epa, small drinking water systems, 2005
TRANSCRIPT
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Small Drinking Water Systems:
State o the Industry andTreatment Technologies to Meetthe Sae Drinking Water ActRequirements
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EPA 600/X-05/021November 2005
Small Drinking Water Systems:State o the Industry and Treatment Technologiesto Meet the Sae Drinking Water Act Requirements
by
Chrstopher A. Impelltter, Crag L. Patterson, Roy C. Haught, and James A. Goodrch
Water Supply and Water Resources DvsonNatonal Rsk Management Research LaboratoryCncnnat, OH 45268
Ths report was compled n cooperaton wth Shaw Envronmental, Inc.Under EPA Contract EP-C-04-034 WA1-03 and WA 2-03
Work Assgnment Manager - Crag L. PattersonWater Supply and Water Resources Dvson
Natonal Rsk Management Research LaboratoryCncnnat, OH 45268
Natonal Rsk Management Research Laboratory
Oce o Research and DevelopmentU.S. Envronmental Protecton Agency
Cncnnat, OH 45268
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Notice
The EPA has not subjected ths report to nternal revew. Thereore, the research results presented
heren do not, necessarly, refect Agency polcy. Menton o trade names o commercal products does
not consttute endorsement or recommendaton or use.
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Abstract
Ths document summarzes the current natonal statstcs or small drnkng water systems (servng less
than ten thousand people). It descrbes the current status o regulatons, treatment technologes, source
water ssues, dstrbuton system characterstcs, waste resdual ssues, securty/emergency response,
and montorng as these ssues pertan to small systems. Ths objectve o ths document s to provde
researchers n the Water Supply and Water Resources Dvson n the Natonal Rsk Management Research
Laboratory wth a bass to desgn and mplement uture research projects that wll ocus on the most
pressng needs o small systems. The majorty o ths report ncludes data and normaton acqured
between June 1, 2004 and October 1, 2005, and most o the work was completed on November 1, 2005.
Secton 5.6, related to small systems treatment opton aordablty and denton o unreasonable rsk
to health, presents more recent updates (perormed n August 2006) based on revewer comments.
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Foreword
The U.S. Envronmental Protecton Agency (EPA) s charged by Congress wth protectng the Natons
land, ar, and water resources. Under a mandate o natonal envronmental laws, the Agency strves to
ormulate and mplement actons leadng to a compatble balance between human actvtes and the ablty
o natural systems to suppor t and nurture le. To meet ths mandate, EPAs research program s provdng
data and techncal support or solvng envronmental problems today and buldng a scence knowledge
base necessary to manage our ecologcal resources wsely, understand how pollutants aect our health,
and prevent or reduce envronmental rsks n the uture.
The Natonal Rsk Management Research Laboratory (NRMRL) s the Agencys center or nvestga-
ton o technologcal and management approaches or preventng and reducng rsks rom polluton
that threaten human health and the envronment. The ocus o the Laboratorys research program s
on methods and ther cost-eectveness or preventon and control o polluton to ar, land, water, and
subsurace resources; protecton o water qualty n publc water systems; remedaton o contamnated
stes, sedments and ground water; preventon and control o ndoor ar polluton; and restoraton o
ecosystems. NRMRL collaborates wth both publc and prvate sector partners to oster technologes
that reduce the cost o complance and to antcpate emergng problems. NRMRLs research provdessolutons to envronmental problems by: developng and promotng technologes that protect and
mprove the envronment; advancng scentc and engneerng normaton to support regulatory and
polcy decsons; and provdng the techncal support and normaton transer to ensure mplementaton
o envronmental regulatons and strateges at the natonal, state, and communty levels.
Ths publcaton has been produced as part o the Laboratorys strategc long-term research plan. It s
publshed and made avalable by EPAs Oce o Research and Development to assst the user com-
munty and to lnk researchers wth ther clents.
Sally Guterrez, Drector
Natonal Rsk Management Research Laboratory
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Table of Contents1.0 Introducton ..................................................................................................................................1-1
1.1 Goals and Objectves o ths Document .................................................................................1-11.2 Document Organzaton .........................................................................................................1-1
2.0 Current Status and Issues o Small Drnkng Water Systems ......................................................2-12.1 Introducton ............................................................................................................................2-1
2.2 Prole o Small Systems n the U.S. .......................................................................................2-12.3 Status o Drnkng Water Plant Volatons ...............................................................................2-42.4 Source Water Issues ..............................................................................................................2-52.5 Common Current Treatment Technologes .............................................................................2-52.6 Partculate/Turbdty Removal Technologes ...........................................................................2-8
2.6.1 Smple Fltraton .............................................................................................................2-82.6.2 Advanced Fltraton ........................................................................................................2-92.6.3 Reverse Osmoss (RO) .................................................................................................2-9
2.7 Chemcal Contamnant Removal............................................................................................2-92.7.1 Ion Exchange (IX) ..........................................................................................................2-92.7.2 Sorpton Technologes ....................................................................................................2-92.7.3 Other Technologes ......................................................................................................2-10
2.8 Bologcal Contamnant Removal .........................................................................................2-10
2.8.1 Chlornaton ..................................................................................................................2-102.8.2 Ultravolet Lght (UV) ....................................................................................................2-102.8.3 Ozone ..........................................................................................................................2-102.8.4 Other Dsnecton Technologes ...................................................................................2-10
2.9 Dstrbuton System Inrastructure ........................................................................................2-102.9.1 Storage Facltes..........................................................................................................2-142.9.2 Pumpng acltes .........................................................................................................2-162.9.3 Dstrbuton Lnes .........................................................................................................2-16
2.10 Remote Telemetry Supervsory Control and Data Acquston (SCADA) ..........................2-172.11 Key Questons ......................................................................................................................2-202.12 Reerences ...........................................................................................................................2-22
3.0 Regulatory Background ...............................................................................................................3-13.1 Sae Drnkng Water Act (SDWA) ...........................................................................................3-1
3.2 SDWA Provsons ...................................................................................................................3-13.2.1 Natonal Prmary Drnkng Water Regulatons (NPDWR) ...............................................3-13.2.2 Natonal Secondary Drnkng Water Regulatons (NSDWR) ..........................................3-23.2.3 Contamnant Canddate Lst (CCL) ................................................................................3-2
3.3 Current Regulatory Issues .....................................................................................................3-23.3.1 Perchlorate .....................................................................................................................3-23.3.2 Arsenc ...........................................................................................................................3-23.3.3 Complance wth Surace Water Treatment Rule ............................................................3-33.3.4 Stage 1 and 2 Dsnecton Byproducts (DBP) Rules .....................................................3-43.3.5 Proposed Ground Water Rule ........................................................................................3-53.3.6 Methyl Tertary Butyl Ether (MTBE) ................................................................................3-53.3.7 Radonucldes ................................................................................................................3-5
3.4 Source Water Assessments ...................................................................................................3-63.5 Wellhead Protecton ...............................................................................................................3-73.6 Vulnerablty Assessments (VA), Emergency Plannng and Securty .....................................3-73.7 Varances and Exemptons ....................................................................................................3-8
3.7.1 Small System Varances ................................................................................................3-83.7.2 Exemptons ....................................................................................................................3-8
3.8 DWSRF .................................................................................................................................3-93.9 Key Questons ........................................................................................................................3-93.10 Reerences .............................................................................................................................3-9
4.0 Source Water Issues....................................................................................................................4-14.1 Background ...........................................................................................................................4-14.2 Drnkng Water Research Program Mult-Year Plan ...............................................................4-1
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4.2.1 Long-Term Goals ...........................................................................................................4-14.2.2 Ongong and Future Research ......................................................................................4-1
4.3 Source Water Assessments ...................................................................................................4-24.3.1 Delneaton .....................................................................................................................4-24.3.2 Contamnaton Sources .................................................................................................4-24.3.3 Susceptblty Determnaton ..........................................................................................4-3
