Small Drinking Water Systems: 

State of the Industry and 

Treatment Technologies to 

Meet the Safe Drinking Water Act 

Requirements

EPA/600/R-07/110 

September 2007 

Small Drinking Water Systems: 

State of the Industry and Treatment Technologies 

to Meet the Safe Drinking Water Act Requirements 

by 

Christopher A. Impellitteri, Craig L. Patterson, Roy C. Haught, and James A. Goodrich 

Water Supply and Water Resources Division 

National Risk Management Research Laboratory 

Cincinnati, OH 45268 

This report was compiled in cooperation with Shaw Environmental, Inc. 

Under EPA Contract EP-C-04-034 WA1-03 and WA 2-03 

Work Assignment Manager - Craig L. Patterson 

Water Supply and Water Resources Division 

National Risk Management Research Laboratory 

Cincinnati, OH 45268 

National Risk Management Research Laboratory 

Office of Research and Development 

U.S. Environmental Protection Agency 

Cincinnati, OH 45268 

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Notice

The EPA has not subjected this report to internal review. Therefore, the research results presented 

herein do not, necessarily, reflect Agency policy. Mention of trade names of commercial products does 

not constitute endorsement or recommendation for use. 

ii 
Abstract

This document summarizes the current national statistics for small drinking water systems (serving less 

than ten thousand people). It describes the current status of regulations, treatment technologies, source 

water issues, distribution system characteristics, waste residual issues, security/emergency response, 

and monitoring as these issues pertain to small systems. This objective of this document is to provide 

researchers in the Water Supply and Water Resources Division in the National Risk Management Research 

Laboratory with a basis to design and implement future research projects that will focus on the most 

pressing needs of small systems. The majority of this report includes data and information acquired 

between June 1, 2004 and October 1, 2005, and most of the work was completed on November 1, 2005. 

Section 5.6, related to small systems treatment option “affordability” and definition of “unreasonable risk 

to health,” presents more recent updates (performed in August 2006) based on reviewer comments. 

iii 
Foreword 

The U.S. Environmental Protection Agency (EPA) is charged by Congress with protecting the Nation’s 

land, air, and water resources. Under a mandate of national environmental laws, the Agency strives to 

formulate and implement actions leading to a compatible balance between human activities and the ability 

of natural systems to support and nurture life.To meet this mandate, EPA’s research program is providing 

data and technical support for solving environmental problems today and building a science knowledge 

base necessary to manage our ecological resources wisely, understand how pollutants affect our health, 

and prevent or reduce environmental risks in the future. 

The National Risk Management Research Laboratory (NRMRL) is the Agency’s center for investigation of technological and management approaches for preventing and reducing risks from pollution 

that threaten human health and the environment. The focus of the Laboratory’s research program is 

on methods and their cost-effectiveness for prevention and control of pollution to air, land, water, and 

subsurface resources; protection of water quality in public water systems; remediation of contaminated 

sites, sediments and ground water; prevention and control of indoor air pollution; and restoration of 

ecosystems. NRMRL collaborates with both public and private sector partners to foster technologies 

that reduce the cost of compliance and to anticipate emerging problems. NRMRL’s research provides 

solutions to environmental problems by: developing and promoting technologies that protect and 

improve the environment; advancing scientific and engineering information to support regulatory and 

policy decisions; and providing the technical support and information transfer to ensure implementation 

of environmental regulations and strategies at the national, state, and community levels. 

This publication has been produced as part of the Laboratory’s strategic long-term research plan. It is 

published and made available by EPA’s Office of Research and Development to assist the user community and to link researchers with their clients. 

Sally Gutierrez, Director 

National Risk Management Research Laboratory 

iv
Table of Contents 

1.0 Introduction..................................................................................................................................1-1 

1.1 Goals and Objectives of this Document.................................................................................1-1 

1.2 Document Organization .........................................................................................................1-1 

2.0 Current Status and Issues of Small Drinking Water Systems......................................................2-1 

2.1 Introduction ............................................................................................................................2-1 

2.2 Profile of Small Systems in the U.S........................................................................................2-1 

2.3 Status of Drinking Water Plant Violations...............................................................................2-4 

2.4 Source Water Issues..............................................................................................................2-5 

2.5 Common Current Treatment Technologies.............................................................................2-5 

2.6 Particulate/Turbidity Removal Technologies...........................................................................2-8 

2.6.1 Simple Filtration .............................................................................................................2-8 

2.6.2 Advanced Filtration ........................................................................................................2-9 

2.6.3 Reverse Osmosis (RO) .................................................................................................2-9 

2.7 Chemical Contaminant Removal............................................................................................2-9 

2.7.1 Ion Exchange (IX) ..........................................................................................................2-9 

2.7.2 Sorption Technologies....................................................................................................2-9 

2.7.3 Other Technologies ......................................................................................................2-10 

2.8 Biological Contaminant Removal .........................................................................................2-10

2.8.1 Chlorination..................................................................................................................2-10 

2.8.2 Ultraviolet Light (UV)....................................................................................................2-10 

2.8.3 Ozone ..........................................................................................................................2-10 

2.8.4 Other Disinfection Technologies...................................................................................2-10 

2.9 Distribution System Infrastructure........................................................................................2-10 

2.9.1 Storage Facilities..........................................................................................................2-14 

2.9.2 Pumping facilities.........................................................................................................2-16 

2.9.3 Distribution Lines .........................................................................................................2-16 

2.10 Remote Telemetry – Supervisory Control and Data Acquisition (SCADA) ..........................2-17 

2.11 Key Questions......................................................................................................................2-20 

2.12 References...........................................................................................................................2-22 

3.0 Regulatory Background ...............................................................................................................3-1 

3.1 Safe Drinking Water Act (SDWA) ...........................................................................................3-1 

3.2 SDWA Provisions...................................................................................................................3-1 

3.2.1 National Primary Drinking Water Regulations (NPDWR)...............................................3-1 

3.2.2 National Secondary Drinking Water Regulations (NSDWR)..........................................3-2 

3.2.3 Contaminant Candidate List (CCL)................................................................................3-2 

3.3 Current Regulatory Issues .....................................................................................................3-2 

3.3.1 Perchlorate.....................................................................................................................3-2 

3.3.2 Arsenic...........................................................................................................................3-2 

3.3.3 Compliance with Surface Water Treatment Rule............................................................3-3 

3.3.4 Stage 1 and 2 Disinfection Byproducts (DBP) Rules.....................................................3-4 

3.3.5 Proposed Ground Water Rule........................................................................................3-5 

3.3.6 Methyl Tertiary Butyl Ether (MTBE)................................................................................3-5 

3.3.7 Radionuclides ................................................................................................................3-5 

3.4 Source Water Assessments...................................................................................................3-6 

3.5 Wellhead Protection...............................................................................................................3-7 

3.6 Vulnerability Assessments (VA), Emergency Planning and Security .....................................3-7 

3.7 Variances and Exemptions ....................................................................................................3-8 

3.7.1 Small System Variances ................................................................................................3-8

3.7.2 Exemptions ....................................................................................................................3-8 

3.8 DWSRF .................................................................................................................................3-9 

3.9 Key Questions........................................................................................................................3-9 

3.10 References.............................................................................................................................3-9 

4.0 Source Water Issues....................................................................................................................4-1 

4.1 Background ...........................................................................................................................4-1 

4.2 Drinking Water Research Program Multi-Year Plan ...............................................................4-1 

v
1

2

3

4

5

6

7

4.2.1 Long-Term Goals ...........................................................................................................4-1 

4.2.2 Ongoing and Future Research ......................................................................................4-1 

4.3 Source Water Assessments...................................................................................................4-2 

4.3.1 Delineation.....................................................................................................................4-2 

4.3.2 Contamination Sources .................................................................................................4-2

4.3.3 Susceptibility Determination ..........................................................................................4-3

4.3.4 Public Involvement.........................................................................................................4-3 

4.3.5 Benefits of Source Water Assessment Plans (SWAPs).................................................4-3 

4.3.6 Source Water Protection................................................................................................4-3

4.4 Other Source Water Assessment and Protection Tools .........................................................4-3 

4.4.1 Sanitary Survey .............................................................................................................4-3 

4.4.2 Wellhead Protection Program (WHPP)..........................................................................4-3 

4.5 Sustainability of Community Water Systems (CWSs)............................................................4-4 

4.6 EPA Source Water Assessment and Protection Programs ....................................................4-4 

4.7 Key Questions........................................................................................................................4-4 

4.8 References.............................................................................................................................4-4 

5.0 Treatment Processes...................................................................................................................5-1 

5.1 Introduction ...........................................................................................................................5-1 

5.2 Packaged Filtration ...............................................................................................................5-1 

5.2.1 Filtration .........................................................................................................................5-2 

5.2.2 Bag Filtration..................................................................................................................5-3 

5.2.3 Cartridge Filtration .........................................................................................................5-4 

5.2.4 Membrane Filtration.......................................................................................................5-4 

5.2.5 Ultra Filtration (UF) ........................................................................................................5-4 

5.3 Disinfection ............................................................................................................................5-4 

5.3.1 Disinfection by Chlorination ...........................................................................................5-5 

5.3.2 Disinfection by Ozonation ..............................................................................................5-6 

5.3.3 Advanced Oxidation Process for Disinfection & Destruction..........................................5-6 

5.3.4 Disinfection System Observations .................................................................................5-7 

5.4 Sorption Technologies............................................................................................................5-7 

5.4.1 Ion exchange (IX)...........................................................................................................5-8 

5.4.2 Activated Alumina (AA) and Iron-based Media..............................................................5-8 

5.4.3 Powdered Activated Carbon/Granular Activated Carbon (PAC/GAC) ............................5-8 

5.5 Lime Softening.......................................................................................................................5-9 

5.6 Affordability of Recommended Treatment Technologies and Protectiveness of Public Health 

by Variance Technologies for Small Systems.........................................................................5-9 

5.7 Point-of-Use/Point-of-Entry (POU/POE) Applications ..........................................................5-10 

5.7.1 POU/POE Treatment Cost ...........................................................................................5-11 

5.7.2 Use of POU/POE Treatment and Bottled Water in Small Systems ..............................5-11 

5.8 Key Questions......................................................................................................................5-13 

5.9 References...........................................................................................................................5-13 

6.0 Distribution Systems....................................................................................................................6-1 

6.1 Distribution System Overview ................................................................................................6-1 

6.2 Distribution System Issues.....................................................................................................6-

6.3 Infrastructure Issues ..............................................................................................................6-1 

6.4 Operational Issues.................................................................................................................6-

6.4.1 Biofilm Growth................................................................................................................6-2 

6.4.2 Nitrification .....................................................................................................................6-

6.4.3 Finished Water Storage and Aging ................................................................................6-4 

6.5 Contamination Events............................................................................................................6-

6.5.1 Cross-connection Control ..............................................................................................6-4

6.5.2 Permeation and Leaching..............................................................................................6-

6.5.3 Intrusion and Infiltrations................................................................................................6-6 

6.6 Distribution System Summary................................................................................................6-

6.7 Key Questions........................................................................................................................6-7 

6.8 References.............................................................................................................................6-

vi
7.0 Waste Residuals Generated by Small Systems ..........................................................................7-1 

7.1 Introduction ............................................................................................................................7-1 

7.2 Types of Waste Residuals and Disposal ................................................................................7-1 

7.3 Liquid Residuals Handling & Disposal ...................................................................................7-1 

7.3.1 Direct Discharge of Liquids............................................................................................7-2

7.3.2 Indirect Discharge of Liquids .........................................................................................7-3

7.3.3 Land Disposal of Liquids................................................................................................7-3 

7.4 Solid Residuals ......................................................................................................................7-4 

7.4.1 Land Disposal of Solids .................................................................................................7-4 

7.4.2 Land Application of Solids .............................................................................................7-4 

7.4.3 Incineration of Solids and Liquids ..................................................................................7-4 

7.5 Technologically Enhanced Normally Occurring Radioactive Material (TENORM) Residuals 7-4 

7.6 Conclusions and Future Research.........................................................................................7-5 

7.7 Key Questions........................................................................................................................7-5 

7.8 References.............................................................................................................................7-5 

8.0 Homeland Security/Emergency Response..................................................................................8-1 

8.1 Background and Directives ....................................................................................................8-1 

8.1.1 Bioterrorism Act .............................................................................................................8-1 

8.1.2 Homeland Security Presidential Directive (HSPD)-7 - Critical Infrastructure Identification, 

Prioritization, and Protection..........................................................................................8-1 

8.1.3 HSPD-8 - National Preparedness..................................................................................8-1 

8.1.4 HSPD-9 - Defense of United States Agriculture and Food ...........................................8-1 

8.1.5 HSPD-10 - BioDefense for the 21st Century ................................................................8-1 

8.1.6 EPA’s Strategic Plan for Homeland Security..................................................................8-2 

8.2 EPA’s Homeland Security and Emergency Response Initiatives and Resources..................8-2 

8.3 Threats and Risks to the Water Supply..................................................................................8-3 

8.3.1 Chemical and Radiological Contaminants .....................................................................8-3 

8.3.2 Biological Contaminants ................................................................................................8-3 

8.3.3 Risk Assessment and Mitigation....................................................................................8-3 

8.4 Response Protocol Toolbox....................................................................................................8-3 

8.5 Recommended Procedures for Securing Small Systems ......................................................8-4 

8.6 Infrastructure and Bulk Water ................................................................................................8-4 

8.7 Telemetry ...............................................................................................................................8-5 

8.8 Early Warning Systems for Drinking Water Systems .............................................................8-5 

8.9 Disinfection in Distribution Systems.......................................................................................8-6 

8.10 Preparedness Assessment for Handling Threats...................................................................8-6 

8.11 Local/State Emergency Planning Committees.......................................................................8-7 

8.12 Alternative Drinking Water Supplies in the Event of an Incident ............................................8-7 

8.13 Key Questions........................................................................................................................8-8 

8.14 References.............................................................................................................................8-8 

9.0 Remote Monitoring and Control...................................................................................................9-1 

9.1 Introduction ............................................................................................................................9-1 

9.2 Rationale for Online Monitoring .............................................................................................9-1 

9.3 Selection and Implementation of Supervisory Control and Data Acquisition (SCADA) Systems.. 9-1 

9.4 Fundamentals of SCADA.......................................................................................................9-3 

9.4.1 Monitoring Equipment....................................................................................................9-3 

9.4.2 Control Equipment .........................................................................................................9-4 

9.4.3 Data Collection and Processing Unit(s) .........................................................................9-4 

9.4.4 Communication Media and Field Wiring ........................................................................9-4 

9.5 Remote Telemetry Applications for Small Systems................................................................9-4 

9.5.1 West Virginia Remote Monitoring Case Study...............................................................9-4 

9.5.2 Puerto Rico Remote Monitoring Case Study.................................................................9-5 

9.6 General Security Issues with Remote Monitoring .................................................................9-7 

9.7 Contamination Warning Systems...........................................................................................9-7 

9.8 Key Questions........................................................................................................................9-7 

9.9 References.............................................................................................................................9-7 

vii
10.0 Summary ...................................................................................................................................10-1 

10.1 Introduction ..........................................................................................................................10-1 

10.2 Memorandum of Understanding (MOU) with the National Rural Water Association (NRWA) ..... 10-1 

10.3 Chapter-Specific Key Questions ..........................................................................................10-1 

viii
1

2

3

4

5

List of Tables 

Table 2.1 Technologies for inorganic contaminants ......................................................................2-1 

Table 2.2 Technologies for volatile organic contaminants .............................................................2-11 

Table 2.3 Technologies for synthetic organic contaminants ..........................................................2-1 

Table 2.4 Technologies for radionuclides ......................................................................................2-12 

Table 2.5 Technologies for disinfection..........................................................................................2-1 

Table 2.6 Technologies for filtration...............................................................................................2-13 

Table 2.7 Compliance technology for the Total Coliform Rule.......................................................2-1 

Table 2.8 Percentage of CWSs (within each system service population category) that have treatedwater storage, before distribution system......................................................................2-1 

Table 2.9 Percentage of CWSs (within each system service population category) that have treatedwater storage within the distribution system..................................................................2-15 

Table 2.10 System service connections by system owner..............................................................2-20 

Table 3.1 Reduced monitoring for radionuclides .............................................................................3-6

Table 5.1 Surface Water Treatment Rule compliance technologies for disinfection ........................5-1 

Table 5.2 Surface Water Treatment Rule compliance technologies for filtration..............................5-2 

Table 5.3 Summary of disinfectant characteristics relating to biocidal efficiency..................................... 5-5 

Table 5.4 Key Feature Summary of commonly used POU/POE technologies..............................5-12 

Table 9.1 Amenability of treatment technologies to remote monitoring used for small water ...................9-2 

Table 9.2 Cost estimates of SCADA system components ..............................................................9-5 

Table 9.3 Puerto Rico remote monitoring system component costs...............................................9-6 

List of Figures 

Figure 2.1 PWSs by system type......................................................................................................2-2 

Figure 2.2 Small systems by system type - FY2004.........................................................................2-2 

Figure 2.3 Number of people served by system type - All systems FY2004 ....................................2-2 

Figure 2.4 Number of PWSs for each service population group.......................................................2-3 

Figure 2.5 Population served, service connections and number of systems - CWSs only FY2004 .2-3 

Figure 2.6 Drinking water system owners – FY 2004-159,796 total systems...................................2-4 

Figure 2.7 Violations reported FY2005.............................................................................................2-4 

Figure 2.8 Drinking water system violations for all system sizes - FY2005 ......................................2-5 

Figure 2.9 Violations reported for systems serving population from 25-10,000 - FY2005 ......................2-5 

Figure 2.10 MCL violations vs. populations served FY2005...............................................................2-6 

Figure 2.11 Source water comparison by size category.....................................................................2-6 

Figure 2.12 Percentage of ground water plants using each treatment technique...............................2-7 

Figure 2.13 Percentage of surface water plants using each treatment technique ..............................2-7 

Figure 2.14 Percentage of mixed plants using each treatment technique..........................................2-8 

Figure 2.15 Percentage of CWSs within each system service population category that have a 

clearwell type finished water storage.............................................................................2-15 

Figure 2.16 Average number of miles of distribution mains (public vs. private systems)..................2-16 

Figure 2.17 Public vs. private average annual pipe replaced (for CWSs) 5-year average................2-17 

Figure 2.18 System service connections..........................................................................................2-18 

Figure 2.19 Average number of miles of pipes in distribution systems – privately owned.......................2-18 

Figure 2.20 Average number of miles of pipes in distribution systems – publicly owned........................2-19 

Figure 2.21 Percentage of pipe in each age category for CWSs......................................................2-19 

Figure 2.22 Percentage of Pipe in Each Age Category by Source for CWSs...................................2-20 

Figure 2.23 Percentage of ground water CWS plants (lacking 24/7 operator presence) that have 

SCADA systems for process monitoring or control........................................................2-21 

Figure 2.24 Percentage of surface water CWS plants (lacking 24/7 operator presence) that have 

SCADA systems for process monitoring or control........................................................2-21 

Figure 3.1 Structure of the DWSRF program ...................................................................................3-7 

ix
Figure 5.1 Particle size distribution of common contaminants and associated filtration technology....5-3 

Figure 5.2 Clogged Prefilter..............................................................................................................5-3 

Figure 6.1 Distribution System as a “Reactor”..................................................................................6-3 

Figure 6.2 Negative Pressure Transient Associated with a Power Outage.......................................6-6 

Figure 7.1 Federal regulations governing the disposal of residuals..................................................7-2 

Figure 9.1 Possible layout of remote monitoring system ..................................................................9-3 

Figure 9.2 Schematic layout of the small sytstem in San German, Puerto Rico ..............................9-6 

x
Acronyms and Abbreviations 

AA Activated Alumina 

ABPA American Backflow Prevention 

Association

ANSI American National Standards 

Institute

AOP Advanced Oxidation Processes 

APG Annual Performance Goal 

APM Annual Performance Measure 

ASCE American Society of Civil Engineers 

ASDWA Association of State Drinking Water 

Administrators 

AWQC Ambient Water Quality Criteria 

AWWA American Water Works Association 

BAT Best Available Technology 

BMP Best Management Practices 

CCL Contaminant Candidate List 

CESQG Conditionally Exempt Small Quantity 

Generator 

CFR Coliform Rule 

CSO Combined Sewer Overflows 

CT Contact Time 

CWA Clean Water Act 

CWS Community Water System 

DBP Disinfection By-Product 

DBPR Disinfection By-Product Rule 

DE Diatomaceous Earth 

DHS Department of Homeland Security 

DWSRF Drinking Water State Revolving Fund 

EBCT Empty Bed Contact Time 

ED Electrodialysis

EPA Environmental Protection Agency 

EPCRA Emergency Planning and Community 

Right-to-Know Act 

EPTDS Entry Point to the Distribution 

System

ERP Emergency Response Plan 

ETV Environmental Technology 

Verification 

FBRR Filter Backwash Recycle Rule 

GAC Granular Activated Carbon 

GFH Granular Ferric Hydroxide 

GPM Gallons per Minute 

GWUDI Ground Water Under Direct Influence 

HAA5 Haloacetic Acids 

HFGP Horizontal Flow Gravel Prefilter 

HSPD Homeland Security Presidential 

Directive 

IT Information Technology 

IUP Intended Use Plan 

IX Ion Exchange 

LEPC Local Emergency Planning 

Committee

LGR Local Government Reimbursements 

LLRW Low-level Radioactive Waste 

LT1ESWTR Long Term 1 Enhanced Surface 

Water Treatment Rule 

LT2ESWTR Long Term 2 Enhanced Surface 

Water Treatment Rule 

M/R Monitoring and Reporting 

MCL Maximum Contaminant Level 

MCLG Maximum Contaminant Level Goal 

MF Microfiltration 

MGD Million Gallons per Day 

MHI Median Home Income 

MOU Memorandum of Understanding 

MRDLG Maximum Residual Disinfectant Level 

Goal

MTBE Methyl Tertiary Butyl Ether 

MWCO Molecular Weight Cut-off 

NAS National Academy of Science 

NDWAC National Drinking Water Advisory 

Council

NDWC National Drinking Water 

Clearinghouse 

NRMRL National Risk Management 

Research Laboratory 

NF Nanofiltration 

NHSRC National Homeland Security 

Research Center 

NIPDWR National Interim Primary Drinking 

Water Regulations 

NOM Natural Organic Matter 

NPDES National Pollution Discharge 

Elimination System 

NPDWR National Primary Drinking Water 

Regulations

NRC National Research Council (also 

used for Nuclear Regulatory 

Commission in Chapter ) 

NRWA National Rural Water Association 

xi
NSDWR National Secondary Drinking Water 

Regulation

NSF National Sanitation Foundation 

NTNCWS Non-Transient Non-Cmmunity Water 

System

NTU Nephelometric Turbidity Units 

O3 Ozone 

O&M Operation and Maintenance 

OCMS Online Contaminant Monitoring 

System

OEM Office of Emergency Management 

ORD Office of Research and Development 

PAC Powdered Activated Carbon 

PDCO Pore Diameter Cut-off 

PDD Presidential Decision Directive 

POE Point-of-Entry 

POTW Publicly Owned Treatment Works 

POU Point-of-Use 

ppb Parts per billion 

PTA Packed Tower Aeration 

PVC Polyvinyl Chloride 

PWS Public Water System 

RCRA Resource Conservation and 

Recovery Act 

RfD Reference Dose 

RMCL Recommended Maximum 

Contaminant Level 

RO Reverse Osmosis 

RPTB Response Protocol Toolbox 

SAB Science Advisory Board 

SBA Strong Base Anion 

SCADA Supervisory Control and Data 

Acquisition

SDWA Safe Drinking Water Act 

SDWIS State Drinking Water Information 

System

SEMS Security Emergency Management 

Systems

SEMS/ICS Standardized Emergency 

Management System/Incident 

Command System 

SSCT Small System Compliance 

Technology 

SSF Slow Sand Filter 

SWAP Source Water Assessment Plan 

SWP Source Water Protection 

SWR Solid Waste Residuals 

SWTR Surface Water Treatment Rule 

TCLP Toxicity Characteristic Leaching 

Procedure

TCR Total Coliform Rule 

T&E Test and Evaluation 

TENORM Technologically Enhanced Naturally 

Occurring Radioactive Material 

THM Trihalomethane 

TMDL Total Maximum Daily Load 

TNCWS Transient Community Water System 

TOC Total Organic Carbon 

TT Treatment Technique 

TTHM Total Trihalomethanes 

UCMR Unregulated Contaminants 

Monitoring Rule 

UF Ultrafiltration 

USACE United States Army Corps of 

Engineers

UV Ultraviolet light 

VA Vulnerability Assessment 

VOC Volatile organic compound 

WBA Weak Base Anion 

WHP Well Head Protection 

WHPA Well Head Protection Area 

WHPP Well Head Protection Plan 

WSD Water Security Division 

WSWRD Water Supply and Water Resources 

Division

xii
Acknowledgements 

This report was submitted in partial fulfillment of contract number EP-C-04-034 WA1-03 and 2-03 by 

Shaw Environmental, Inc. under the sponsorship of the United States Environmental Protection Agency. 

The authors extend their thanks to EPA Region 5 reviewers: Ronald Kovach, Miguel Del Toral, Sahba 

Rouhani, and William Spaulding. The authors would also like to thank Eric Bissonette, Jenny Bielanski, 

and Francine St. Denis in the EPA’s Office of Water for their comments. Lastly, the authors extend their 

deepest appreciation to the National Rural Water Association, specifically Jerry Biberstine and Dr. John 

Regnier for their comments and suggestions. Collaboration with NRWA is made possible through a 

Memorandum of Understanding between the EPA and NRWA. 

xiii

Chapter 1 

Introduction 

1.1 Goals and Objectives of this 

Document

The objective of this document is to summarize the 

existing status of drinking water supply in the United 

States (U.S.) with particular emphasis on small systems (i.e., systems serving less that 10,000 people). 

This document will then form the backdrop to craft a 

research plan that will serve as a roadmap for researchers in the U.S. Environmental Protection Agency’s (EPA’s), Office of Research and Development 

(ORD), Water Supply and Water Resources Division 

(WSWRD) by providing focus and direction to the 

WSWRD’s research efforts. Specifically, the Strategy 

for Small Systems Research aims to: 

• Provide timely and appropriate research that will 

contribute to small system management schemes 

for reducing Safe Drinking Water Act (SDWA) 

violations and public health risks. 

• Chart a research course that will drive new 

technologies and improve existing technologies 

with emphasis on costs/benefits (reduce costs 

and increase simplicity). 

This strategy document focuses on the current state of 

the following items as they pertain to small systems 

and on the direction of future research activities for 

these 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 of the six-year review of National Primary 

Drinking Water Regulations (NPDWR) and the fiveyear update of 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 Organization 

This document is organized into the following sections:

Chapter 1 – Introduction – This section presents a 

brief introduction to this report 

Chapter 2 – Current Status and Issues of Small 

Drinking Water Systems 

Chapter 3 – Regulatory Background – This section 

presents a brief background of the 

regulations impacting operators of 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 

1-1

Chapter 2 

Current Status and 

Issues of Small 

Drinking Water 

Systems

2.1 Introduction

This Chapter provides an introduction to the current 

status of small drinking water systems and the issues 

facing small systems in maintaining compliance and 

providing safe drinking water to the populace served 

by these systems. The chapter begins with a detailed 

snapshot profile (Section 2.2) of the distribution of 

small systems based on the number of people served 

and then provides brief overviews on the compliance 

status (Section 2.3) of these small systems and source 

water issues (Section 2.4). This chapter also provides 

a brief introduction to the following topics: 

• Common technologies currently used by small 

systems to treat source water to meet drinking 

water standards (Sections 2.5, 2.6, 2.7 and 2.8), 

• Distribution system infrastructure (including 

storage facilities, pumping facilities and 

distribution lines) currently employed by small 

systems (Section 2.9), 

• Status of the use of remote telemetry to monitor 

small systems operation (Section 2.10) 

• Key questions to be answered through ongoing 

research (Section 2.11) 

2.2 Profile of Small Systems in the 

U.S. 

The EPA’s Safe Drinking Water Information 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 of it are periodically updated. The profile data presented in this 

section includes a conglomeration of data extracted 

periodically from the SDWIS during the preparation 

of this report (between 2004 and 2005). Depending upon when the data was extracted and when the 

underlying SDWIS was updated, the exact numbers 

and percentages for individual categories described 

in the figures may vary slightly. However, the overall trends and statistics are consistent throughout the 

period during which the SDWIS was updated. Most 

of the SDWIS updates were performed between the 

years 2000 and 2005; where information is available, 

the specific year of the data presented is clearly identified. 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 multidimensional spreadsheets/databases that provide analytical 

processing capability. The Pivot tables allow for quick 

summarization, cross-tabulation, and analysis of large 

amounts of data. 

A PWS is any water system which provides water to 

at least 25 people for at least 60 days annually. These 

PWSs provide water from wells, rivers and other 

sources to the majority (~85%) of the population in 

the U.S. and territories (EPA, 2005b). The PWSs are 

classified as follows: 

• Community Water Systems (CWS) – A water 

system which supplies drinking water to 25 or 

more of the same people year-round in their 

residences.

• Non-Transient Non-Community Water Systems 

(NTNCWS) – A water system which supplies 

water to 25 or more of the same people at 

least six months per year in places other than 

their residences. Some examples are schools, 

factories, office buildings, and hospitals that 

have their own water systems. 

• Transient Non-Community Water Systems 

(TNCWS) – A water system which provides 

water in a place such as a gas station or 

campground where people do not remain for 

long periods of time. These systems do not have 

to test or treat their water for contaminants that 

pose long-term health risks because fewer than 

25 people drink the water over a long period (6 

months/year). They still must test their water 

for microbes and several chemicals. 

