA 70160504-568-5105

Drinking Water SectionNew Mexico Health and Environment Department1190 St. Francis DriveRoom South 2058Santa Fe, NM 87503505-827-2778

Water Quality ServiceOklahoma State Department of HealthP.O. Box 53551Oklahoma City, OK 73152405-271-5204

Bureau of Environmental HealthTexas Department of Health1100 W. 49th StreetAustin, TX 78756-3199512-458-7533

Region VII

Surface and Groundwater Protection BureauEnvironmental Protection DivisionIowa Department of Natural ResourcesWallace State Office Building900 East Grand StreetDes Moines, IA 50319

515-281-8998Public Water Supply SectionBureau of WaterKansas Department of Health and EnvironmentForbes Field, Building 740Topeka, KS 66620913-296-1500

Public Drinking Water ProgramDivision of Environmental QualityMissouri Department of Natural ResourcesP.O. Box 176Jefferson City, MO 65102314-751-5331

Division of Drinking Water and EnvironmentalQsini fat innOd 11 ltd MUM

Nebraska Department of Health301 Sentenial Mall SouthP.O. Box 95007, 3rd FloorLincoln, NE 68509A H A M ^V J f^ #^ A J

402-471-2541

Region VIII

Drinking Water ProgramColorado Department of Health4210 East 11th AvenueDenver, CO 80220303-320-8333

Water Quality BureauDepartment of Health and Environmental Scien-cesCogswell Building, Room A20GHelena, MT 59620406-444-2406

Division of Water Supply and Pollution ControlND State Department of Health and ConsolidatedLaboratories1200 Missouri AvenueP. O. Box 5520Bismark, ND 58502-5520702-224-2370

Office of Drinking WaterDepartment of Water and Natural Resources

Joe Foss Building523 East Capital AvenuePierre, SD 57501605-773-3151


65

Table 8-2. State Drinking Water Agencies (continued)

Bureau of Drinking Water/SanitationUtah Department of HealthP.O. Box 16690Salt Lake City, UT 84116-0690801-538-6159

DEQ - Water QualityHerschler Building, 4 West122 West 25th StreetCheyenne, WY 82002307-777-7781

Region IX

Field Services SectionOffice of Water Quality2655 East Magnolia StreetPhoenix, AR 85034602-257-2305

Office of Drinking WaterCalifornia Department of Health Services714 P Street, Room 692Sacramento, CA 95814916-323-6111

Safe Drinking Water BranchEnvironmental Management DivisionP.O. Box 3378Honolulu, HI 96801-9984808-548-4682

Public Health EngineeringNevada Department of Human ResourcesConsumer Health Protection Services505 East King Street, Room 103Carson City, NV 89710702-885-4750

Guam Environmental Protection AgencyGovernment of GuamHarmon Plaza Complex Unit D-107130 Rojas StreetHarmon, Guam 96911

Division of Environmental QualityCommonwealth of the Northern Mariana IslandsP.O. Box 1304Saipan, CM 96950670-322-9355

Marshall Islands Environmental ProtectionAuthorityP.O. Box 1322Majuro, Marshall Islands 96960Via Honolulu

Government of the Federated States of MicronesiaDepartment of Human ResourcesKolonia, Pohnpei 96941

Palau Environmental Quality Protection BoardHospitalKoror, Palau 96940

Region XAlaska Drinking Water ProgramWastewater and Water Treatment SectionDepartment of Environmental ConservationP.O. Box 0Juneau.AK 99811-1800907-465-2653

Bureau of Water QualityDivision of Environmental QualityIdaho Department of Healthand WelfareStatehouse MailBoise, ID 83720208-334-5867

Drinking Water ProgramDepartment of Human ResourcesHealth Division1400 S.W. 5th Avenue, Room 608Portland, OR 97201503-229-6310

Drinking Water SectionDepartment of HealthMail Stop LD-11, Building 3Airdustrial ParkOlympia, WA 98504206-753-5954

66

Table 8-3. Rural Community Assistance Program (RCAP) Agencies

Community Resources Group, Inc.2705 ChapmanSpringdale, AR 72764501 -756-2900

Great Lakes Rural Network109 South Front StreetFreemont, OH 43420419-334-8911

Midwest Assistance Program, Inc.P.O. Box 81New Prague, MN 56071612-758-4334

Rural Community Assistance Corporation2125 19th Street, Suite 203Sacramento, CA 95818916-447-2854