4.3.4 Publc Involvement .........................................................................................................4-34.3.5 Benets o Source Water Assessment Plans (SWAPs) .................................................4-34.3.6 Source Water Protecton ................................................................................................4-3
4.4 Other Source Water Assessment and Protecton Tools .........................................................4-34.4.1 Santary Survey .............................................................................................................4-34.4.2 Wellhead Protecton Program (WHPP) ..........................................................................4-3
4.5 Sustanablty o Communty Water Systems (CWSs) ............................................................4-44.6 EPA Source Water Assessment and Protecton Programs ....................................................4-44.7 Key Questons ........................................................................................................................4-44.8 Reerences .............................................................................................................................4-4
5.0 Treatment Processes ...................................................................................................................5-15.1 Introducton ...........................................................................................................................5-15.2 Packaged Fltraton ...............................................................................................................5-1
5.2.1 Fltraton .........................................................................................................................5-25.2.2 Bag Fltraton ..................................................................................................................5-35.2.3 Cartrdge Fltraton .........................................................................................................5-45.2.4 Membrane Fltraton .......................................................................................................5-45.2.5 Ultra Fltraton (UF) ........................................................................................................5-4
5.3 Dsnecton ............................................................................................................................5-45.3.1 Dsnecton by Chlornaton ...........................................................................................5-55.3.2 Dsnecton by Ozonaton ..............................................................................................5-65.3.3 Advanced Oxdaton Process or Dsnecton & Destructon ..........................................5-65.3.4 Dsnecton System Observatons .................................................................................5-7
5.4 Sorpton Technologes ............................................................................................................5-75.4.1 Ion exchange (IX) ...........................................................................................................5-85.4.2 Actvated Alumna (AA) and Iron-based Meda ..............................................................5-8
5.4.3 Powdered Actvated Carbon/Granular Actvated Carbon (PAC/GAC) ............................5-85.5 Lme Sotenng .......................................................................................................................5-95.6 Aordablty o Recommended Treatment Technologes and Protectveness o Publc Health
by Varance Technologes or Small Systems .........................................................................5-95.7 Pont-o-Use/Pont-o-Entry (POU/POE) Applcatons ..........................................................5-10
5.7.1 POU/POE Treatment Cost ...........................................................................................5-115.7.2 Use o POU/POE Treatment and Bottled Water n Small Systems ..............................5-11
5.8 Key Questons ......................................................................................................................5-135.9 Reerences ...........................................................................................................................5-13
6.0 Dstrbuton Systems ....................................................................................................................6-16.1 Dstrbuton System Overvew ................................................................................................6-16.2 Dstrbuton System Issues .....................................................................................................6-16.3 Inrastructure Issues ..............................................................................................................6-16.4 Operatonal Issues .................................................................................................................6-2
6.4.1 Bolm Growth................................................................................................................6-26.4.2 Ntrcaton .....................................................................................................................6-36.4.3 Fnshed Water Storage and Agng ................................................................................6-4
6.5 Contamnaton Events ............................................................................................................6-46.5.1 Cross-connecton Control ..............................................................................................6-46.5.2 Permeaton and Leachng ..............................................................................................6-56.5.3 Intruson and Inltratons ................................................................................................6-6
6.6 Dstrbuton System Summary................................................................................................6-66.7 Key Questons ........................................................................................................................6-76.8 Reerences .............................................................................................................................6-7
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7.0 Waste Resduals Generated by Small Systems ..........................................................................7-17.1 Introducton ............................................................................................................................7-17.2 Types o Waste Resduals and Dsposal ................................................................................7-17.3 Lqud Resduals Handlng & Dsposal ...................................................................................7-1
7.3.1 Drect Dscharge o Lquds ............................................................................................7-27.3.2 Indrect Dscharge o Lquds .........................................................................................7-3
7.3.3 Land Dsposal o Lquds ................................................................................................7-37.4 Sold Resduals ......................................................................................................................7-47.4.1 Land Dsposal o Solds .................................................................................................7-47.4.2 Land Applcaton o Solds .............................................................................................7-47.4.3 Incneraton o Solds and Lquds ..................................................................................7-4
7.5 Technologcally Enhanced Normally Occurrng Radoactve Materal (TENORM) Resduals 7-47.6 Conclusons and Future Research .........................................................................................7-57.7 Key Questons ........................................................................................................................7-57.8 Reerences .............................................................................................................................7-5
8.0 Homeland Securty/Emergency Response ..................................................................................8-18.1 Background and Drectves ....................................................................................................8-1
8.1.1 Boterrorsm Act .............................................................................................................8-18.1.2 Homeland Securty Presdental Drectve (HSPD)-7 - Crtcal Inrastructure Identcaton,
Prortzaton, and Protecton ..........................................................................................8-18.1.3 HSPD-8 - Natonal Preparedness ..................................................................................8-18.1.4 HSPD-9 - Deense o Unted States Agrculture and Food ...........................................8-18.1.5 HSPD-10 - BoDeense or the 21st Century ................................................................8-18.1.6 EPAs Strategc Plan or Homeland Securty ..................................................................8-2
8.2 EPAs Homeland Securty and Emergency Response Intatves and Resources ..................8-28.3 Threats and Rsks to the Water Supply ..................................................................................8-3
8.3.1 Chemcal and Radologcal Contamnants .....................................................................8-38.3.2 Bologcal Contamnants ................................................................................................8-38.3.3 Rsk Assessment and Mtgaton ....................................................................................8-3
8.4 Response Protocol Toolbox....................................................................................................8-38.5 Recommended Procedures or Securng Small Systems ......................................................8-48.6 Inrastructure and Bulk Water ................................................................................................8-4
8.7 Telemetry ...............................................................................................................................8-58.8 Early Warnng Systems or Drnkng Water Systems .............................................................8-58.9 Dsnecton n Dstrbuton Systems .......................................................................................8-68.10 Preparedness Assessment or Handlng Threats ...................................................................8-68.11 Local/State Emergency Plannng Commttees .......................................................................8-78.12 Alternatve Drnkng Water Supples n the Event o an Incdent ............................................8-78.13 Key Questons ........................................................................................................................8-88.14 Reerences .............................................................................................................................8-8
9.0 Remote Montorng and Control ...................................................................................................9-19.1 Introducton ............................................................................................................................9-19.2 Ratonale or Onlne Montorng .............................................................................................9-19.3 Selecton and Implementaton o Supervsory Control and Data Acquston (SCADA) Systems .. 9-19.4 Fundamentals o SCADA .......................................................................................................9-3
9.4.1 Montorng Equpment ....................................................................................................9-39.4.2 Control Equpment .........................................................................................................9-49.4.3 Data Collecton and Processng Unt(s) .........................................................................9-49.4.4 Communcaton Meda and Feld Wrng ........................................................................9-4