There are differing standards for PWSs of different 

sizes and types. Most (approximately 55%) of the 

PWSs in the U.S. belong to the TNCWS variety (EPA, 

2005b). Figure 2.1 illustrates the percentage breakdown of the different system types. Most of these 

systems represent the very small category (serving 25 

– 500 people). Figure 2.2 shows the breakdown of 

the number of small systems by system type. For the 

purposes of this document, a small system is defined 

as a CWS, NTNCWS, or TNCWS serving fewer than 

10,000 persons (please note that a PWS serving 3001-

10,000 persons may be referenced as medium in some 

graphics).

While most of the PWSs are TNCWSs, the vast majority 

2-1
33%

12%

55% CWS

NTNCWS

TNCWS

Figure 2.1 PWSs by system type (EPA, 

2005b).

90,000

80,000

70,000 Small (501-3300) 

60,000 Medium (3301-10,000) 30,006 14,212 4,70716,545 2,720 96

2,700

110

84,750

Very Small (25-500) 

Number of Systems

50,000

40,000

30,000

20,000

10,000

0

CWS NTNCWS TNCWS

System Type 

of people using PWSs actually obtain their water from 

CWSs. As illustrated in Figure 2.3, approximately 

90% of all people using public drinking water systems 

obtain their water from CWSs. Figure 2.4 shows the 

breakdown of system types by population category. 

As indicated, approximately 84% of CWSs serve 

populations of 3,300 or less. TNCWSs are mostly 

represented 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 of systems and the distribution of 

the population served. Very small CWSs account for 

57% of the total number of systems, although these

Figure 2.2 Small systems by system type - FY2004 (EPA, 2005b). 272,495,677 5,933,320

18,484,660

CWS NTNCWS TNCWS

300,000,000

Number of Systems250,000,000

200,000,000

150,000,000

100,000,000

50,000,000

0

Figure 2.3 Number of people served by system type - All systems FY2004 (EPA, 2005b). 

2-2
Population/Number of Service

Connections

Service Connections 

Population 

Systems 

140,000,000 

120,000,000 

100,000,000 

80,000,000 

60,000,000 

40,000,000 

20,000,000 

0

35,000 

30,000 

25,000 

20,000 

15,000 

10,000 

5,000 

0

Very Small Small Medium Large Very Large 

Number of Systems

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 

System Size

90,000

80,000

70,000

60,000

50,000

40,000

30,000

20,000

10,000

0

CWS 

NTNCWS 

TNCWS 

30,006

16,545

84,740

14,212

2,7202,700

4,707

96110

3,541

14

29

372

04

Number of Systems 

Very Small Small Medium Large Very Large 

(25-500) (501-3,300) (3,301-10,000) (10,001-100,000) (>100,000) 

System Type 

Figure 2.4 Number of PWSs for each service population group (EPA, 2005b). 

Figure 2.5 Population served, service connections and number of systems - CWSs only 

FY2004 (EPA, 2005b). 

systems serve less than 2 percent of the population PWSs are owned by various governmental, tribal, pubserved by CWSs. In contrast, the large and very large lic, or private entities. There is a relationship between 

systems account for roughly 7 percent of the total system size and ownership, with the vast majority of 

number of systems but serve over 80% of the popula- very small systems (25-500 persons served) being 

tion. Figure 2.5 shows a breakdown of population privately owned and a majority of larger systems being 

served, number of service connections, and number of owned by local government. Figure 2.6 shows the 

systems for CWSs by system size. breakdown of ownership for all systems. 

2-3
100,000 

16,000 

14,000 

12,000 

10,000 

8,000 

6,000 

4,000 

2,000 

Number of Systems

0

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

7.90%

0.0004%

1.67%

86.02%

4.40%

MCL

Maximum Residual Disinfectant

Level

Treatment Technique

Monitoring or Reporting

Other

Figure 2.6 Drinking water system owners – FY 2004-159,796 total systems (EPA, 2005b). 

2.3 Status of Drinking Water Plant 

Violations

The SDWIS classifies drinking water system violations 

into the following four 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 of a 

contaminant in drinking water. A few examples 

of treatment techniques are disinfection, 

filtration, and aeration (further 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 of system violations 

for all PWSs. This figure shows that most PWS violations are attributed to M/R. 

Figure 2.8 shows system violations by population 

served, number of systems, and violation type. Very 

small systems have the largest number of violations, 

with the vast majority of these being M/R violations. 

Figure 2.9 shows the breakdown of system violations 

for small systems. Figure 2.9 looks very similar to 

Figure 2.8 because the total violation statistics are 

overwhelmingly dominated by small systems. Very 

Figure 2.7 Violations reported FY2005 (EPA, 2005b). 

2-4
7.90%

4.47% 0.0004%

1.52%

86.11%

MCL

Maximum Residual Disinfectant

Level

Treatment Technique

Monitoring or Reporting

Other

Number of Violations

1400000 

1200000 

1000000 

800000 

600000 

400000 

200000 

0

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

52

000

15732

85352733

3320519 

1307260 

183057

4305148078

7176

66847

10438

2366

1565

117 

MCL Maximum Residual Treatment Monitoring or Other 

Disinfectant Level Technique Reporting 

Figure 2.8 Drinking water system violations for all system sizes - FY2005 (EPA, 2005b). 

small systems also experience the greatest number of 

MCL and TT violations. In addition, PWSs experienced a total of 145,962 MCL violations (2005 data), 

with 135,495 (93%) of the violations attributed to 

small systems (population served less than 3,300). 

Figure 2.10 illustrates the relationship between the 

number of MCL violations and population served. 

Very small systems (those serving 25 to 500 people) 

experience approximately one MCL violation for 

every 80 persons served, which is the highest ratio of 

all system service population categories. In comparison, very large systems (population served greater 

than 100,000) experience approximately one MCL 

violation for every 196,204 persons served. 

2.4 Source Water Issues 

PWSs obtain drinking water from either surface or 

ground water sources. Over 90% of the PWSs obtain 

their water from ground water sources, with a vast 

majority (87%) of those using ground water being 

represented by small systems (serving a population 

less than 3,300). Figure 2.11 shows the distribution of 

water sources, by each of the five size categories. 

Source waters from streams, rivers, lakes, or aquifers 

are used to supply private water systems and PWSs. 

The source water moves within a watershed via 

overland flow (i.e., surface water), shallow subsurface 

storm flow or ground water flow. The surface water 

is vulnerable to contamination from both surface 

runoff and ground water infiltration. Ground water 

can become contaminated through infiltration from 

Figure 2.9 Violations reported for systems serving 

population from 25-10,000 - FY2005 (EPA, 2005b). 

the surface, incursion of contaminants from underground storage tanks, septic systems, injection wells, 

or by naturally occurring substances in the soil or rock 

through which it flows. These issues are discussed in 

further detail in Chapter 4. 

2.5 Common Current Treatment 

Technologies 

Most PWSs treat drinking water so that it will be safe 

and palatable for the consumer. The application of a 

specific TT depends on source water quality, system 

size, and operator sophistication. Figures 2.12, 2.13 

and 2.14 illustrate the variety and percent predominance of individual TTs used by the different size 

classes of PWSs. 

2-5
0

5,000

10,000

15,000

20,000

25,000

30,000

35,000

40,000

45,000

Number of Violations

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

Population in Violation

Violations

Population

Very Small Small Medium Large Very Large

(25-500) (501-3,300) (3,301-10,000) (10,001-100,000) (>100,000)

Figure 2.10 MCL violations vs. populations served FY2005 (EPA, 2005b). 125,587 5,70415,514 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

Number of Systems

Ground Water

Surface Water

Very Small

(25-500)

Small

(501-3,300)

Medium

(3,301-10,000)

Large

(10,001-100,000)

Very Large

(>100,000)

Figure 2.11 Source water comparison by size category (EPA, 2005b). 

2-6
Percentage

90

80

70

60

50

40

30

20

10

0

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

100 or 101- 501- 3,301- 10,001- 50,001- 100,001- Over

less 500 3,300 10,000 50,000 100,000 500,000 500,000

System Service Population

70

60 Disinfection with no

additional treatment

50 Other chemical addition

Ion exchange,

Membranes

Softening

Percentage 40

30

20

10

0

activated alumina,

aeration

Filtration other than

direct or conventional

Direct filtration

Conventional filtration

100 or 101- 501- 3,301- 10,001- 50,001- 100,001- Over

less 500 3,300 10,000 50,000 100,000 500,000 500,000

System Service Population

Figure 2.12 Percentage of ground water plants using each treatment technique (EPA, 2002). 

Figure 2.13 Percentage of surface water plants using each treatment technique (EPA, 2002). 

2-7
100

90

80

70

60

50

40

30

20

10

0

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

100 or 101- 501- 3,301- 10,001- 50,001- 100,001- Over

less 500 3,300 10,000 50,000 100,000 500,000 500,000

System Service Population

Figure 2.14 Percentage of mixed plants using each treatment technique (EPA, 2002). 

The individual TTs are designed to be effective in 

removing one or more types of contaminants including particulate, chemical and biological contaminants. 

Depending upon the type of contamination present in 

the source water, one or more TTs may be applied by 

the PWS to provide safe drinking water to consumers. A general discussion of available TTs to remove 

particulate (Section 2.6), chemical contaminants (Section 2.7) and biological contaminants (Section 2.8) 

is presented in this Chapter. A more comprehensive 

discussion of TTs is presented in Chapter 5. 

2.6 Particulate/Turbidity Removal 

Technologies 

Particulate and turbidity removal is an almost universally used technology for the primary treatment of 

drinking water. The primary means of particulate removal is by means of simple filtration either by using 

media filtration (e.g., sand filter) or by the use of bag 

and/or cartridge filters. Advanced filtration techniques 

include membrane filtration and other technologies. 

This section provides a very brief overview of these 

technologies.

2.6.1 Simple Filtration 

Filtration is a process for removing particulate matter 

from water by passage through porous media. There 

are numerous types of filtration processes. Some common filtration processes are summarized below (these 

descriptions are available in many standard text books, 

where applicable references have been provided for 

specific usage and equipment descriptions): 

Slow Sand Filtration – is a process where untreated 

water percolates slowly down through a layer 

of fine sand, then through a layer of gravel, and 

ultimately collects in a system of underdrains. 

A biological layer or “schmutzdecke” forms on 

the surface of the sand, trapping small particles. 

The schmutzdecke also helps to degrade organic 

material in the water. 

Diatomaceous Earth (DE) – also known as precoat or diatomite filtration, can be used to 

directly treat low turbidity raw water supplies 

or chemically coagulated, more turbid water 

sources. DE filters consist of a pre-coat layer of 

DE, approximately 1/8-inch thick, supported by 

a septum or filter element (EPA, 1998). 

Conventional Filtration – is a method of treating 

water to remove particulates. The method 

consists of the addition of coagulant chemicals, 

flash mixing, coagulation-flocculation, 

sedimentation and filtration. 

Direct Filtration – also known as “dead-end 

filtration” is similar to conventional filtration 

with the sedimentation process omitted. 

Packaged Filtration – consists of all of the features of filtration – chemical addition, flocculation, 

sedimentation, filtration – mounted as a unit on a 

frame for simple hookup of pipes and services. It 

is most widely used to treat surface water supplies 

for removal of turbidity, color, and coliform organ2-8
isms with filtration processes. Packaged filtration is 

often 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 Filtration 

Membrane Filtration – Membrane filtration (as 

defined under the Long Term 2 Enhanced 

Surface Water Treatment Rule-LT2ESWTR) is 

a pressure-driven separation process in which 

particulate matter larger than 1-micrometer is 

rejected by an engineered barrier, primarily 

through a size-exclusion mechanism and which 

has a measurable removal efficiency for a 

target organism that can be verified through 

the application of a direct integrity test (EPA, 

2003a). Some common types of membrane 

filtration are: 

Microfiltration – is a pressure-driven membrane 

filtration process that typically employs 

hollow-fiber membranes with a pore size 

range of approximately 0.1 – 0.2 micrometers 

(nominally 0.1 micrometers) (EPA, 2003a). 

Ultrafiltration – is a pressure-driven membrane 

filtration process that typically employs 

hollow-fiber membranes with a pore size range 

of approximately 0.01 – 0.05 micrometer 

(nominally 0.01 micrometers) (EPA, 2003a). 

Nanofiltration – is a pressure-driven membrane 

separation process that employs the principles 

of reverse osmosis to remove dissolved 

contaminants from water and is typically 

applied for membrane softening or the removal 

of dissolved organic contaminants (EPA, 

2003a). 

2.6.3 Reverse Osmosis (RO) 

RO resembles membrane filtration processes in that 

contamination from water is removed by the use 

of a membrane. However, unlike membrane filtration where water is forced through a media leaving 

behind the contaminant, RO uses hydraulic pressure 

to oppose the liquid osmotic pressure across a semipermeable membrane, forcing the water from the 

concentrated solution side to the dilute solution side. 

Thus, the RO membrane allows the passage of 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, diffuses across, and then dissolves 

into the permeate (EPA, 1998b). RO can effectively 

remove nearly all contaminants from water including arsenic (III), arsenic (V), barium, cadmium, 

chromium (VI), radium, natural organic substances, 

pesticides, and microbiological contaminants. The 

liquid produced is demineralized water. 

2.7 Chemical Contaminant 

Removal 

Chemical contaminants are commonly removed using 

ion exchange and sorption technologies. This section 

provides a brief overview of these technologies along 

with other TTs that are used to remove chemical contaminants in drinking water. 

2.7.1 Ion Exchange (IX) 

Ion exchange involves the selective removal of charged 

inorganic species from water using an ion-specific 

resin. The surface of the ion exchange resin contains 

charged functional groups that hold ionic species by 

electrostatic attraction. As water containing undesired 

ions passes through a column of resin beds, charged 

ions on the resin surface are exchanged for the undesired species in the water. The resin, when saturated 

with the undesired species, is regenerated with a solution of the exchangeable ion (EPA, 1998b). 

Generally, resins can be categorized as anion exchange 

or cation exchange resins. Anion exchange resins selectively remove anionic species such as nitrate (NO3

–),

sulfate (SO4

2–), or fluoride (F–) and exchange them 

for hydroxyl (OH–) or chloride (Cl–) ions. Cation 

exchange resins are used to remove undesired cations 

such as cadmium (Cd2+) or Barium (Ba2+) from water 

and exchange them for protons (H+), sodium ions 

(Na+) or potassium ions (K+) (EPA, 1998b). The pH 

of the source water is important when employing IX 

resins. For example, uranium exists in water at pH 

levels of 6.0 and higher as a carbonate complex, which 

is an anion, and thus has a strong affinity for anion 

resin in the chloride form. The process is effective 

on water with a pH of up to 8.2. A higher pH could 

result in uranium precipitation; a lower pH changes 

the nature of uranium to non-ionic and/or cationic species, which would prevent the exchange reaction from 

operating efficiently. 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 off the 

resin (DeSilva 1996). 

2.7.2 Sorption Technologies 

Adsorption involves the removal of ions and molecules 

from solution and concentrating them on the surface 

of adsorbents. Adsorption is driven by the interfacial 

forces of 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 for the removal of 

organics, taste and odor, and inorganic contaminants 

(such as arsenic). 

2-9
2.7.3 Other Technologies 

Aeration Technologies – Aeration technologies are 

typically used for removal of volatile organic 

compounds and for removal of excess carbon 

dioxide. In general, aeration is the contacting of 

the water with air wherein the target chemical 

is transferred from the water to the air stream. 

There are a number of methods used for the 

mixing of air and water including packed 

aeration towers, shallow tray air strippers, 

mechanical aeration, and spray aeration. 

Softening – Softening is used to remove calcium 

and magnesium ions from water. Types of 

technologies used include ion exchange, 

chemical flocculation, and precipitation. 

Electrodialysis (ED) – Another less commonly 

used technology for chemical removal is ED, 

which is a process in which ions are transferred 

through ion-selective membranes by means of 

an electromotive force from a less concentrated 

solution to a more concentrated solution (EPA, 

2003a). ED is very effective in removing 

fluoride and nitrate, and can also remove barium, 

cadmium, and selenium (NDWC, 1997). 

Reverse Osmosis – Can remove many chemical 

contaminants effectively. See Section 2.6.3 for 

further details. 

2.8 Biological Contaminant 

Removal 

Disinfection is a process for reducing the number of 

pathogenic microbes in water and is required by the 

Surface Water Treatment Rule (SWTR) for all PWSs 

that obtain their water from surface water or ground 

water under the influence of surface water. In addition, 

PWSs must maintain a residual level of disinfectant 

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 disinfection concentration not fall below 0.2 mg/L. In addition, the 

residual disinfection concentration must be maintained 

throughout the distribution system such that non-detection results are measured in no more than 5% of the 

samples collected each month. 

2.8.1 Chlorination

Chlorine is the most common method used for disinfection. There are a number of methods of delivery 

and chemical reactions utilized for chlorination. These 

include chlorine gas, chloramines, chlorine dioxide, 

and sodium hypochlorite. The goal of all these methods is to release free chlorine in the form of hypochlorite, or in the case of 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 of an organism. UV disrupts 

the organism’s 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). This 

lamp emits a broad spectrum of radiation with intense 

peaks at UV wavelengths of 253.7 nanometers (nm) 

and a lesser peak at 184.9 nm. Research has shown 

that the optimum UV wavelength range to destroy bacteria is between 250 nm and 270 nm. At shorter wavelengths (e.g.185 nm), UV light is powerful enough to 

produce ozone, hydroxyl, and other free radicals that 

destroy bacteria (NDWC, 2000). 

2.8.3 Ozone

Ozone is a colorless, very unstable gas that is effective 

as an oxidizing agent in removing bacteria with a relatively short exposure time. Since the gas is unstable 

and has a very short life, ozone generators are used to 

produce ozone gas on site. 

2.8.4 Other Disinfection Technologies 

There are a number of other disinfection technologies 

used in ultra pure water applications, but are not applicable nor typically used in water supply situations. 

These include ammonium compounds, non-oxidizing 

biocides (i.e. formaldehyde), heat, and peracetic acid. 

Tables 2.1, 2.2, 2.3, 2.4, 2.5 and 2.6 present candidate 

technologies for treatment of inorganic contaminants, 

volatile organic contaminants, synthetic organic contaminants, radionuclides, disinfection, and filtration 

respectively. Table 2.7 identifies compliance technology for the Total Coliform Rule. 

2.9 Distribution System 

Infrastructure 

Drinking water is delivered from a water treatment 

facility to its customers by means of a distribution 

system. This infrastructure generally consists of a 

combination of three key elements: treated water storage facilities (e.g., ground storage tanks, elevated storage tanks, standpipes, hydropneumatic tanks), pumping facilities (e.g., booster pumps, piping, control, 

pump building), and the distribution lines (e.g., piping, 

valves, fire hydrants, meters). Most of the distribution 

system infrastructure is located underground, making 

it more difficult to detect problems such as leaks and 

pipe deterioration. Various standards and procedures 

for design, material selection, plumbing code, operation, and maintenance have been established that help 

maintain the integrity of the system (EPA, 1999). The 

distribution system issues facing small systems are 

2-10
Table 2.1 Technologies for inorganic contaminants (NDWC, undated). 

Unit Technology Limitations*

Operator Skill 

Level Required Raw Water Quality Range 

1. Activated Alumina (a) Advanced 

Ground waters, competing anion concentrations will 

affect run length. 

2. Ion Exchange Intermediate 

Ground waters with low total dissolved solids, competing ion concentrations will affect run length. 

3. Lime Softening (b) Advanced Hard ground and surface waters 

4. Coagulation/ Filtration (c) Advanced Can treat wide range of water quality. 

5. Reverse Osmosis (RO) (d) Advanced Surface water usually require prefiltration. 

6. Alkaline Chlorination (e) Basic All ground waters. 

7. Ozone Oxidation Intermediate All ground waters. 

8. Direct Filtration Advanced Needs high raw water quality. 

9. Diatomaceous Earth Filtration Intermediate Needs very high raw water quality. 

10. Granular Activated Carbon Basic Surface waters may require prefiltration. 

11. Elecrodialysis Reversal Advanced Requires prefiltration for surface water. 

12. Point of Use (POU)-IX (f) Basic Same as Technology #2. 

13. POU-RO (f) Basic Same as Technology #5. 

14. Calcium Carbonate Precipitation (g) Basic Water with high levels of alkalinity and calcium. 

15. pH and Alkalinity Adjustment 

(chemical feed) (g) Basic All ranges. 

16. pH and Alkalinity Adjustment 

(limestone contactor) (h) Basic

Waters that are low in iron and turbidity. Raw water 

should be soft and slightly acidic. 

17. Inhibitors Basic All ranges. 

18. Aeration (i) Basic Waters with moderate to high carbon dioxide content. 

Limitation Footnotes 

a) Chemicals required during regeneration and pH adjustments may be difficult for small systems to handle. 

b) Softening chemistry may be too complex for small systems 

c) It may not be advisable to install coagulation/filtration solely for inorganics removal. 

d) If all of the influent water is treated, post-treatment corrosion control will be necessary. 

e) pH must exceed pH 8.5 to ensure complete oxidation without build-up of cyanogen chloride. 

f) When POU devices are used for compliance, programs for long-term operation, maintenance, and monitoring must be provided by water utility 

to ensure proper performance. 

g) Some chemical feeds require high degree of operator attention to avoid plugging. 

h) This technology is recommended primarily for the smallest size category. 

i) Any of the first five aeration technologies listed for volatile organic contaminants (Table 2.2) can be used. 

Table 2.2 Technologies for volatile organic contaminants (NDWC, undated). 

Unit Technology 

Limitations

(see footnotes) 

Operator Skill Level 

Required

Raw Water 

Quality Range 

1. Packed Tower Aeration (PTA) (a) Intermediate All ground waters. 

2. Diffused Aeration (a,b) Basic All ground waters. 

3. Multi-Stage Bubble Aerators (a,c) Basic All ground waters. 

4. Tray Aeration (a,d) Basic All ground waters. 

5. Shallow Tray Aeration (a,e) Basic All ground waters. 

6. Spray Aeration (a,f) Basic All ground waters. 

7. Mechanical Aeration (a,g) Basic All ground waters. 

8. Granular Activated Carbon (GAC) (h) Basic All ground waters. 

Limitation Footnotes 

a) Pretreatment for the removal of microorganisms, iron, manganese, and excessive particulate matter may be needed. Post-treatment disinfection may have to be used. 

b) May not be as efficient as other aeration methods because it does not provide for convective movement of the water thus limiting air-water 

contact. It is generally used only to adapt existing plant equipment. 

c) These units are highly efficient; however, the efficiency depends upon the air-to-water ratio. 

d) Costs may increase if a forced draft is used. Slime and algae growth can be a problem but can be controlled with chemcials such as copper 

sulfate or chlorine. 

e) These units require high air-to-water ratios (100-900 m3/m3). 

f) For use only when low removal levels are needed to reach a MCL because these systems may not be as energy efficient as other aeration 

methods because of 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 efficient as other aeration 

methods. The units often require large basins, long residence times, and high energy inputs, which may increase costs. 

h) See table 2.3 for limitations regarding these technologies. 

2-11
Table 2.3 Technologies for synthetic organic contaminants (NDWC, undated). 

Unit Technology 

Limitations

(see footnotes) 

Operator Skill Level 

Required

Raw Water Quality Range 

and Considerations 

1. Granular Activated Carbon (GAC) (h) Basic Surface water may require prefiltration. 

2. Point of Use GAC (a, h) Basic Surface water may require prefiltration. 

3. Powdered Activated Carbon (b, h) Intermediate All waters 

4. Chlorination (c) Basic Better with high quality waters. 

5. Ozonation (c) Basic Better with high quality waters. 

6. Packed Tower Aeration (PTA) (d) Intermediate All ground waters. 

7. Diffused Aeration (d,e) Basic All ground waters. 

8. Multi-Stage Bubble Aerators (d,f) Basic All ground waters. 

9. Tray Aeration (d,g) Basic All ground waters. 

10. Shallow Tray Aeration (d,f) Basic All ground waters. 

Limitation Footnotes 

a) When POU devices are used for compliance, programs for long-term operation, maintenance, and monitoring must be provided by water utility 

to ensure proper performance. 

b) Most applicable to small systems that already have a process train including basins, mixing, precipitation or sedimentation, and filtration. Site 

specific design should be based on studies conducted on the system’s particular water. 

c) See the Surface Water Treatment Rule compliance technology tables for limitations associated with this technology. 

d) Pretreatment for the removal of microorganisms, iron, manganese, and excessive particulate matter may be needed. Post-treatment disinfection may have to be used. 

e) May not be as efficient as other aeration methods because it does not provide for convective movement of the water thus limiting air-water 

contact. It is generally used only to adapt existing plant equipment. 

f) These units are highly efficient; however, the efficiency depends upon the air-to-water ratio. 

g) Forces may increase if a forced draft is used. 

h) Pretreatment for removal of suspended solids is an important design consideration. Spent carbon must be regenerated or disposed properly. 

Table 2.4 Technologies for radionuclides (NDWC, undated). 

Unit Technology 

Limitations

(see footnotes) 

Operator Skill Level 

Required

Raw Water Quality Range 

and Considerations 

IX (a) Intermediate All ground waters. 

Point of Use (POU) IX (b) Basic All ground waters. 

Reverse Osmosis (RO) (c) Advanced Surface waters, usually require prefiltration. 

POU RO (b) Basic Surface waters, usually require prefiltration. 

Lime Softening (d) Advanced All waters. 

Green Sand Filtration (e) Basic

Co-precipitation with Barium Sulfate (f)

Intermediate to 

Advanced Ground waters with suitable water quality 

Electrodialysis/Electrodialysis Reversal Advanced All ground waters. 

Pre-formed Hydrous Manganese 

Oxide Filtration (g) Intermediate All ground waters. 

Limitation Footnotes 

a) The regeneration solution contains high concentrations of the contaminant ions. Disposal options should be carefully considered before 

choosing the technology. 

b) When POU devices are used for compliance, programs for long-term operation, maintenance, and monitoring must be provided by water utility 

to ensure proper performance. 

c) Reject water disposal options should be carefully considered before choosing this technology. See other RO limitations described in the Surface Water Treatment Rule Compliance Table. 

d) The combination of variable source water quality and the complexity of the chemistry involved in lime softening may make this technology too 

complex for small surface water systems. 

e) Removal efficiencies can vary depending on water quality. 

f) This technology may be very limited in application to small systems. Since the process requires static mixing, detention basins, and filtration; it 

is most applicable to systems with sufficiently high sulfate levels that already have a suitable filtration treatment train in place. 

g) This technology is most applicable to small systems that already have filtration in place. 

2-12
Table 2.5 Technologies for disinfection (NDWC, undated). 

Unit Technology 

Limitations

(see footnotes) 

Operator Skill 

Level Required 

Raw Water Quality Range 

and Considerations 

Free Chlorine (a,b) Basic

Better with high quality. High iron or manganese may require 

sequestration or physical removal. 

Ozone (c,d, h) Intermediate 

Better with high quality. High iron or manganese may require 

sequestration or physical removal. 

Chloramines (e) Intermediate 

Better with high quality. Ammonia dose should be tempered 

by natural ammonia levels in water. 

Chlorine Dioxide (f) Intermediate Better with high quality. 

Onsite Oxidant Generation (g) Basic Better with high quality. 

Ultraviolet (UV) Radiation (h) Basic

Relatively clean source water required. Iron, natural organic 

matter and turbidity affect UV dose. 

Limitation Footnotes 

a) Providing adequate CT may be a problem for 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 disinfectant (i.e., no residual protection). 

e) Long CT. Requires care in monitoring of ratio of added chlorine to ammonia. 

f) Chlorine dioxide requires special storage and handling precautions. 

g) Oxidants other than chlorine not detected in solution by significant research effort. CT should be based on free chlorine until new research 

determines appropriate CT values for electrolyzed salt brine. 

h) No disinfectant residual protection for distributed water. 

Table 2.6 Technologies for filtration (NDWC, undated). 

Unit Technology 

Limitations

(see footnotes) 

Operator Skill Level 

Required Raw Water Quality Range and Considerations 

Conventional Filtration 

(includes dual-stage and 

dissolved air flotation (a) Advanced 

Wide range of water quality. Dissolved air flotation is more 

applicable for removing particulate matter that doesn’t 

readily settle: algae, high color, low turbidity--up to 30-50 

nephelometric turbidity units (NTU) and low-density turbidity. 

Direct Filtration (includes 

in-line filtration (a) Advanced 

High quality. Suggested limits: average turbidity 10 NTU; 

maximum turbidity 20 NTU; 40 color units; algae on a caseby-case basis. 

Slow Sand Filtration (b) Basic

Very high quality or pretreatment. Pretreatment required if 

raw water is high in turbidity, color, and/or algae. 

Diatomaceous Earth 

Filtration (c) Intermediate 

Very high quality or pretreatment. Pretreatment required if 

raw water is high in turbidity, color, and/or algae. 

Reverse Osmosis (d,e,f) Advanced 

Requires prefiltrations for surface water-may include removal of turbidity, iron, and/or manganese. Hardness and 

dissolved solids may also affect performance. 

Nanofiltration (e) Intermediate 

Very high quality of pretreatment. See reverse osmosis 

pretreatment.

Ultrafiltration (g) Basic High quality or pretreatment. 

Microfiltration (g) Basic High quality or pretreatment required. 

Bag Filtration (g,h,i) Basic

Very high quality or pretreatment required, due to low 

particulate loading capacity. Pretreatment if high turbidity 

or algae. 

Cartridge Filtration (g,h,i) Basic

Very high quality or pretreatment required, due to low 

particulate loading capacity. Pretreatment if high turbidity 

or algae. 

Backwashable Depth 

Filtration (g,h,i) Basic

Very high quality or pretreatment required, due to low 

particulate loading capacity. Pretreatment if high turbidity 

or algae. 