Rural Housing Improvement, Inc.213 Centra! Street, Box 429Winchendon, MA 01475-0429617-297-1376

Virginia Water Project, Inc.Southeastern Rural CommunityAssistance Program702 Shenandoah Avenue, NWP.O. Box 2868Roanoke, VA 24001703-345-6781

Publications (continued)

Schautz, Jane W. The Self-HelpHandbook. This manual gives specificguidelines and techniques for estab-lishing self-help projects (projectswhere the community does some ofthe work itself to save money). Focusis on improving or creating water andwastewater systems in small ruralcommunities. For ordering information,contact: Rensselaerville Institute,Rensselaorville, NY 12147 (518-797-3783).

U.S. Environmental ProtectionAgency, Office of Drinking Water.Guidance Manual for Compliance withthe Filtration and Disinfection Require-ments for Public Water Systems Using

Surface Water Sources. EPA 570/9-89-018. October 1989.

U.S. Environmental ProtectionAgency, Office of Drinking Water.Manual of Individual Water SupplySystems. EPA 570/9-82-004. October1982.

Sampling

U.S. Environmental Protection Agen-cy, Office of Research and Develop-ment. Handbook for Sampling andSample Preservation of Water andWastewater. EPA 600/4-82-029. Sep-tember 1982.

nitration

American Water Works AssociationResearch Foundation. Manual ofDesign for Slow Sand Filtration. (To bepublished Fall 1990.)

Huisman, L, and Wood, WE. SlowSand Filtration. World Health Or-ganization, Geneva. 1974.

Slezak, L.A. and Sims, R.C. "The Ap-plication and Effectiveness of SlowSand Filtration in the United Slates."JournalAWWA, 76:1238-43. 1984.

Visscher, J.T., Paramasivam, R.,Raman, A., and Heijnen, H.A. SlowSand Filtration for Community WaterSupply. Technical Paper 24. Interna-tional Reference Centre for Com-munity Water Supply and Sanitation,The Hague, The Netherlands. 1987.

Disinfection

American Water Works Association.Water Chlorination Principles andPractices (M20). 1973.

SMC Martin, Inc. MicroorganismRemoval for Small Water Systems.EPA 570/9-83-012. Valley Forge, PA.June 1983.

Corrosion Control

U.S. Environmental Protection Agen-cy, Office of Drinking Water. CorrosionManual for Internal Corrosion of WaterDistribution Systems. EPA 570/9-84-001. April 1984.

Economic and Engineering Services.Lead Control Strategies. AmericanWater Works Association ResearchFoundation. Denver, CO. 1989.

Radlonucllde Removal

«inner, N.E., Lessar, CE., Schell,G.S., and Fox, K.R., "Low Cost/Low-Technology Aeration Techniques forRemoving Radon from DrinkingWater." EPA/600/M-87-031. U.S.Environmental Protection Agency,Office of Research and Development.September 1987.

67

SMC Martin, Inc. RadionuclideRemoval for Small Public Water Sys-tems. EPA 570/9-83-010. ValleyForge, PA. June 1983.

Wellhead Protection

U.S. Environmental Protection Agency,Office of Ground-Water Protection.Wellhead Protection: A DecisionMaker's Guide. 1987.

U.S. Environmental Protection Agency,Office of Ground-Water Protection.Developing a State Wellhead Protec-tion Program: A User's Guide to AssistState Agencies Under the Safe Drink-ing Water Act. 1988.

U.S. Environmental Protection Agency,Office of Ground-Water Protection.Ground-Water Protection DocumentRequest Form.

Costs/Financial Management

American Water Works Association.Water Utility Capital Financing (M 29).1988.

Gumerman, R.C., Burris, B.E., andHansen, S.P. Estimation of Small Sys-tem Water Treatment Costs. FinalReport. Culp/Wesner/Culp. MunicipalEnvironmental Research Lab, Cincin-nati, OH, 1984.

U.S. Environmental Protection Agency,Office of Water. A Water and Waste-water Manager's Guide for StayingFinancially Healthy. EPA 430/09-89-004. July 1989.

U.S. Environmental Protection Agency,Office of Ground-Water Protection,Local Financing for Wellhead Protec-tion. 1989.