9.5 Remote Telemetry Applcatons or Small Systems ................................................................9-49.5.1 West Vrgna Remote Montorng Case Study ...............................................................9-49.5.2 Puerto Rco Remote Montorng Case Study .................................................................9-5
9.6 General Securty Issues wth Remote Montorng .................................................................9-79.7 Contamnaton Warnng Systems ...........................................................................................9-79.8 Key Questons ........................................................................................................................9-79.9 Reerences .............................................................................................................................9-7
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10.0 Summary ...................................................................................................................................10-110.1 Introducton ..........................................................................................................................10-110.2 Memorandum o Understandng (MOU) wth the Natonal Rural Water Assocaton (NRWA) ..... 10-110.3 Chapter-Specc Key Questons ..........................................................................................10-1
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List of Figures
Fgure 2.1 PWSs by system type ......................................................................................................2-2Fgure 2.2 Small systems by system type - FY2004 .........................................................................2-2Fgure 2.3 Number o people served by system type - All systems FY2004 ....................................2-2Fgure 2.4 Number o PWSs or each servce populaton group .......................................................2-3Fgure 2.5 Populaton served, servce connectons and number o systems - CWSs only FY2004 .2-3Fgure 2.6 Drnkng water system owners FY 2004-159,796 total systems ...................................2-4Fgure 2.7 Volatons reported FY2005 .............................................................................................2-4Fgure 2.8 Drnkng water system volatons or all system szes - FY2005 ......................................2-5Fgure 2.9 Volatons reported or systems servng populaton rom 25-10,000 - FY2005 ......................2-5Fgure 2.10 MCL volatons vs. populatons served FY2005 ...............................................................2-6Fgure 2.11 Source water comparson by sze category .....................................................................2-6Fgure 2.12 Percentage o ground water plants usng each treatment technque ...............................2-7Fgure 2.13 Percentage o surace water plants usng each treatment technque ..............................2-7Fgure 2.14 Percentage o mxed plants usng each treatment technque ..........................................2-8Fgure 2.15 Percentage o CWSs wthn each system servce populaton category that have a
clearwell type nshed water storage .............................................................................2-15
Fgure 2.16 Average number o mles o dstrbuton mans (publc vs. prvate systems) ..................2-16Fgure 2.17 Publc vs. prvate average annual ppe replaced (or CWSs) 5-year average ................2-17Fgure 2.18 System servce connectons ..........................................................................................2-18Fgure 2.19 Average number o mles o ppes n dstrbuton systems prvately owned .......................2-18Fgure 2.20 Average number o mles o ppes n dstrbuton systems publcly owned ........................2-19Fgure 2.21 Percentage o ppe n each age category or CWSs ......................................................2-19Fgure 2.22 Percentage o Ppe n Each Age Category by Source or CWSs...................................2-20Fgure 2.23 Percentage o ground water CWS plants (lackng 24/7 operator presence) that have
SCADA systems or process montorng or control........................................................2-21Fgure 2.24 Percentage o surace water CWS plants (lackng 24/7 operator presence) that have
SCADA systems or process montorng or control........................................................2-21Fgure 3.1 Structure o the DWSRF program ...................................................................................3-7
List of Tables
Table 2.1 Technologes or norganc contamnants ......................................................................2-11Table 2.2 Technologes or volatle organc contamnants .............................................................2-11Table 2.3 Technologes or synthetc organc contamnants ..........................................................2-12Table 2.4 Technologes or radonucldes ......................................................................................2-12
Table 2.5 Technologes or dsnecton ..........................................................................................2-13Table 2.6 Technologes or ltraton ...............................................................................................2-13Table 2.7 Complance technology or the Total Colorm Rule .......................................................2-14Table 2.8 Percentage o CWSs (wthn each system servce populaton category) that have treated-
water storage, beore dstrbuton system. .....................................................................2-15Table 2.9 Percentage o CWSs (wthn each system servce populaton category) that have treated-
water storage wthn the dstrbuton system. .................................................................2-15Table 2.10 System servce connectons by system owner ..............................................................2-20Table 3.1 Reduced montorng or radonucldes .............................................................................3-6Table 5.1 Surace Water Treatment Rule complance technologes or dsnecton ........................5-1Table 5.2 Surace Water Treatment Rule complance technologes or ltraton ..............................5-2Table 5.3 Summary o dsnectant characterstcs relatng to bocdal ecency ..................................... 5-5Table 5.4 Key Feature Summary o commonly used POU/POE technologes ..............................5-12
Table 9.1 Amenablty o treatment technologes to remote montorng used or small water ...................9-2Table 9.2 Cost estmates o SCADA system components ..............................................................9-5Table 9.3 Puerto Rco remote montorng system component costs ...............................................9-6
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Fgure 5.1 Partcle sze dstrbuton o common contamnants and assocated ltraton technology....5-3Fgure 5.2 Clogged Prelter ..............................................................................................................5-3Fgure 6.1 Dstrbuton System as a Reactor ..................................................................................6-3Fgure 6.2 Negatve Pressure Transent Assocated wth a Power Outage .......................................6-6Fgure 7.1 Federal regulatons governng the dsposal o resduals..................................................7-2Fgure 9.1 Possble layout o remote montorng system ..................................................................9-3
Fgure 9.2 Schematc layout o the small sytstem n San German, Puerto Rco ..............................9-6
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AA Actvated Alumna
ABPA Amercan Backfow PreventonAssocaton
ANSI Amercan Natonal StandardsInsttute
AOP Advanced Oxdaton Processes
APG Annual Perormance Goal
APM Annual Perormance Measure
ASCE Amercan Socety o Cvl Engneers
ASDWA Assocaton o State Drnkng WaterAdmnstrators
AWQC Ambent Water Qualty Crtera
AWWA Amercan Water Works Assocaton
BAT Best Avalable Technology
BMP Best Management Practces
CCL Contamnant Canddate Lst
CESQG Condtonally Exempt Small QuanttyGenerator
CFR Colorm Rule
CSO Combned Sewer Overfows
CT Contact Tme
CWA Clean Water Act
CWS Communty Water System
DBP Dsnecton By-Product
DBPR Dsnecton By-Product RuleDE Datomaceous Earth
DHS Department o Homeland Securty
DWSRF Drnkng Water State Revolvng Fund
EBCT Empty Bed Contact Tme
ED Electrodalyss
EPA Envronmental Protecton Agency
EPCRA Emergency Plannng and CommuntyRght-to-Know Act
EPTDS Entry Pont to the DstrbutonSystem
ERP Emergency Response Plan
ETV Envronmental TechnologyVercaton
FBRR Flter Backwash Recycle Rule
GAC Granular Actvated Carbon
GFH Granular Ferrc Hydroxde
GPM Gallons per Mnute
GWUDI Ground Water Under Drect Infuence
HAA5 Haloacetc Acds
Acronyms and Abbreviations
HFGP Horzontal Flow Gravel Prelter
HSPD Homeland Securty PresdentalDrectve
IT Inormaton TechnologyIUP Intended Use Plan
IX Ion Exchange
LEPC Local Emergency PlannngCommttee
LGR Local Government Rembursements
LLRW Low-level Radoactve Waste
LT1ESWTR Long Term 1 Enhanced SuraceWater Treatment Rule
LT2ESWTR Long Term 2 Enhanced SuraceWater Treatment Rule
M/R Montorng and Reportng
MCL Maxmum Contamnant Level
MCLG Maxmum Contamnant Level Goal
MF Mcroltraton
MGD Mllon Gallons per Day
MHI Medan Home Income
MOU Memorandum o Understandng
MRDLG Maxmum Resdual Dsnectant LevelGoal
MTBE Methyl Tertary Butyl Ether
MWCO Molecular Weght Cut-oNAS Natonal Academy o Scence
NDWAC Natonal Drnkng Water AdvsoryCouncl
NDWC Natonal Drnkng WaterClearnghouse
NRMRL Natonal Rsk ManagementResearch Laboratory
NF Nanoltraton
NHSRC Natonal Homeland SecurtyResearch Center
NIPDWR Natonal Interm Prmary DrnkngWater Regulatons
NOM Natural Organc Matter
NPDES Natonal Polluton DschargeElmnaton System
NPDWR Natonal Prmary Drnkng WaterRegulatons
NRC Natonal Research Councl (alsoused or Nuclear RegulatoryCommsson n Chapter )
NRWA Natonal Rural Water Assocaton
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NSDWR Natonal Secondary Drnkng WaterRegulaton
NSF Natonal Santaton Foundaton
NTNCWS Non-Transent Non-Cmmunty WaterSystem
NTU Nephelometrc Turbdty Unts
O3 Ozone
O&M Operaton and Mantenance
OCMS Onlne Contamnant MontorngSystem
OEM Oce o Emergency Management
ORD Oce o Research and Development
PAC Powdered Actvated Carbon
PDCO Pore Dameter Cut-o
PDD Presdental Decson Drectve
POE Pont-o-Entry
POTW Publcly Owned Treatment WorksPOU Pont-o-Use
ppb Parts per bllon
PTA Packed Tower Aeraton
PVC Polyvnyl Chlorde
PWS Publc Water System
RCRA Resource Conservaton andRecovery Act
RD Reerence Dose
RMCL Recommended MaxmumContamnant Level
RO Reverse Osmoss
RPTB Response Protocol Toolbox
SAB Scence Advsory Board
SBA Strong Base Anon
SCADA Supervsory Control and DataAcquston
SDWA Sae Drnkng Water Act
SDWIS State Drnkng Water InormatonSystem
SEMS Securty Emergency ManagementSystems
SEMS/ICS Standardzed EmergencyManagement System/IncdentCommand System
SSCT Small System ComplanceTechnology
SSF Slow Sand Flter
SWAP Source Water Assessment Plan
SWP Source Water Protecton
SWR Sold Waste Resduals
SWTR Surace Water Treatment Rule
TCLP Toxcty Characterstc LeachngProcedure
TCR Total Colorm Rule
T&E Test and Evaluaton
TENORM Technologcally Enhanced NaturallyOccurrng Radoactve Materal
THM Trhalomethane
TMDL Total Maxmum Daly Load
TNCWS Transent Communty Water System
TOC Total Organc Carbon
TT Treatment Technque
TTHM Total Trhalomethanes
UCMR Unregulated ContamnantsMontorng Rule
UF Ultraltraton
USACE Unted States Army Corps oEngneers
UV Ultravolet lght
VA Vulnerablty Assessment
VOC Volatle organc compound
WBA Weak Base Anon
WHP Well Head Protecton
WHPA Well Head Protecton Area
WHPP Well Head Protecton Plan
WSD Water Securty Dvson
WSWRD Water Supply and Water ResourcesDvson
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Ths report was submtted n partal ulllment o contract number EP-C-04-034 WA1-03 and 2-03 by
Shaw Envronmental, Inc. under the sponsorshp o the Unted States Envronmental Protecton Agency.