Limitations Footnotes 

a. Involves coagulation. Coagulation chemistry requires advanced operator skill and extensive monitoring. A system needs to have direct full-time 

access or full-time remote access to a skilled operator to use this technology properly. 

b. Water service interruptions can occur during the periodic filter-to-waste cycle, which can last from six hours to two weeks. 

c. Filter cake should be discarded if filtration is interrupted. For this reason, intermittent use is not practical. Recycling the filtered water can remove 

this potential problem. 

d. Blending (combining treated water with untreated raw water) cannot be practiced at risk of increasing microbial concentration in finished water. 

e. Post-disinfection recommended as a safety measure and for residual maintenance. 

f. Post-treatment corrosion control will be needed prior to distribution. 

g. Disinfection required for viral inactivation. 

h. Site-specific pilot testing prior to installation likely to be needed to ensure adequate performance. 

i. Technologies may be more applicable to system serving fewer than 3,300 people. 

2-13
Table 2.7 Compliance technology for the Total Coliform Rule (NDWC, undated). 

40 CFR 141.63(d) - Best technologies or other 

means to comply 

(Complexity level indicated) Comments/Water Quality Concerns 

Protecting wells from contamination, e.g., placement and construction of well(s) (Basic). Ten State Standards and other standards (AWWA, 1995) apply; interfacing 

with other programs essential (e.g., source water protection program). 

Maintenance of a disinfection residual for distribution system protection (Intermediate). Source water constituents may affect disinfection: iron, manganese, organics, ammonia, and other factors may affect dosage and water quality. Total 

Coliform Rule (TCR) remains unspecific on type/amount of disinfectant, as 

each type differs in concentration, time, temperature, pH, interaction with 

other constituents, etc. 

Proper maintenance of distribution system: pipe 

repair/replacement, main flushing programs, 

storage/reservoir, and O&M programs (including 

cross-connection control/backflow prevention), 

and maintenance of positive pressure throughout 

(Intermediate). 

O&M programs particularly important for smaller systems needing to maintain water purity. States may vary on distribution protection measures. 

See also EPA’s Cross-Connection Control Manual (EPA, 2003b) 

Filtration and/or disinfection of surface water or 

other ground water under direct influence; or disinfection of ground water (Basic thru Advanced). 

Same issues as cited above under maintaining disinfection residual; 

pretreatment requirements affect complexity of operation. Refer to Surface 

Water Treatment Rule Compliance Technology List; and other regulations 

under development. 

Ground waters: Compliance with State Wellhead 

Protection Program (Intermediate). 

EPA/State Wellhead Protection Program implementation (per §1428 

SDWA): may be used to assess vulnerability to contamination, and in 

determination of sampling and sanitary survey frequencies. 

further discussed in Chapter 6. The following is a 

brief description of each of the key distribution system 

infrastructure elements. 

2.9.1 Storage Facilities 

Storage facilities 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 first treated water storage tank and is located at the end of the treatment train 

or at the end of a well system. Their primary purpose is 

to provide for contact time when chemical treatment additives (e.g., chlorine) are used. These storage structures 

have limited use as storage reservoirs due to their location. The added storage or reserve capability of clearwells are an advantage for small system operators that 

need time for maintenance of equipment or structures, 

or other storage needs such as fire flows, but this is not 

their intended use. Utilities should not rely on clearwell 

storage as their only means of reserve for the distribution 

system. The clearwell tank also serves as a reservoir 

for the storage of filtered water of sufficient capacity to 

prevent the need to vary the filtration rate with variations in demand. Clearwell tanks provide both a treated 

water reserve for delivery to the distribution system and 

additional detention time for more effective disinfection (EPA, 1999). Figure 2.15 shows the percentage of 

CWSs that use clearwell tanks for treated-water storage. 

Depending on the complexity and size of the distribution system, the other storage tanks are designed 

to provide pressure maintenance for the distribution 

system. If the system serves a small number of customers, a pressurized tank called a hydropneumatic 

tank (controlled by both water and air pressures) is 

used to maintain the system pressure, because it is 

cheaper to build than an elevated tank. Different 

sections of the distribution system are maintained at 

different pressures (commonly referred to as pressure zones), depending on the water demand and 

pressure head requirements. (EPA, 1999). 

Tables 2.8 and 2.9 show the percentage of CWSs that 

have treated-water storage either before or within the 

distribution system. 

Storage tank capacities are designed to be adequate 

to meet the water demands of the system, meet 

applicable state requirements and industry standards, and be consistent with accepted engineering 

practice. For example, the total capacity of both 

ground and elevated storage tanks could be based on 

a recommended level of 200 gallons per connection. 

For elevated storage tanks alone, a recommended 

capacity of 100 gallons per connection is often used. 

For systems using hydropneumatic tanks instead 

of elevated tanks, recommended capacities are 20 

gallons per connection with ground storage and 50 

gallons per connection without ground storage (EPA, 

1999). 

2-14
Table 2.8 Percentage of CWSs (within each system service population category) that have 

treated-water storage, before distribution system. 

Primary Source 

of Water Configuration

System Service Population Category 

25-

500

501-

3,300

3,301-

10,000

10,001-

100,000

Over

100,000

Ground Water With Dedicated Entry and Exit Points 31.6 17.0 23.1 26.2 32.4

Systems With a Common Inlet and Outlet 16.8 15.6 8.8 16.5 25.3

Surface Water With Dedicated Entry and Exit Points 41.3 16.6 27.7 32.3 33.1

Systems With a Common Inlet and Outlet 6.5 18.3 16.7 7.4 25.9

Purchased Water With Dedicated Entry and Exit Points 10.6 5.3 13.5 11.9 33.6

Systems With a Common Inlet and Outlet 10.5 7.6 15.3 1.5 0.0

Table 2.9 Percentage of CWSs (within each system service population category) that have 

treated-water storage within the distribution system. 

Primary Source 

of Water Configuration

System Service Population Category 

25-

500

501-

3,300

3,301-

10,000

10,001-

100,000

Over

100,000

Ground Water With Dedicated Entry and Exit Points 2.9 10.0 16.5 31.9 51.8

Systems With a Common Inlet and Outlet 11.9 68.6 54.0 70.7 82.8

Surface Water With Dedicated Entry and Exit Points 6.0 4.1 29.2 39.8 58.6

Systems With a Common Inlet and Outlet 20.5 73.6 73.0 72.8 72.0

Purchased Water With Dedicated Entry and Exit Points 3.5 8.8 22.6 35.5 56.8

Systems With a Common Inlet and Outlet 14.4 55.4 61.6 63.9 64.6

0

10

20

30

40

50

60

70

80

90

100

Percentage of Systems

Primarily Ground Water Systems Primarily Surface Water Systems Primarily Purchased Water Systems

100 or 101- 501- 3,301- 10,001- 50,001- 100,001- Over

less 500 3,300 10,000 50,000 100,000 500,000 500,000

System Service Population

Figure 2.15 Percentage of CWSs within each system service population category that have 

a clearwell type finished water storage (EPA, 2002). 

2-15
Average Number of Miles

4,000

3,500

3,000

2,500

2,000

1,500

1,000

500

0

2,771

Public Systems Private Systems

2,382

560

339

203

25

61

3

5

777

871

390

217

1

4

37

100 or less 101-500 501-3,300 3,301- 10,001- 50,001- 100,001- Over

10,000 50,000 100,000 500,000 500,000

System Service Population

2.9.2 Pumping facilities 

Pumps are used for moving fluid (e.g., water, chemical) through the distribution system, sludge removal, 

air compression and sampling. The three types of 

pumps generally used to pump water at a treatment 

plant are: positive displacement, centrifugal, and 

ejector. A positive displacement pump delivers water 

at a constant rate regardless of the pressure it must 

overcome. A centrifugal pump is used when an even 

flow rate is needed to meet the demands placed on it. 

Ejector pumps are typically used to deliver treatment 

chemical to the water being treated. Pump capacity is 

typically dependent on the application or purpose. 

Most pumping applications rely on a pumping station 

that includes a pump(s), a structure to house or support 

the pump, piping – suction and discharge, lighting, 

ventilation, an electrical center and control panel for 

the pump(s) and lighting, and appurtenances. 

2.9.3 Distribution Lines 

Underground pipes are the largest component of the 

distribution system and as such, design standards are 

established that specify the minimum requirements for 

all water lines. Typically, the design standards also 

specify many of the following items (EPA, 1999): 

• Minimum pipe size (typically there should be no 

lines less than 2-inch); 

• Minimum line size criteria (either maximum 

water velocity or number of connections served 

for a given line size); 

• Minimum line size where fire hydrants are to be 

provided (6-inch is the minimum); 

• Minimum line size for specific requirement of 

the distribution system (e.g., transmission line 

should be at least 12-inches); 

• Design flow for each type of connection (e.g., 

residential, commercial, industrial); 

• Design fire flow for specific areas of 

development (e.g., residential, commercial, 

industrial);

• Location of line relative to other utilities 

(sanitary sewer, in particular) and right-of-way 

limits;

• Location or spacing of valves; 

• Direction of valves (right or left opening); 

• Type of valves to be used (vacuum/air release, 

butterfly, or gate valve); 

• Location or spacing of fire hydrants; 

• Type of fire hydrants to be used (dry or wet barrel); 

• Pipe material, including requirements for 

internal as well as external corrosion; 

• Appurtenances required for flushing of dead-end 

lines;

Figure 2.16 Average number of miles of distribution mains (public vs. private systems). Error 

bars represent the 95% confidence interval (EPA, 2002). 

2-16
300

Public Systems Private Systems

250

200

150

100

154

58

Average Annual Pipe Replaced (miles)

0

0

00

112

20

5

5

8

3

50

20

20

0

100 or less 101-500 501-3,300 3,301- 10,001- 50,001- 100,001- Over

10,000 50,000 100,000 500,000 500,000

System Service Population

• Minimum cover or depth-to-bury requirements; 

• Pressure testing to determine that there are no 

leaks in the line; 

• Construction or installation requirements; and 

• Location and construction of appurtenances in 

the floodplain. 

The vast majority of piping used for distribution lines 

in CWSs is used by very large systems serving populations over 500,000 persons. Also, for small systems, 

private systems tend to have more miles of pipe in 

place than public systems (when comparing the same 

system service population size) (Figure 2.16). 

Most of the piping replaced each year is performed in 

the private rather than the public sector (Figure 2.17) 

and as would be expected, very large systems replace 

more piping per year than smaller systems. 

There are 293,087,350 customer connections, over 

55% of which are part of CWSs (Figure 2.18). Very 

small systems account for almost 73% of customer 

connections, with the majority of those systems being 

privately owned (Table 2.10). 

CWS distribution pipes are of various diameters. In 

all but the very largest of systems (those serving over 

500,000 persons), there is a tendency to use more distribution pipes that average less than 6-inches than it 

is to use distribution pipes of 6-to 10-inches or greater 

than 10-inches. Very large systems (especially those 

that are privately owned) on average use more distribution pipes of the 6-to 10-inch variety than either of the 

other two sizes (Figures 2.19 and 2.20). Typically, as 

would be expected, the distribution mains (or trunk 

lines) are of the larger diameter in size. 

The vast majority of CWS piping (approximately 

78%) is less than 40 years old. Approximately 18% is 

between 40 and 80 years old and the remaining 4% is 

over 80 years old (Figure 2.21). Publicly owned systems tend to have slightly older piping on average than 

do privately owned systems, with approximately 24% 

of public systems piping averaging 40 to 80 years old 

as compared to approximately 8% of private systems 

in the same age range (Figure 2.22). 

2.10 Remote Telemetry – 

Supervisory Control and Data 

Acquisition (SCADA) 

Remote telemetry or SCADA is used to control all 

aspects of a device from a centralized location. In 

the past, small systems did not always use SCADA 

to their fullest potential due to complex operating 

systems and controls that usually required specially 

Figure 2.17 Public vs. private average annual pipe replaced (for CWSs) 5-year average. 

Error bars represent the 95% confidence interval (EPA, 2002). 

2-17
2,400

Distribution Mains Less Than 6 Inches

1,484.0

Average Number of Mains

454.6

2,200

2,000

1,800

1,600

1,400

1,200

1,000

800

600

400

200

0

Distribution Mains 6 to 10 Inches

Distribution Mains Greater Than 10 Inches

1.1

0.0

0.0

3.50.1

0.0

33.9

2.4

0.3

190.3

23.8

2.5

191.0

184.6

14.6

192.7

114.1

63.6

361.3

249.5

166.5

676.9

100 or less 101-500 501-3,300 3,301- 10,001- 50,001- 100,001- Over

10,000 50,000 100,000 500,000 500,000

System Service Population

0

20,000,000

40,000,000

60,000,000

80,000,000

100,000,000

120,000,000

140,000,000

160,000,000

180,000,000

Number of Connections

CWS 83,572,950 7,279,586 9,140,490 30,871,660 31,703,961 162,568,647

NTNCWS 72,247,798 111,881 24,432 1,931 98 72,386,140

TNCWS 58,042,062 84,909 3,253 141 2,198 58,132,563

Very Small

(25-500)

Small

(501-3,300)

Medium

(3,301-10,000)

Large

(10,001-100,000)

Very Large

(>100,000) Grand Total

System Service Population

Figure 2.18 System service connections (EPA, 2002). 

Figure 2.19 Average number of miles of pipes in distribution systems – privately owned (EPA, 

2002).

2-18
1,100

1,000

Distribution Mains Less Than 6 Inches

900 Distribution Mains 6 to 10 Inches

800 Distribution Mains Greater Than 10 Inches

700

600

500

400

300

835.1

864.9

704.5

Average Number of Mains

1.5

1.2

0.5

3.3

1.1

0.1

21.4

3.2

0.8

38.5

17.0

4.9

108.8

58.8

34.1

136.0

122.4

80.4

250.4

175.4

200

137.0

100

0 100 or less 101-500 501-3,300 3,301-

10,000

10,001-

50,000

50,001-

100,000

100,001-

500,000

Over

500,000

System Service Population

Figure 2.20 Average number of miles of pipes in distribution systems – publicly owned (EPA,

2002).

Figure 2.21 Percentage of pipe in each age 

category for CWSs (EPA, 2002). 

4% 

18% 

78% 

Less than 

40 Years 

More than 

80 Years 

Between 40 

and 80 

Years

2-19
Percentage

120.0

100.0

80.0

60.0

40.0

20.0

0.0

75.2

21.1

3.8

67.3

24.6

8.1

89.6

9.6

0.8

Less than 40 years old

Between 40 and 80 years old

More than 80 years old

GW SW Purchased

Water Source

Figure 2.22 Percentage of Pipe in Each Age Category by Source for CWSs (EPA, 2005b). 

trained computer programmers or technicians and 

costly service agreements. In the last few years, 

SCADA vendors have changed the way they design 

and fabricate their systems, thus making them more 

accessible to small drinking water treatment operators 

(EPA, 2003c). 

Figures 2.23 and 2.24 illustrate how large CWSs (lacking continuous operator presence) use more SCADA 

systems than small CWSs, for both process control 

and process monitoring. Chapter 9 presents further 

details on the use of SCADA for small systems. 

2.11 Key Questions 

• How will demographic changes in the US 

change the way small systems obtain, treat, and 

distribute drinking water? 

• How can the EPA help minimize monitoring 

and reporting violations? (e.g., develop simple, 

standardized forms with sampling timetables, 

etc., with input from primacy agencies). 

• Should resources be concentrated in any one 

area between NTNCWS, TNCWS, and CWS? 

Table 2.10 System service connections by system owner (EPA, 2002). 

System Service Population 

Owner

Very Small 

25-500

Small

501-3,300

Medium

3,301-10,000

Large 

10,001-

100,000

Very Large 

>100,000 Grand Total 

Federal Government 5,539,450 42,023 99,527 210,244 3 5,891,247

Local Government 38,323,943 5,306,605 7,455,702 25,591,319 27,338,611 104,016,180

Native American 24,287 44,279 15,852 66 NA 84,484

Private 169,809,399 1,685,804 1,267,290 4,408,959 3,995,009 181,166,461

Public/Private 95,004 298,709 190,848 422,711 372,491 1,379,763

State Government 38,750 55,126 91,817 180,955 143 366,791

Unknown 31,977 43,830 47,139 59,478 NA 182,424

Grand Total 213,862,810 7,476,376 9,168,175 30,873,732 31,706,257 293,087,350

2-20
4.4

5.4

1.4

3.8

14

15.5

58.7

20.1

64.4

53.2

81.3

57.6

85.6

42.4

82.8

82.8

0

10

20

30

40

50

60

70

80

90

Systems (percentage)

Process Monitoring

Process Control

100 or 101-500 501-3,300 3,301- 10,001- 50,001- 100,001- Over

less 10,000 50,000 100,000 500,000 500,000

System Service Population 

Figure 2.23 Percentage of ground water CWS plants (lacking 24/7 operator presence) that 

have SCADA systems for process monitoring or control (EPA, 2002). 6.3

3

21.6

18.5

43.7

0.9

50.6

26.4

74.5

61

96

93

96.4

67.5

100

75

0

10

20

30

40

50

60

70

80

90

100

Systems (percentage)

Process Monitoring

Process Control

100 or 101-500 501-3,300 3,301- 10,001- 50,001- 100,001- Over

less 10,000 50,000 100,000 500,000 500,000

System Service Population 

Figure 2.24 Percentage of surface water CWS plants (lacking 24/7 operator presence) that 

have SCADA systems for process monitoring or control (EPA, 2005b). 

2-21
(These systems have different demands. For 

example, CWSs typically have demands 

throughout the year, while the non-community 

systems may have more sporadic demands.) 

2.12 References 

All references to Code of Federal Regulations (CFR) 

Documents in this chapter may be found at http:// 

www.access.gpo.gov/nara/cfr and Federal Register 

Documents may be found at http://www.gpoaccess. 

gov/fr/index.html 

American Water Works Association (AWWA). 

AWWA Standard for Water Wells - ANSI/AWWA 

A100-90, 

AWWA, Denver, CO, 1995. 

DeSilva, F.J. At the Heart of POU -- Ion Exchange 

Resins, available at: http://www.watertechonline.com/ 

article.asp?IndexID=5190203, 1996. 

EPA. Small System Compliance Technology List for 

the Surface Water Treatment Rule and Total Coliform 

Rule, EPA 815-R-98-001, 1998. 

EPA. Small System Compliance Technology List for 

the Non-Microbial Contaminants Regulated Before 

1996, EPA 815-R-98-002, 1998b. 

EPA. Guidance Manual for Conducting Sanitary 

Surveys of Public Water Systems; Surface Water and 

Ground Water Under the Direct Influence (GWUDI), 

EPA 815-R-99-016, 1999. 

EPA. Community Water System Survey 2000. EPA 

815-R-02-005B, 2002. 

EPA. Membrane Filtration Guidance Manual, EPA 

815-D-03-008, 2003a. 

EPA. Cross-Connection Control Manual, EPA 816-R03-002, 2003b. 

EPA. Small Drinking Water Systems Handbook: A 

Guide to Packaged Filtration and Disinfection Technologies with Remote Monitoring and Control Tools, 

EPA 600-R-03-041, 2003c. 

EPA. Safe Drinking Water Information System (SDWIS), available at: http://www.epa.gov/enviro/html/sdwis/, 2005a. 

EPA. Data & Databases PivotTables, available at: 

http://www.epa.gov/safewater/data/pivottables.html, 

2005b. 

National Drinking Water Clearinghouse (NDWC). 

NDWC Fact Sheet - Technical Brief on Filtration, 

available at: http://www.nesc.wvu.edu/ndwc/pdf/OT/ 

TB/TB2_filtration.pdf, 1996. 

NDWC. NDWC Fact Sheet – Technical Brief on Ion 

Exchange and Demineralization, available at: http://

www.nesc.wvu.edu/ndwc/pdf/OT/TB/TB4_IonExchange.pdf, 1997. 

NDWC. NDWC Fact Sheet – Technical Brief on Ultraviolet Disinfection, available at: http://www.nesc.wvu. 

edu/ndwc/pdf/OT/TB/OT_TB_f00.pdf, 2000. 

NDWC. NDWC Fact Sheet – Technical Brief Poster 

on Treatment Technologies for Small Drinking Water 

Systems, available at: http://www.nesc.wvu.edu/ndwc/ 

pdf/OT/TB/TB11_TTposter.pdf, undated. 

2-22
Chapter 3 

Regulatory 

Background 

3.1 Safe Drinking Water Act 

(SDWA) 

In response to the public health community’s and 

general public’s increased concern and awareness of 

drinking water contamination, Congress passed the 

Safe Drinking Water Act (SDWA) in 1974. The Act 

was intended to protect public health by regulating the 

Nation’s public drinking water supply. The SDWA 

establishes national enforceable standards for drinking 

water quality and makes certain that water suppliers 

monitor their water to ensure that it meets national 

standards.

From 1974 to 1986 when the SDWA was amended, 

state regulations varied in many respects, including 

differing requirements for ground water disinfection, 

mandated filtration, monitoring of organic chemicals, and operator certification requirements. Interim 

standards known as maximum contaminant levels 

(MCLs) were developed in 1975. The 1986 Amendments declared these interim standards to be final, 

required the EPA to regulate 83 contaminants within 

three years after enactment, and required disinfection 

of all public water supplies and filtration for surface 

water systems. States that have primary enforcement 

responsibility, known as primacy, were required to 

adopt regulations and begin enforcing them within 18 

months of EPA’s promulgation. The 1986 Amendments also required the EPA to regulate an additional 

25 contaminants every three years and to designate 

the best available treatment technology for each 

contaminant regulated. The amendment initiated the 

ground water protection program, established funding for sole source aquifer special needs identification 

and protection, and created a new category of water 

system (non-transient, non-community water system) 

which greatly increased the number of systems that 

states were required to regulate. 

The SDWA was amended again in 1996 (Public Law 

[P.L.] 104-183), addressing concerns about an overly 

burdensome regulatory structure and funding needs 

for PWS infrastructure and state program management. The Amendments allowed EPA to establish a 

process for selecting contaminants to regulate based 

on scientific merit rather than having to regulate an 

additional 25 contaminants every three years and 

established the Drinking Water State Revolving 

Fund (DWSRF) to help public water systems finance 

the costs of drinking water infrastructure needs. 

The Amendments also changed the emphasis from 

drinking water treatment to contaminant prevention (through source water protection and enhanced 

water system management). The 1996 Amendments 

allowed for flexibility of regulations and monitoring 

for small systems, and required the EPA to conduct 

cost-benefit analyses of new regulations and analyze 

the likely effect of the regulation on the viability of 

public water systems (EPA-Drinking Water Academy, 

2003). Over the years, EPA has released many documents related to SDWA. The most recent document 

that provides a detailed understanding of the SDWA 

was released on the 30th Anniversary of its promulgation in June 2004 (EPA, 2004). 

3.2 SDWA Provisions 

The SDWA has many regulatory provisions; a detailed 

review of all these provisions is beyond the scope of 

this document. A brief overview of SDWA regulatory 

provisions related to PWS operations is presented in 

the following subsections. 

3.2.1 National Primary Drinking Water 

Regulations (NPDWR) 

The 40 CFR 141 establishes the NPDWR and 40 CFR 

142 establishes the implementation of NPDWR pursuant to section 1412 of the SDWA of 1974, as amended 

(P.L. 93-523). The NPDWR established both Recommended Maximum Contaminant Levels (RMCLs) 

and MCLs. As part of the 1986 amendments to the 

SDWA, RMCLs were renamed MCLGs or Maximum 

Contaminant Level Goals and the National Interim 

Drinking Water Regulations were renamed as the 

NPDWR. The NPDWR is designed to protect drinking water quality by limiting the levels of specific 

contaminants that can adversely affect public health 

and are known or anticipated to occur in water. The 

NPDWR specifies two types of numeric standards. 

The first is the primary standard which is enforceable 

and establishes the MCL. The other (non-enforceable) secondary standard is referred to as a MCLG. 

The 40 CFR 141.2 defines MCL as the maximum 

permissible level of a contaminant in water which is 

delivered to any user of a PWS. This is water “delivered to the free flowing outlet of the ultimate user 

of a PWS, except in the case of turbidity where the 

maximum permissible level is measured at the point 

of entry to the distribution system.” Contaminants 

added to the water under circumstances controlled 

by the user are excluded from this definition, except 

those contaminants resulting from the corrosion of 

piping and plumbing caused by water quality. 

MCLGs are set at a level at which no known or an3-1
ticipated adverse human health effects occur. Where 

it is not economically or technologically feasible to 

determine the level of a contaminant, a treatment technique (TT) is prescribed by EPA in lieu of establishing 

an MCL. For example, Giardia lamblia is a microbial 

contaminant that is difficult to measure. To ensure 

proper removal, experimental work has established 

optimum treatment conditions for the water at a specified pH, temperature, and chlorine concentration for 

a specified length of time to achieve a fixed level of 

inactivation. 

3.2.2 National Secondary Drinking Water 

Regulations (NSDWR) 

The 40 CFR 143 establishes NSDWR pursuant to section 1412 of the SDWA, as amended (42 U.S.C. 300g1). These standards are non-enforceable guidelines 

for controlling contaminants in drinking water for 

aesthetic considerations, such as taste, color, and odor. 

Although the EPA recommends secondary standards, 

it does not enforce compliance. States may, however, 

choose to adopt them as enforceable standards. 

3.2.3 Contaminant Candidate List (CCL) 

The 1996 SDWA Amendments require the EPA to 

publish a list of contaminants that are not regulated by 

any NPDWR provisions (at the time the list is published), are anticipated or known to occur in PWSs, 

and may later require regulation under the SDWA. 

This list, CCL, was required to be published initially 

within 18 months of enactment of the Amendments 

and every 5 years thereafter. Contaminants for priority 

drinking water research, occurrence monitoring, and 

guidance development, including health advisories, are 

drawn from the CCL. The first CCL was published in 

1998. The second was issued in February of 2005. 

3.3 Current Regulatory Issues 

Besides the SDWA, there are several other rules and 

contaminants of interest which may impact small 

systems. A brief summary of these rules and contaminants of interest are presented in the following 

subsections.

3.3.1 Perchlorate 

The EPA’s National Center for Environmental Assessment first released an external review draft report 

concerning perchlorate in 1998 and later released a 

revised document entitled Perchlorate Environmental Contamination: Toxicological Review and Risk 

Characterization in 2002. According to this document, “perchlorate (ClO4

–) is an anion that originates 

as a contaminant in ground water and surface waters 

when the salts of ammonium, potassium, magnesium, 

or sodium dissolve in water. One major source of 

contamination is the manufacture or improper disposal 

of ammonium perchlorate that is used as the primary 

component in solid propellant for rockets, missiles, 

and fireworks.” The document also states that an “appreciation of widespread contamination in the United 

States emerged in the Spring of 1997 when development of an analytical method with a quantitation level 

at 4 ppb became available.” 

The EPA draft assessment concludes that the potential 

human health risks of perchlorate exposures include 

effects on the developing nervous system and thyroid 

tumors and presents a reference dose (RfD) that is 

intended to be protective for both types of effects. 

The draft RfD is 0.00003 milligrams per kilogram per 

day (mg/kg/day), which is a preliminary estimate of a 

protective health level. The RfD is undergoing science 

review and deliberations by the external scientific 

community and within EPA. The National Research 

Council (NRC) released a report that suggested a safe 

level of perchlorate at 24.5 micrograms/liter (based on 

2 liter/day consumption by a 70 kg individual) (NRC, 

2005).

EPA may at some point issue a Health Advisory that 

will provide information on protective levels for drinking water. The draft document goes on to state that 

“this is one step in the process of developing a broader 

response to perchlorate including, for example, technical guidance, possible regulations and additional 

health information. A federal drinking water regulation 

for perchlorate, if ultimately developed, could take 

several years.” 

Perchlorate was placed on EPA’s CCL, for consideration for possible regulation, in 1998. The next year 

EPA required drinking water monitoring for perchlorate under the Unregulated Contaminant Monitoring 

Rule (UCMR). Under this rule, monitoring was required of all large public water systems and a representative sample of small public water systems over 

a two year period (from 2001 to 2003) to determine 

whether the public was being exposed to perchlorate 

in drinking water nationwide. As of March 2004, the 

sampling period had expired; however, the EPA had 

not received all the data from the PWSs. The EPA will 

not disseminate a final revision of its draft risk assessment until it has fully evaluated the recommendations 

made by a National Academy of Science (NAS) panel. 

3.3.2 Arsenic 

The first arsenic drinking water standard was established by the U.S. Public Health Service in 1942 for 

interstate water carriers. The standard was set at 0.05 

mg/L, and under the SDWA of 1974 the EPA issued 

this limit as a National Interim Primary Drinking Water Regulation (NIPDWR). The 1986 SDWA renamed 

3-2
the NIPDWRs to NPDWRs, directed the EPA to revise 

NPDWRs by 1989, and specified that MCLGs be 

promulgated simultaneously with MCLs (EPA, 2002a) 

The 1996 SDWA Amendments set deadlines for 

regulating arsenic. The EPA was required to propose 

a revised Arsenic Rule by January 1, 2000, and issue a 

Final Rule by January 1, 2001. On June 22, 2000, the 

EPA proposed to revise the existing NPDWR MCL for 

arsenic to 0.005 mg/L. The Final Rule was published 

on January 22, 2001 and established an MCL for 

arsenic at 0.010 mg/L, which became enforceable on 

January 23, 2006 (40 CFR 141) (EPA, 2002a). 

According to EPA’s Report to Congress: Small Systems Arsenic Implementation Issues (EPA, 2002b), 

“small systems are being asked – in some cases for the 

first time – to grapple with a whole new set of public 

health challenges. This situation poses enormous 

implementation, timing, resource, technical, and capacity challenges for public water systems across the 

country.” The document also states that small system 

infrastructure may be outdated and in poor condition. Source water available to small systems may be 

of poor quality and limited quantity. Technical water 

system planning and operations expertise necessary to 

evaluate and install new treatment technologies may 

also be lacking. In addition, small systems face considerable financial challenges in that they have a small 

customer base and, thus, often lack the opportunity to 

benefit from economies of scale. 

The above referenced Report to Congress estimates 

that 3,341 small systems out of a total of an estimated 

75,000 potentially affected systems nationally will 

have to make improvements or take other measures 

(e.g., locate a different source of water) to meet the 

new arsenic standard. This represents a substantial 

number of small systems, particularly ground water 

systems, that will need to make treatment changes. 