Consultants

Directory—Professional Engineers inPrivate Practice. Published by theNational Society of ProfessionalEngineers. Contact SPE Order Depart-ment, 1420 King Street, Alexandria,VA 22314.

Who's Who in Environmental Engineer-ing. Published by the AmericanAcademy of Environmental Engineers.Contact the American Academy ofEnvironmental Engineers, 132 HolidayCourt, Suite 206, Annapolis, MD21401.

The Federal Register

The Federal Register is publisheddaily to make available to the publicregulations and legal notices issuedby federal agencies. It is distributed bythe U.S. Government Printing Office,Washington, DC 20402. To ordercopies, call 1 -202-783-3238.

A wide variety of publications onspecific topics of concern to water sys-tems is available from the AmericanWater Works Association and the Na-tional Rural Water Association.

68

Appendix A

How to TakeBacteriologicalSamples

Routine and special bacteriologicalsamples must be taken in accordancewith established procedures to preventaccidental contamination, andanalyzed by an EPA- or state-certifiedlaboratory. The laboratory will usuallyprovide specially prepared samplingcontainers, properly sterilized and con-taining sodium thiosulfate to destroyany remaining chlorine. The followingsteps should be followed in coliformsampling:

1. Use only containers that areprovided by the bacteriologicallaboratory and that have beenprepared for coliform sampling. Fol-low all instructions for sample con-tainer handling and storage.

The containers are sterile. Donot open them before use and donot rinse them.

2. Take samples at the consumer'sfaucet, but avoid:

* Faucets with aerators (unlessremoved) or swivel spouts

• Taps inside homes served byhome water treatment unitssuch as water softeners

* Locations where the waterenters separate storage tanks

• Leaking faucets that permitwater to run over the outside ofthe faucet

3. Always allow the water to flowmoderately from a faucet 2 or 3minutes before taking the sample.

4. Hold the sample container at thebase, keeping hands away fromthe container neck. Be sure the in-side of the container cap isprotected and does not touchanything.

5. Without adjusting the flow, fill thesample container, leaving about 20percent air space at the top.Replace the cap immediately. If thesample is taken incorrectly, takeanother sample container —do notreuse the original bottle.

6. Take a second sample andmeasure the concentration of thedisinfectant and record relevant in-formation (date, time, concentra-tion, place, sampler, etc.).

7. Package the bacteriological samplefor delivery to the laboratory.Record all pertinent field informa-tion on a form and on the samplecontainer label.

8. Samples must be cool during ship-ment to the laboratory. Use insu-lated boxes for shipping containersif needed, or refrigerate duringtransit.

Do not allow more than 30 hours be-tween sampling and test times.

Be sure the laboratory can processthe samples immediately upon receipt.

Source: SMC Martin, Inc., Microorganism Removal for Small Water Systems, June 1983.EPA 570/9-83-010.

69

Appendix B

Checklist:Some FactorsAffecting WaterTreatmentSystemPerformance

Administration

1. Does the manager have first-handknowledge of plant needs throughplant visits and discussions withoperators?

2. Are there long-range plans forfacility replacement, alternativesource waters, emergencyresponse, etc.?

3. Is there an adequate number of per-sonnel to accomplish necessaryoperational activities?

4. Are staff adequately trained andable to make proper operation andmaintenance decisions?

5. Are adequate funds available forspare parts, improvements or re-placement of equipment, requiredchemicals, etc.?

6. Are the plant unit processes ade-quate to meet the demand forfinished water?

7. Is the staff aware of the potentialsources of contamination that mightaffect the drinking water supply andthe available managementmethods?

Maintenance

1. Is there an effective scheduling andrecording procedure to preventequipment failures, excessivedowntime, etc resulting in plant per-formance or reliability problems?

2. Is the spare parts inventory ade-quate to prevent long delays inequipment repairs?

3. Are procedures available to initiatemaintenance activities on equip-ment operating irregularities? Areemergency response procedures inplace to protect process needs ifcritical equipment breaks down?

4. Are good housekeeping proce-dures followed?

5. Are equipment reference sourcesavailable (such as operation andmaintenance manuals, equipmentcatalogs, etc.)?

6. Does the plant staff have neces-sary expertise to keep equipmentoperating and to make equipmentrepairs when necessary?

7. Are technical resources (such asequipment suppliers or contract ser-vice) available to provide guidancefor repairing, maintaining, or install-ing equipment?