The authors extend ther thanks to EPA Regon 5 revewers: Ronald Kovach, Mguel Del Toral, Sahba
Rouhan, and Wllam Spauldng. The authors would also lke to thank Erc Bssonette, Jenny Belansk,
and Francne St. Dens n the EPAs Oce o Water or ther comments. Lastly, the authors extend ther
deepest apprecaton to the Natonal Rural Water Assocaton, speccally Jerry Bberstne and Dr. John
Regner or ther comments and suggestons. Collaboraton wth NRWA s made possble through a
Memorandum o Understandng between the EPA and NRWA.
Acknowledgements
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Chapter 1Introduction
1.1 Goals and Objectves o ths
DocumentThe objective o this document is to summarize the
existing status o drinking water supply in the United
States (U.S.) with particular emphasis on small sys-
tems (i.e., systems serving less that 10,000 people).
This document will then orm the backdrop to crat a
research plan that will serve as a roadmap or research-
ers in the U.S. Environmental Protection Agen-
cys (EPAs), Oce o Research and Development
(ORD), Water Supply and Water Resources Division
(WSWRD) by providing ocus and direction to the
WSWRDs research eorts. Specically, the Strategy
or Small Systems Research aims to:
Provide timely and appropriate research that willcontribute to small system management schemesor reducing Sae Drinking Water Act (SDWA)violations and public health risks.
Chart a research course that will drive newtechnologies and improve existing technologieswith emphasis on costs/benets (reduce costsand increase simplicity).
This strategy document ocuses on the current state o
the ollowing items as they pertain to small systems
and on the direction o uture research activities orthese items:
Source water issues
Monitoring/Reporting
Treatment processes
Distribution systems
Residuals Management
Homeland Security
Overall Utility Management
All research planning in the document should be in
the context o the six-year review o National Primary
Drinking Water Regulations (NPDWR) and the ve-
year update o the Contaminant Candidate List (CCL).
Note that the last NPDWR review was in August 2002
and the last CCL update was in February 2005.
1.2 Document OrganzatonThis document is organized into the ollowing sec-
tions:
Chapter 1 Introduction This section presents a
brie introduction to this report
Chapter 2 Current Status and Issues o Small
Drinking Water Systems
Chapter 3 Regulatory Background This section
presents a brie background o the
regulations impacting operators o small
drinking water systems
Chapter 4 Source Water Issues
Chapter 5 Treatment Processes
Chapter 6 Distribution Systems
Chapter 7 Waste Residuals
Chapter 8 Homeland Security/Emergency Response
Chapter 9 Remote Telemetry
Chapter 10 Summary
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Chapter 2Current Status andIssues o Small
Drinking WaterSystems
2.1 IntroductonThis Chapter provides an introduction to the current
status o small drinking water systems and the issues
acing small systems in maintaining compliance and
providing sae drinking water to the populace served
by these systems. The chapter begins with a detailed
snapshot prole (Section 2.2) o the distribution o
small systems based on the number o people served
and then provides brie overviews on the compliance
status (Section 2.3) o these small systems and source
water issues (Section 2.4). This chapter also provides
a brie introduction to the ollowing topics:
Common technologies currently used by smallsystems to treat source water to meet drinkingwater standards (Sections 2.5, 2.6, 2.7 and 2.8),
Distribution system inrastructure (including
storage acilities, pumping acilities and
distribution lines) currently employed by small
systems (Section 2.9),
Status o the use o remote telemetry to monitor
small systems operation (Section 2.10)
Key questions to be answered through ongoing
research (Section 2.11)
2.2 Prole o Small Systems n theU.S.
The EPAs Sae Drinking Water Inormation System
(SDWIS) estimates that there are 159,796 public
water systems (PWSs) in the U.S. (EPA, 2005a). The
SDWIS is a living database and portions o it are pe-
riodically updated. The prole data presented in thissection includes a conglomeration o data extracted
periodically rom the SDWIS during the preparation
o this report (between 2004 and 2005). Depend-
ing upon when the data was extracted and when the
underlying SDWIS was updated, the exact numbers
and percentages or individual categories described
in the gures may vary slightly. However, the over-
all trends and statistics are consistent throughout the
period during which the SDWIS was updated. Most
o the SDWIS updates were perormed between the
years 2000 and 2005; where inormation is available,
the specic year o the data presented is clearly identi-
ed. Unless otherwise stated, the graphs and statistics
relating to system types, population served, ownership,
violations, sizes, treatment scheme, piping distance
were all developed using the Pivot tables underlying
SDWIS (EPA, 2005b). Pivot tables are multidimen-sional spreadsheets/databases that provide analytical
processing capability. The Pivot tables allow or quick
summarization, cross-tabulation, and analysis o large
amounts o data.
A PWS is any water system which provides water to
at least 25 people or at least 60 days annually. These
PWSs provide water rom wells, rivers and other
sources to the majority (~85%) o the population in
the U.S. and territories (EPA, 2005b). The PWSs are
classied as ollows:
Community Water Systems (CWS) A watersystem which supplies drinking water to 25 ormore o the same people year-round in theirresidences.
Non-Transient Non-Community Water Systems(NTNCWS) A water system which supplieswater to 25 or more o the same people atleast six months per year in places other thantheir residences. Some examples are schools,actories, oce buildings, and hospitals thathave their own water systems.
Transient Non-Community Water Systems
(TNCWS) A water system which provideswater in a place such as a gas station orcampground where people do not remain orlong periods o time. These systems do not haveto test or treat their water or contaminants thatpose long-term health risks because ewer than25 people drink the water over a long period (6months/year). They still must test their wateror microbes and several chemicals.
There are diering standards or PWSs o dierent
sizes and types. Most (approximately 55%) o the
PWSs in the U.S. belong to the TNCWS variety (EPA,
2005b). Figure 2.1 illustrates the percentage break-down o the dierent system types. Most o these
systems represent the very small category (serving 25
500 people). Figure 2.2 shows the breakdown o
the number o small systems by system type. For the
purposes o this document, a small system is dened
as a CWS, NTNCWS, or TNCWS serving ewer than
10,000 persons (please note that a PWS serving 3001-
10,000 persons may be reerenced as medium in some
graphics).
While most o the PWSs are TNCWSs, the vast majority
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o people using PWSs actually obtain their water rom
CWSs. As illustrated in Figure 2.3, approximately
90% o all people using public drinking water systems
obtain their water rom CWSs. Figure 2.4 shows the
breakdown o system types by population category.
As indicated, approximately 84% o CWSs serve
populations o 3,300 or less. TNCWSs are mostlyrepresented in the very small category.
There are 159,796 CWSs, which includes both large
and small systems. There exists a great discrepancy
between the number o systems and the distribution o
the population served. Very small CWSs account or
57% o the total number o systems, although these
33%
12%
55%CWS
NTNCWS
TNCWS
Figure 2.1 PWSs by system type (EPA,2005b).
System Type
NumberofSystems
Very Small (25-500)
Small (501-3300)
Medium (3301-10,000)
30,
006
14,
212
4,707
16,545
2,720
96
84,
750
2,700
110
0
10,000
20,000
30,000
40,000
50,000
60,000
70,000
80,000
90,000
CWS NTNCWS TNCWS
Figure 2.2 Small systems by system type - FY2004 (EPA, 2005b).
272,
495,
677
5,
933,
320
18,
484,
66
0
0
50,000,000
100,000,000
150,000,000
200,000,000
250,000,000
300,000,000
Numbero
fSystems
CWS NTNCWS TNCWS
Figure 2.3 Number o people served by system type - All systems FY2004 (EPA, 2005b).
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systems serve less than 2 percent o the population
served by CWSs. In contrast, the large and very large
systems account or roughly 7 percent o the total
number o systems but serve over 80% o the popula-
tion. Figure 2.5 shows a breakdown o population
served, number o service connections, and number o
systems or CWSs by system size.
PWSs are owned by various governmental, tribal, pub-
lic, or private entities. There is a relationship between
system size and ownership, with the vast majority o
very small systems (25-500 persons served) being
privately owned and a majority o larger systems being
owned by local government. Figure 2.6 shows the
breakdown o ownership or all systems.