Because of the importance of the Arsenic Rule and 

the national debate surrounding it related to science 

and costs, EPA’s Administrator publicly announced on 

March 20, 2001, that the Agency would take additional 

steps to reassess the scientific and cost issues associated with this Rule. After taking public comment on the 

Agency’s plan to review the basis for the Arsenic Rule, 

EPA extended the effective date to February 22, 2002, 

while maintaining the compliance dates of January 

23, 2006, for the arsenic MCL and January 22, 2004, 

for the clarifications to compliance and new source 

contaminants monitoring (66 FR 28350). The EPA 

implementation guidance (EPA, 2002a) specifies a 

request by the EPA for a review of the Arsenic Rule by 

the National Academy of Science (interpretation and 

application of arsenic research), the National Drinking 

Water Advisory Council (assumptions and methodologies), and the EPA’s Science Advisory Board (benefits). Information on the findings is available in the 

EPA implementation guidance (EPA, 2002a). 

The EPA announced on October 31, 2001 that the 10 

ppb standard for arsenic would remain. The “EPA will 

continue to evaluate the expert panel reports, the voluminous public comments received, and other relevant 

information and comments as they become available 

as part of the next round of review of the existing 

NPDWR under SDWA §1412(b)(9). As part of this 

review due August 2008, EPA expects to make a decision on whether to further revise the arsenic standard” 

(EPA, 2002a). 

EPA expects that new, more cost effective approaches 

to comply with drinking water requirements will be 

developed, and that small systems will be better able to 

meet the challenges posed by the new arsenic drinking 

water standard as well as other, future drinking water 

standards (EPA, 2002b). 

3.3.3 Compliance with Surface Water 

Treatment Rule 

The Surface Water Treatment Rule (SWTR) was first 

published in June 1989. A final Long Term 1 Enhanced SWTR (LT1ESWTR) was later published (for 

systems serving fewer than 10,000 persons - EPA, 

2002c). Thereafter, the Long Term 2 Enhanced 

Surface Water Treatment Rule (LT2ESWTR) was 

published for all PWSs using surface water or ground 

water under direct influence-GWUDI (EPA, 2003a). 

These regulations appear in 40 CFR 141, Subpart H 

and establish criteria under which filtration is required 

as a treatment technique for public water systems supplied by surface water or GWUDI. These regulations 

also establish TT requirements (in lieu of MCLs) for: 

Giardia lamblia, viruses, heterotrophic plate count 

bacteria, Legionella, and turbidity. 

The regulations state that a system is in compliance 

with 40 CFR 141.70(a) if it meets the requirements for 

avoiding filtration (40 CFR 141.71) and the disinfection requirements (40 CFR 141.72(a)) or it meets the 

requirements for avoiding filtration (40 CFR 141.73) 

and the disinfection requirements (40 CFR 141.72(b)). 

In other words, “systems must either provide filtration 

and disinfection or comply with the requirements to 

avoid filtration” (EPA, 2003b) 

The criteria for avoiding filtration may be summarized 

as follows: 

• Limitations on source water quality conditions 

concerning fecal coliform concentrations and 

3-3
turbidity levels; 

• Site-specific conditions concerning disinfection; 

• Maintaining a watershed control program which 

minimizes the potential for Giardia lamblia cyst 

and virus contamination in the source water; 

• An annual on-site inspection to assess the 

watershed control program and disinfection 

treatment process; 

• Conditions for being an identified source of a 

waterborne disease outbreak; 

• Conditions for complying with the MCL for 

total coliforms; and 

• Conditions for complying with specified 

requirements for total trihalomethanes, 

haloacetic acids, bromate, chlorite, chlorine, 

chloramines, and chlorine dioxide. 

The regulations for disinfection are presented in 40 

CFR 141.72 and are subdivided into disinfection requirements for PWSs that do not provide filtration and 

those that do provide filtration. The filtration regulations are provided in 40 CFR 141.733. In general, 

“systems may avoid filtration if they have low coliform 

and turbidity in their source water and meet other 

site-specific criteria. Systems that do not meet these 

criteria must install one of the following filtration 

treatments: conventional filtration treatment or direct 

filtration; slow sand filtration; diatomaceous earth filtration; or another filtration if the state determines that, 

in combination with disinfection, the proper amount 

of Giardia and virus removal and/or inactivation is 

achieved” (EPA, 2003b). 

As stated above, the LT1ESWTR affects those PWSs 

that use surface water or GWUDI (Subpart H system) 

serving fewer than 10,000 persons. The regulations 

governing this rule are meant to improve control 

of microbial contaminants and prevent increases in 

microbial risk while systems control for disinfection 

by products (DBPs) and are presented in 40 CFR 141, 

Subpart T. The regulations establish requirements for 

filtration and disinfection that are in addition to Subpart H criteria. The regulations in Subpart T establish 

or extend treatment technique requirements in lieu 

of MCLs for: Giardia lamblia, viruses, heterotrophic 

plate count bacteria, Legionella, Cryptosporidium and 

turbidity. Management at Subpart T systems must 

establish a Disinfection Profile and Benchmark. Also, 

if a Subpart T system plans on making significant 

changes to its disinfection practices, it must first get 

approval from the state. 

The LT2ESWTR is applicable to all Subpart H systems and is intended to require higher levels of treatment for source waters of lower quality. Depending on 

the initial monitoring results, systems that filter would 

be put into groups or “bins.” Under the proposed rule, 

each bin (except the bin for the lowest levels) requires 

a system to install a treatment technology and sets a 

monitoring schedule, both based on contamination 

levels in the source water. Under the proposed rule, 

some new treatment options could possibly involve 

watershed control, reducing influent Cryptosporidium

concentrations, improving system performance, and 

including additional treatment barriers such as pretreatment” (EPA, 2003b). 

3.3.4 Stage 1 and 2 Disinfection Byproducts 

(DBP) Rules 

As discussed in Chapter 2, a disinfectant is any 

oxidant, including but not limited to chlorine, chlorine dioxide, chloramines, and ozone, that is added 

to water in any part of the treatment or distribution 

process and is intended to kill or inactivate pathogenic 

microorganisms. A DBP is a compound formed by 

the reaction of a disinfectant such as chlorine with 

naturally occurring organic material in the water 

supply. Many of the DBPs are suspected of causing 

cancer, reproductive and developmental problems in 

humans (EPA 2003b). The Stage 1 Disinfectants/ 

Disinfection Byproducts Rule (Stage 1 DBPR) was 

published in December 1998 to reduce the levels of 

disinfectants and DBPs in drinking water supplies, 

including byproducts that were not previously covered 

by drinking water rules. The rule sets MCLs for 

haloacetic acids (HAA5), chlorite (a major chlorine 

dioxide byproduct), bromate (a major ozone byproduct), and total trihalomethanes (TTHM). It also set 

Maximum Residual Disinfectant Levels and Maximum Residual Disinfectant Level Goals for chlorine, 

chloramines, and chlorine dioxide. 

The Stage 1 DBPR affects CWSs and NTNCWSs 

that add a chemical disinfectant to the water in any 

part of the drinking water treatment process. Certain 

requirements apply to TNCWSs that use chlorine 

dioxide (EPA, 2003b) Systems that use conventional 

filtration must remove specified percentages of total 

organic carbon (TOC) using either enhanced coagulation or enhanced softening. The removal requirement 

depends on the TOC concentration and alkalinity of 

the source water. 

The Stage 2 DBPR builds on the public health protection provided by the Stage 1 DBPR. Along with the 

proposed LT2ESWTR, it aims to reduce the risks 

associated with DBPs without increasing the risk of 

microbial contamination. The rule affects CWSs and 

NTNCWSs that add a disinfectant other than ultra3-4
violet light or deliver water that has been disinfected 

(EPA, 2003b). 

3.3.5 Proposed Ground Water Rule 

In addition to regulations guiding surface water treatment, the EPA published the proposed Ground Water 

Rule in May of 2000. A final rule is expected in 

late 2006. This rule has the potential to affect small 

systems that use ground water as a source. The rule 

proposes periodic sanitary surveys; once every three 

years for community water systems (CWS) and once 

every five years for non-community water systems 

(NCWS). Any deficiencies uncovered during the 

survey would need to be corrected in 90 days. Sanitary 

survey methodology would be based on the eight components found in the “Guidance Manual for Conducting Sanitary Surveys of Public Water Systems; Surface 

Water and Ground Water Under the Direct Influence of 

Surface Water” (EPA 815-R-99-016). The proposed 

rule also seeks comment on the use of grandfathered 

data from surveys used for the Total Coliform Rule 

(TCR). The proposed Ground Water Rule would also 

require a hydrogeologic sensitivity analysis for all nondisinfecting ground water systems in order to identify 

systems that may be prone to fecal contamination (e.g. 

Karst topography). Source water monitoring would be 

required for systems that do not treat for 4-log removal 

of viruses. A system would be required to collect 

a source water sample within 24 hours of receiving 

notification of a positive total-coliform sample taken 

in compliance with the TCR and test the sample for E. 

coli, enterococci or coliphage. Any system deemed 

hydrogeologically sensitive would be required to 

conduct monthly monitoring for E. coli, enterococci 

or coliphage. If the deficiency can not be corrected at 

the source, systems would be required to implement 

treatment for 4-log removal/inactivation of viruses 

before or at the first customer. Examples of treatment 

technologies capable of 4-log virus removal include: 

chlorination, chloramination, and ultraviolet radiation. 

Systems serving 3,300 or less people would be required 

to monitor disinfectant levels via daily grab samples. 

3.3.6 Methyl Tertiary Butyl Ether (MTBE) 

MTBE is a chemical compound that is manufactured 

by the chemical reaction of methanol and isobutylene. It is a gasoline additive (used to help prevent 

engine “knocking”) that can leak into the environment 

wherever gasoline is stored, transported, or transferred. 

MTBE has been used at higher concentrations in some 

gasoline to fulfill the oxygenate requirements set by 

Congress in the 1990 Clean Air Act Amendments. A 

growing number of studies have detected MTBE in 

ground water throughout the country; in some instances, these contaminated waters are sources of drinking 

water. Low levels of MTBE can make drinking water 

supplies undrinkable due to its offensive taste and odor 

(Squillace et al., 2000). 

Most human health-related studies have so far focused 

on the effects of inhaling MTBE. Researchers have 

limited data regarding the health effects MTBE may 

have on a person who ingests it. EPA’s Office of Water 

has concluded that available data are not adequate 

to estimate potential health risks of MTBE at low 

exposure levels in drinking water but that the data support the conclusion that MTBE is a potential human 

carcinogen at high doses. Recent work by EPA and 

other researchers is expected to help determine more 

precisely the potential for health effects from MTBE 

in drinking water (EPA, 2003c). 

MTBE is also on the EPA’s CCL and the EPA is 

continuing to study both the potential health effects 

and the occurrence of MTBE. Beginning in 2001, the 

EPA required (under the Unregulated Contaminants 

Monitoring Rule-UCMR) all large drinking water 

systems and a representative sample of small systems 

to monitor for MTBE and report their findings. 

3.3.7 Radionuclides 

The EPA began regulating radionuclides in 1976, as 

interim regulations under the authority of the SDWA 

of 1974. On December 7, 2000, the EPA issued the 

Radionuclides Rule, which refined the legally binding 

requirements for radionuclides set forth in the 1986 

SDWA Amendments. The Radionuclide Rule took 

effect on December 8, 2003, setting MCLs as well as 

monitoring, reporting, and public notification requirements for radionuclides. Under this rule, all systems 

must complete initial monitoring for radionuclides 

by December 31, 2007. States will determine initial 

monitoring requirements during this 4-year initial 

monitoring period. 

Radionuclides generally enter drinking water through 

the erosion or chemical weathering of naturally occurring mineral deposits, although human activity (such 

as mining, industrial activities, or military activities 

that use or produce man-made radioactive materials) 

can also contribute to their presence in water (EPA, 

2002d).

There are three basic kinds of high-energy radiation: 

alpha, beta, and gamma. The EPA has set limits (i.e. 

MCLs) for four groupings of radionuclides: alpha 

particles, beta particles and photon emitters, Radium226 and Radium-228 (combined), and uranium (EPA, 

2002d).

The Radionuclides Rule changed monitoring requirements for small drinking water systems by requiring 

3-5
monitoring at each entry point to the distribution 

system (EPTDS), rather that just monitoring at a “representative” point in the distribution system. It may 

be possible to reduce the frequency of monitoring at 

each EPTDS based on the initial sample results. The 

following table (Table 3.1) shows the reduced monitoring frequencies. 

Table 3.1 Reduced monitoring for 

radionuclides (EPA, 2002d). 

If the initial monitoring results 

are:

Monitoring frequency 

is reduced to: 

< Defined detection limit 1 sample every 9 years 

> Defined detection limit, 

but less than or equal to 1⁄2 the MCL 1 sample every 6 years 

> 1⁄2 the MCL, 

but less than or equal to the MCL 1 sample every 3 years 

> MCL Quarterly samples 

Systems with EPTDS on a reduced monitoring schedule (i.e., collecting 1 sample every 3, 6, or 9 years) can 

remain on that reduced schedule so long as the most 

recent sample results support that monitoring schedule. An increase in a radionuclide level at an EPTDS 

may increase the frequency of monitoring for that 

radionuclide at that sampling point. If an entry point 

result is above the MCL while on reduced monitoring, the system operator must begin to take quarterly 

samples in the next quarter. Quarterly sampling must 

continue until four consecutive quarterly samples are 

below the MCL” (EPA, 2002d) 

Unless told otherwise by the state, a system which 

uses an intermittent source of supply (i.e., a source that 

is used seasonally) or that uses more than one source 

and that blends water from more than one source 

before distribution, must sample at an EPTDS during 

periods of normal operating conditions. Normal operating conditions include when water is representative 

of all the sources being used. (EPA, 2002d) 

There are several ways that small systems with high 

levels of radionuclides can protect their customers, 

including: source water changes, water blending, consolidation, and treatment (EPA, 2002d). Treatment to 

lower the levels of radionuclides in drinking water will 

be necessary if the source water contains high levels of 

radionuclides and an alternative source is not available 

or switching sources is cost prohibitive. A listing of 

the best available technologies (BATs) and small system compliance technologies (SSCTs) for removing 

radionuclides from water is provided by EPA (EPA, 

2002d). Additionally, information on complying with 

the Radionuclide Rule is also provided by EPA (EPA, 

2002e).

3.4 Source Water Assessments 

Source water is water in its natural state, prior to any 

treatment for drinking. The water may come from 

rivers, lakes, or underground aquifers used to supply 

private wells and PWSs. Source water is vulnerable to 

contamination by (EPA, 2003d): 

• Surface water – runoff (from surface areas in a 

watershed, either near a drinking water supply 

intake or in upstream tributaries) and ground 

water infiltration (recharge streams or lakes) 

• Ground water – infiltration from the surface, 

injection of contaminants through injection 

wells (including septic systems), or by naturally 

occurring substances in the soil or rock. 

Source water may contain many different contaminants prior to treatment, such as: 

• microbial contaminants (viruses and bacteria, 

primarily from human and animal wastes), 

• inorganic contaminants (salts and metals), 

• pesticides and herbicides, 

• organic contaminants (including synthetic and 

volatile organic chemicals), and 

• radioactive contaminants. 

Contaminated source water can be very costly to a 

community and state, both economically and public 

health-wise, as the burden falls to the community to 

solve the problem. “Reducing the threat of waterborne illnesses helps save hundreds of millions of 

dollars annually by eliminating costly health care 

expenses, lost wages, work absences, decreased job 

productivity, and additional treatment costs incurred 

by PWSs required to meet federal drinking water 

quality standards” (EPA, 2002f). In the long term, it 

is much more economical to protect source water from 

contamination than it is to treat contaminated water or 

find a new source. Source water protection is also the 

first line of defense in preventing waterborne illnesses. 

“The government regulates land-use and the construction-location(s) of water treatment facilities to control 

potential source(s) of pollution from contaminating 

source water” (EPA, 2003e). 

The 1996 Amendments to the SDWA (Section 1453) 

placed a new focus on source water protection, requiring each state to develop and implement a Source 

Water Assessment Program (SWAP). Indian tribes are 

not explicitly required by the amendments to implement SWAPs; however, the EPA recommends such 

implementation. Source water assessment is unique to 

each water system which provides basic information 

3-6
about the water used to provide drinking 

water. These assessments identify the 

area of land that most directly contributes 

the raw water used for drinking water, 

and identifies the major potential sources 

of contamination to drinking water supplies. The information gathered can then 

be used to determine how susceptible 

the water system is to contamination. 

The State Source Water Assessment and 

Protection Programs Guidance, Final 

Guidance (EPA, 1997) provides implementation guidance for State SWAPs 

and Source Water Protection (SWP) 

Programs. This document also defines 

the goals for SWAPs as follows: “to 

provide for the protection and benefit of 

public water systems and for the support 

of monitoring flexibility.” SWAPs are 

further discussed in Section 4.3. 

3.5 Wellhead Protection 

The 1986 Amendments to the SDWA, specifically 

Section 1428, strengthened the regulations governing ground water protection by requiring each state 

to develop and implement a Wellhead Protection Plan 

(WHPP). The SDWA requires that every state wellhead protection plan address the following areas of 

concern (Thompson et al., 1997): 

• The roles and duties of state and local 

governments and public water suppliers with 

respect to the development and implementation 

of a wellhead protection plan for a public water 

supply. 

• Acceptable criteria and methodologies for 

delineation of Wellhead Protection Areas 

(WHPAs) for each wellhead based on 

reasonably available hydrogeologic data and 

other information. 

• Identification and risk assessment of 

contaminant sources within each WHPA, 

including all potential sources that may have an 

adverse health impact. 

• Management approaches that may include 

technical assistance, financial assistance, 

implementation of control measures, education, 

training, and demonstration projects. 

• Development of contingency plans for PWSs 

indicating the location of alternate drinking 

water supplies in the event of well or well-field 

contamination.

• Recommendations for proper siting of new wells 

to minimize potential contamination. 

Federal

EPA Grant State Add 20% 

State Match

*Repayments return to Fund for future assistance 

*

Revolving Loan Fund 

(includes repayments,

bond proceeds,

interest, etc.) 

Assistance to Public

Water Systems 

• Treatment

• Sources

• Storage

• Transmission & 

distribution

Set-asides (up to 31%) 

• Administration of DWSRF

• Small system tech assistance 

• Source water assessments 

• Source water protection 

• Drinking water program

• Capacity development

• Operator certification

Figure 3.1 Structure of the DWSRF program (EPA 2003f). 

• Development of processes to ensure public 

participation. 

State WHP Programs vary greatly. For example, some 

require CWSs to develop management plans, while 

others rely on education and technical assistance to 

encourage voluntary action. WHPPs are the foundation for many of the state SWAPs required under the 

1996 SDWA amendments. 

Despite the obvious need for source water protection, 

just 28 percent of the smallest systems and only 50 

percent of systems serving 10,000 or more persons 

participate in some form of source water or wellhead 

protection program. Some small systems might 

be less likely to adopt wellhead protection or SWP 

programs than larger systems because they lack the 

technical and financial resources to implement and 

manage such programs (EPA, 1999). 

3.6 Vulnerability Assessments 

(VA), Emergency Planning and 

Security 

The Public Health Security and Bioterrorism 

Preparedness and Response Act of 2002 (Bioterrorism Act) amended the SDWA by adding Section 

1433 (Public Law 107-188). The Bioterrorism 

Act required every community water system that 

serves a population of greater than 3,300 persons to 

conduct a vulnerability assessment and to develop 

an Emergency Response Plan (ERP). Chapter 8 

presents further information on VAs, ERPs and 

other security related information. 

3-7
3.7 Variances and Exemptions 

PWSs can request variances or exemptions from the 

primacy agency. Variances and exemptions allow 

PWSs to not meet a specific drinking water standard 

while continuing to protect public health to the maximum extent possible. They are identified and defined 

in the SDWA. The following subsections present a 

brief overview of these allowances. A more detailed 

summary of variances and exemptions specific to 

small systems may be found in Variances and Exemptions for Small Drinking Water Systems (EPA, 1998). 

3.7.1 Small System Variances 

Section 1415(e) of the SDWA authorizes the Administrator i.e., EPA (for states that do not have primary 

enforcement responsibility) or a state (for states that 

do have primary enforcement responsibility) to issue 

variances from the requirement to comply with MCLs 

or treatment techniques to systems serving fewer than 

10,000 persons. 

States exercising primary enforcement responsibility 

may grant a small system variance to PWSs serving 

3,300 or fewer persons without EPA approval, but 

must receive EPA approval to grant a small system 

variance to PWSs serving more than 3,300 persons but 

fewer than 10,000 persons. 40 CFR 142.312 specifies 

what EPA action is necessary when a state proposes 

to grant a small system variance to a PWS serving a 

population of more than 3,300 and fewer than 10,000 

persons. A small system variance is not available for 

microbial contaminants or for contaminants regulated 

prior to 1986 (if the EPA revises a pre-1986 MCL 

making it more stringent, then a small system variance 

could be granted but only up to the pre-1986 MCL). 

In order to obtain a small system variance, it must be 

determined that the PWS cannot afford to comply with 

the NPDWR (in accordance with state criteria or, for 

states that do not have primary enforcement responsibility, with the EPA established criteria). According to 

40 CFR 142.306, this includes: 

• Treatment; 

• Alternative sources of water supply; 

• Restructuring or consolidation changes, 

including ownership change and/or physical 

consolidation with another public water system; 

or

• Obtaining financial assistance pursuant to 

Section 1452 of the SDWA or any other federal 

or state program. 

Another requirement for obtaining a small system 

variance is that the PWS must meet the source water 

quality requirements for installing the small system 

variance technology developed pursuant to guidance 

published under Section 1412(b)(15) of the SDWA. 

The PWS must also be financially and technically 

capable of installing, operating and maintaining the 

applicable small system variance technology. The 

terms and conditions of the small system variance 

must ensure adequate protection of human health, 

taking into consideration the quality of the source 

water and the removal efficiencies and expected useful 

life of the small system variance technology. 40 CFR 

142.307 specifies the terms and conditions that must 

be included in a small system variance. 

Notice of a proposed small system variance must be 

provided to all persons served by the PWS at least 15 

days prior to the date of proposal and at least thirty 

days prior to a public meeting to discuss the variance. 

The state or EPA will decide who does the notifying 

(i.e. state, EPA, or PWS). Also, a state or the EPA 

must hold at least one public meeting on the variance 

no later than 15 days after the variance is proposed. 

Any person served by the PWS may obtain an EPA 

review of a state proposed small system variance by 

petitioning the EPA to object to the granting of a small 

system variance. The petition must be submitted 

within 30 days after a state proposes to grant a small 

system variance for a PWS. The Administrator has 60 

days (from petition receipt) to respond. 

40 CFR 142.311 specifies what procedures allow 

the EPA to object to a proposed small system variance or overturn a granted small system variance for 

a PWS serving 3,300 or fewer persons. Periodically 

EPA must review each state program to determine if 

state-granted small system variances comply with the 

requirements of the SDWA, 40 CFR 142.313, and the 

affordability criteria developed by the state. 

3.7.2 Exemptions 

For granting an exemption, the state or EPA must determine whether management or restructuring changes 

(or both) would improve water quality or achieve 

compliance. Additionally, a schedule for compliance must be developed when granting an exemption. 

Schedules for compliance must include “increments 

of progress” (retained from old law) or “measures to 

develop an alternative source of water supply” (new 

law). A system is not eligible for an exemption if the 

system receives a small system variance. The period 

of an exemption is lengthened from 1 year (old law) 

to 3 years. Eligibility for renewable exemptions is 

expanded from systems serving fewer than 500 service 

connections (approximately 1500 persons) under the 

old law, to systems serving fewer than 3,300 persons. 

3-8
Renewals are limited to a total of 6 years (SDWA 1416 

Sec. 117). 

In granting exemptions, a state may consider whether 

a community may be defined as “disadvantaged” for 

the purpose of receiving Drinking Water State Revolving Funds (DWSRF), or whether DWSRF funds are 

reasonably likely to be received. If qualified, the community (PWS operator) may receive funding that can 

be used improve the infrastructure to meet the drinking 

water standards. The DWSRF is further discussed in 

Section 3.8. 

3.8 DWSRF 

The 1996 SDWA Amendments addressed the problem 

many PWSs were facing; a lack of funding for infrastructure improvements that would enable systems 

to comply with NPDWS and protect public health. 

The SDWA Amendments created the DWSRF which 

makes funding available to PWSs to finance infrastructure improvements. EPA provides these funds to states 

in the form of capitalization grants; states, in turn, 

provide low-interest loans to drinking water systems 

(EPA, 2002g). The DWSRF program encourages 

states to develop long-term sources of drinking water 

infrastructure funding. States that do not meet certain 

requirements are subject to withholding of a portion of 

their DWSRF allotment. EPA provides capitalization 

grants to states based on the DWSRF allotment. States 

must annually prepare “intended use plans” (IUP) 

as part of their DWSRF capitalization grant application. IUPs identify eligible projects and their priorities 

based primarily on three criteria: 

• Projects that address the most serious human 

health risks; 

• Projects that ensure or maintain compliance; and 

• Projects that assist systems with greatest 

economic needs. 

Public involvement in developing the IUP is mandated. 

Figure 3.1 shows the overall structure of the DWSRF 

program.

As Figure 3.1 shows, a state may set-aside up to 31 

percent of its capitalization grant for other eligible 

drinking water program related activities. Of this setaside, the state may use (EPA, 2003f): 

• Up to 4 percent for administering the DWSRF 

and/or providing technical assistance 

• Up to 10 percent for source water protection, 

capacity development, and operator certification 

programs, as well as for the state’s drinking 

water program. 

• Up to 15 percent (but no more than 10 percent 

for any one purpose) for projects in water 

systems, including source water protection 

loans, technical and financial aid for capacity 

development, source water assessments, and 

wellhead protection. 

• Up to 2 percent for technical assistance for water 

systems serving fewer than 10,000 people. 

Referring to set-asides, the EPA report to congress 

(EPA, 2003f) states “Nationally, states have reserved 

approximately 16 percent of federal grants for these 

purposes, although on an individual state basis the 

amount reserved has ranged from 7 to 31 percent. 

Through state FY 2001, states had expended 43 percent of the $576 million in funds they reserved to conduct set-aside activities.” In this report, EPA also expressed concerns about slow progress in expenditures 

of set-asides, but expenditures have increased from 9 

to 42 percent from state FY 1998 through 2001. 

States must make funds available to small systems and 

can establish provisions for disadvantaged community 

assistance as part of their DWSRF programs. Through 

its disadvantaged assistance program, a state may 

provide additional subsidies such as principal forgiveness, or extend loan repayment periods for up to 30 

years. The DWSRF program also encourages the use 

of funds for programs that use pollution prevention to 

ensure safe drinking water (EPA, 2002g). 

3.9 Key Questions 

• What are the most crucial areas of research 

for small systems with regard to regulations 

that have already been promulgated? (e.g. 

radionuclides, arsenic, residual disposal?) 

• What contaminants on the CCL should 

WSWRD researchers focus on with respect to 

treatment, distribution system issues, and source 

water protection? 

• How can research help small systems to 

comply with the LT2ESWTR (e.g. source water 

monitoring costs)? 

3.10 References 

All references to Code of Federal Regulations (CFR) 

Documents in this chapter may be found at http://

www.access.gpo.gov/nara/cfr and Federal Register 

Documents may be found at http://www.gpoaccess. 

gov/fr/index.html 

EPA. State Source Water Assessment and Protection 

Programs Guidance, Final Guidance, EPA-816-R-97-

009, 1997. 

3-9
EPA. Variances and Exemptions for Small Drinking 

Water Systems, EPA-816-F-98-008, 1998. 

EPA. National Characteristics of Drinking Water 

Systems Serving Populations Under 10,000, EPA-816-

R-99-010, 1999. 

EPA. Implementation Guidance for the Arsenic Rule, 

EPA-816-K-02-018, 2002a. 

EPA. Small Systems Arsenic Implementation Issues, 

EPA-815-R-02-003, 2002b. 

EPA. Final Long Term 1 Enhanced Surface Water 

Treatment Rule, EPA-815-F-02-001, 2002c. 

EPA. Radionuclides in Drinking Water: A Small Entity Compliance Guide, EPA-815-02-001, 2002d. 

EPA. Implementation Guidance for Radionuclides, 

EPA-816-F-00-002, 2002e. 

EPA. Consider the Source: A Pocket Guide to Protecting Your Drinking Water, Drinking Water Pocket 

Guide #3, available at: http://www.epa.gov/safewater/ 

protect/pdfs/swppocket.pdf, 2002f. 

EPA. Sources of Technical and Financial Assistance 

for Small Drinking Water Systems, EPA-816-K-02-

005, 2002g. 

EPA-Drinking Water Academy. An Overview of the 

Safe Drinking Water Act, available at: 

http://www.epa.gov/safewater/dwa/electronic/presentations/sdwa/sdwa.pdf, 2003. 

EPA. Proposed Long Term 2 Enhanced Surface Water 

Treatment Rule, EPA-815-F-03-005, 2003a. 

EPA. Small Systems Guide to Safe Drinking Water 

Act Regulations, EPA 816-R-03-017, 2003b. 

EPA. Methyl Tertiary Butyl Ether (MTBE) - FAQ, 

available at: http://www.epa.gov/mtbe/faq.htm, 2003c. 

EPA. Introduction to EPA’s Drinking Water Source 

Protection Programs, available at: 

http://www.epa.gov/safewater/dwa/electronic/presentations/swp/swp.pdf, 2003d. 

EPA. Small Drinking Water Systems Handbook: A 

Guide to Packaged Filtration and Disinfection Technologies with Remote Monitoring and Control Tools, 

EPA 600-R-03-041, 2003e. 

EPA. The Drinking Water State Revolving Fund Program Financing America’s Drinking Water from the 

Source to the Tap, EPA-918-R-03-009, 2003f 

EPA. Safe Drinking Water Act 30th Anniversary Understanding the Safe Drinking Water Act, 

EPA 816-F-04-030, 2004. 