8. Are old or outdated pieces of equip-ment replaced as necessary toprevent excessive equipmentdowntime or inefficient process per-formance/reliability?

Design

1. Is the plant design adequate forraw water quality (e.g., turbidity,temperature, seasonal variation,etc.)?

2. Do facilities exist to control rawwater quality entering the plant(e.g., can intake levels be varied,can chemicals be added to controlaquatic growth, do watershedmanagement practices adequatelyprotect raw water quality)?

3. Are the size of filters and type,depth, and effective size of filtrationmedia adequate? Are the surfacewash and backwash facilities ade-quate to maintain a clear filter bed?

4. Are design features of the disinfec-tion system adequate (propermixing, detention time, feed rates,proportional feed, etc.)?

5. Are sludge facilities and size of thesludge disposal area adequate?

6. Do process control features provideadequate measurement of plantflow rate, backwash flow rate, filtra-tion rate, and flocculation mixing in-

71

puts? Do chemical feed facilitiesprovide adjustable feed ranges thatare easily set for operation at all re-quired dosages? Are chemicalfeed rates easily measured?

7. Are automatic monitoring or controldevices used where needed toavoid excessive operator time forprocess control and monitoring?

8. Are standby units for key equip-ment available to maintain processperformance during breakdown orduring preventive maintenance ac-tivities?

Operation

1. Are plant and distribution monitor-ing tests representative of perfor-mance?

2. Is the proper process control test-ing performed to support opera-tional control decisions?

3. Does the plant staff have sufficientunderstanding of water treatmentprocess control testing and plantneeds to make proper process con-trol adjustments?

4. Has the plant staff received ap-propriate operational informationfrom technical resources (e.g.,design engineer, equipment repre-sentative, state trainer or inspector)to enable them to make properoperational decisions?

5. Does the operation and main-tenance manual/procedure provideappropriate guidance for operation-al decisions? Do operators utilizethe manual?

6. Are distribution system operatingprocedures adequate to protect theintegrity of finished water (e.g.,flushing, reservoir management)?

Source. Adapted from U.S. Environmental Protection Agency, Office of Research and Development and Center for Environmental Re-search Information, Summary Report: Optimizing Water Treatment Plant Performance with the Composite Correction Program, March1990. EPA625/8-90/017.

72

Appendix C

Selecting aConsultingEngineer

Selecting the right consultant involvesthe following stops:

1. Identifying potential engineeringfirms. Start by drawing up a list ofat least five firms that might be ableto meet your needs. Sources ofnames include your own past ex-perience or that of neighboringtowns, lists maintained by yourstate drinking water agency, andsuggestions received from the localRural Community AssistanceProgram. Local professional en-gineering societies may be able toprovide lists of members who spe-cialize in drinking water treatmentwork. The National Society ofProfessional Engineers and theAmerican Academy of Environmen-tal Engineers have lists of theirmembers available (see Chapter 8,Resources).

2. Issuing a Request for Proposals.Notify engineering firms that youare interested in their services. Onegood way to do this is by preparinga Request for Proposals (RFP), Inyour RFP, briefly describe yourtown's water treatment problemand request proposals from consult-ants on how they would solve it.

Depending on your community'ssize and the nature of yourproblem, the RFP may be a letter tothe engineering firms on your list orit may be a longer, more formaldocument. You may wish to adver-tise your RFP. In any case, itshould include at least the following:

• A brief description of the problem

• A statement telling what it is youwant the consulting firm to do

• The deadline by which yourtown must receive the proposal

• The person in your town to con-tact for additional information

• Standards by which theproposals will be judged

• The place and time the proposalmust be submitted

3. Interviewing candidate engineer-ing firms. When you receive theproposals, check to see if theymeet your judging standards, andare within an acceptable costrange. From those that meet thestandards, select three or four andinterview each firm individually.

The following criteria may be help-ful in evaluating engineering firms:

• Small town experience. Doesthe firm have experience withcommunities like yours? Whichtowns have they worked with inthe recent past?

• System design experience.Does the firm have experiencein designing systems for smallcommunities? What types ofsystems has the firm actuallyrecommended, designed, and in-stalled? When were they in-stalled? How are these systemsworking? What were the es-timated costs? What are thepresent operation and main-tenance needs and costs ofthese systems? What systemshas the firm recommended forcommunities that are most likeyour own? Ask for the cost perdwelling serviced, the up-frontassessments, and monthly char-ges for the last few projects of asize and technology comparableto your situation.