CWS
NTNCWS
TNCWS
30
,006
16
,545
84
,740
14
,212
2,
720
2,
700
4,
707
96
110
3,
541
14
29
372
0 4
0
10,000
20,000
30,000
40,000
50,000
60,000
70,000
80,000
90,000
NumberofSystem
s
Very Small
(25-500)
Small
(501-3,300)
Medium
(3,301-10,000)
Large
(10,001-100,000)
Very Large
(>100,000)
System Type
Figure 2.4 Number o PWSs or each service population group (EPA, 2005b).
0
20,000,000
40,000,000
60,000,000
80,000,000
100,000,000
120,000,000
140,000,000
System Size
Population/NumberofService
Connections
0
5,000
10,000
15,000
20,000
25,000
30,000
35,000
Number
ofSystems
2,594,626 7,333,945 9,473,250 32,152,151 32,984,472
4,957,131 20,137,604 27,346,264 99,808,668 120,246,010
30,006 14,212 4,707 3,541 372
Very Small Small Medium Large Very Large
Service Connections
Population
Systems
Figure 2.5 Population served, service connections and number o systems - CWSs onlyFY2004 (EPA, 2005b).
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2.3StatusofDrinkingWaterPlant
ViolationsThe SDWIS classifes drinking water system violations
into the ollowing our major categories:
Maximum contaminant level (MCL) violations;
Chapter 3 discusses MCLs in detail.
Treatment Technique (TT) violations; according
to EPA, a treatment technique is a required
process intended to reduce the level o a
contaminant in drinking water. A ew examples
o treatment techniques are disinection,
fltration, and aeration (urther discussed in
Chapter 3).
Monitoring or Reporting (M/R) Violations.
These violations are primarily record-keeping
issues.
Violations other than the three types mentioned
above.
Figure 2.7 shows the breakdown o system violations
or all PWSs. This fgure shows that most PWS viola-
tions are attributed to M/R.
Figure 2.8 shows system violations by population
served, number o systems, and violation type. Verysmall systems have the largest number o violations,
with the vast majority o these being M/R violations.
Figure 2.9 shows the breakdown o system violations
or small systems. Figure 2.9 looks very similar to
Figure 2.8 because the total violation statistics are
overwhelmingly dominated by small systems. Very
0
2,000
4,000
6,000
8,000
10,000
12,000
14,000
16,000
100,000
NumberofSystems
Very Small 25-500
Small 501-3,300
Medium 3,301-10,000
Large 10,001-100,000
Very Large >100,000
Federal Govt Local Govt Tribal Govt Private Public/Private State Govt Unknown
3,374 14,522 583 101,108 5,580 4,328 1,796
307 10,755 210 6,210 885 959 306
106 3,681 32 658 145 130 161
71 2,878 6 407 69 43 110
0 312 0 53 6 4 1
Figure 2.6 Drinking water system owners FY 2004-159,796 total systems (EPA, 2005b).
7.90%
0.0004%
1.67%
86.02%
4.40%
MCL
Maximum Residual DisinfectantLevel
Treatment Technique
Monitoring or Reporting
Other
Figure 2.7 Violations reported FY2005 (EPA, 2005b).
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small systems also experience the greatest number o
MCL and TT violations. In addition, PWSs experi-
enced a total o 145,962 MCL violations (2005 data),
with 135,495 (93%) o the violations attributed to
small systems (population served less than 3,300).
Figure 2.10 illustrates the relationship between the
number o MCL violations and population served.
Very small systems (those serving 25 to 500 people)
experience approximately one MCL violation orevery 80 persons served, which is the highest ratio o
all system service population categories. In compari-
son, very large systems (population served greater
than 100,000) experience approximately one MCL
violation or every 196,204 persons served.
2.4 Source Water IssuesPWSs obtain drinking water rom either surace or
ground water sources. Over 90% o the PWSs obtain
their water rom ground water sources, with a vast
majority (87%) o those using ground water being
represented by small systems (serving a populationless than 3,300). Figure 2.11 shows the distribution o
water sources, by each o the ve size categories.
Source waters rom streams, rivers, lakes, or aquiers
are used to supply private water systems and PWSs.
The source water moves within a watershed via
overland fow (i.e., surace water), shallow subsurace
storm fow or ground water fow. The surace water
is vulnerable to contamination rom both surace
runo and ground water inltration. Ground water
can become contaminated through inltration rom
the surace, incursion o contaminants rom under-
ground storage tanks, septic systems, injection wells,
or by naturally occurring substances in the soil or rock
through which it fows. These issues are discussed in
urther detail in Chapter 4.
2.5 Common Current TreatmentTechnologes
Most PWSs treat drinking water so that it will be sae
and palatable or the consumer. The application o a
specic TT depends on source water quality, system
size, and operator sophistication. Figures 2.12, 2.13
and 2.14 illustrate the variety and percent predomi-
nance o individual TTs used by the dierent size
classes o PWSs.
Very Small 25-500
Small 501-3,300
Medium 3,301-10,000
Large 10,001-100,000
Very Large >100,000
115861
19634
5136
5111
220
5 20 0 01
5732
8535
2733
3320
519
1307260
183057
43051
48078
7176
66847
10438
2366
1565
117
0
200000
400000
600000
800000
1000000
1200000
1400000
NumberofViolations
MCL MaximumResidual
Disinfectant Level
Treatment
Technique
Monitoring or
Reporting
Other
Figure 2.8 Drinking water system violations or all system sizes - FY2005 (EPA, 2005b).
7.90%
0.0004%
1.52%
86.11%
4.47%
MCL
Maximum Residual Disinfecta
Level
Treatment Technique
Monitoring or Reporting
Other
Figure 2.9 Violations reported or systems servingpopulation rom 25-10,000 - FY2005 (EPA, 2005b).
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0
5,000
10,000
15,000
20,000
25,000
30,000
35,000
40,000
45,000
NumberofViolations
0
5,000,000
10,000,000
15,000,000
20,000,000
25,000,000
30,000,000
35,000,000
40,000,000
PopulationinViolation
Violations
Population
Very Small
(25-500)
Small
(501-3,300)
Medium
(3,301-10,000)
Large
(10,001-100,000)
Very Large
(>100,000)
Figure 2.10 MCL violations vs. populations served FY2005 (EPA, 2005b).
125,5
87
5,704 1
5,514
4,
118
2,
826
2,
087
1,
493
2,
091
78
298
0
20,000
40,000
60,000
80,000
100,000
120,000
140,000
NumberofSystems
Very Small(25-500)
Small(501-3,300)
Medium(3,301-10,000)
Large(10,001-100,000)
Very Large(>100,000)
Ground Water
Surface Water
Figure 2.11 Source water comparison by size category (EPA, 2005b).
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Figure 2.12 Percentage o ground water plants using each treatment technique (EPA, 2002).
0
10
20
30
40
50
60
70
80
90
Percen
tage
100 orless
101-500
501-3,300
3,301-10,000
10,001-50,000
50,001-100,000
100,001-500,000
Over500,000
System Service Population
Disinfection with no
additional treatment
Other chemical addition
Ion exchange,
activated alumina,
aeration
Filtration other than
direct or conventional
Direct filtration
Conventional filtration
Membranes
Softening
Figure 2.13 Percentage o surace water plants using each treatment technique (EPA, 2002).
0
10
20
30
40
50
60
70
Percen
tage
System Service Population
100 orless
101-500
501-3,300
3,301-10,000
10,001-50,000
50,001-100,000
100,001-500,000
Over500,000
Disinfection with no
additional treatment
Other chemical addition
Ion exchange,
activated alumina,
aeration
Filtration other than
direct or conventional
Direct filtration
Conventional filtration
Membranes
Softening
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Figure 2.14 Percentage o mixed plants using each treatment technique (EPA, 2002).
0
10
20
30
40
50
60
70
80
90
100
Disinfection with no
additional treatment
Other chemical addition
Ion exchange,activated alumina,
aeration
Filtration other than
direct or conventional
Direct filtration
Conventional filtration
Membranes
Softening
Percentage
System Service Population
100 orless
101-500
501-3,300
3,301-10,000
10,001-50,000
50,001-100,000
100,001-500,000
Over500,000
The individual TTs are designed to be eective in
removing one or more types o contaminants includ-
ing particulate, chemical and biological contaminants.
Depending upon the type o contamination present in
the source water, one or more TTs may be applied by
the PWS to provide sae drinking water to consum-
ers. A general discussion o available TTs to remove
particulate (Section 2.6), chemical contaminants (Sec-
tion 2.7) and biological contaminants (Section 2.8)
is presented in this Chapter. A more comprehensive
discussion o TTs is presented in Chapter 5.