National Research Council (NRC). Health Implications of Perchlorate Ingestion. The National Academies Press. Washington, D.C. 2005. 

Squillace, P.J., J.S. Zogorski, W.G. Wilber, and C.V. 

Price. A Preliminary Assessment of the Occurrence 

and Possible Sources of MTBE in Ground Water of the 

United States, 1993-94. U.S. Geological Survey OpenFile Report 95-456, available at: http://sd.water.usgs. 

gov/nawqa/pubs/ofr/ofr95.456/ofr.html. March 2000. 

Thompson, C.A., E.N. Nealson, and M.K. Anderson. 

Iowa Wellhead Protection Plan, available at: http:// 

www.iowadnr.com/water/iwp/files/iwpp_full.pdf, 

September, 1999. 

3-10
Chapter 4 

Source Water Issues 

4.1 Background 

PWSs derive their source water from both ground and/ 

or surface water. Most (over 90%) systems use ground 

water as their source of drinking water; however, the 

majority of people (65%) are served by PWSs that 

use surface water as their source (EPA, 2005). Source 

water is untreated water from streams, rivers, lakes, 

or aquifers which is used to supply private wells and 

public drinking water systems. Most public and some 

private well drinking water is treated prior to delivery 

to our homes. While some treatment is usually necessary, the treatment costs and public health risks can 

be reduced by ensuring that source water is protected 

from contamination. 

Contaminated source water can cause both acute and 

chronic health effects if consumed without proper 

treatment. Acute health effects are immediate effects 

that may result from exposure to certain contaminants 

such as pathogens (e.g. viruses, bacteria, parasites, 

protozoa or cysts), organic chemicals (e.g. pesticides), 

and/or inorganic chemicals (e.g. arsenic) that may be 

in source water. Sources of contaminants that cause 

acute health effects include industry, animal feeding 

operations, agriculture, septic systems, and cesspools. 

Chronic health effects are the possible result of exposure over many years to a drinking water contaminant 

at levels above its maximum level established by EPA. 

Sources of contaminants that cause chronic health 

effects include industrial and commercial activities, 

agriculture, landfills, surface impoundments, and 

urban activities. 

Long-term exposure to contaminants such as volatile 

organic chemicals, inorganic chemicals, or synthetic 

organic chemicals can result in chronic health effects 

including birth defects, cancer, and other long-term 

health effects. 

Considerable information about source water protection is already available, much of it from EPA. This 

chapter presents a strategy for small systems source 

water research based on the EPA ORD’s Multi-Year 

Plan, descriptions of source water assessment and protection tools, and problems and solutions for building 

sustainable community water systems. 

4.2 Drinking Water Research 

Program Multi-Year Plan 

The scientific questions associated with source water 

protection encompass a broad range of issues. Source 

water protection is a component of other ORD research programs, although the protection of drinking 

water quality may not be their primary goal. The water industry has an active research program in source 

water protection. ORD’s drinking water research program is therefore focused on areas that are not being 

fully addressed by other means and that match ORD’s 

technical capabilities. 

The Drinking Water Research Program Multi-Year 

Plan (EPA, 2003) presents ORD’s proposed research in 

source water issues over the next 5 to 8 years. Many 

of these issues are broad in scope and are intended to 

apply to all PWSs. The source water program goals 

focus on the protection of the source water supply, 

including both surface and ground water. Because 

most of small CWSs use ground water as their source, 

programs that address ground water have the potential 

to have the greatest benefit to small community water 

systems. The plan establishes long-term goals and 

research projects that are discussed in the following 

sub-sections.

4.2.1 Long-Term Goals 

Annual Performance Goals (APGs) for source water 

protection from FY 2006 to 2009 are designed to 

assist decision makers at the national, state and local 

level by providing tools and information that contribute to more effective management practices. Annual 

Performance Measures (APMs) include reports that 

describe how to better assess the vulnerability of watersheds, how to detect specific contaminants and other 

changes in water quality using improved diagnostic 

tools, and how to more effectively manage different 

types of contamination problems. Potential areas of 

additional research include: 

• Source water assessment and protection, with 

a focus on such areas as reducing impacts of 

septic systems and other non-point sources, wet 

weather flow and the development of real-time 

monitoring systems. 

• Expansion of the new program on molecular 

technologies for screening, prioritizing and 

monitoring contaminants of concern. This 

would have applications for risk assessment 

(e.g., to support hazard evaluations), risk 

management (e.g., to monitor water sources), 

and research planning in general. 

4.2.2 Ongoing and Future Research 

Research projects have been developed specific to 

source water assessments. These are applicable to 

drinking water systems of all sizes and source water, but several will benefit small community water 

4-1
systems that do not have the resources to complete this 

type of work. Specific projects include the following: 

• Report on siting of wells and operations to 

control arsenic. 

• Report on the use of geochemical data to 

manage risks to public water supply wells from 

arsenic contamination. 

• Report on early warning upstream monitoring 

network to protect source waters. 

• Report on the role of municipal sewage 

effluents in contributing to the occurrence 

of enterohemorrhagic Escherichia coli in 

watersheds. 

• Assessment of Best Management Practices 

(BMPs) for atrazine in rural watersheds. 

• Optimization of BMPs design/location for 

atrazine. 

• Final report on the characterization of 

Cryptosporidium and Giardia in combined 

sewer overflows (CSOs). 

• Biosensor evaluation and demonstration as a 

tool to protect source waters. 

• State-of-the-science report for on-site sewage 

management and septic systems technology. 

• Placement of BMPs in urban watersheds to meet 

water quality goals. 

• Watershed boundary condition identification. 

• Report on modeling and placement of structural 

BMPs as a source water protection approach. 

• Report on molecular microarrays for detection 

of non-pathogenic bacteria and bacterial 

pathogens in drinking water source waters. 

• State-of-the-science report on real time early 

warning systems for source water protection. 

• Determine the fate and transport of 

Nitrosodimethyl Amine and other disinfection 

byproducts in aquifer and large multiple-use 

source waters. 

• Evaluate the effectiveness of selected structural 

BMPs to help macronutrient balances and 

sediments in source water turbidity, algae, taste 

and odor. 

By 2009, EPA plans to provide data, tools, and 

technologies to support management decisions by the 

Office of Water, state, and local authorities to protect 

source waters. 

4.3 Source Water Assessments 

Under the SDWA, states are required to develop 

comprehensive Source Water Assessment Programs 

(SWAPs) that will: 

• identify the areas that supply public drinking 

water; 

• inventory contaminants and assess water system 

susceptibility to contamination; 

• inform the public of the results. 

States are required by the SDWA Amendments of 

1996, Sections 1453 and 1428(b), to complete a source 

water assessment for each public water system PWS. 

These assessments can be done for each system or on 

an “area-wide” basis involving more than one PWS. 

A source water assessment provides important information for carrying out protection programs. This 

“know your resource and system susceptibility” part 

of protection involves identifying the land that drains 

to the drinking water source and the most prominent 

potential contaminant risks associated with it. To be 

considered complete, a SWAP must include various elements described in the following sub-sections 

(EPA, 1997). 

4.3.1 Delineation

The source water protection area should be delineated in accordance with wellhead protection methods. 

Sometimes, it may be necessary to delineate source 

water protection areas either inside of or in addition to 

typical wellhead protection areas. A wellhead protection area is the surface and subsurface area surrounding a well or well field though which contaminants can 

reach a water supply. 

4.3.2 Contamination Sources 

Community groups can become especially involved in 

the second step of an assessment: identifying potential 

sources of pollutants that could contaminate the water 

supply. This inventory usually results in a list and a 

map of facilities and activities within the delineated 

area that may release contaminants into the ground 

water supply (for wells) or the watershed of the river 

or lake (for surface water sources). 

Some examples of the many different types of potential pollutant sources include landfills, underground or 

above-ground fuel storage tanks, residential or commercial septic systems, storm water runoff from streets 

and lawns, farms that apply pesticides and fertilizers, 

and sludge disposal sites. 

4-2
4.3.3 Susceptibility Determination 

A susceptibility determination refers to a determination of the susceptibility of the water supply to 

contamination, based on the contamination source 

inventory and other relevant factors. The susceptibility determination is useful for decisions regarding 

management of the source water protection area and 

source water protection activities. The susceptibility determination may be based on: 

• Hydrologic and hydrogeologic factors such as 

ground water or surface water movement; 

• Characteristics of the contaminants (e.g., 

toxicity, environmental fate and transport); 

• Characteristics of the potential source of the 

contaminant (location, likelihood of release, 

effectiveness of mitigation measures); and 

• Other factors such as well intake and well 

integrity. 

The susceptibility determination may be an absolute 

measure of the potential for contamination of the 

public water supply, a relative comparison between 

sources within the source water protection area, or 

a relative comparison to findings by other assessments. 

4.3.4 Public Involvement 

After a state completes the assessment of a particular water system, it will summarize the information 

for the public. Such summaries help communities 

understand the potential threats to their water supplies 

and identify priority needs for protecting the water 

from contamination. States will make the assessment 

summaries available to the public in a variety of ways 

including: public workshops, making copies available 

in public libraries and from local government offices 

or water suppliers, and posting assessment summaries 

on the Internet. The results of the assessments will 

also be included in the annual water quality reports 

that community water systems are required to prepare 

for their customers. 

4.3.5 Benefits of Source Water Assessment 

Plans (SWAPs) 

The 1996 Safe Drinking Water Act Amendments has 

given states access to funding for implementation of 

SWAPs. With this funding, states are now able to assess areas serving as public sources of drinking water 

in order to identify potential threats and initiate protection efforts. 

Once completed, the source water assessments can 

be used to focus prevention resources on drinking 

water protection. EPA strongly encourages linking the 

source water assessments to implementation of source 

water protection programs. 

4.3.6 Source Water Protection 

Protection of drinking water at the source can be 

successful in providing public health protection and 

reducing the treatment challenge for public water 

suppliers. Source water quality can be threatened by 

many everyday activities and land uses, ranging from 

industrial wastes to the chemicals applied to suburban 

lawns. Water systems are heavily regulated through 

the Public Water System Supervision Program, and 

must respond to this threat to public health with regular water quality monitoring and actions ranging from 

well closure to expensive treatment. In some cases, 

source water protection can eliminate or forestall the 

need to change or modify treatment processes, saving 

consumers significant money. 

4.4 Other Source Water 

Assessment and Protection 

Tools 

Two valuable tools for source water assessment and 

protection activities include the Sanitary Survey and 

the Wellhead Protection Program. 

4.4.1 Sanitary Survey 

A sanitary survey is an inspection of all components 

of a water system from source to tap. The inspection 

should identify potential sources of contamination 

and can provide the opportunity for states to conduct 

source water delineations and assessments, update 

SWAPs, and follow up on the development of source 

water protection (SWP) activities. In addition, states 

could use information collected in source water assessments, whether done separately or concurrently, 

to enhance sanitary survey information and to identify 

systems of concern that should receive priority for 

surveys. 

4.4.2 Wellhead Protection Program (WHPP) 

Wellhead protection (WHP) efforts are significant 

because many small community water systems use 

ground water as their primary source of drinking 

water. Establishing and implementing a local WHP 

program includes: forming a WHP planning team, 

delineating a WHP area, identifying potential sources 

of contamination, choosing management tools, and 

planning for contingencies. 

The public information requirements for the SWP 

program do not apply to the WHP program. However, throughout its development and implementation, 

education and outreach are essential to the success of a 

local WHP effort. 

4-3
4.5 Sustainability of Community 

Water Systems (CWSs) 

A water system must have technical, managerial, and 

financial “capacity,” according to the SDWA. Technical capacity may be defined in terms of three issues: 

source water adequacy, infrastructure adequacy, and 

technical knowledge. Source water adequacy is 

related to the availability of reliable water sources, 

awareness of source water issues, and should be 

included a SWAP plan. Source water assessments can 

provide information directly relevant to determining 

source water adequacy, and, in turn, building of the 

infrastructure capacity and an infrastructure capacity development strategy. The technical knowledge of 

a fully-trained operator, as the on-site professional, 

requires understanding the benefits of multiple barriers 

to prevent contamination of drinking water supplies. 

The technical knowledge of the operator should also 

include insights into the risks to water supplies from 

different, potential sources of contamination. The 

managerial and financial capacities are self explanatory. The three major problems that can potentially 

impede the sustainability of a CWS include: 

• A major source of contamination of drinking 

water source water from wastewater intrusion 

from septic systems and/or contaminant spills 

from industrial activities. It is costly to provide 

supplemental treatment processes to improve the 

water quality of contaminated drinking water 

source waters. 

• Seasonal weather changes can result in floods 

and droughts. Remedies include design options 

to bypass treatment during rain and storm events 

and identification of alternative water supplies 

(including water reuse sources) to increase 

capacity during droughts. 

• Deteriorating collection and distribution systems 

compromise source water quality and increase 

the cost of water treatment. Remedies include 

replacement of collection and distribution 

systems and the use of point of use systems in 

homes and businesses. 

4.6 EPA Source Water Assessment 

and Protection Programs 

The EPA’s Office of Ground Water and Drinking Water 

has extensive information available about source water 

protection on the Internet at: http://www.epa.gov/safewater/protect.html.

4.7 Key Questions 

The key scientific questions for source water protection fall into the following categories: (a) water quality 

criteria; (b) source water assessments; (c) preventative 

measures to address sources of contamination; and (d) 

contingency planning. A range of scientific issues exists within each of these categories. Some of the most 

important questions include (EPA, 2003): 

• How adequately do the Ambient Water Quality 

Criteria (AWQC) that address the major 

drinking water contaminants protect public 

health?

• What improved techniques are needed to better 

define source water characteristics and sources 

of contamination? 

• What are the fate and transport characteristics of 

certain types of contaminants in surface water 

and ground water? 

• How effective are candidate protection measures 

(i.e., Best Management Practices) on improving 

the quality of the source water? 

• What are the impacts of sudden increases in 

source water contaminant concentrations on 

drinking water treatment performance? 

• What early warning and monitoring systems 

should be developed to alert utility operators 

of contaminant incursions at the source so that 

corrective actions might be employed? 

• Should source water research focus on ground 

water for small systems? 

4.8 References 

EPA. State Source Water Assessment and Protection 

Programs Guidance, Final Guidance, EPA-816-R-97-

009, 1997. 

EPA. Drinking Water Research Program Multi-Year 

Plan, available at: http://www.epa.gov/osp/myp/ 

dw.pdf, 2003 

EPA. Data & Databases PivotTables, available at: 

http://www.epa.gov/safewater/data/pivottables.html, 

2005

4-4
Chapter 5 

Treatment Processes 

5.1 Introduction

When the SDWA was reauthorized in 1996, it addressed Small System drinking water concerns and 

required EPA to assess treatment technologies relevant 

to small systems serving fewer than 10,000 people. 

The 1996 SDWA Amendments also identified two 

classes of treatment technologies for small systems: 

• Compliance technologies which may refer to: 

1. a technology or other means that is affordable 

and that achieves compliance with the MCL, and 

2. a technology or other means that satisfies a 

treatment technique requirement. 

• Variance technologies which are only specified 

for those system size/source water quality 

combinations for which there are no listed 

compliance technologies (EPA, 1998a). 

While variance technologies may not achieve compliance with the MCL or treatment technique requirement, they must achieve the maximum reduction or 

inactivation efficiency that is affordable considering 

the size of the system and the quality of the source 

water. Variance technologies must also achieve a level 

of contaminant reduction that is protective of public 

health. Possible compliance technologies include 

packaged or modular systems and point-of-use (POU) 

or point-of-entry (POE) treatment units. 

The 1996 SDWA Amendments do not specify the 

format for the compliance technology lists and state 

that the variance technology lists can be issued either 

through guidance or regulations. Rather than provide 

the compliance technology list through rule-making, EPA provided the listing in the form of guidance 

without any changes to existing rules or the passing of 

new ones. A sample of this guidance for disinfection 

technologies is summarized in Table 5.1, which may 

also be found in: 

• Small System Compliance Technology List for 

the Surface Water Treatment Rule and Total 

Coliform Rule (EPA, 1998b) 

• Small System Compliance Technology List for 

the Non-Microbial Contaminants Regulated 

Before 1996 (EPA,1998a) 

• Variance Technology Findings for Contaminants 

Regulated Before 1996 (EPA, 1998c) 

5.2 Packaged Filtration 

Table 5.2 presents a summary of filtration compliance 

technology for surface water (EPA, 2003), a majority of the EPA WSWRD small systems research has 

focused on the evaluation of “packaged” filtration 

and disinfection technologies that are most useful 

to small system operators. Filtration efforts have 

focused on evaluating various bag, cartridge and 

membrane filters. Disinfection techniques evaluated 

include a variety of onsite chlorine generators and 

packaged UV/ozonation plants. Details regarding 

these treatment methods and research are presented 

in Table 5.2. 

Table 5.1 Surface Water Treatment Rule compliance technologies for disinfection (EPA, 

2003).

Unit Technologies 

Removals: 

Log Giardia & Log Virus w/CT’s 

indicated in ( ) Comment

Free Chlorine 3 log (104) & 4 log (6) Basic operator skills. Better for larger drinking water systems 

with good quality source water, low in organics and iron/manganese. Concerns with disinfection byproducts. Storage and 

handling precautions required. 

Ozone 3 log (1.43) & 4 log (1.0) Intermediate operator skills. Ozone leaks can be hazardous. 

Does not provide residual disinfection protection for distributed 

water. 

Chloramines 3 log (1850) & 4 log (1491) Intermediate operator skills. The ratio of chlorine to ammonia 

must be carefully monitored. Requires long CT. 

Ultraviolet Radiation 1 log Giardia (80-120) & 4 log viruses (90-140) mWsec/cm2 doses in 

parentheses 2 

Basic operator skills. Relatively clean water source necessary. 

Does not provide residual disinfection protection for distributed 

water. 

On-Site Oxidant 

Generation 

Research pending on CT values Basic operator skills. May be inexpensive to procure and operate. Chlorine production rates may vary. 

Chlorine 

Dioxide 

3 log (23) & 4 log (25) Intermediate operator skills. Better for larger drinking water 

systems. Storage and handling precautions required. 

5-1
Table 5.2 Surface Water Treatment Rule compliance technologies for filtration (EPA, 2003). 

Unit Technologies 

Removals: 

Log Giardia & Log Virus Comment

Conventional Filtration 

and Specific Variations 

on Conventional 

2-3 log Giardia & 1 log viruses Advanced operator skills required. High monitoring requirements. 

May require coagulation, flocculation, sedimentation or flotation as 

prefiltration. Will not remove all microorganisms. 

Direct Filtration 0.5 log Giardia & 1-2 log 

viruses (and 1.5-2 log Giardia

with w/coagulation) 

Advanced operator skills required. High monitoring requirements. 

May require coagulation, flocculation, sedimentation or flotation as 

prefiltration. Will not remove all microorganisms. 

Slow Sand Filtration 4 log Giardia & 1-6 log viruses Basic operator skills required. Most effective on high quality water 

source. Will not remove all microorganisms. 

Diatomaceous Earth 

Filtration 

Very effective for Giardia (2 

to 3-log) and Cryptosporidium 

(up to 6-log); low bacteria and 

virus removal 

Intermediate operator skills required. Good for source water with low 

turbidity and color. Will not remove all microorganisms. 

Reverse Osmosis Very effective, absolute barrier 

(cysts and viruses) 

Intermediate to advanced operator skills required, depending on the 

amount of pretreatment necessary. Post disinfection required under 

regulation. Briny waste can be toxic for disposal. 

Nanofiltration Very effective, absolute barrier 

(cysts and viruses) 

Intermediate to advanced operator skills required, depending on the 

amount of pretreatment necessary. Post disinfection required under 

regulation.

Ultrafiltration Very effective Giardia, >5-6 

log 7 ; Partial removal viruses 

disinfect for virus credit) 

Intermediate to advanced operator skills required, depending on the 

amount of pretreatment necessary. Post disinfection required under 

regulation.

Microfiltration Very effective Giardia, >5-6 

log; Partial removal viruses 

(disinfect for virus credit) 

Intermediate to advanced operator skills required, depending on the 

amount of pretreatment necessary. Disinfection required for viral 

inactivation. 

Cartridge/ 

Bag/Backwashable 

Depth

Filtration 

Variable Giardia removal & 

Disinfection required for virus 

Removal 

Basic operator skills required. Requires low turbidity water. Disinfection required for viral inactivation. Care must be taken towards end of 

bag/cartridge life to prevent breakthrough. 

5.2.1 Filtration

Source water may contain turbidity, particles, and/or 

organic material. Filtration is the removal of particulates, and thus some contaminants, by water flowing 

through a porous media. Filtration is considered to be 

the most likely and practical treatment process or technology to be used for removal of suspended particles 

and turbidity from a drinking water supply. Federal 

and state laws require all surface water systems and 

systems under the influence of surface water to filter 

their water. Filtration methods include slow and rapid 

sand filtration, diatomaceous earth filtration, direct 

filtration, membrane filtration, bag filtration, and cartridge filtration. The other filtration methods typically 

use natural filtration media (e.g., granulated media 

particles such as carbon, garnet, or sand, alone or in 

combination). Bag and cartridge filtration media are 

commonly made from synthetic fibers designed with a 

specific pore size. The type of filter media most suited 

for an application depends mainly on the impurities 

present in the source (raw) water. Specifically, the 

particle size of the impurity present in the raw water 

typically dictates the type of filter media. The particle 

sizes of common water contaminants and the filtration 

devices required for their treatment (or removal) are 

shown in Figure 5.1. 

If the source water contains particle (large size) 

impurities, prefiltration is generally applied in front 

of bag or cartridge type filters. Prefiltration removes 

the larger particulate material from the water stream 

by using coarse, often back-washable granular media. 

The prefilters protect the more expensive bag and/or 

cartridge type units from frequent “fouling.” Figure 

5.2 shows a picture of a clogged prefilter. 

Bag and cartridge filters can be used to remove contaminants down to around the 1-micron particle size 

(1/10th the size of a human hair). However, a prefilter 

(such as another bag or cartridge filter of greater pore 

size) is typically recommended prior to using a submicron filter. Microfiltration is used to remove particles 

in the 0.5 to 10 micron size range with the membrane 

acting as a simple sieving device. In ultrafiltration, nanofiltration, and reverse osmosis processes, one stream 

of untreated water enters the unit but two streams 

of water leave the unit: one is treated water and the 

other is reject water containing the concentrated 

contaminants removed from the water. Microfiltration 

systems will remove some microbes such as protozoa 

and bacteria but not viruses. Unlike nanofiltration 

and reverse osmosis, microfiltration cannot remove 

calcium and magnesium from water. Ultrafiltration is 

5-2
Microns 0.001 0.01 0.1 1.0 10 100 1000 

(Log Scale) 

Approx. Molecular Wt. 100 

Nanofiltration 

Herbicide

Pesticide 

200 1000 10,000 20,000 100,000 500,000 

Dissolved 

Metal Compound Relative 

Size of 

Common 

Materials 

Salt Cryptosporidium

Filtration 

Technology 

Reverse Osmosis 

Giarda

Cyst 

Pollen 

Beach Sand 

Human Hair 

Virus 

Tobacco Smoke 

Coal Dust 

Bacteria 

Ultrafiltration Cartridge/Bag/Granular Filtration 

Microfiltration 

Figure 5.1 Particle size distribution of common contaminants and associated filtration technology (EPA, 

2003).

used to remove some dissolved material (such as large 

organic molecules) from water (0.001 to 0.02 micron 

size range). Most microbial contaminants are removed 

by ultrafiltration including bacteria, protozoa, and the 

larger virus sizes. Nanofiltration is used to remove 

particles in the 0.001 to 0.002 micron size range, 

polyvalent ions, and smaller organic molecules (down 

to a molecular weight of about 200–500 daltons). 

Reverse osmosis (RO) can remove most contaminants 

dissolved in water including arsenic, asbestos, protozoa, pyrogens, sediment, and viruses (Craun et al., 

1997).

5.2.2 Bag Filtration 

Bag filtration systems are based on physical screening 

processes. If the pore size of the bag filter is smaller 

than the microbe, some removal will occur. Depending on the quality of the raw water, EPA suggests a 

series of filters, such as sand or multimedia filters 

followed by bag or cartridge filtration, to increase 

particulate removal efficiencies and to extend the life 

Figure 5.2 Clogged Prefilter (EPA, 2003). 

of the secondary filter. Bag filters can be used as prefiltration for other filters as well. 

Bag filters are disposable, non-ridged replaceable 

fabric units contained either singly in series or parallel 

or grouped together in multiples within one vessel. 

The vessels are usually fabricated of stainless steel for 

corrosion resistance, strength, cleaning, and disinfection. Supply (non-treated or treated) water can be introduced into the vessel from the top, side, or bottom, 

and flows from the inside of the bag to the outside. 

Research conducted by EPA has not shown any specific method of water introduction into the vessel to be 

superior to others (EPA, 2003). 

Bag filtration is generally not recommended for 

use as a single barrier to remove parasites such as 

Cryptosporidium. However, it can be used as a 

pretreatment step before cartridge filtration to remove 

large particles and high levels of turbidity to improve 

parasite removal. The water can then be polished or 

treated to remove any remaining microbial or bacterial contaminant (EPA, 2003). For smaller systems 

that have a very high quality of source water, such as 

ground waters under the influence of surface waters, 

bag filters may serve as an effective single barrier 

against parasites such as Cryptosporidium. In an 

EPA sponsored Environmental Technology Verification (ETV) study conducted by NSF, a log removal 

range between 1.9 and 3.7 was observed for similar 

sized micro-sphere particles. Micro-spheres of 3.7 

μm and 6.0 μm size were selected for testing due to 

their similarity in size to Cryptosporidium oocysts 

and Giardia cysts, respectively. The source water 

characteristics for this testing were: turbidity average 

0.75 NTU, pH 7.1, and temperature 12.1°C (NSF, 

2001). 

5-3
5.2.3 Cartridge Filtration 

Cartridge filtration is a technology suitable for removing microbes and reducing turbidity. These filters are 

easy to operate and maintain, making them suitable for 

treating low-turbidity water. They can become fouled 

relatively quickly and must be replaced with new 

units. Although these filter systems are operationally 

simple, they are not automated and can require relatively large operating budgets. A disinfectant may be 

recommended to prevent surface-fouling via microbial 

growth on the cartridge filters and to reduce microbial 

pass-through.

Cartridge filters are rigid cores (usually poly vinyl 

chloride-PVC) with surrounding deep-pleated filter 

media. Cartridge filters housings are generally made 

of stainless steel or fiberglass-reinforced plastic for 

chemical resistance. The filters are available in various pore sizes and materials depending on the intention of filtration and the source water quality. The 

filter media are typically constructed of polypropylene 

or polyester but may be of other fibers for specific 

applications. The pore sizes available may vary by 

vendor and material, but are typically 100, 50, 25, 10, 

5, and 1 micron. Cartridge filters may be disposable or 

washable, depending on the material and vendor. Depending on the inlet water quality, flow rate, and filter 

pore size, a filter may last from one hour to longer than 

a month. If inlet water quality is poor, a pre-filtration 

step may be best to reduce filter changes and minimize 

cost. This can be achieved by using one cartridge filter 

system with a 50 or 25 micron filter for pre-filtration, 

followed by another cartridge filter system with a 5 or 

1 micron filter for finer filtration (EPA, 2003). 

Like a bag filter, one of the most cost-effective benefits 

of the cartridge filter is that it is commonly used 

without costly chemical additions such as those used 

in coagulation and flocculation. Like bag filtration 

technology, cartridge filters are designed for protozoan, parasite, or oocyst capture. These filters have 

“absolute” pore sizes designed and engineered into 

them that are reported to be uniform to contain and 

capture oocysts, protozoans, or parasites. At the same 

time, these filters permit bacteria, viruses, and fine 

colloids to pass through, depending on the pore size 

(EPA, 2003). 

5.2.4 Membrane Filtration 

Membranes act as selective barriers, allowing some 

contaminants to pass through the membrane while 

blocking the passage of others. Membranes may be 

made from a wide variety of polymers consisting of 

several different materials for the substrate, the thin 

film, and other functional layers of the membranes. 

The thin film is typically made from materials like 

cellulose acetate that have tiny pores that allow the 

passage of water while blocking bigger molecules 

(EPA, 2003). 

The movement of material across a membrane typically requires water pressure as the driving force. 

There are four categories of pressure-driven membrane 

processes: microfiltration (MF), ultrafiltration (UF), 

nanofiltration (NF), and RO. Membrane filters (such 

as MF and UF) act as sieves, much like the bag and 

cartridge filters, just with smaller pore sizes (0.003 

to 0.5 microns). Other membrane systems, NF and 

RO, actually block contaminants dissolved in water 

down to the molecular level. RO and NF processes 

are typically applied for the removal of dissolved 

contaminants, including both inorganic and organic 

compounds (EPA, 2003). 

5.2.5 Ultra Filtration (UF) 

UF systems have shown to be effective for the removal of pathogens, while being affordable for small 

systems. UF is one of many processes used to remove 

particles and microorganisms from water. The UF 

technology falls between NF and MF on the filtration 

spectrum. Systems may be designed to operate in a 

single pass or in a recirculation mode. 

UF systems are operated by pumping water through a 

recirculation loop containing the membrane housing, 

and through several membranes, which are usually 

positioned in series. The UF membranes are usually 

large cartridges that can range in pore size from 0.003 

to 0.1 microns. They are usually constructed of plastic 

material. These can be hollow-fiber or spiral-wound 

membranes. The membranes are also classified by 

pore diameter cut off (PDCO) which is the diameter of 

the smallest particles that are retained by it, typically 

in the range of 0.1 to 10 microns. UF is used for the 

separation of large macromolecules such as proteins 

and starches in other industry sectors. Sometimes, UF 

membranes are classified by the molecular weight cut 

off (MWCO) number. MWCO is defined as the molecular weight of the smallest molecule, 90% of which 

is filtered by the membrane. The range of UF systems 

typically spans between 10,000 to 500,000 MWCO 

(EPA, 2003). 