Sources: Adapted from U.S. Environmental Protection Agency, Office of Municipal PollutionControl, It's Your Choice: A Guidebook for Local Officials on Small Community WastewaterManagement Options, September 1987. EPA 430/9-87-006; SMC Martin, Inc., Microor-ganism Removal for Small Water Systems, June 1983. EPA 570/9-83-012.

73

• Experience with financial in-stitutions and funding agen-cies. What experience has thefirm had in helping communitiesget financing from commercialsources (banks, bond sales)?What experience has the firmhad in dealing with state grantor loan programs or FarmersHome Administration grant andloan programs? What ex-perience has the firm had inworking with lending institutionsor financial consultants?

• Experience with state andcounty agencies. What ex-perience does the firm have inworking with the state and countyenvironmental agencies, thehealth department, etc.?

• Willingness to work with thecommunity. If your communitycame up with a range of accept-able user costs, would the en-gineer be willing to use theseestimates as guidelines todesign a drinking water treat-ment system? How does thefirm plan to handle public par-ticipation in this project?

• Willingness to work for thecommunity. Does the firm haveany experience in using tech-nologies and maintenanceprograms that are different fromwhat the state and county agen-cies have traditionally ac-cepted? Does the firm have thewillingness and capability to util-ize innovative or alternative tech-nology where appropriate?(Some engineers have dealtonly with large centralized treat-ment systems and might not befamiliar or experienced withother alternatives.)

• Staff capabilities andworkload. What projects is thefirm now working on and whatnew ones may be coming soon?Which people on their staff willbe devoted to your project?What time schedule does the

firm propose for completing yourwork? Does the firm use sub-contractors for certain work? Ifso, which firms and for whatwork?

• Cost of engineering work. Beprepared to pay for good en-gineering work. Do not chooseyour engineer only on the basisof cost. It is well worth spendinga little extra to get an engineerwho will design a system thatwill provide service at lower costfor years to come. Ask the en-gineer to briefly explain thefirm's estimated fee. Make sureyou understand exactly what ser-vices will be provided. Is there adistinction between basic ser-vices and additional services?What circumstances could sig-nificantly change the estimate?

4. Checking references. Be sure tocheck references for the firms youthought were best. Talk to repre-sentatives from communities thefirm has recently worked for. Askabout the overall experience,problems or special situations thatarose, delays, etc.

5. Selecting a firm and contractingfor its services. The final selectionof a firm involves evaluating all theinformation you have gathered.Once you have selected a firm, youmust negotiate and sign a contractfor their services. The form of thiscontract and the payment may begoverned by the method your townwill use to finance this part of yourproject. Be sure to consider thisaspect in your evaluation. Whenthat is done, you are ready to beginworking with the engineer toevaluate and solve your town'sdrinking water treatment problems.

The consultant should do the followingto achieve the best system design andto simplify the operator's job:

• Establish a high level of com-munication with the community and

representatives of the drinkingwater treatment facility, and be-come familiar with the unique fea-tures and requirements of theutility, as well as the responsive-ness of regional chemical suppliersand equipment vendors.

• Conduct sufficient laboratory andpilot plant studies and observationsof the source waters to fully charac-terize them. New facilities shouldbe adequate to handle the fullrange of expected water condi-tions, including foreseeable waterquality deterioration.

• Initiate the design process with athorough review of all possible non-treatment or minimal treatment ap-proaches. Consider potential easeof maintenance, adequate spaceand light, and simplicity in thedesign and equipment. Avoid over-ly elaborate control systems, and in-clude appropriate redundance (I.e.,never only one chlorinator).

• Avoid dead ends in the distributionsystem. Provide equipment forflushing and sampling, for storage,and for emergency chlorination ofthe distribution system.

• Allow operating personnel to par-ticipate in design decisions and ob-serve construction progress.

• Prepare operation and main-tenance manuals, which includethe following information;

- the original design concepts

- description and drawings ofthe facility as constructed

- normal operational procedures

- emergency operational proce-dures

- organized collection ofvendors' literature

- safety considerations and re-quirements

74

- schematics with all valves num-bered to correspond todetailed operational procedures

- maintenance procedures

Provide startup assistance andtraining and followup engineeringservices.