2.6 Partculate/Turbdty RemovalTechnologes
Particulate and turbidity removal is an almost univer-
sally used technology or the primary treatment o
drinking water. The primary means o particulate re-
moval is by means o simple ltration either by using
media ltration (e.g., sand lter) or by the use o bag
and/or cartridge lters. Advanced ltration techniques
include membrane ltration and other technologies.
This section provides a very brie overview o these
technologies.
2.6.1 Simple FiltrationFiltration is a process or removing particulate matter
rom water by passage through porous media. There
are numerous types o ltration processes. Some com-
mon ltration processes are summarized below (these
descriptions are available in many standard text books,
where applicable reerences have been provided or
specic usage and equipment descriptions):
Slow Sand Filtration is a process where untreatedwater percolates slowly down through a layero ne sand, then through a layer o gravel, andultimately collects in a system o underdrains.A biological layer or schmutzdecke orms onthe surace o the sand, trapping small particles.The schmutzdecke also helps to degrade organic
material in the water.Diatomaceous Earth (DE) also known as pre-
coat or diatomite ltration, can be used todirectly treat low turbidity raw water suppliesor chemically coagulated, more turbid watersources. DE lters consist o a pre-coat layer oDE, approximately 1/8-inch thick, supported bya septum or lter element (EPA, 1998).
Conventional Filtration is a method o treatingwater to remove particulates. The methodconsists o the addition o coagulant chemicals,fash mixing, coagulation-focculation,
sedimentation and ltration.
Direct Filtration also known as dead-endltration is similar to conventional ltrationwith the sedimentation process omitted.
Packaged Filtration consists o all o the ea-
tures o ltration chemical addition, focculation,
sedimentation, ltration mounted as a unit on a
rame or simple hookup o pipes and services. It
is most widely used to treat surace water supplies
or removal o turbidity, color, and coliorm organ-
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isms with ltration processes. Packaged ltration is
oten used to treat small community water supplies,
as well as supplies in recreational areas, state parks,
construction sites, ski areas, and military installations
(NDWC, 1996).
2.6.2 Advanced FiltrationMembrane Filtration Membrane ltration (as
dened under the Long Term 2 EnhancedSurace Water Treatment Rule-LT2ESWTR) isa pressure-driven separation process in whichparticulate matter larger than 1-micrometer isrejected by an engineered barrier, primarilythrough a size-exclusion mechanism and whichhas a measurable removal eciency or atarget organism that can be veried throughthe application o a direct integrity test (EPA,2003a). Some common types o membraneltration are:
Microltration is a pressure-driven membraneltration process that typically employshollow-ber membranes with a pore sizerange o approximately 0.1 0.2 micrometers(nominally 0.1 micrometers) (EPA, 2003a).
Ultraltration is a pressure-driven membraneltration process that typically employshollow-ber membranes with a pore size rangeo approximately 0.01 0.05 micrometer(nominally 0.01 micrometers) (EPA, 2003a).
Nanoltration is a pressure-driven membrane
separation process that employs the principleso reverse osmosis to remove dissolvedcontaminants rom water and is typicallyapplied or membrane sotening or the removalo dissolved organic contaminants (EPA,2003a).
2.6.3 Reverse Osmosis (RO)RO resembles membrane ltration processes in that
contamination rom water is removed by the use
o a membrane. However, unlike membrane ltra-
tion where water is orced through a media leaving
behind the contaminant, RO uses hydraulic pressure
to oppose the liquid osmotic pressure across a semi-permeable membrane, orcing the water rom the
concentrated solution side to the dilute solution side.
Thus, the RO membrane allows the passage o the
solvent (water) but not the dissolved solids (solutes).
Since the membrane is non-porous, the water does
not travel through pores, but rather dissolves into
the membrane, diuses across, and then dissolves
into the permeate (EPA, 1998b). RO can eectively
remove nearly all contaminants rom water includ-
ing arsenic (III), arsenic (V), barium, cadmium,
chromium (VI), radium, natural organic substances,
pesticides, and microbiological contaminants. The
liquid produced is demineralized water.
2.7 Chemcal ContamnantRemoval
Chemical contaminants are commonly removed using
ion exchange and sorption technologies. This sectionprovides a brie overview o these technologies along
with other TTs that are used to remove chemical con-
taminants in drinking water.
2.7.1 Ion Exchange (IX)Ion exchange involves the selective removal o charged
inorganic species rom water using an ion-specic
resin. The surace o the ion exchange resin contains
charged unctional groups that hold ionic species by
electrostatic attraction. As water containing undesired
ions passes through a column o resin beds, charged
ions on the resin surace are exchanged or the unde-
sired species in the water. The resin, when saturatedwith the undesired species, is regenerated with a solu-
tion o the exchangeable ion (EPA, 1998b).
Generally, resins can be categorized as anion exchange
or cation exchange resins. Anion exchange resins se-
lectively remove anionic species such as nitrate (NO3),
sulate (SO42), or fuoride (F) and exchange them
or hydroxyl (OH) or chloride (Cl) ions. Cation
exchange resins are used to remove undesired cations
such as cadmium (Cd2+) or Barium (Ba2+) rom water
and exchange them or protons (H+), sodium ions
(Na+) or potassium ions (K+) (EPA, 1998b). The pH
o the source water is important when employing IX
resins. For example, uranium exists in water at pH
levels o 6.0 and higher as a carbonate complex, which
is an anion, and thus has a strong anity or anion
resin in the chloride orm. The process is eective
on water with a pH o up to 8.2. A higher pH could
result in uranium precipitation; a lower pH changes
the nature o uranium to non-ionic and/or cationic spe-
cies, which would prevent the exchange reaction rom
operating eciently. It is advisable to control the inlet
water pH to above 6.0. Sudden pH changes to below
5.6 can dump any previously removed uranium o the
resin (DeSilva 1996).
2.7.2 Sorption TechnologiesAdsorption involves the removal o ions and molecules
rom solution and concentrating them on the surace
o adsorbents. Adsorption is driven by the interacial
orces o the ions and the adsorbent. Adsorption media
employed at drinking water plants include granular
activated carbon, activated alumina, and iron media.
Sorption technologies are used or the removal o
organics, taste and odor, and inorganic contaminants
(such as arsenic).
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2.7.3 Other Technologies
Aeration Technologies Aeration technologies aretypically used or removal o volatile organiccompounds and or removal o excess carbondioxide. In general, aeration is the contacting othe water with air wherein the target chemical
is transerred rom the water to the air stream.There are a number o methods used or themixing o air and water including packedaeration towers, shallow tray air strippers,mechanical aeration, and spray aeration.
Sotening Sotening is used to remove calciumand magnesium ions rom water. Types otechnologies used include ion exchange,chemical focculation, and precipitation.
Electrodialysis (ED) Another less commonlyused technology or chemical removal is ED,which is a process in which ions are transerred
through ion-selective membranes by means oan electromotive orce rom a less concentratedsolution to a more concentrated solution (EPA,2003a). ED is very eective in removingfuoride and nitrate, and can also remove barium,cadmium, and selenium (NDWC, 1997).
Reverse Osmosis Can remove many chemicalcontaminants eectively. See Section 2.6.3 orurther details.
2.8 Bologcal Contamnant
RemovalDisinection is a process or reducing the number opathogenic microbes in water and is required by the
Surace Water Treatment Rule (SWTR) or all PWSs
that obtain their water rom surace water or ground
water under the infuence o surace water. In addition,
PWSs must maintain a residual level o disinectant
in the distribution system per 40 CFR 141.72. It is
required that, at the point where the water enters the
distribution system, the residual disinection con-
centration not all below 0.2 mg/L. In addition, the
residual disinection concentration must be maintained
throughout the distribution system such that non-de-
tection results are measured in no more than 5% o thesamples collected each month.
2.8.1 ChlorinationChlorine is the most common method used or disin-
ection. There are a number o methods o delivery
and chemical reactions utilized or chlorination. These
include chlorine gas, chloramines, chlorine dioxide,
and sodium hypochlorite. The goal o all these meth-
ods is to release ree chlorine in the orm o hypochlo-
rite, or in the case o chloramines, combined available
chlorine (NH2Cl and NHCl2).