5.3 Disinfection 

Disinfection is the process used to reduce the number 

of pathogenic microbes in water. The Surface Water Treatment Rules require PWSs to disinfect water 

obtained from surface water supplies or ground water 

sources under the influence of surface water (EPA, 

1989). The Ground Water Rule requires PWSs to 

disinfect their well water supplies. As shown by 

the MCL and M/R violations of the SDWA and its 

5-4
amendments over the years, small systems are either 

(1) unable to simply disinfect their water or (2) record 

and submit their data to the appropriate state agency. 

Typically, some form of chlorine is used as a disinfectant; more recently, ultraviolet (UV) radiation, ozonation (O3) or a combination of UV/O3 technologies are 

being used for disinfection. 

On-site ozone generating equipment is costly compared to other disinfection technologies. The effectiveness of the forms of chlorine and ozone in killing 

micro-organisms (i.e., biocidal efficiency) varies with 

the type of micro-organism and the water quality 

conditions (such as pH). The relative effectiveness of 

chlorine and ozone in killing microbes and the stability 

of each disinfectant are summarized in Table 5.3. 

The use of UV light as a mean for water disinfection 

has been a proven process for many years. The benefit 

of the UV disinfection process is that it does not use 

any chemicals and is effective for Cryptosporidium inactivation. However, residual disinfection via UV (to 

account for contamination via the distribution system) 

is not possible. 

The optimum amount of disinfecting agent needs to be 

used to achieve appropriate disinfection and minimize 

DBP formation. Currently, the regulated DBPs in 

the United States are total triaholmethanes (TTHMs) 

with a MCL of 80 parts per billion (ppb). However, 

the practice of chlorination for pre-oxidation or for 

disinfection purposes can result in the formation of 

chlorinated organic by-products. The Stage 1 DBP 

Rule will result in the regulation of several other 

by-products of chlorination such as haloacetic acids 

(HAA5) to 0.060 mg/L, along with a potential reduction in the current trihalomethane (THM) standard of 

80 ppb. In some cases, this might result in a change 

to an alternative pre-oxidant, or disinfectant, use of 

membranes, or elimination of the use of free chlorine 

(Pollack et al., 1999). To minimize the formation of 

DBPs under the SWTR (EPA, 1989) and the Enhanced 

Surface Water Treatment Rule (EPA, 2002), most 

utilities are required to filter their water unless the following conditions are met in the surface water prior to 

disinfection:

• fecal coliform bacteria <20/100 mL in 90% of 

samples,

• total coliform bacteria <100/100 mL in 90% of 

samples,

• turbidity <5 Nephelometric Turbidity Units 

(NTU), and 

• other MCLs met. 

Treatment plants exempted from filtration must 

disinfect to achieve 99.99% inactivation of viruses, 

and 99.9% inactivation of Giardia lamblia cysts. For 

systems that use chlorine for disinfection, compliance 

with these requirements must be demonstrated with 

the CT approach (the product of the average disinfectant concentration and contact time). CT values estimated for actual disinfection systems must be equal to 

or greater than those published in the SWTR Guidance 

Manual for viruses and G. Lamblia cysts (Pollack et 

al., 1999). 

Also, EPA studies have demonstrated that the pliability of Cryptosporidium oocysts may permit the 

pass-through of oocysts through a filtration system 

thus making disinfection that much more important 

as a barrier (Li, 1994). Just like large systems, small 

systems have to be concerned with the safety, ease of 

handling, shipping, storage, capital costs, and operation and maintenance (O&M) costs associated with the 

use of appropriate disinfectant technology. 

EPA has evaluated several disinfection technologies 

that are affordable and easy to use from a small systems perspective. A summary of these technologies is 

presented in the following subsections. 

5.3.1 Disinfection by Chlorination 

The use of chlorine as a disinfectant is commonly 

accepted worldwide. Chlorination is a popular choice 

because of its residual disinfection characteristics. Its 

effectiveness is very simple to test; one needs only to 

measure the residual chlorine at the point of consumption to ensure proper disinfection. 

People are becoming more concerned about the DBPs 

Table 5.3 Summary of disinfectant characteristics relating to biocidal efficiency (Lykins et al., 

1990).

Disinfectant 

Ranka

pH Effects on Efficiency 

Biocidal Efficiency Stability (pH ranges 6-9) 

Ozone 1 4 Little effect 

Chlorine dioxideb 2 2 pH increase is beneficial 

Free Chlorineb 3 3 pH increase is detrimental 

aRanking: 1 = best, 4 = worst. 

bRanking influenced by pH. 

5-5
of chlorine, and alternatives to chlorine are being 

investigated. Chlorine reduces bacteria levels, but it 

also reacts with other organic impurities present in 

water producing various DPBs which are listed as 

probable or possible human carcinogens (cancer-causing agents). Other disadvantages of chlorination are 

undesirable tastes and odors, requirement of additional 

equipment (such as tanks) to guarantee proper contact 

time, and extra time to monitor and ensure proper 

residual concentration level. It also performs poorly 

in reducing viruses (such as enterovirus and hepatitis 

A) and protozoa (such as Cryptosporidia and Giardia)

(EPA, 2003). 

Chlorine is generally obtained for disinfection in the 

form of gaseous chlorine, onsite chorine dioxide generators, solid calcium hypochlorite tablets, or liquid 

sodium hypochlorite (bleach). Gaseous chlorine and 

onsite chlorine dioxide generators are typically found 

at larger drinking water systems. Small drinking water 

systems sometimes use solid calcium hypochlorite, 

which is typically sold as a dry solid or in the form of 

tablets for use in proprietary dispensers. This method 

of disinfection however, is expensive, suitable mainly 

for low flow applications, and the use of calcium 

can lead to scale formation. For the most part, small 

system operators continue to disinfect water using 

common household liquid bleach or swimming pool 

chlorine (EPA, 2003). 

There are, however, other chlorination processes that 

small system operators should consider. One such alternative that has been evaluated extensively by EPA’s 

WSWRD is the on-site salt brine electrolysis chlorine 

generator system. The salt brine solution, together 

with the electrolytic cell, generates a solution (liquor) 

of primarily sodium hypochlorous (chlorine) acid. 

Operators should be aware that some vendors claim 

that their electrolytic generator enhances pathogen 

(Cryptosporidium sp. and Giardia sp.) inactivation by 

using the combined actions of various mixed oxidant 

reactions that are generated from the electrolytic 

cell. The claim is that this mix of oxidants minimizes 

the formation of DBPs. However, EPA has not been 

able to demonstrate the presence of any other oxidant 

(other than sodium hypochlorous acid) generated from 

these units (EPA, 2003). 

5.3.2 Disinfection by Ozonation 

Ozonation is another disinfection method. Ozone is effective as an oxidizing agent in removing bacteria with 

a relatively short exposure time. Ozone generators 

are used to produce ozone gas on site, since the gas 

is unstable and has a very short life. These generators 

must be installed and monitored cautiously, because 

high concentration levels of ozone will oxidize and 

deteriorate all downstream piping and components. 

With home ozone systems, leftover ozone must be 

removed with an off-gas tank to ensure homeowners 

are not exposed to ozone gas, which is a strong irritant. 

Ozone reacts with bromide resulting in the formation of highly carcinogenic DBPs including bromate, 

bromoform, and dibromeacetic acid. In PWSs, UV 

equipment or biological filters are typically installed to 

remove ozone residuals prior to filtration (EPA, 2003). 

5.3.3 Advanced Oxidation Process for 

Disinfection & Destruction 

EPA evaluated a packaged UV/O3 (also referred to 

as Advanced Oxidation Process or AOP) system for 

removal of microorganisms. The unit evaluated was 

capable of processing up to 10 gpm of water and 

engineered to ensure adequate UV intensity and ozone 

residuals for AOPs. 

The combined UV/O3 system achieved the highest 

removal rates for bacterial contamination. The UV/O3 

disinfection technology is also useful in removing 

chemical organic contaminants such as MTBE, perchloroethylene, and trichloroethylene (EPA, 2003). 

Advanced oxidation processes use oxidants to destroy 

organic and microbial contaminants in drinking water. 

Several different oxidants, such as ozone, hydrogen 

peroxide, and hydroxyl radicals, may be used. EPA 

evaluated the use of an AOP system comprised of 

UV/O3 for disinfection potential and MTBE destruction. This effort was intended to investigate if an AOP 

system could be used to disinfect the water and, at the 

same time, destroy organic compounds. 

Ultraviolet irradiation and ozonation are known to effectively destroy organic compounds in drinking water 

and other matrices. Thus, in addition to treatment for 

Cryptosporidium, UV/O3 systems have also shown 

the ability to treat MTBE in drinking water. The 

combined UV/O3 process showed the best potential 

for MTBE removal. Complete MTBE removal was 

observed within a 20 minute reaction time. Several 

byproducts are generated as a result of MTBE treatment. These by-products include t-butyl alcohol, 

t-butyl formate, formaldehyde, isopropyl alcohol, 

acetone, and acetic acid methyl ester (Vel Leitner et 

al., 1994, Liang, 1999). 

In anticipation of the states’ needs for innovative and 

cost-effective small system treatment technology, 

EPA’s WSWRD has focused on the smallest of these 

systems in the 25-500 population range and on those 

technologies that are easy to operate and maintain. 

Alternative treatment systems/technologies (package 

plants) are perceived as “high tech” and are some5-6
times more expensive to purchase than state-accepted 

conventional technologies. However, in many cases, 

alternative treatment systems/technologies are easier to 

operate, monitor, service, and less expensive to maintain and service in the long-term (EPA, 2003). 

Operators should find a mechanism to filter particles, 

turbidity or organic material from the source water 

and should realize that each particle removed by a 

filter could be a microscopic parasite such as Cryptosporidium sp. . Removing particles also allows the 

disinfectant to be more effective. However, the best 

option would be to find a good quality source water, 

i.e., a source water that has very low particle counts, 

turbidity, or organic material (EPA, 2003). 

In anticipation of small system needs in meeting the 

Stage 1 DBPR, the proposed Ground Water Rule, and 

the LT1ESWTR, the EPA’s WSWRD has investigated 

alternative technologies focusing on their ability to inactivate Cryptosporidium while at the same time being 

affordable and easy to operate and maintain. 

Several guidance manuals are available to assist PWS 

operators in complying with the Stage 1 DBP Rule. 

Examples of such guidance manuals include: 

• Disinfection Profiling and Benchmarking 

Guidance Manual (EPA, 1999a). 

• Alternative Disinfectants and Oxidants 

Guidance Manual (EPA, 1999b). 

• Microbial and Disinfection Byproduct Rules 

Simultaneous Compliance Guidance Manual 

(EPA, 1999c). 

On-site salt-brine electrolysis chlorine generator systems can be very attractive to small system operators, 

because they are generally safer to handle and operate than chlorine gas or liquid (sodium hypochlorite 

or calcium hypochlorite) systems. EPA conducted 

studies to evaluate three different on-site salt brine 

based chlorine generators and compared them to each 

other and to liquid bleach. EPA noted a wide variation 

in prices when purchasing these units. The costs for 

the three salt-brine generators, designed specifically 

for small systems, range from $18,000 to $35,000 

(depending on the manufacturer). Since most small 

treatment system operators and facilities have a limited 

budget, EPA evaluated other avenues and options for 

the small system operator. As a fourth system, EPA 

purchased a salt-brine generator from a swimming 

pool supply company for $750 and added other accessories such as plumbing, a pump, a pressure gauge, 

flow control and a brine tank for $525 for a total 

equipment cost of $1,275 (EPA, 2003). 

5.3.4 Disinfection System Observations 

Research on on-site chlorine generators and UV/O3 

treatment technologies has resulted in the following 

observations: 

The disinfection capabilities of disinfection systems 

are a function of dosage and contact time. For the onsite chlorine generators, the chlorine dosage and free 

residual chlorine are critical performance parameters. 

For UV/O3 treatment technologies, the UV intensity 

and ozone dosage are critical performance parameters. 

For both technologies, a reaction chamber or a contact 

tank provides a mixing “area” for the disinfecting 

agent(s) and microorganisms in the water. 

On-site chlorine generators are designed to convert 

salt to chlorine via an electrolytic cell. As a result, the 

hazards associated with the handling of liquid chlorine 

are not a concern. Salt is added to the chlorine generator or contact tank in bulk and requires lifting by the 

operator. Brine concentration levels are critical for 

proper operation of on-site chlorine generators. The 

accumulation of salt residue requires maintenance of 

system tanks and piping. 

UV/O3 systems oxidize organics instantaneously. 

Ozone reacts quickly without leaving a residual disinfectant. UV disinfection is dependent on the intensity 

of the light contacting the water. As a result, waters 

with low turbidity and color are preferred for UV treatment. Providing stable ozone dosage and UV intensity 

is critical for providing consistent disinfection. 

Several things can be done to improve UV/O3 system 

performance. The air dryer dessicant can be replaced 

on a regular basis to improve ozone generation. Ozone 

dosage can be improved by increasing the air flow into 

the ozone generator and optimizing the vacuum at the 

venturi injector. For optimal performance, the UV/O3 

system should be operated as specified by the manufacturer. Alternatively, an oxygen generator can be 

used to feed the ozone generator; this, however, can be 

an expensive option. 

5.4 Sorption Technologies 

Sorption is the common term used for both absorption 

and adsorption. When a substance is incorporated into 

another substance, the process is called absorption. 

Adsorption is a surface phenomenon in which the ions 

and molecules of one substance physically adheres or 

bonds onto the surface of another molecule. In many 

cases, it is not always clear which process (or both) is 

responsible for the removal of a contaminant. Sorption is the preferred term for these processes. 

5-7
Sorption mechanisms are generally categorized as 

either physical adsorption, chemisorption, or electrostatic adsorption. Weak molecular forces, such as Van 

der Waals forces, provide the driving force for physical 

adsorption, while a chemical reaction forms a chemical bond between the compound and the surface of 

the solid in chemisorption. Electrostatic adsorption 

involves the adsorption of ions through Coulombic 

forces, and is normally referred to as ion exchange, 

which is addressed separately in the ion exchange 

modules. Common sorption technologies include ion 

exchange, activated alumina, iron-based media, and 

Granular Activated Carbon (GAC) (EPA, 2000). 

5.4.1 Ion exchange (IX) 

IX is a physical/chemical process in which ions held 

electrostatically on the surface of a solid phase are 

exchanged for ions of similar charge in a solution (i.e., 

drinking water). The solid is typically a synthetic ion 

exchange resin which is used to preferentially remove 

particular contaminants of concern. Ion exchange is 

commonly used in drinking water treatment for softening (i.e., removal of calcium, magnesium, and other 

cations in exchange of sodium), as well as removing 

nitrate, arsenate, chromate, and selenate from municipal water. Due to its higher treatment cost compared 

to conventional treatment technologies, IX application 

is limited primarily to small/medium-scale and pointof-entry (POE) systems. 

Anion exchange resins come in two classes, strongbase anion (SBA) and weak-base anion (WBA). The 

functional groups on the SBA resins are strongly basic 

and ionized to act as ion exchangers over the pH range 

of 0 to 13. The WBA resins are useful only in the 

acidic pH region where the functional groups are protonated to form positively charged exchange sites for 

anions. Both SBA and WBA resins may be present in 

the hydroxide or chloride form. Typically, SBA resins 

are used for arsenic removal because they tend to be 

more effective over a larger pH range than WBA resins 

(EPA, 2000). 

5.4.2 Activated Alumina (AA) and Iron-based 

Media

AA adsorption is a physical/chemical process by 

which ions in solution are removed by the available 

adsorption sites on an oxide surface. AA is porous 

and highly adsorptive. AA filters a variety of contaminants, including fluoride, arsenic, and selenium. The 

alumina can be regenerated. AA is usually prepared 

through dehydration of Al(OH)3 at high temperatures 

and consists of amorphous and gamma alumina oxide. 

AA is used primarily in packed beds to remove contaminants such as fluoride, arsenic, selenium, silica, 

and natural organic matter (NOM). To remove contaminants, feed water is passed continuously through 

one or more AA beds. When all available adsorption 

sites are occupied, the AA media may be regenerated with a strong base, NaOH, or simply disposed 

of. Many studies have shown that AA is an effective 

treatment technique for arsenic removal. Factors such 

as arsenic oxidation state (As [III] vs. As[V]), pH, 

competing ions, and empty bed contact time (EBCT) 

significantly affect arsenic removal. Other factors 

affecting the use of the AA process include regeneration practice, spent regenerant disposal, and alumina 

disposal (EPA, 2000). 

The competition for adsorption sites by other ions such 

as phosphate, silicate, sulfate and fluoride somewhat 

limits the use of AA. More recently, iron based media 

such as granular ferric hydroxide (GFH) and zerovalent iron are being used for arsenic removal. Both of 

these methods involve chemical adsorption of As(III) 

and As(V) species to iron oxides. In most cases 

neither media is intended to be regenerated. The spent 

iron media generally passes the EPA leaching tests. 

Recent adsorption tests conducted by EPA (EPA, 

2001), demonstrate the potential of iron-based media 

and resins to remove arsenic. In the adsorption testing, 

the iron-based GFH media have outperformed the AAbased media and IX resin for removal of arsenic over a 

wide pH range. Although the GFH appears to be more 

specific than AA for arsenic binding, it also suffers 

from competitive adsorption of phosphate and silicate. 

Competitive displacement of arsenic by sulfate is minor. The optimal system design will depend upon the 

specific treatment scenario and source water quality. 

5.4.3 Powdered Activated Carbon/Granular 

Activated Carbon (PAC/GAC) 

Activated carbon is carbon that has been exposed to 

very high temperatures, creating a vast network of 

internal pores. Two types of activated carbon, granular and powdered, are used widely in drinking water 

treatment. Powdered activated carbon (PAC), which 

is frequently used for taste and odor control, is added 

directly to raw water and removed by settling in sedimentation basins (NDWC, 1997). 

PAC and GAC remove many organic contaminants 

as well as taste and odor from water supplies. GAC 

removes contaminants through adsorption, primarily 

a physical process in which dissolved contaminants 

adhere to the porous surface of the carbon particles. 

In some cases, the adsorption process can be reversed 

relatively easily. The ease of reversing adsorption is 

another key factor in activated carbon’s usefulness because it facilitates the recycling or reuse of the carbon 

(NDWC, 1997). 

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GAC can be used as a replacement for existing media 

(such as sand) in a conventional filter, or it can be used 

in a separate contactor (a vertical steel pressure vessel 

used to hold the activated carbon bed) (NDWC, 1997). 

5.5 Lime Softening 

Although lime softening has been used successfully by 

ground water systems serving fewer than 3,000 people, 

it is unlikely to be suitable for treating ground water 

in systems serving 500 or fewer people unless those 

systems have some form of contract or satellite operation that would enable a trained operator to monitor 

the treatment process. Prefabricated lime softening 

equipment is available for small systems. Also, there 

is an American Water Works Association Standard for 

quicklime and hydrated lime (ANSI/AWWA B202-93) 

that provides purchasers, manufacturers, and suppliers 

with the minimum requirements, including physical, 

chemical, packaging, shipping, and testing requirements (NDWC 1998). 

Either hydrated lime [Ca(OH)2] or quicklime (CaO) 

may be used in the softening process. The choice 

depends upon economic factors, such as the relative 

cost per ton of the two materials as well as the size 

and equipment of the softening plant. Hydrated lime 

is generally used more in smaller plants because it 

stores better and does not require slaking (producing a 

chemical change in lime by combining it with water) 

equipment. On the other hand, quicklime costs less 

per ton of available calcium oxide and is thus more 

economical for use in large plants (NDWC, 1998). 

Softened water has high causticity and scale-formation 

potential; hence, recarbonation is employed to reduce 

pH and mitigate scaling of downstream processes and 

pipelines. Onsite combustion generation of carbon dioxide (CO2) or liquid CO2 is the most common source 

of carbon dioxide for recarbonation (NDWC, 1998). 

5.6 Affordability of Recommended 

Treatment Technologies and 

Protectiveness of Public Health 

by Variance Technologies for 

Small Systems 

Many small system operators have argued that some 

of the treatment technologies mentioned in this report 

are simply not affordable to them. The SDWA requires 

EPA to identify affordable compliance treatment technologies for small systems for each new drinking water standard. EPA must evaluate treatment technologies 

and their costs for three categories of small systems: 

systems serving 25 to 500 people, systems serving 501 

to 3,300 people and systems serving 3,301 to 10,000 

people. If EPA cannot identify affordable compliance 

technologies for some or all of the systems in these 

categories, EPA must identify variance treatment technologies that achieve the maximum reduction affordable, and determine if the variance technologies are 

protective of public health. 

EPA currently determines if compliance with a drinking water standard is affordable by comparing the 

current cost of water plus the estimated additional 

treatment cost of the new standard to an affordability 

threshold of about $1,000 (this threshold is calculated by taking 2.5% of the annual median household 

income (MHI) of ~$40,000 among small systems). 

Since the small system variance provisions became a 

part of the SDWA in 1996, EPA has found compliance 

with all new drinking water regulations to be “affordable” using the 2.5% of MHI criteria for all small 

systems. As a result, states have not had the ability to 

grant small system variances. However, evidence suggests that there may in fact be significant numbers of 

systems that have struggled with compliance costs for 

some recent regulations. 

As part of the 2002 appropriations process, Congress 

directed EPA to review the methodology by which it 

evaluates the affordability of drinking water standards 

for small systems. In response, EPA sought the advice 

of Science Advisory Board (SAB) and National Drinking Water Advisory Council (NDWAC). The SAB 

and NDWAC both recommended that EPA consider 

modifications to its current methodology. Additionally, 

small system operators have argued that the current 

criteria are too stringent and fail to recognize situations in which small systems may find a regulation 

unaffordable. After seven years of experience with 

the current criteria, EPA agreed that it was time to 

consider refinements to address the situations of communities with below average incomes and/or above 

average drinking water and treatment costs. 

The SAB and NDWAC made a number of recommendations regarding the method by which EPA evaluates 

the affordability of compliance with drinking water 

standards. Some key recommendations made by both 

the SAB and the NDWAC include: (1) EPA should 

consider the household cost of each new regulation 

on an incremental basis rather than a total cost of all 

water treatment regulations, and (2) EPA should consider reducing the current affordability threshold. The 

options being considered by EPA are based on a range 

of income percentages significantly below the current 

threshold (2.5% of MHI) and are much more likely to 

make variances available to small drinking water systems. Both SAB and NDWAC reports (listed below) 

are available online on the EPA website. 

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• SAB report - Affordability Criteria for Small 

Drinking Water Systems: An EPA Science 

Advisory Board Report 

• NDWAC report - Recommendations of the 

National Drinking Water Advisory Council 

to U.S. EPA on Its National Small Systems 

Affordability Criteria - July 2003 

Even after these variance technologies become available to small systems, the SDWA limits these variance technologies to those that are determined to be 

“protective of public health.” The SDWA does not 

specify how one makes this determination; however, 

it is clear from the provisions, that Congress intended 

that a technology could be considered “protective” for 

the purpose of SDWA even if the concentration of a 

contaminant in the treated water was greater than the 

concentration allowed by the drinking water standard (i.e. a MCL). Subsequently, on March 2, 2006, 

EPA issued a proposed regulation for small drinking 

water systems variances that proposed revisions to 

the existing national-level affordability methodology 

and the methodology to identify variance technologies 

that are protective of public health. In this regulation, 

EPA proposed that a variance technology for future 

regulated contaminants is considered to sufficiently 

protective of public health for purposes of the SDWA 

provision 1412(b)(15) if the concentration of the target 

contaminant after treatment by the variance technology is no more than three times the MCL. EPA views 

this 3x level as a general guideline which might be 

modified for a specific contaminant if unusual factors 

are associated with the contaminant or if risk assessment suggests that an alternate level, whether higher 

or lower, was appropriate. In addition, EPA requested 

comments on a number of questions related to the 

methodology EPA uses to evaluate the affordability of 

national primary drinking water regulations. Three of 

the key issues are: 

1. The size of the system EPA should consider 

as representative of each of the system size 

categories specified under the SDWA. This 

question is critical to determining the cost 

each household must pay for the treatment 

to comply with a new regulation. Smaller 

systems have fewer households over which 

the fixed costs of treatment can be distributed 

and, therefore, experience higher household 

costs. EPA specifically asked if the median (or 

middle sized) or tenth percentile (a system that 

serves fewer people than 90 percent of the other 

systems in the category) should be selected as 

the representative system for the category. 

2. The affordability threshold (the maximum 

cost that is affordable to customers served by 

small systems). EPA proposed to calculate the 

affordability threshold by taking a percentage 

of the MHI among small systems (which as 

of September 2005 was between $40,000 and 

$44,000). EPA requested comments on the 

following three different alternative thresholds: 

• 0.25% MHI ($100 to $110 under Sept. 2005 

income estimates) 

• 0.50% MHI ($200 to $220 under Sept. 2005 

income estimates) 

• 0.75% MHI ($310 to $330 under Sept. 2005 

income estimates) 

3. Whether or not EPA should evaluate 

affordability strictly on a national level, or use 

a two step process that includes both a national 

level evaluation of affordability, and a second 

analysis conducted at the County level. EPA 

would perform this second step only when the 

first step found a standard to be affordable at the 

national level. EPA would evaluate economic 

data to identify economically disadvantaged 

areas in the U.S. that cannot afford to comply 

regardless of the outcome of the national 

determination.

These methodologies, once finalized, will be applied 

by EPA in evaluating small system affordability for 

future drinking water standards with the exception 

of regulations that address microbial contaminants 

(including bacteria, viruses, or other organisms) or indicators for microbial contaminants. The law does not 

allow small system variances for microbial contaminants (SDWA section 1415(e)(b)(B)). 

5.7 Point-of-Use/Point-of-Entry 

(POU/POE) Applications 

In many cases, small drinking water treatment systems 

such as POU/POE units may be the best solution for 

providing safe drinking water to individual homes, 

businesses, apartment buildings, and even small towns. 

Such consumers may not have the financial resources, 

technical ability, or physical space to own and operate custom-built treatment plants. These small system 

alternatives can be used for not only treating some raw 

water problems, but are excellent for treating finished 

water that may have degraded in distribution or storage or to ensure that susceptible consumers such as 

the very young, very old, or immuno-compromised 

receive safe drinking water. 

The 1996 SDWA Amendments provided that POU/ 

POE units could now be considered a “Final Solution”. The 1996 regulations required the POU/POE 

units to be “owned, controlled, and maintained by 

5-10
the PWS or by a person under contract with the PWS 

operator to ensure proper operation and maintenance 

and compliance with the MCLs or treatment technique 

and equipped with mechanical warnings to ensure that 

customers are automatically notified of operational 

problems” (EPA, 1998a). Under this rule, POE devices are considered an acceptable means of compliance because POE can provide water that meets MCLs 

at all points in the home. It is also possible that POE 

devices may be cost effective for small systems or NTNCWS. In many cases, these devices are essentially 

the same as central treatment. In 1998, POU devices 

were listed as “compliance technologies” for inorganics, synthetic organic chemicals, and radionuclides, but 

not for volatile organic chemicals. 

Basically, the same technology used in treatment 

plants for community water systems can be used in 

POU/POE treatment. POU/POE treatment is applied 

to reduce levels of organic contaminants, turbidity, 

fluoride, iron, chlorine, arsenic, nitrate, ammonia, 

microorganisms including cysts, and many other contaminants. Aesthetic parameters such as taste, odor, 

or color can also be improved with POU/POE treatment (Lykins et al., 1992). Table 5.4 summarizes key 

features of commonly used POU/POE technologies 

(EPA, 2003). 

5.7.1 POU/POE Treatment Cost 

The cost and application of POU/POE units as a final 

solution for a small system or portion of a larger system is highly dependent on the situation. A major factor is whether there is an in-place distribution system 

versus whether additional treatment must be installed 

in the existing central system. Approximately 80% 

of the total cost of any water utility is the installation 

and maintenance of the distribution system. In cases 

where a distribution system would have to be installed 

to treat a contaminated drinking water source, it may 

be more cost-effective to install POU/POE units (EPA, 

2003). An example of this would be a community 

where each home has a well and it was discovered that 

the ground water was contaminated with a pesticide, 

fertilizer, or chemical. Rather than install miles of 

pipe, pumps, and storage facilities, a small system 

could get state approval to install and maintain units 

in each home. This might be economical for upward 

of 100 homes depending on the cost of the home units 

versus the amount and difficulty of installing a distribution system and central treatment facility. For those 

small systems that already have a distribution system 

in-place, the break-even point could be for fewer home 

units (< 50). However, in situations where the existing 

treatment plant could not be economically or physically upgraded or if the water quality is severely degraded 

while in the distribution system, POU/POE treatment 

may once again be a practical alternative (Goodrich et 

al., 1992). 

A recent report from EPA (EPA, 2005) on POU/POE 

systems for As removal in a small rural town (pop. 

400) concluded that centralized treatment modifications would result in monthly cost increases of 

$24.71 per connection. POU/POE unit costs ranged 

from $11.46 to $18.00 per connection depending on 

frequency of monitoring and POU/POE cartridge 

replacement.

5.7.2 Use of POU/POE Treatment and Bottled 

Water in Small Systems 

The financial instability of many small PWSs to comply with the SDWA often forces state and local governments to seek alternatives to centralized treatment 

as sources of safe drinking water. For example, EPA’s 

new arsenic standard of 10 μg/L is expected to affect 

5% of CWSs, but 77% of these affected CWSs serve 

1,500 or fewer customers. POU treatment, approved 

by EPA for permanently complying with this drinking water standard, may be an economical alternative 

for arsenic removal when compared to a centralized treatment for these smaller CWSs. Gurian and 

Small (2002) studied three (base-case, high-cost, and 

low-cost) POU scenarios to meet the 10 μg/L arsenic 

standard by calculating the per-household cost for 

implementing each POU option. The per-household 

costs were compared with those of the least-expensive 

centralized treatment methods for removing arsenic 

(presented in published studies). The authors found 

that POU treatment costs varied significantly with the 

monitoring and maintenance schedule adopted by the 

CWS; annual arsenic monitoring of each POU device 

coupled with frequent maintenance and filter replacement increased the POU costs to the point where 

centralized treatment was more cost-effective. The 

published costs of centralized treatment, however, also 

varied significantly, and these discrepancies somewhat 

masked the economic advantage of POU treatment. 