75

Appendix D

ChlorineResidualMonitoring

Chlorine in its most activa form—as"free residual chlorine*—is stable onlyin the absence of agitation, sunlight,and certain organic and inorganicmaterials with which it can react.

Reactions of free residual chlorinewith chlorine demanding substancescontinue over long periods of time.Therefore, the sample taken for disin-fectant analysis should be analyzedimmediately. Specially prepared sam-pling containers, properly cleansed,sterilized, and not containing sodiumthiosulfate should be used.

In general, the same sampling precau-tions described in Appendix A fortaking coljform samples should be ob-served, but in addition:

1. Draw the sample gently, avoidingagitation.

2. Analyze immediately in the shadeor subdued light. Do not store thesample.

3. Oo not use a bacteriological sam-pling container, which may containa chemical to counteract or destroythe disinfecting agent."

Demonstration of Maintaining aResidual6

The Surface Water Treatment Rule(SWTR) establishes two requirementspertaining to the maintenance of aresidual. The first requirement is tomaintain a minimum residual of 0.2mg/L entering the distribution system.Also, a detectable residual must bemaintained throughout the distributionsystem. These requirements are fur-ther explained in the following sections.

Maintaining a Residual Enteringthe System

The SWTR requires that a residual of0,2 mg/L be maintained in the waterentering the distribution system at alltimes. Continuous monitoring at theentry point(s) to the distribution sys-tem is required to ensure that a detec-table residual is maintained. Any timethe residual drops below 0.2 mg/L, thesystem must notify the Primacy Agen-cy0 prior to the end of the next busi-ness day. The system is in violation ofa treatment technique if the residuallevel is not restored to 0.2 mg/L within4 hours and filtration must be installed.(If the Primacy Agency finds that theexceedence was caused by an un-usual and unpredictable circumstance,it may choose not to require filtration.)In cases where the continuousmonitoring equipment fails, grabsamples every 4 hours may be usedfor a period of 5 working days whilethe equipment is restored to operableconditions.

The system must record, each day ofthe month, the lowest disinfectantresidual entering the system and thisresidual must not be less than 0.2mg/L Systems serving less than orequal to 3,300 people may take grabsamples in lieu of continuous monitor-ing at the frequencies shown in thebox below:

System Population Samples/day*

<500501-1,0001,001-2,500>2,501-3,000

'Samples must be taken at dispersedtime intervals as approved by thePrimacy Agency.

* From SMC Martin, Inc., Microbiological Removal for Small Water Systems, June 1983.EPA 570/9-83-010.b Adapted from U.S. Environmental Protection Agency, Guidance tor Compliance with theFiltration and Disinfection Requirements for Public Water Systems Using Surface WaterSources, October 1989.0 The Primary Agency is a state with primary enforcement responsibility for public water sup-plies, or EPA in the case of a state that has not obtained primacy.

77

If the residual concentration fallsbelow 0.2 mg/L, another sample mustbe taken within 4 hours and samplingcontinued at least every 4 hours untilthe disinfectant residual is a minimumof 0.2 mg/L.

Maintaining a Residual within theSystem

The SWTR also requires that a detec-table disinfectant residual be main-tained throughout the distributionsystem, with measurements taken at aminimum frequency equal to that re-quired by the Total Coliform Rule (54FR 27543-27568). The same samplinglocations as required for the coliforrnregulation must be used for taking thedisinfectant residual or HPC (hetero-trophic plate count) samples. How-ever, for systems with both ground-water and surface water sources (orground water under the direct in-fluence of surface water) entering thedistribution system, residuals may bemeasured at points other than coliformsampling points if these points aremore representative of the disinfectedsurface water and allowed by thePrimacy Agency. An HPC level of lessthan 500/mL is considered equivalentto a detectable residual for the pur-pose of determining compliance withthis requirement, since the absence ofa disinfectant residual does not neces-sarily indicate microbiological con-tamination.