2.8.2 Ultraviolet Light (UV)Contaminated water is exposed to UV light, which
penetrates the cell walls o an organism. UV disrupts
the organisms genetic material which inactivates the
organism. A special lamp generates the radiation that
creates UV light by striking an electric arc through
low-pressure mercury vapor (low-pressure UV). Thislamp emits a broad spectrum o radiation with intense
peaks at UV wavelengths o 253.7 nanometers (nm)
and a lesser peak at 184.9 nm. Research has shown
that the optimum UV wavelength range to destroy bac-
teria is between 250 nm and 270 nm. At shorter wave-
lengths (e.g.185 nm), UV light is powerul enough to
produce ozone, hydroxyl, and other ree radicals that
destroy bacteria (NDWC, 2000).
2.8.3 OzoneOzone is a colorless, very unstable gas that is eective
as an oxidizing agent in removing bacteria with a rela-
tively short exposure time. Since the gas is unstableand has a very short lie, ozone generators are used to
produce ozone gas on site.
2.8.4 Other Disinection TechnologiesThere are a number o other disinection technologies
used in ultra pure water applications, but are not ap-
plicable nor typically used in water supply situations.
These include ammonium compounds, non-oxidizing
biocides (i.e. ormaldehyde), heat, and peracetic acid.
Tables 2.1, 2.2, 2.3, 2.4, 2.5 and 2.6 present candidate
technologies or treatment o inorganic contaminants,
volatile organic contaminants, synthetic organic con-taminants, radionuclides, disinection, and ltration
respectively. Table 2.7 identies compliance technol-
ogy or the Total Coliorm Rule.
2.9 Dstrbuton SystemInrastructure
Drinking water is delivered rom a water treatment
acility to its customers by means o a distribution
system. This inrastructure generally consists o a
combination o three key elements: treated water stor-
age acilities (e.g., ground storage tanks, elevated stor-
age tanks, standpipes, hydropneumatic tanks), pump-ing acilities (e.g., booster pumps, piping, control,
pump building), and the distribution lines (e.g., piping,
valves, re hydrants, meters). Most o the distribution
system inrastructure is located underground, making
it more dicult to detect problems such as leaks and
pipe deterioration. Various standards and procedures
or design, material selection, plumbing code, opera-
tion, and maintenance have been established that help
maintain the integrity o the system (EPA, 1999). The
distribution system issues acing small systems are
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Table 2.1 Technologies or inorganic contaminants (NDWC, undated).
Unit Technology Limitations*Operator Skill
Level Required Raw Water Quality Range
1. Actvated Alumna (a) AdvancedGround waters, competng anon concentratons wllaect run length.
2. Ion Exchange IntermedateGround waters wth low total dssolved solds, com-petng on concentratons wll aect run length.
3. Lme Sotenng (b) Advanced Hard ground and surace waters
4. Coagulaton/ Fltraton (c) Advanced Can treat wde range o water qualty.
5. Reverse Osmoss (RO) (d) Advanced Surace water usually requre preltraton.
6. Alkalne Chlornaton (e) Basc All ground waters.
7. Ozone Oxdaton Intermedate All ground waters.
8. Drect Fltraton Advanced Needs hgh raw water qualty.
9. Datomaceous Earth Fltraton Intermedate Needs very hgh raw water qualty.
10. Granular Actvated Carbon Basc Surace waters may requre preltraton.
11. Elecrodalyss Reversal Advanced Requres preltraton or surace water.
12. Pont o Use (POU)-IX () Basc Same as Technology #2.
13. POU-RO () Basc Same as Technology #5.
14. Calcum Carbonate Precptaton (g) Basc Water wth hgh levels o alkalnty and calcum.
15. pH and Alkalnty Adjustment(chemcal eed) (g) Basc All ranges.
16. pH and Alkalnty Adjustment(lmestone contactor) (h) Basc
Waters that are low n ron and turbdty. Raw watershould be sot and slghtly acdc.
17. Inhbtors Basc All ranges.
18. Aeraton () Basc Waters wth moderate to hgh carbon doxde content.
Limitation Footnotesa) Chemicals required during regeneration and pH adjustments may be dicult or small systems to handle.b) Sotening chemistry may be too complex or small systemsc) It may not be advisable to install coagulation/ltration solely or inorganics removal.d) I all o the infuent water is treated, post-treatment corrosion control will be necessary.e) pH must exceed pH 8.5 to ensure complete oxidation without build-up o cyanogen chloride.) When POU devices are used or compliance, programs or long-term operation, maintenance, and monitoring must be provided by water utility
to ensure proper perormance.g) Some chemical eeds require high degree o operator attention to avoid plugging.h) This technology is recommended primarily or the smallest size category.i) Any o the rst ve aeration technologies listed or volatile organic contaminants (Table 2.2) can be used.
Table 2.2 Technologies or volatile organic contaminants (NDWC, undated).
Unit TechnologyLimitations
(see ootnotes)Operator Skill Level
RequiredRaw Water
Quality Range
1. Packed Tower Aeraton (PTA) (a) Intermedate All ground waters.
2. Dused Aeraton (a,b) Basc All ground waters.
3. Mult-Stage Bubble Aerators (a,c) Basc All ground waters.
4. Tray Aeraton (a,d) Basc All ground waters.
5. Shallow Tray Aeraton (a,e) Basc All ground waters.
6. Spray Aeraton (a,) Basc All ground waters.
7. Mechancal Aeraton (a,g) Basc All ground waters.8. Granular Actvated Carbon (GAC) (h) Basc All ground waters.
Limitation Footnotesa) Pretreatment or the removal o microorganisms, iron, manganese, and excessive particulate matter may be needed. Post-treatment disinec-
tion may have to be used.b) May not be as ecient as other aeration methods because it does not provide or convective movement o the water thus limiting air-water
contact. It is generally used only to adapt existing plant equipment.c) These units are highly ecient; however, the eciency depends upon the air-to-water ratio.d) Costs may increase i a orced drat is used. Slime and algae growth can be a problem but can be controlled with chemcials such as copper
sulate or chlorine.e) These units require high air-to-water ratios (100-900 m3/m3).) For use only when low removal levels are needed to reach a MCL because these systems may not be as energy ecient as other aeration
methods because o the contacting system.g) For use only when low removal levels are needed to reach an MCL because these systems may not be as energy ecient as other aeration
methods. The units oten require large basins, long residence times, and high energy inputs, which may increase costs.h) See table 2.3 or limitations regarding these technologies.
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Table 2.3 Technologies or synthetic organic contaminants (NDWC, undated).
Unit TechnologyLimitations
(see ootnotes)Operator Skill Level
RequiredRaw Water Quality Range
and Considerations
1. Granular Actvated Carbon (GAC) (h) Basc Surace water may requre preltraton.
2. Pont o Use GAC (a, h) Basc Surace water may requre preltraton.
3. Powdered Actvated Carbon (b, h) Intermedate All waters
4. Chlornaton (c) Basc Better wth hgh qualty waters.
5. Ozonaton (c) Basc Better wth hgh qualty waters.
6. Packed Tower Aeraton (PTA) (d) Intermedate All ground waters.
7. Dused Aeraton (d,e) Basc All ground waters.
8. Mult-Stage Bubble Aerators (d,) Basc All ground waters.
9. Tray Aeraton (d,g) Basc All ground waters.
10. Shallow Tray Aeraton (d,) Basc All ground waters.
Limitation Footnotesa) When POU devices are used or compliance, programs or long-term operation, maintenance, and monitoring must be provided by water utility
to ensure proper perormance.b) Most applicable to small systems that already have a process train including basins, mixing, precipitation or sedimentation, and ltration. Site
specic design should be based on studies conducted on the systems particular water.c) See the Surace Water Treatment Rule compliance technology tables or limitations associated with this technology.d) Pretreatment or the removal o microorganisms, iron, manganese, and excessive particulate matter may be needed. Post-treatment disinec-
tion may have to be used.
e) May not be as ecient as other aeration methods because it does not provide or convective movement o the water thus limiting air-watercontact. It is generally used only to adapt existing plant equipment.
) These units are highly ecient; however, the eciency depends upon the air-to-water ratio.g) Forces may increase i a orced drat is used.h) Pretreatment or removal o suspended solids is an important design consideration. Spent carbon must be regenerated or disposed properly.
Table 2.4 Technologies or radionuclides (NDWC, undated).
Unit TechnologyLimitations
(see ootnotes)Operator Skill Level
RequiredRaw Water Quality Range
and Considerations
IX (a) Intermedate All ground waters.
Pont o Use (POU) IX (b) Basc All ground waters.
Reverse Osmoss (RO) (c) Advanced Surace waters, usually requre preltraton.
POU RO (b) Basc Surace waters, usually requre preltraton.