Also, the results of this study point out some of the 

difficulties in designing and running a POU treatment 

program. For a POU program to be successful, CWS 

operators must get cooperation from their customers. 

This POU treatment scenario complexity may discourage CWSs from implementing POU treatment, even 

when centralized treatment is not cost feasible. In 

these cases, the authors suggest providing bottled water to customers as a temporary compliance measure. 

Bottled water can be considered as a principal alternative source for use in emergencies and/or on an interim 

(or permanent) basis for small PWSs. Bottled water 

can serve as a permanent supply of potable water for 

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Table 5.4 Key Feature Summary of commonly used POU/POE technologies (EPA, 2003). 

Technology Comments

Filtration Filtration and disinfection of water supplies are highly effective public health practices. MF, UF, and RO 

filtration systems have been shown to be effective technologies for the removal of pathogens while being 

affordable for small systems. Generally, pore-size of the filtration media determines its effectiveness in 

teh removal of a specific pathogen. Filtration media such as bags, cartridges and membranes require 

periodic maintenance and/or replacement. 

Activated Carbon Activated Carbon is the most widely used POU/POE systems for home treatment of water. Easy to install 

and maintain with low operating costs, usually limited to filter replacement. Can remove most organic and 

some inorganic contaminants. 

Membranes Most POU membrane systems are reverse osmosis filters installed under the kitchen sink, typically with 

either an activated carbon prefilter or an additional UV light disinfection step such as to combat bacteria 

since the water is often stored under the sink until used. 

Ion Exchange Commonly called water softeners when used for removal of calcium and magnesium from water. Other 

types of units remove anions such as arsenic (arsenate), hexavalent chromium, selenium (selenate), and 

sulfate. 

Distillation Distillation is most effective in removing inorganic compounds such as metal (iron and lead) and nitrates, 

hardness, and particulates from contaminated water. Distillation also removes most pathogens. The 

effectiveness of distillation in removing organic compounds varies, depending on the chemical characteristics of the compounds such as water solubility and boiling point. Distilling units have relatively high 

electrical demands and require about 3 kilowatt-hours per gallon of water treated. 

Air Stripping or 

Aeration 

Aeration is a proven technology for removing volatile organic chemicals (for example, dry cleaning fluid) 

from drinking water supplies for POE applications. Aeration systems include: packed tower systems, 

diffused bubble aerators, multiple tray aerators, spray aerators, and mechanical aerators. Storage, repumping, and possibly disinfection facilities are needed after air stripping to distribute treated water. Air 

stripping is typically used for POE applications where high concentrations of volatile organics have to be 

removed from drinking water where carbon can be used only for short periods of operation. Radon gas 

can also be removed by aeration. 

Modular Slow Sand 

Filtration 

Slow sand filters housed in round fiberglass tanks (approx. 6 ft tall x 2.5 ft in diameter) can treat 400-500 

gallons daily. The systems are simple to operate and have low capital (approx. $2,000) and operating 

costs. The unique feature of this system is a very thin 1/8” thick filter blanket followed by a 1” thick polypropylene filter blanket (similar to a furnace filter) to replace the biological mat that typically grows on top 

of the sand (schmutzdecke). The blankets can simply be replaced when flow is restricted without losing 

much sand or significant down-time. 

Disinfection and 

Destruction 

Disinfection is an important consideration for POU/POE systems. Disinfectants that are usually used in 

POU/POE systems are ultraviolet light, ozone, chlorine, silver impregnated carbon, and iodine. 

Chlorine - The most widely used water disinfectant. Can be used in the form of liquid bleach, solid tablets, or generated onsite in portable generators. 

Ultraviolet Light (UV) - Ultraviolet light is a popular home disinfection method in combination with other 

treatment techniques. Does not add chemicals that can cause secondary tast and odor problems. Units 

require little maintenance and overdose is not a danger. 

Ozone – Ozone has been for disinfection and destruction of iron, manganese, and some chemical contaminants. Ozone has to be generated and used on-site as needed. 

Iodine – Iodine has been used as an alternate disinfectant to chlorine because it is easier to maintain a 

residual.

Silver impregnated carbon - These units contain a small amount of silver to keep bacteria growth under 

control. They are not designed to remove or kill bacteria. However, the effectiveness of the silver in the 

carbon filter is questionable. The only advantage noted in studies of silver-impregnated carbon was that 

in the first month of use, the bacterial counts were lower than carbon without silver (Seelig, B., Bergsrud, 

F., and Derickson, R, 1992). 

an entire small community or non-community system, 

or for residential areas served by private wells in an 

aquifer that has become contaminated. This option is 

attractive when centralized treatment is costly. Bottled 

water can serve as a temporary solution during the intermediate period while permanent solutions are being 

devised. Bottled water may be used by water systems 

facing water quality problems due to an emergency 

situation. The use of bottled water has been expressly 

recognized by the U. S. Army Corps of Engineers 

(USACE), the Federal Emergency Water Administration and the EPA under the National Contingency Plan 

for responding to contamination of drinking water supplies. Bottled water can serve as a permanent alternative source for special segments of the population such 

as small children and pregnant women who require 

low nitrate levels in the water supply. The SDWA allows EPA to authorize the use of bottled water, where 

appropriate, to achieve the goals of the SDWA. Other 

government policies authorizing the use of bottled water to meet drinking water needs are: EPA’s National 

Contingency Plan under the Superfund Act, the Department of Interior’s Emergency Water Supply Plan, 

and the USACE’s’ Emergency Water Plan (Harker, 

1985). In some scenarios, a central treatment station 

with bottled water delivered to each customer may be 

5-12
advantageous. This option provides high quality water 

for consumption and at the same time obviates the 

need for expensive treatment of water that is used for 

activities such as toilets, yard watering, and laundry. 

5.8 Key Questions 

• How can WSWRD research begin to address 

treatment of multiple contaminants in Small 

Systems?

• Should research focus on treatment of ground 

water since most Small Systems source waters 

are underground? 

• What are the most pressing future needs for 

water treatment technology in small systems? 

• Should research focus on inexpensive treatment 

technologies rather than “cutting-edge” 

technologies which tend to be more expensive? 

5.9 References 

ANSI/AWWA. AWWA Standard for Quicklime and 

Hydrated Lime. Revision of ANSI/AWWA B202-93, 

AWWA, Denver, CO. 1993. 

Craun, G., Goodrich, J. A, Lykins, B. W., Schwartz, 

E., How to Select a Personal and Household Drinking Water Treatment System: A Guide to Peace Corps 

Personnel, 1997. 

EPA. 40 CPR Parts 141 and 142; Drinking Water; National Primary Drinking Water Regulations; Filtration, 

Disinfection

EPA. Turbidity, Giardia lamblia, Viruses, Legionella, 

and Heterotrophic Bacteria; Final Rule, Federal Register, 54(124), 27486-27541, 1989. 

EPA. Small System Compliance Technology List for 

the Non-Microbial Contaminants Regulated Before 

1996, EPA-815-R-98-002, 1998a. 

EPA. Small System Compliance Technology List for 

the Surface Water Treatment Rule and Total Coliform 

Rule, EPA-815-R-98-001, 1998b. 

EPA. Variance Technology Findings for Contaminants 

Regulated Before 1996, EPA-815-R-98-003, 1998c. 

EPA. Disinfection Profiling and Benchmarking Guidance Manual, EPA-815-R-99-013, 1999a. 

EPA. Alternative Disinfectants and Oxidants Guidance Manual, EPA-815-R-99-014, 1999b. 

EPA. Microbial and Disinfection Byproduct Rules 

Simultaneous Compliance Guidance Manual, EPA815-R-99-015, 1999c. 

EPA. Arsenic Removal from Drinking Water by Ion 

Exchange and Activated Alumina Plants, EPA-600-R00-088, 2000. 

EPA. Treatment of Arsenic Residuals from Drinking 

Water Removal Processes, EPA 600/R-01/033, 2001 

EPA. Final Long Term 1 Enhanced Surface Water 

Treatment Rule, EPA-815-F-02-001, 2002. 

EPA. Small Drinking Water Systems Handbook: A 

Guide to Packaged Filtration and Disinfection Technologies with Remote Monitoring and Control Tools, 

EPA-600-R-03-041, 2003. 

EPA. Feasibility of an Economically Sustainable 

Point-of-Use/Point-of-Entry Decentralized Public 

Water System, Final Report. EPA Grant: X82952301, 

2005.

Goodrich, J.A., J.O. Adams, B.W. Lykins, and R.M. 

Clark. Safe Drinking Water from Small Systems and 

Treatment Options. Journal American Water Works 

Association, 84(5): 49-55 1992. 

Gurian, P.L. and Small, M.J. Point-of-Use Treatment 

and the Revised Arsenic MCL, Journal American Water Works Association, 94(3): 101–108, 2002. 

Harker,T.L. Regulatory Flexibility and Consumer Options Under the Safe Drinking Water Act, Safe Drinking Water: The Impact of Chemicals on a Limited 

Resource. Lewis Publishers, Chelsea Michigan. 1985. 

Li, S. Y. Cryptosporidium potential surrogate and 

compressibility investigations for evaluating filtrationbased water treatment technologies. Master’s thesis, 

Miami University, Oxford, Ohio, November 1994. 

Liang, S. Oxidantion of MTBE by Ozone and Peroxone Processes” Journal American Water Works 

Association, 91(6): 104-114 (1999). 

Lykins, B.W., J.A. Goodrich, and J.C. Hoff, Concerns 

with using Chlorine-dioxide Disinfection in the USA. 

Journal of Water Supply Research Technology 39(6): 

376-386 (1990). 

Lykins, B. W., R.M. Clark, and J.A. Goodrich. Pointof-Use/Point-of-Entry for Drinking Water Treatment, 

Lewis Publishers, Ann Arbor, MI. 1992. 

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National Drinking Water Clearinghouse (NDWC). 

NDWC Fact Sheet - Technical Brief on Organic 

Removal, available at: http://www.nesc.wvu.edu/ndwc/ 

pdf/OT/TB/TB5_organic.pdf, 1997. 

NDWC. NDWC Fact Sheet - Technical Brief on Lime 

Softening, available at: 

http://www.nesc.wvu.edu/ndwc/pdf/OT/TB/TB8_ 

lime_softening.pdf, 1998. 

NSF. ETV Report - Physical Removal of Giardia- and 

Cryptosporidium-sized Particles in Drinking Water, 

Lapoint Industries Aqua-Rite Potable Water Filtration System Used in Drinking Water Treatment, NSF 

01/24/EPADW395, available at: http://nsf.org/business/drinking_water_systems_center/pdf/lapoint_final_report.pdf, 2001 

Pollack, A. J., A.S.C. Chen, R.C. Haught, J.A. 

Goodrich. Options for Remote Monitoring and Control of Small Drinking Water Facilities, Battelle Press, 

Columbus, Ohio. 1999. 

Seelig, B., Bergsrud, F., and Derickson, R. Treatment 

Systems for Household Water Supplies Activated 

Carbon Filtration. AE-1029, available at: http://www. 

ext.nodak.edu/extpubs/h2oqual/watsys/ae1029w.htm, 

1992

Vel Leitner, N.K., A.L. Papailhou, J.P. Croue, J. Peyrot, and M. Dore. Oxidation of Methyl t-Butyl Ether 

(MTBE) and Ethyl-Butyl Ether (ETBE) by Ozone and 

Combined Ozone/ Hydrogen Peroxide. Ozone Science 

and Engineering 16: 41-44 (1994). 

5-14 
Chapter 6 

Distribution Systems 

6.1 Distribution System Overview 

Drinking water distribution system infrastructure 

is generally the most valuable asset of a water utility, even though most of the components are either 

buried or located inconspicuously. These systems 

are designed to deliver water from a source (usually a treatment facility) to individual consumers in 

a utility’s service area in the required quantity at a 

satisfactory pressure. In general, to continuously and 

reliably move water between a source and a customer, 

a distribution system requires storage reservoirs/tanks, 

pipes, pumps, valves and other appurtenances. This 

infrastructure is collectively referred to as the distribution system (Walski et al. 2003). 

Almost universally, the manner in which industrial 

and residential customers use water drives the overall 

design and operation of a water distribution system. 

Generally, water use varies both spatially and temporally. Besides customer consumption, a major function 

of most distribution systems is to provide adequate 

standby fire-flow (Fair and Geyer 1956). For this 

purpose, fire hydrants are installed in areas that are easily accessible by fire fighters and are not obstacles to 

pedestrians and vehicles. In order to satisfy this need 

for adequate standby capacity and pressure, most distribution systems use standpipes, elevated tanks, and large 

storage reservoirs. Additionally, for service areas with 

significant differences in ground elevation, the distribution systems are “zoned” to maintain relatively constant 

pressures. Sometimes, zoning may also result from the 

way in which the system has expanded over time. 

6.2 Distribution System Issues 

Proper operation and maintenance of distribution 

systems plays a key role in ensuring that safe drinking 

water is provided to the consumers. The PWS operators need to adequately understand and address the following three categorical issues facing the distribution 

system infrastructure components: 

• Infrastructure issues (repair and rehabilitation). 

• Operational issues (e.g., biofilm growth/ 

disinfectant by product [DBP] formation, 

nitrification, and finished water aging). 

• Contamination events (e.g., cross-connections, 

permeation/leaching, and intrusion/infiltration). 

A brief discussion of these three categorical issues is 

presented in this chapter. 

6.3 Infrastructure Issues 

A majority of distribution piping installed in the U. 

S., beginning in the late 1800s and up until the late 

1960s, was manufactured from cast iron. Specifically, 

the three older vintages of cast iron pipe (pit cast, spun 

cast, and spun cast with leadite joints) that were primarily installed prior to the 1960s are of biggest concern 

to PWSs. The thicknesses of the pipes between the 

1800s and 1960s were gradually lowered as new technology improved the performance of the pipe during 

this period. However, because of the design changes 

during this period, the failure rates also increased 

over time. The result is that the three aforementioned 

vintage types of cast iron pipes, installed in different 

time periods, may be reaching the end of their respective service lives at approximately the same time. This 

will increase the financial burden on the PWSs, as the 

cost of replacement will be borne over a shorter time 

span than that of the original installation period (EPA, 

2002a).

The American Society of Civil Engineers (ASCE) 

rates the Nation’s drinking water infrastructure at a 

D- (A through F scale). The report card states that the 

Nation’s 54,000 drinking water systems face an annual 

shortfall of $11 billion needed to replace facilities that 

are nearing the end of their useful life and to comply 

with federal water regulations (ASCE, 2005). However, most (77.6% - 80.5%) small PWS pipes are less 

than 40 years old (EPA, 2002b). Small PWS piping 

age ranges are as follows (according to EPA’s 2000 

Community Water System Survey, EPA, 2002b): less 

than 40 years old (77.6% - 80.5%), between 40 and 80 

years old (17.5% - 19.4%), and more than 80 years old 

(0.1% - 4.0%). Furthermore, the small system piping 

age ranges for private systems are as follows: less 

than 40 years old (92.6% - 98.7%), between 40 and 80 

years old (1.3% - 7.4%), and more than 80 years old 

(0.0% - 0.6%). 

For small PWSs that have to repair, replace, and/or 

install new pipes, an understanding of the risks to 

distribution systems is necessary. The American Water 

Works Association (AWWA) white paper, “New or Repaired Water Mains” (AWWA, undated) indicates that 

the installation and/or repair of water mains provides a 

potential route for direct contamination of the distribution system. According to the white paper, contamination can occur before, during, or after construction/repair activities. For example, before the construction 

activities have commenced, the piping materials may 

be exposed to contaminant sources at the manufacturer, including: 

• Accumulation of soils, sediments, and trash 

6-1
which can carry and/or harbor microbial 

contaminants.

• Exposure to storm water runoff and other 

waters that can carry microbial and chemical 

contaminants.

• Exposure to harmful chemicals. 

• Exposure to chemically contaminated soils and 

sediments.

• Exposure to animals and humans and their 

wastes. 

Water main construction or repairs are most commonly 

done in open trenches or excavations. Therefore, during construction activities, the interiors of pipes and 

fittings can come into contact with soil and water in 

the trench. In addition, the chance of soil and water 

contacting pipe materials during construction or repair 

activities is potentially much greater than it is during storage and handling prior to construction/repair. 

The damp soil of a main repair trench is a potential 

source of bacterial contamination during repairs (EPA, 

2002c).

Finally, after construction or repair activity has been 

completed, contamination can occur from external 

sources such as: 

• Leaking pipe joints with stagnant, unsanitary 

water infiltrating into the distribution system, 

• Cross-connections, back-flow, and 

• Transitory pressures. 

To address these potential infrastructure issues, the 

small PWS operators must carefully inspect and disinfect the pipe material before commencing the repairs. 

The AWWA Standard C-651-99 (AWWA, 1999) has 

been developed to address potential microbial contamination during main construction or repair. Small 

PWS operators should closely follow the guidance 

provided in this Standard C-651-99. The external 

contamination events are discussed in Section 6.5 of 

this report. 

6.4 Operational Issues 

PWS operators must operate their distribution system 

in a manner to minimize the deterioration of water 

quality delivered to the consumer after it leaves the 

treatment plant. The water quality can potentially 

degrade in a distribution system due to a variety of 

reasons. The main reasons include: excessive growth 

of biofilm, DBP formation, nitrification, and improper 

storage of finished water. These issues are briefly 

discussed in the following subsections. 

6.4.1 Biofilm Growth 

Virtually anywhere a surface comes into contact 

with the water in a distribution system, one can find 

biofilms. Biofilms are formed in distribution system 

pipelines when microbial cells attach to pipe surfaces 

and multiply to form a film or slime layer on the pipe 

(EPA, 2001). Biofilms are complex and dynamic 

microenvironments, that include processes such as metabolism, growth, and product formation, and finally 

detachment, erosion, or “sloughing” of the biofilm 

from the surface. The rate of biofilm formation and 

its release into a distribution system can be affected by 

many factors including surface characteristics, availability of nutrients, and flow velocities. Biofilms grow 

until the surface layers begin to slough off into the 

water (Geldreich and Rice 1987). The pieces of biofilm released into the water may continue to provide 

protection for the organisms until they can colonize 

a new section of the distribution system. In addition, 

biofilms may increase pipe corrosion (microbially induced corrosion), adversely affect pipe hydraulics and 

reduce the utility of total coliforms as indicator organisms. Thus, microbial growth in biofilms may result in 

deterioration of water quality, generation of bad tastes, 

colors, and odors, and proliferation of macroinvertebrates (EPA, 2002d). 

Few organisms living in distribution system biofilms 

pose a threat to the average consumer. Bacteria, 

viruses, fungi, protozoa, and other invertebrates have 

been isolated from drinking water biofilms (EPA 

1992). The fact that such organisms are present within 

distribution system biofilms shows that, although 

water treatment is intended to remove all pathogenic 

(disease-causing) bacteria, treatment does not produce sterile water. In fact, some otherwise harmless 

organisms (opportunistic pathogens) may survive the 

treatment process and cause disease in individuals 

with low immunity or compromised immune systems (EPA, 2001). Therefore, a disinfectant residual 

in the distribution system is necessary to inactivate 

pathogens, maintain water quality, and protect the 

distribution system against regrowth (Snead et al., 

1980). The SWTR provides minimum requirements 

on the amount of disinfection residual that must exist 

in treated water. Specifically, the SWTR requires that 

filtration and disinfection must be provided to ensure 

that the total treatment of the system achieves at least 

a 3-log (99.9 percent) removal/inactivation of Giardia 

cysts and a 4-log (99.99 percent) removal/inactivation 

of viruses (EPA, 1989). In addition, the PWS must 

demonstrate, by monitoring and recording, that the 

disinfectant residual concentration in water entering 

the distribution system is never less than 0.2 mg/L and 

that a detectable residual is maintained in the distribution system. 

6-2
Although a disinfectant residual is generally necessary to maintain water quality, it is recognized that an 

excessive amount of disinfectant residual may also 

pose a threat to health by contributing to the increased 

formation of harmful DBPs. Natural organic matter 

(NOM) contained in water (in the form of humic and 

non-humic [or fulvic] substances) serves as a precursor in DBP formation. NOM belongs to a family of 

compounds having similar structural and chemical 

properties and are formed during the decomposition 

of carbon-based life forms. The NOM reacts with the 

residual disinfectant (e.g., chlorine, chloramine) in the 

distribution system to form DBPs such as chloroform, 

bromodichloromethane, and haloacetic acids (HAA5). 

Many of these DBPs are suspected of causing cancer, 

reproductive and developmental problems in humans. 

To minimize the formation of DBPs, EPA has promulgated regulations that specify maximum residual 

disinfectant level goals (MRDLGs) for chlorine (4 

mg/L), chloramines (4 mg/L), and chlorine dioxide (0.8 mg/L). In addition, MCLs for TTHMs and 

HAA5 have been established at 0.080 mg/L and 0.060 

mg/L, respectively. The TTHMs include: chloroform, 

bromodichloromethane, dibromochloromethane and 

bromoform. The HAA5 include: monochloroacetic 

acid, dichloroacetic acid, trichloroacetic acid, monobromoacetic acid and dibromoacetic acid. In order to 

meet these requirements, PWSs may need to remove 

the DBP precursor material from the water prior to 

disinfection by applying appropriate treatment techniques.

In a cooperative effort with the Montana State University’s Biofilm Research Center, EPA is studying the 

interactions among factors that influence biofilms, bacterial regrowth, and corrosion in distribution systems. 

The goal of this work is to generate information which 

can lead to a better understanding of the interactions 

among those factors which influence microbial growth 

in water distribution systems and the mitigating effects 

of chlorination and commonly used corrosion control 

techniques. This research is also designed to address 

specific fundamental questions about the availability 

of sorbed humic substances for biofilm growth. Figure 

6.1 shows the various distribution system interactions 

that can potentially affect water quality. 

In summary, the distribution system can act as a giant 

reactor; with excess residence times, the water quality can deteriorate substantially. Small PWSs must 

be aware of these issues and optimally operate their 

system to control both biofilms and DBPs. 

6.4.2 Nitrification

Nitrification is a microbial process by which reduced 

nitrogen compounds (primarily ammonia) are sequentially oxidized to nitrite (NO2

–) and nitrate (NO3–).

Ammonia is present in drinking water through either 

naturally-occurring processes or through ammonia addition during secondary disinfection to form 

chloramines (EPA, 2002e). The use of chloramine is 

expected to increase in the near future as a result of 

more stringent DBP MCLs associated with the Stage 

I and Stage II DBP rule. Nitrification can adversely 

impact the distribution system by increasing nitrite and 

nitrate levels, reducing alkalinity, pH, dissolved oxygen, and chloramine residuals, and promoting bacterial 

regrowth (EPA, 2002e). 

The formation of nitrite and nitrate within the distribution system poses a potential direct public health 

threat. Human babies are extremely susceptible to 

acute nitrate poisoning because of certain bacteria 

that may live in their digestive system during the first 

few months of life. These bacteria change nitrate into 

toxic nitrite (NO2

–). The nitrite reacts with hemoglobin (which carries oxygen to all parts of the body) 

to form methemoglobin, which does not carry oxygen. 

The level of oxygen being carried throughout the body 

decreases in proportion to the amount of hemoglobin 

converted to methemoglobin. As the oxygen level decreases, the baby is suffocated. This condition is called 

methemoglobinemia. The most obvious symptom of 

nitrate poisoning is a bluish color of the skin, particularly around the eyes and mouth. These symptoms are 

referred to as cyanosis (Runyan, C. 2002). 

Under the Safe Drinking Water Act (SDWA), primary 

MCLs have been established for nitrite (measured as 

Nitrogen [N]), nitrate (as N), and the sum of nitrite 

plus nitrate. The MCLs are 1 mg/L for nitrite, 10 

mg/L for nitrate, and 10 mg/L for nitrite + nitrate (as 

N). These standards are measured at the point of entry 

to the distribution system; any subsequent elevated 

nitrite/nitrate levels resulting from nitrification within 

Figure 6.1 Distribution System as a “Reactor” 

(Figure used with permission from the Montana 

State University Center for Biofilm Research). 

6-3
the distribution system are typically not identified 

by compliance monitoring. Therefore, small PWS 

operators must be aware of nitrification and optimally 

operate their system to minimize it. 

6.4.3 Finished Water Storage and Aging 

Finished water facilities (including ground storage and 

elevated storage, but not clearwells which are part of 

treatment) are designed to meet temporary surges in 

water demands, reduce pressure fluctuations in the distribution system, and provide reserves for fire-fighting, 

power outages, and other emergencies. Many finished 

storage facilities are operated to provide adequate 

pressure and are kept full to be better prepared for 

emergency demands. This emphasis on hydraulic considerations in past designs has resulted in many storage facilities operating today with larger water storage 

capacity than is needed for normal (non-emergency) 

usage (EPA, 2002c). This built-in excess capacity, 

if not properly utilized, can result in water quality 

deterioration. In addition to underutilization, short 

circuiting within a storage reservoir can also cause 

long detention times, resulting in excessive water age. 

Furthermore, poor mixing (including stratification) 

can exacerbate the water quality problems by creating zones within the storage facility where water age 

significantly exceeds the average water age throughout the facility. For larger distribution systems that 

contain storage facilities where water cascades from 

one facility to another (such as pumping up through 

a series of pressure zones), poor mixing can result in 

exceedingly long water age in the most distant tanks 

and reservoirs (EPA, 2002c). 

Long detention times can allow the disinfectant residual to be completely depleted, thereby not protecting 

the finished water from additional microbial contaminants that may be present in the distribution system 

downstream of the storage facility. Although the loss 

of disinfectant residual within a storage facility does 

not necessarily pose a direct public health threat (many 

systems throughout the world are operated without 

use of a disinfectant residual), disinfectant decay 

can contribute to biofilm growth and related problems described in Section 6.4.1. The rate of residual 

disinfectant decay can be further affected by external 

contamination, temperature, nitrification, exposure 

to ultraviolet light (sun), and the amount and type of 

chlorine demanding compounds present such as organics and inorganics. Chlorine decay in storage facilities 

can normally be attributed to bulk water decay rather 

than wall effects due to the large volume-to-surface 

area ratio (EPA, 2002c). 

Sediment accumulation may also occur within storage 

facilities due to quiescent conditions which promote 

particle settling. Potential water quality problems associated with sediment accumulation include increased 

disinfectant demand, microbial growth, DBP formation, and intermittent increased turbidity within the 

bulk water (EPA, 2002c). 

Finally, uncovered finished water storage reservoirs 

provide the greatest opportunity for contaminant entry 

into the distribution system. These reservoirs are 

potentially subject to contamination from bird and 

other animal excrement that can transmit disease-causing organisms to the finished water. Microorganisms 

can also be introduced into open reservoirs from 

windblown dust, debris and algae. Algae proliferate 

in open reservoirs with adequate sunlight and nutrients 

and impart color, taste and odor to the water on a seasonal basis. Organic matter, such as leaves and pollen, 

is also a concern in open reservoirs. Water fowl are 

known carriers for many different waterborne pathogens and have the ability to disseminate these pathogens over a wide area. Even reservoirs with floating 

covers are susceptible to bacterial contamination and 

regrowth from untreated water that collects on the cover surface. Also, if the cover rips or is otherwise damaged, any untreated water on the cover would mix with 

the stored water, potentially causing health problems. 

Floating covers on storage reservoirs are susceptible 

to rips and tears due to ice damage, vandalism, and/or 

variable operating water levels (EPA, 2002c). 

6.5 Contamination Events 

Distribution systems are vulnerable to a variety of 

external contamination events such as cross-connections, permeation/leaching, and intrusions/infiltrations. 

These issues are briefly discussed in the following 

subsections.

6.5.1 Cross-connection Control 

Distribution systems contain locations where nonpotable water can be accidentally cross-connected to 

potable sources. These cross-connections can provide 

a pathway for backflow of non-potable water into 

potable sources. Backflow can occur either because 

of reduced pressure in the distribution system (termed 

backsiphonage) or the presence of increased pressure from a non-potable source (termed backpressure). Backsiphonage may be caused by a variety of 

circumstances, such as main breaks, flushing, pump 

failure, hilly terrain, limited pumping capacity, high 

demand by consumers, or emergency firefighting water 

drawdown. Backpressure may occur when heating/ 

cooling, waste disposal, or industrial manufacturing 

systems are connected to potable supplies and the 

pressure in the external system exceeds the pressure in 

the distribution system. Both situations act to change 

the direction of water, which normally flows from the 

6-4
distribution system to the customer, so that non-potable and potentially contaminated water from industrial, 

commercial, or residential sites flows back into the 

distribution system through a cross-connection (EPA, 

2002f).

The risk posed by cross-connection backflow can be 

mitigated through preventive and corrective measures. For example, preventative measures include the 

installation of backflow prevention devices and assemblies and formal programs to seek out and correct 

cross-connections within the distribution system and, 

in some cases, within individual service connections. 

Corrective measures include activities such as flushing 

and cleaning the distribution system after a detected 

incident. This may help mitigate any further adverse 

health effects from any contaminants that may remain 

in the distribution system (EPA, 2002f). 

There are no national reporting requirements for backflow incidents, and no central repository for backflow 

incident information. Nonetheless, data on backflow 

incidents have been actively collected by several 

organizations. EPA compiled data on 459 reported 

backflow incidents that occurred in the U. S. between 

1970 and 2001. During these reported incidents of 

backflow, chemical and/or biological contaminants 

have caused illness and deaths, with contamination affecting a number of service connections. This number 

of reported incidents is believed to be a small percentage of the total number of backflow incidents in the 

U. S. (EPA, 2002f). Because backflow incidents are 

underreported, this data cannot support conclusions 

about the full magnitude of risks associated with backflow (EPA, 2002f). 