Disinfectant residual can be measuredas total chlorine, free chlorine, com-bined chlorine, or chlorine dioxide (orHPC level). The SWTR lists the ap-proved analytical methods for theseanalyses. For example, several testmethods can be used to test forchlorine residual in the water, includingamperometric titration, DPDcolorimetric method, DPD ferroustitrimetrlc method, and iodometricmethod, as described in the 16th Edi-tion of Standard Methods for the Ex-amination of Water and Wastewater,

APHA, AWWA, and WPCF, Wash-ington, DC, 1985.d

The SWTR requires that a detectabledisinfectant residual be present in 95percent or more of the monthly distribu-tion system samples. In systems thatdo not filter, a violation of this require-ment for 2 consecutive months causedby a deficiency in treating the sourcewater will trigger a requirement forfiltration to be installed. Therefore, asystem that does not maintain aresidual in 95 percent of the samplesfor 1 month because of treatmentdeficiencies, but is maintaining aresidual in 95 percent of the samplesfor the following month, will meet thisrequirement.

The absence of a detectable disinfec-tant residual in the distribution systemmay be due to a number of factors,including:

• Insufficient chlorine applied at thetreatment plant

• Interruption of chlorination

• A change in chlorine demand ineither the source water or the dis-tribution system

• Long standing times and/or longtransmission distances

Available options for systems to cor-rect the problem of low disinfectantresiduals within their distribution sys-tem include:

• Routine flushing

• Increasing disinfectant doses at theplant

• Cleaning of the pipes (eithermechanically by pigging or by theaddition of chemicals to dissolvethe deposits) in the distribution sys-tem to remove accumulated debris

that may be exerting a disinfectantdemand

• Flushing and disinfection of the por-tions of the distribution system inwhich a residual is not maintained

• Installation of satellite disinfectionfeed facilities with boosterchlorinators within the distributionsystem

For systems unable to maintain aresidual, the Primacy Agency maydetermine that it is not feasible for thesystem to monitor HPCs and judgethat disinfection is adequate based onsite-specific conditions.

Additional information on maintaininga residual in the system is available inthe American Water Works Assoc-iation's Manual of Water Supply Prac-tices and Water Chlorination Principiosand Practices.

d Also, portable test kits are available that can be used in the field to detect residual upon approval of the Primacy Agency. Those kits mayemploy titration or colorimetric test methods. The colorimetric kits employ either a visual detection of a residual through the use of a colorwheel, or the detection of the residual through the use of a hand held spectrophotometer.

78

Appendix E

CT Values CT Values for Achieving Inactivation of Viruses a(in mg.'L-m)

through 9

Freechlorine8

Ozone

aCT values

LogInactf-vaton

CM

CO

^

CM

CO

^

0.5'C

6912

0.91.41.8

5'C

468

0.60.91.2

include a safety factor of 3.

Temperature

10'C

346

0.50.81.0

15'C

234

0.30.50.6

20'C

123

0.250.40.5

25'C

112

0.150.250.3

CT Values for Achieving 99.9 Percent Inactivation ofCiardia Lamblia1

Disinfectant

Freechlorine"

P H

6789

0.5'C

165236346500

5'C

116165243353

Temperature

10"C

87124182265

15'C

5883

122177

20*C

446291132

25'C

29416188

Ozone 6-9 2.9 1.9 1.4 0.95 0.72 0.48

"These CT values for free chlorine, chlorine dioxide, and ozone will guaran-tee greater than 99.99 percent inactivation of enteric viruses.

b CT values will vary depending on concentration of free chlorine. Valuesindicated are for 2.0 mgA. of free chlorine. CT values for different freechlorine concentrations are specified in tables in the EPA Guidance Manualfor Compliance with the Filtration and Disinfection Requirements for PublicWater Systems Using Surface Water Sources.

79

CT Values for Achieving 90 Percent Inactivation of Giardia Lamblia(in mg/L-m)

Disinfectant

Freechlorine11

(2 mg/L)

Ozone

PH

6789

6-9

0.5'C

5579115167

0.97

Temperature

5'C

395581118

0.63

10-C

29416188

0.48

15'C

19284159

0.32

20C

15213044

0.24

25C

10142029

0.16

aCT values will vary depending on concentration of free chlorine. Values indi-cated are for 2.0 mg/L of free chlorine. CT values for different free chlorine con-centrations are specified in tables in the EPA Guidance Manual for Compliancewith the Filtration and Disinfection Requirements for Public Water SystemsUsing Surface Water Sources.