Lme Sotenng (d) Advanced All waters.
Green Sand Fltraton (e) Basc
Co-precptaton wth Barum Sulate ()Intermedate to
Advanced Ground waters wth sutable water qualty
Electrodalyss/Electrodalyss Reversal Advanced All ground waters.
Pre-ormed Hydrous ManganeseOxde Fltraton (g) Intermedate All ground waters.
Limitation Footnotesa) The regeneration solution contains high concentrations o the contaminant ions. Disposal options should be careully considered beore
choosing the technology.b) When POU devices are used or compliance, programs or long-term operation, maintenance, and monitoring must be provided by water utility
to ensure proper perormance.
c) Reject water disposal options should be careully considered beore choosing this technology. See other RO limitations described in the Sur-ace Water Treatment Rule Compliance Table.
d) The combination o variable source water quality and the complexity o the chemistry involved in lime sotening may make this technology toocomplex or small surace water systems.
e) Removal eciencies can vary depending on water quality.) This technology may be very limited in application to small systems. Since the process requires static mixing, detention basins, and ltration; it
is most applicable to systems with suciently high sulate levels that already have a suitable ltration treatment train in place.g) This technology is most applicable to small systems that already have ltration in place.
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Table 2.5 Technologies or disinection (NDWC, undated).
Unit TechnologyLimitations
(see ootnotes)Operator Skill
Level RequiredRaw Water Quality Range
and Considerations
Free Chlorne (a,b) BascBetter wth hgh qualty. Hgh ron or manganese may requresequestraton or physcal removal.
Ozone (c,d, h) Intermedate
Better wth hgh qualty. Hgh ron or manganese may requre
sequestraton or physcal removal.
Chloramnes (e) IntermedateBetter wth hgh qualty. Ammona dose should be temperedby natural ammona levels n water.
Chlorne Doxde () Intermedate Better wth hgh qualty.
Onste Oxdant Generaton (g) Basc Better wth hgh qualty.
Ultravolet (UV) Radaton (h) BascRelatvely clean source water requred. Iron, natural organcmatter and turbdty aect UV dose.
Limitation Footnotesa) Providing adequate CT may be a problem or some water supplies.b) Chlorine gas requires special caution in handling and storage, and operator training.c) Ozone leaks represent hazard: air monitoring required.d) Ozone used as primary disinectant (i.e., no residual protection).e) Long CT. Requires care in monitoring o ratio o added chlorine to ammonia.) Chlorine dioxide requires special storage and handling precautions.g) Oxidants other than chlorine not detected in solution by signicant research eort. CT should be based on ree chlorine until new research
determines appropriate CT values or electrolyzed salt brine.
h) No disinectant residual protection or distributed water.
Table 2.6 Technologies or ltration (NDWC, undated).
Unit TechnologyLimitations
(see ootnotes)Operator Skill Level
Required Raw Water Quality Range and Considerations
Conventonal Fltraton(ncludes dual-stage anddssolved ar fotaton (a) Advanced
Wde range o water qualty. Dssolved ar fotaton s moreapplcable or removng partculate matter that doesntreadly settle: algae, hgh color, low turbdty--up to 30-50nephelometrc turbdty unts (NTU) and low-densty turbdty.
Drect Fltraton (ncludesn-lne ltraton (a) Advanced
Hgh qualty. Suggested lmts: average turbdty 10 NTU;maxmum turbdty 20 NTU; 40 color unts; algae on a case-by-case bass.
Slow Sand Fltraton (b) BascVery hgh qualty or pretreatment. Pretreatment requred raw water s hgh n turbdty, color, and/or algae.
Datomaceous EarthFltraton (c) Intermedate
Very hgh qualty or pretreatment. Pretreatment requred raw water s hgh n turbdty, color, and/or algae.
Reverse Osmoss (d,e,) Advanced
Requres preltratons or surace water-may nclude re-moval o turbdty, ron, and/or manganese. Hardness anddssolved solds may also aect perormance.
Nanoltraton (e) IntermedateVery hgh qualty o pretreatment. See reverse osmosspretreatment.
Ultraltraton (g) Basc Hgh qualty or pretreatment.
Mcroltraton (g) Basc Hgh qualty or pretreatment requred.
Bag Fltraton (g,h,) Basc
Very hgh qualty or pretreatment requred, due to lowpartculate loadng capacty. Pretreatment hgh turbdtyor algae.
Cartrdge Fltraton (g,h,) Basc
Very hgh qualty or pretreatment requred, due to lowpartculate loadng capacty. Pretreatment hgh turbdty
or algae.
Backwashable DepthFltraton (g,h,) Basc
Very hgh qualty or pretreatment requred, due to lowpartculate loadng capacty. Pretreatment hgh turbdtyor algae.
Limitations Footnotesa. Involves coagulation. Coagulation chemistry requires advanced operator skill and extensive monitoring. A system needs to have direct ull-time
access or ull-time remote access to a skilled operator to use this technology properly.b. Water service interruptions can occur during the per iodic lter-to-waste cycle, which can last rom six hours to two weeks.c. Filter cake should be discarded i ltration is interrupted. For this reason, intermittent use is not practical. Recycling the ltered water can remove
this potential problem.d. Blending (combining treated water with untreated raw water) cannot be practiced at risk o increasing microbial concentration in nished water.e. Post-disinection recommended as a saety measure and or residual maintenance.. Post-treatment corrosion control will be needed prior to distribution.g. Disinection required or viral inactivation.h. Site-specic pilot testing prior to installation likely to be needed to ensure adequate perormance.i. Technologies may be more applicable to system serving ewer than 3,300 people.
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urther discussed in Chapter 6. The ollowing is a
brie description o each o the key distribution system
inrastructure elements.
2.9.1 Storage FacilitiesStorage acilities may be closed tanks or reservoirs and
are designed to store treated water (ground storage)
or to maintain adequate service pressure (elevated,hydropneumatic, or ground storage that is built at a
location to act as elevated storage).
A clearwell tank is generally the rst treated water stor-
age tank and is located at the end o the treatment train
or at the end o a well system. Their primary purpose is
to provide or contact time when chemical treatment ad-
ditives (e.g., chlorine) are used. These storage structures
have limited use as storage reservoirs due to their loca-
tion. The added storage or reserve capability o clear-
wells are an advantage or small system operators that
need time or maintenance o equipment or structures,
or other storage needs such as re fows, but this is nottheir intended use. Utilities should not rely on clearwell
storage as their only means o reserve or the distribution
system. The clearwell tank also serves as a reservoir
or the storage o ltered water o sucient capacity to
prevent the need to vary the ltration rate with varia-
tions in demand. Clearwell tanks provide both a treated
water reserve or delivery to the distribution system and
additional detention time or more eective disinec-
tion (EPA, 1999). Figure 2.15 shows the percentage o
CWSs that use clearwell tanks or treated-water storage.
Table 2.7 Compliance technology or the Total Coliorm Rule (NDWC, undated).
40 CFR 141.63(d) - Best technologies or othermeans to comply
(Complexity level indicated) Comments/Water Quality Concerns
Protectng wells rom contamnaton, e.g., place-ment and constructon o well(s) (Basc).
Ten State Standards and other standards (AWWA, 1995) apply; nteracngwth other programs essental (e.g., source water protecton program).
Mantenance o a dsnecton resdual or dstrbu-ton system protecton (Intermedate).
Source water consttuents may aect dsnecton: ron, manganese, organ-cs, ammona, and other actors may aect dosage and water qualty. TotalColorm Rule (TCR) remans unspecc on type/amount o dsnectant, aseach type ders n concentraton, tme, temperature, pH, nteracton wthother consttuents, etc.
Proper mantenance o dstrbuton system: pperepar/replacement, man fushng programs,storage/reservor, and O&M programs (ncludngcross-connecton control/backfow preventon),and mantenance o postve pressure throughout(Intermedate).
O&M programs partcularly mportant or smaller systems needng to man-tan water purty. States may vary on dstrbuton protecton measures.See also EPAs Cross-Connecton Control Manual (EPA, 2003b)
Fltraton and/or dsnecton o surace water orother ground water under drect nfuence; or dsn-ecton o ground water (Basc thru Advanced).
Same ssues as cted above under mantanng dsnecton resdual;pretreatment requrements aect complexty o operaton. Reer to SuraceWater Treatment Rule Complance Technology Lst; and other regulatonsunder development.
Ground waters: Complance wth State WellheadProtecton Program (Intermedate). EPA/State Wellhead Protecton Program mple