80

Appendix F

Sample CTCalculation forAchieving1-log Giardia,2-log VirusInactivationwith ChlorineDisinfection

A 50,000 GPD «low sand filtrationplant supplies a community of 500people with drinking water from areservoir in a protected watershed.The raw water supply has the follow-ing characteristics:

• Turbidity: 5 to iONTU

• Total estimated Giardia cyst level:less than 1 per 100 mL

• pH: 6.5 to 7.5

• Temperature: 5* to 15'C

An overall removal/inactivation of 3logs for Giardia and 4 logs for virusesis sufficient for this system. ThePrimacy Agency credits the slow sandfilter, which produces water with tur-bidity ranging from 0.6 to 0.8 NTU,with a 2-log Giardia and virus removal.Disinfection must achieve an addition-al 1 -log Giardia and 2-log virusremoval/inactivation to meet overalltreatment objectives.

To begin the calculations for determin-ing the adequacy of the inactivationsachieved by the disinfection system,the total contact time must be deter-mined.

In this plant, chlorine for disinfection isadded prior to the clearwell, which hasa 2,000-galton capacity. The distancefrom the plant to the first customer isbridged by a 1,000-foot 2-inch trans-mission main. The contact timeprovided in both the clearwell basinand the distribution pipe up to the firstcustomer comprises the total contacttime for disinfection.

In the calculations, contact time is rep-resented by Tío -Mhe time needed for10 percent of the water to passthrough the basin. In other words, Tíodescribes the time, in minutes, that 90percent of the water remains in thebasin. (For the distribution pipe, con-tact time is 100 percent of the timethat water remains in the pipe.)

The contact time multiplied by the con-centration (mg/L) of residual chlorinein the water is the calculated CT valuefor the system. Proven inactivation ofGiardia and viruses are correlated tocalculated CT values in EPA'sGuidance Manual for Compliance withthe nitration and Disinfection Require-ments for Public Water Systems UsingSurface Water Sources. (Appendix Econtains excerpts from the CT tablesin the manual.)

The Tío for the clearwell basin can bedetermined by tracer studies. (Tracerstudy procedures are described inEPA's Guidance Manual.)

On the day represented in this ex-ample, the tracer study showed thatthe Tío for the clearwell was 40minutes at the peak hourly flow rate.At this flow rate, water travels throughthe transmission main at 211 feet perminute. The distance between theplant and the first customer is 1,000feet. Thus, the Tío for the distributionmain is 4.7 minutes (1,000 feet dividedby 211 feet per minute).

Other data required for the calculationare:

* Measured chlorine residual: 2.0mg/L for the clearwell basin and 1.2mg/L for the distribution main

* Water temperature: 5'C

* Water pH: 7.5

CT values required to achieve variouslevels of inactivation of Giardia andviruses depending on the watertemperature, pH, and chlorine residualare provided in the Guidance Manual.The calculated CT values (CTcaic)based on actual system data are com-pared to the CT values in theGuidance Manual (CT99.9 in the caseof a 1-log inactivation) to determinewhether the inactivations achieved areadequate.

81

Since, with free chlorine, a 1-logGiardia inactivation provides greaterthan a 4-log virus inactivation, inactiva-tion of Giardia is the controlling factorfor determining overall reductions.

The calculation of CT and comparisonto CT values for 1-log inactivation ofGiardia provided in the EPA GuidanceManual is shown in the box below.

For the basin:

CTcaic - Chlorine residual x contact time or- 2.0 mg/Lx 40 minutes » 80 mg/L-min

From the EPA Guidance Manual, CTgg.g (3-log inactivation) is200 mg/L-min at 5"C, 2 mg/L chlorine residual, and 7.5 pH.

CTcale/CTgg.g = 80 ma./L-min - 0.4200 mg/L-min

For the distribution system:

• 1.2 mg/L x 4.7 minutes » 5.64 mg/L-min

From the EPA Guidance Manual, CT999 is 183 mg/L-min at 5"C, 1.2 mg/Lchlorine residual, and 7.5 pH.

CTcalc/CTgg.g - 5:64 mg/L-min - 0.03183 mg/L-min

Summing CTcaic/CTgg.g for both the basin and the main results in 0.43. This isequivalent to a 1.29-log Giardia inactivation determined by:

3 X CTcalc/CT99.9- 3x0.43-1 .29 log

(This calculation is based on a 3-log ¡nactivation; therefore, the ratio ismultiplied by 3.)

Thus, the 1.29-log inactivationachieved by disinfection in this systemexceeds the 1-log additional inactiva-tion required to meet overall treatmentobjectives.

82

•U.S.Oowrnmenl Printing OHIce: 1992—648-003/41811

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