The American Backflow Prevention Association 

(ABPA) created and distributed a survey to collect 

data on cross-connection control programs throughout 

the country. Two separate surveys were created. One 

survey of water system programs was mailed to approximately 400 systems in 44 states asking details of 

their cross-connection control program. Only 135 surveys were returned, representing 30 states. Of the 135 

returned surveys, 25 were from small systems (those 

serving less than 10,000 people). One hundred and 

three responses represented systems serving populations larger than 10,000. Seven systems did not report 

their population size, making it unable to determine if 

they were small or large (ABPA, 1999). Based on the 

survey responses, ABPA estimates that average annual 

cost for cross-connection control programs is $3.40 

per water service connection for a small system and 

$1.28 per water service connection for a large system. 

The EPA’s SDWIS database (for FY2002) shows a 

total of 230,507,361 service connections for small 

systems and a total of 62,579,989 service connections 

for large systems. 

There is a lack of public general awareness about 

the threat posed by cross-connections and backflow 

through illegal and unprotected taps into the distribution system. PWS operators must be aware that there 

is a potential for intentional contamination of a distribution system through such cross-connections. See 

Chapter 8 – Homeland Security/Emergency Response 

for additional information for responding to such 

events. 

6.5.2 Permeation and Leaching 

As presented in Section 6.4.1, distribution system 

infrastructure and appurtenances including piping, linings, fixtures, and solders can react with the water supply as well as the external environment. Permeation 

and leaching are two mechanisms that can result in the 

degradation of the distributed water (EPA, 2002g). 

Permeation of piping materials and non-metallic joints 

can be defined as the passage of contaminants external 

to the pipe, through porous, non-metallic materials, 

into the drinking water. The problem of permeation 

is generally limited to plastic, non-metallic materials. Volatile organic compounds (VOCs) present in 

the ground water or vadose zone can permeate plastic 

piping and gaskets. Permeation is typically most 

severe for small diameter, low-flow pipes. The smaller 

water lines contain the highest ratio of mass transfer 

surface area to pipe volume, and are often associated 

with stagnant or low-flow conditions. Also, there 

are instances where VOC MCL violations have occurred at the point-of-consumption. However, current 

provisions of the SDWA do not require monitoring 

for VOCs beyond the point-of-entry to the distribution system. Additionally, in most instances, the risk 

threshold of chemical contaminants such as VOCs is 

substantially lower than either the taste or odor thresholds, suggesting that utilities cannot rely confidently 

on customers’ perception of taste and odor for identifying contamination events (EPA, 2002g). 

Leaching can be defined as the dissolution of metals, 

solids, and chemicals into drinking water. Leaching 

from cement linings can occur in soft, aggressive, 

poorly buffered waters. Under static conditions, metals such as aluminum, arsenic, barium, chromium, 

and cadmium can leach from cement linings, even 

when NSF-approved materials are used and linings 

are applied according to AWWA standards. Current 

provisions of the SDWA do not require monitoring for 

heavy metals beyond the point-of-entry to the distribution system, and additional research would be required 

to assess the degree of metals accumulation within the 

6-5
distribution system. Vinyl chloride can leach from 

pre-1977 PVC pipe. No instances of MCL violations 

were cited in association with post-1977 PVC pipe 

(EPA, 2002g). 

Unidirectional flushing can be used to rid the distribution system of stagnant, contaminated water, but 

additional research is needed to determine the fraction 

of heavy metals and organics that can be removed 

through flushing. Permeated plastic piping must be 

replaced since the piping retains its swollen porous 

state after permeation (EPA, 2002g). NSF Standard 61 

and numerous AWWA Standards have been developed to prevent the degradation of drinking water due 

to contact with pipe materials. Materials selection, 

design, and installation considerations based on water 

quality and environmental conditions are addressed in 

these Standards. 

Small PWS operators using non-metallic pipes must 

be aware of permeation and leaching problems and 

address them appropriately. 

6.5.3 Intrusion and Infiltrations 

A pressure transient in a drinking water pipeline 

caused by an abrupt change in the velocity or direction 

of water can cause a surge or “water hammer.” When 

a rapidly closed valve suddenly stops water flowing 

in a pipeline, pressure energy is transferred to the 

valve and pipe wall. Shock waves are set up within 

the system and pressure waves travel backward until 

encountering the next solid obstacle, resulting in a 

series of forward and backward movements. The pressure wave’s velocity is equal to the speed of sound; 

therefore it “bangs” as it travels back and forth, until 

dissipated by friction losses. 

A less severe form of water 

hammer is called surge where 

a slow motion mass oscillation 

of water is caused by internal 

pressure fluctuations in the 

system (EPA, 2002h). If these 

pressure transients are not 

controlled, they can damage 

pipes, fittings, and valves, 

causing leaks and shorten 

the life of the system. Both 

the pipe and the water are 

incompressible and therefore 

do not absorb the shock. The 

production of transient lowand negative-pressures creates 

the opportunity for contaminated water to enter the pipe 

from outside. 

In a series of research projects (LeChevallier et al., 

2003; Gullick et al., 2004), the frequency and location 

of low-and negative-pressures in representative distribution systems were measured under normal operating conditions and during specific operational events. 

Figure 6.2 illustrates a transient event that results in a 

negative pressure transient for 20-seconds caused by a 

power outage associated with a lightning strike. 

These investigators also confirmed that fecal indicators and culturable human viruses were present in 

the soil and water exterior to the distribution system 

pipes. Therefore, they concluded that it was possible 

for these micro-organisms to infiltrate/intrude into the 

distribution system. Their research also shows that a 

well-calibrated hydraulic surge model can be used to 

simulate the occurrence of pressure transients under a 

variety of operational scenarios, and a model can also 

be used to determine optimal mitigation measures. 

Although there are insufficient data to indicate 

whether pressure transients pose a substantial risk to 

water quality in the distribution system, mitigation 

techniques can be implemented. These techniques 

include the maintenance of an effective disinfectant residual throughout the distribution system, leak 

control, redesign of air relief venting, installation of 

hydro-pneumatic tanks, and more rigorous application 

of existing engineering standards. 

6.6 Distribution System Summary 

EPA research indicates that there is a different level 

of risk associated with the various distribution system infrastructure components. The relative risk of 

pathogens entering a distribution system (through the 

Figure 6.2 Negative Pressure Transient Associated with a Power

Outage. (Figure used with permission from Kala K. Fleming, 

Ph.D. at American Water.)

6-6
various mechanisms discussed in the previous sections 

of this chapter) can be summarized as follows (EPA, 

2002d):

• High risk – treatment breakthrough, intrusion, 

cross-connections, main repair/break 

• Medium risk – uncovered water storage facilities 

• Low risk – New main installation, covered water 

storage facilities, growth and re-suspension, 

purposeful contamination. 

6.7 Key Questions 

• Do flow models need to be improved/developed 

specifically for small distribution systems? 

• What are typical water residence times in small 

distribution systems? (This will play a key role 

in contaminant sorption/desorption and biofilm 

development). 

• What are the interrelations between biofilms and 

contaminants?

• How do changes in water chemistry affect 

sorption/desorption of contaminants? 

6.8 References 

ABPA. 1999 Survey of State & Public Water System 

Cross Connection Control Programs. Available at: 

http://www.abpa.org/originalsite/ABPA_Survey_Report.pdf. 1999.

ASCE. Report Card for America’s Infrastructure. 

Available at: http://www.asce.org/reportcard/2005/index.cfm. 2005.

AWWA. New or Repaired Water Mains, available at: 

http://www.epa.gov/safewater/tcr/pdf/maincontam.pdf. 

Undated

AWWA. Disinfecting Water Mains, AWWA C651-99, 

AWWA, Denver, CO. 1999. 

EPA. Deteriorating buried infrastructure management 

challenges and strategies. American Water Works 

Service Company, Voorhees, NJ http://www.epa.gov/ 

safewater/tcr/pdf/infrastructure.pdf, 2002a. 

EPA. Community Water System Survey 2000, EPA815-R-02-005B, 2002b 

EPA. Finished water storage facilities. American Water 

Works Association and Economic Engineering Services, Inc., Voorhees, NJ http://www.epa.gov/safewater/ 

tcr/pdf/storage.pdf. 2002c. 

EPA. Health risks from microbial growth and biofilms in drinking water distribution systems. Office of 

Ground Water and Drinking Water, Washington, DC 

http://www.epa.gov/safewater/tcr/pdf/biofilms.pdf. 

2002d.

EPA. Nitrification. American Water Works Association 

and Economic Engineering Services, Inc., Voorhees, 

NJ http://www.epa.gov/safewater/tcr/pdf/nitrification. 

pdf. 2002e. 

EPA. Potential contamination due to cross connections 

and backflow and the associated health risks. Office of 

Ground Water and Drinking Water, Washington, DC 

http://www.epa.gov/safewater/tcr/pdf/ccrwhite.pdf. 

2002f.

EPA. Permeation and leaching. American Water Works 

Association and Economic Engineering Services, Inc., 

Voorhees, NJ. http://www.epa.gov/safewater/tcr/pdf/ 

permleach.pdf. 2002g. 

EPA. The potential for health risks from intrusion 

of contaminants into the distribution system from 

pressure transients. American Water Works Service 

Company, Voorhees, NJ. http://www.epa.gov/safewater/tcr/pdf/intrusion.pdf. 2002h.

EPA. Controlling Disinfection By-Products and 

Microbial Contaminants in Drinking Water, EPA-600-

R-01-110, 2001. 

EPA. National Characteristics of Drinking Water 

Systems Serving Populations Under 10,000, EPA-816-

R-99-010, 1999. 

EPA. Research Plan for Microbial Pathogens and Disinfection By-Products in Drinking Water, EPA-600-R97-122, 1997. 

EPA. Seminar publication: Control of biofilm growth 

in drinking water distribution systems, EPA-625-R-92-

001, 1992. 

EPA. National Primary Drinking Water Regulations; 

Giardia lamblia, viruses, and legionella, maximum 

contaminant levels, and turbidity and heterotrophic 

bacteria (“Surface Water Treatment Rule”), Final Rule. 

43 FR 27486. 1989. 

Fair, G.M., and J.C. Geyer. Water Supply and WasteWater Disposal, John Wiley and Sons, Inc., NY. pp 

339-441. 1956. 

6-7
Geldreich, E.E. and E.W. Rice. Occurrence, significance, and detection of Klebsiella in water systems. 

Journal of the American Water Works Association, 

79(5), 74. (1987). 

Gullick, R.W., M.W. LeChevallier, R.C. Svindland, 

and M. Friedman. Occurrence of Transient Low and 

Negative Pressures in Distribution Systems. Journal of 

the American Water Works Association 96(11): 52-66 

(2004).

Kirmeyer, G., M. LeChevallier, M. Friedman, J. Funk, 

K. Martel, M. Karim, and J. Harbour. Pathogen Intrusion Into the Distribution System, AWWARF and 

AWWA, Denver, CO. 2000. 

LeChevallier, M.W., R.W. Gullick, M.R. Karim, M. 

Friedman and J.E. Funk. The Potential for Health 

Risks from Intrusion of Contaminants into the Distribution System from Pressure Transients. Journal of 

Water and Health, IWA Publishing. pp. 3-14. 2003. 

Montana State University (MSU) Center for Biofilm 

Engineering. Image provided by Pat Dirckx. 2005 

Runyan, C. Nitrate in Drinking Water Guide M-114, 

New Mexico State University, Cooperative Extension 

Service College of Agriculture and Home Economics. 

Available at: http://www.cahe.nmsu.edu/pubs/_m/m114.pdf, 2002. 

Snead, M.C., V.P. Olivieri, and C.W. Krause. Benefits 

of Maintaining a Chlorine Residual in Water Supply 

Systems, EPA-600-2-80-010. 1980. 

Walski, T. M, D.V. Chase, D.A. Savic, W.M. Grayman, 

S. Beckwith, and E. Koelle. Advanced Water Distribution Modeling and Management, Haestad Press, 

Waterbury, CT. pp 1-4. 2003. 

6-8 
Chapter 7 

Waste Residuals 

Generated by Small 

Systems

7.1 Introduction

Issues concerning the generation and treatment of 

waste residuals from small-scale drinking water treatment plants have received little attention in past and 

current research. Yet in a national survey of consulting 

engineers, residual disposal was voted the second most 

pressing need (behind disinfection by-products) in 

the area of “treatment processes and facilities needing 

additional studies” (AWWARF, 1997). Many small 

systems simply dispose of waste residuals on-site and/ 

or by utilizing local waste treatment venues (landfills, 

sewer lines, etc.). There are currently no regulations 

or standards from the EPA that specifically cover water 

treatment plant residuals (National Drinking Water 

Clearinghouse, 1998). Depending on the residuals’ 

composition and method of disposal, general regulations governing the disposal of solid and liquid wastes 

will determine the fate of these materials. These general regulations can be found under the Clean Water 

Act (CWA), the Resource Conservation and Recovery 

Act (RCRA), Safe Drinking Water Act (SDWA), and 

in some instances, the Clean Air Act. 

On December 7, 2000, EPA promulgated the NPDWR 

for radionuclides. With this rule, EPA updated its 

standards for radionuclides in drinking water. In addition, EPA set a new standard for uranium, as required 

by the 1986 amendments to the SDWA. The revised 

standards are: combined radium 226/228 (5 pCi/L); 

beta emitters (4 mrems); gross alpha standard (15 pCi/ 

L); and uranium (30 μg/L). Treating water to remove 

naturally occurring radioactive material (NORM) 

results in residual streams that are classified as “technologically enhanced naturally occurring radioactive 

materials,” or TENORM. TENORM is defined as 

naturally occurring materials, such as rocks, minerals, 

soils, and water whose radionuclide concentrations or 

potential for exposure to humans or the environment 

is enhanced as a result of human activities (e.g., water 

treatment). Numerous regulations govern the disposal 

of waste streams containing radionuclides (although 

there are no federal waste disposal regulations specifically for TENORM wastes), and their interaction is 

complex. States and disposal facilities can place additional restrictions on TENORM disposal. 

Little has been published on the quantities and types of 

residuals generated by PWSs, but waste residuals are 

certainly going to be as varied as are the methods used 

for water treatment in small system scenarios. This 

chapter will discuss the types of waste residuals that 

small systems can potentially generate, disposal possibilities, and future waste residual issues that small 

systems could face in the near future. 

7.2 Types of Waste Residuals and 

Disposal

Liquid residuals from water treatment operations 

include brines, caustics, filter backwash, sedimentation basin wash water, and solutions used for recharging solid media. Solid residuals can include sludge, 

schmutzdecke (biological surface layer in slow sand 

filtration units), and spent treatment media. The residuals (both solid and/or liquid), classified as TENORM, 

may contain non-exempt levels of radioactive material. 

Section 7.5 presents an overview of the options for 

disposing TENORM residual with non-exempt levels 

of radioactive material. Figure 7.1 summarizes federal 

regulations involved with the disposal of solid and 

liquid residuals that contain exempt levels of radioactive material. The majority of liquid waste residuals 

generated by PWSs are most likely disposed on-site 

(land application) or by sanitary sewer. Solid residuals 

are disposed on-site (land application) or discarded for 

transport and disposal in municipal landfills. 

7.3 Liquid Residuals Handling & 

Disposal

A significant source of liquid residuals is filter backwash. In 2001, EPA published the final version of the 

Filter Backwash Recycling Rule (FBRR). The primary goal of the FBRR is to minimize consumer exposure to microbial contaminants (e.g. Cryptosporidium)

during cleaning/backwashing operations. The rule was 

developed following the findings that filter backwash 

waters contributed to the outbreak of waterborne disease. The rule applies to all public water systems that: 

1. Use surface water or ground water under direct 

influence of surface water 

2. Utilize direct or conventional filtration 

processes, and 

3. Recycle filter backwash water, sludge thickener 

supernatant, or liquids from dewatering 

processes.

The FBRR essentially requires that backwash water, 

thickener supernatant, or dewatering liquids be processed through the system’s existing conventional or 

direct filtration units or through an alternate recycle 

location as approved by the state and/or local agencies. 

7-1
Liquid Residuals 

(e.g., brine, filter 

backwash 

Solid/Sludge Residuals 

(e.g., sludge, schmudzdecke, 

spent treatment media) 

Interim Treatment 

(e.g., chemical precipitation, 

evaporation, coagulation/ 

flocculation)

Clean Water Act: 

NPDES Program 

40CFR Parts 

122-133

Clean Water Act: 

Pretreatment

Program 

40CFR Part 403 

Safe Drinking Water Act: 

Underground Injection 

Control Program 

40CFR Parts 141-149 

Resource Conservation 

Recovery Act (RCRA): 

Subtitle C & D Programs 

40CFR Parts 257-270 

RCRA

Subtitle C & D 

Programs 

40CFR Parts 257-266 

Clean Water Act: 

Dredge and Fill 

Program 

40CFR Parts 230-233 

Clean Air Act/ 

RCRA:

40CFR Parts 50, 

60-63, 26 

Liquid Solid

Direct Discharge 

(e.g., surface 

water, wetland, 

ocean) Indirect

Discharge (e.g. 

sanitary sewer) 

Underground 

Injection (e.g., 

deep well) Land Disposal (e.g., 

municipal landfill, 

hazardous landfill) 

Reuse (e.g., land 

application)

Water/ 

Land/Ocean

Disposal

Incineration 

Figure 7.1 Federal regulations governing the disposal of residuals (EPA, 2000). 

Conventional filtration treatment is defined as a series of 

processes including coagulation, flocculation, sedimentation, and filtration resulting in substantial particle 

removal. Direct filtration is defined as a series of processes including coagulation and filtration but excluding 

sedimentation that results in substantial particle removal 

(CWA - 40 CFR Section 141.2). The FBRR was implemented on June 8, 2004. 

Small systems that recycle filter backwash (and other 

liquid residuals listed in the FBRR) will need to ensure 

that the recycle is sent to the appropriate re-entry point 

in the system. The FBRR also requires that PWSs 

notify the primacy agency that the PWS will recycle 

backwash and provide the primacy agency with: 

1. A plant schematic showing recycle origin, 

transport, and location of recycle back into the 

plant,

2. Typical recycle flow (gpm), 

3. Highest observed plant flow experienced in the 

previous year (gpm), 

4. Design flow for the treatment plant (gpm), and 

5. If applicable, the state-approved operating 

capacity for the plant. 

Public water systems must also collect and maintain 

information for review by the primacy agency including copies of all materials submitted to the primacy 

agency, list of recycle flows and recycling frequency, 

average and maximum flows and durations of recycling events, filter run length, type of treatment for 

recycle flows, and information on the physical and 

chemical parameters involved in the recycle treatment 

process (see [EPA, 2001] for details). 

As shown in Figure 7.1, liquid waste residuals may be 

disposed by direct/indirect discharge, underground injection, and land disposal. The following subsections 

briefly describe direct and indirect discharge options. 

For PWSs, underground injection is not a viable option 

because of cost (except in extreme situations). 

7.3.1 Direct Discharge of Liquids 

Direct discharge to surface waters can be performed 

by PWSs under the guidance of the CWA’s National 

Pollutant Discharge Elimination System (NPDES 

– 40 CFR Section 122). The Federal Water Pollu7-2
tion Control Act (which, after the 1977 amendments, 

became known as the CWA) defines “pollutant” as 

dredged spoil, solid waste, incinerator residue, sewage, 

garbage, sewage sludge, munitions, chemical wastes, 

biological materials, radioactive materials, heat, 

wrecked or discarded equipment, rock, sand, cellar dirt 

and industrial, municipal, and agricultural waste. The 

NPDES requires that direct dischargers hold a permit 

and may discharge only those pollutants in accordance 

with the terms in the permit (see http://cfpub.epa.gov/ 

npdes/index.cfm for more information). The NPDES 

permits generally include technology-based effluent 

limits for a particular industry. Currently, EPA does 

not have technology-based effluent limits for water 

treatment plants. In this situation, discharge permits 

are usually based on best professional judgment and 

water quality-based effluent limits. Individual states 

conduct discharge permitting. Alaska, Idaho, Arizona, 

Massachusetts, and New Hampshire are not currently 

authorized to implement the NPDES program (EPA, 

2003).

Public water systems opting to discharge liquid residuals such as filter backwash and sedimentation basin 

wash water to the waters of the Nation must obtain a 

NPDES permit for such discharge. To obtain a permit, 

the PWS operator must first submit a completed Notice of Intent to the appropriate state agency delegated 

to implement the NPDES program. The Notice of Intent requires the submittal of information such as location of the facility, name of the owner/operator, contact 

details, location of the receiving waters, description of 

the plant operations including a listing of any additives 

used in the treatment process, design capacity of the 

plant, the number and volume of sedimentation basins, 

the source of raw water, the number of filters that are 

backwashed, the frequency and volume of backwashes 

and sedimentation basin washouts, a water balance 

for backwashes and sedimentation basin washouts, a 

description of how sludge is disposed, type of treatment provided for backwash and sedimentation basin 

wash waters and the design capacity of the system. In 

addition, a facility location map with boundaries that 

extend a few miles beyond the site property (annotated 

with the specific locations of the discharges) is generally required. Also, the PWSs must comply with the 

Total Maximum Daily Load (TMDL) requirements 

developed and approved for the receiving water body. 

If a TMDL is not developed, the PWS must certify that 

the treatment and control methods employed at this 

location are most appropriate for the reduction of pollutants generated at this site. The PWSs must certify 

that they will neither degrade the environment (commonly referred to as the “anti-degradation” certification) nor threaten any endangered species as a result of 

this discharge. 

It should be noted that as long as a facility producing 

an industrial waste stream has a NPDES permit, liquid 

residuals that could otherwise be classified as hazardous waste under RCRA can be legally discharged 

assuming that the discharge is in compliance with the 

RCRA terms cited in 40 CFR Section 261.4. Direct 

discharges to marine environments are subject to additional restrictions under the CWA (see 40 CFR Section 

125.123 for details). 

7.3.2 Indirect Discharge of Liquids 

Public water systems could also discharge liquid 

residuals to sanitary sewers (i.e. “down the drain”). 

Indirect discharge does not require a NPDES permit, but a pretreatment (prior to indirect discharge) 

program may have to be implemented by the operator. EPA has developed pretreatment guidance and 

regulations for industrial discharges to water treatment plants (see Effluent Guidelines cited in 40 CFR 

Section 403). The small quantities of waste generated 

by PWSs typically do not meet the criteria that EPA 

uses for requiring pretreatment of industrial waste. 

Additionally, the pretreatment program places most 

of the responsibility on organizations at the municipal level. Publicly owned treatment works (POTWs) 

that process 5 MGD (or more) or smaller plants that 

have “significant industrial users” are required to 

have a pretreatment program in place (EPA, 1999). 

Included in the definition of significant industrial 

users are those operations that could adversely affect 

the POTW operations and/or violate any pretreatment 

standards. Thus, it may be necessary for some small 

systems that are utilizing sanitary sewers for liquid 

residual disposal to coordinate with local POTWs 

to ensure that they are meeting the requirements set 

by the POTW and/or state authorities. Furthermore, 

several states (e.g., Ohio) require that significant industrial users discharging to a POTW obtain a permit 

for discharge. 

7.3.3 Land Disposal of Liquids 

Liquid residuals are generally not disposed in landfills 

due to the prohibitive costs involved with transport 

and disposal, the regulations surrounding such disposal, and the availability of alternative methods. Liquid 

residuals generated by PWSs that are reused through 

land application and not classified as hazardous waste 

are subject to little federal regulation, but may be 

regulated by the state. States generally implement 

and enforce the provisions defining sanitary landfills 

(as opposed to open dumping, see RCRA Section 

4005). These provisions include (but are not limited 

to) requirements that address location requirements, 

protection of endangered species, source water protection, non-point discharge violations, minimization of 

disease vectors, protection of air quality, and mini7-3
mization of explosive gases. Thus, on-site disposal 

of non-hazardous liquid residuals by PWSs may be 

regulated by the state. Liquid residuals classified as 

hazardous waste are subject to comprehensive generator, transport, storage, treatment, and land disposal 

restrictions defined in RCRA (see solids disposal 

section). 

It is possible that some PWSs may discharge liquid 

residuals to lagoons or evaporation ponds. In these 

cases, the SDWA and RCRA impose requirements for 

non-hazardous wastes that aim to protect wellhead/ 

source waters, surface water, and ground water. States 

may have further requirements concerning non-hazardous liquid residual lagoons. Lagoons containing 

hazardous waste are subject to RCRA regulations 

covering design and operation standards (40 CFR Part 

264, Subpart K). 

7.4 Solid Residuals 

Examples of solid waste residuals (SWR) generated 

by PWSs include sludge, spent treatment media, and 

schmutzdecke. Solid waste residuals are subject to 

RCRA regulations and therefore classified as hazardous or non-hazardous (as defined in RCRA). A waste 

is characterized as hazardous or non-hazardous based 

on its ignitability, corrosivity, reactivity, and/or toxicity 

(see RCRA 40 CFR Sections 261.21 to 261.24). In 

most cases, state and local regulations may also govern 

the treatment/disposal of SWR as many of the regulations set forth in RCRA are administered by state and 

local governments. Some PWSs may qualify as conditionally exempt small quantity generators (CESQG) 

of hazardous waste (RCRA 40 CFR Section 261.5). 

To be classified as a CESQG, the operation must not 

generate more than 100 kg (220 lbs.) of hazardous 

waste per month. The CESQG may not store more 

than 1000 kg (2200 lbs.) of hazardous waste on-site 

at any time. The regulations governing CESQGs are 

generally less stringent than those governing small 

quantity generators or large quantity generators. At 

a minimum, a PWS that qualifies as a CESQG must 

characterize each waste as hazardous or non-hazardous, maintain monthly waste generation inventories 

for amounts of hazardous waste stored on-site, and 

manage hazardous wastes in compliance with federal, 

state, and local regulations. 

Sludge generated by PWSs is not subject to regulation under the Biosolids Rule (Sewage Sludge Rules 

defined in 40 CFR Section 503.6(i)(e)). The Biosolids 

Rule (included in the CWA Amendments of 1987) was 

promulgated to protect public health and the environment from any anticipated effects from the beneficial 

recycling of sewage sludge biosolids (EPA, 1994). 

7.4.1 Land Disposal of Solids 

Waste residuals generated by PWSs will predominantly be characterized as hazardous or non-hazardous 

based on toxicity. The toxicity of SWRs is assessed 

by the Toxicity Characteristic Leaching Procedure 

(TCLP). If contaminant concentrations in the TCLP 

leachate are in excess of those listed in the Land Disposal Restrictions (RCRA 40 CFR 268.40), the SWR 

would be classified as hazardous and must be disposed 

in a RCRA Subtitle C class landfill. Transport and 

disposal costs for SWRs classified as hazardous will 

be considerably higher than costs for non-hazardous 

SWRs, which can be sent to municipal solid waste 

landfills.

7.4.2 Land Application of Solids 

Because sludge generated by PWSs is not subject to 

the Biosolids Rule, on-site recycling of SWR by land 

application may be an option for PWSs to pursue with 

certain kinds of SWRs (e.g. schmutzdecke from slowsand filtration processes). 

7.4.3 Incineration of Solids and Liquids 

Incineration processes are most likely cost-prohibitive 

for small systems and would not be an option except 

in extreme cases (e.g. disposal of acutely toxic waste). 

Regulations governing incineration are covered in the 

Clean Air Act. 

7.5 Technologically Enhanced 

Normally Occurring 

Radioactive Material 

(TENORM) Residuals 

Low-Level Radioactive Waste (LLRW) landfills may 

be an option for some systems generating wastes with 

radionuclide concentrations deemed to be unacceptable for disposal at a solid or hazardous waste landfill. 

LLRW landfills are licensed by the Nuclear Regulatory Commission (NRC) or by a state under agreement 

with NRC, and guidelines for disposing of radioactive sludges and solids are more stringent than in a 

standard landfill. These facilities are licensed, based 

on projected performance and have packaging and 

burial requirements that are progressively stricter as 

the radionuclide concentrations increase. Currently, 

there are three LLRW disposal facilities in operation 

that are located at Barnwell, SC, Richland, WA and 

Envirocare, UT. EPA has developed a guidance document titled, “A Regulators’ Guide to Management of 

Radioactive Residuals from Drinking Water Treatment 

Technologies (EPA, 2005).” Small system operators 

are encouraged to review this document for guidance 

and then contact the state regulators for state-specific 

requirements and disposal options. 

7-4
7.6 Conclusions and Future 

Research

Residuals transport, treatment, and disposal can be 

a significant cost to small communities. For small 

community wastewater treatment operations, handling 

of residuals may account for 50 percent of the total 

operating budget (EPA, 1992). While it is expected 

that waste residual generation at PWSs would be less 

than that of a wastewater treatment plant, costs and 

regulatory issues surrounding waste residuals may still 

be of concern. It will be important in the short term 

(1 to 2 years) to ascertain both the types and quantities of waste residuals generated by small systems. 

Another area that will require more research will be 

on arsenic, radium, and uranium chemistry and its 

behavior in waste residuals (an active research area for 

large-scale systems also). Once more accurate data are 

obtained on the quantities and types of waste residuals, 

more focused efforts may be made in developing new 

techniques for the disposal of waste residuals, including on-site land application which would minimize 

transport and disposal costs. 

7.7 Key Questions 

• What types of waste residuals are generated by 

small systems? 

• What quantities of waste residuals are generated 

by small systems? 

• Are small systems’ waste residual transport/ 

disposal issues significant? 

• What are future issues regarding small systems’ 

waste residuals? 

7.8 References 

All references to Code of Federal Regulations Documents in this chapter may be found at http://www.access.gpo.gov/nara/cfr and Federal Register Documents 

may be found at http://www.gpoaccess.gov/fr/index. 

html

National Drinking Water Clearinghouse. Tech Brief: 

Water treatment plant residuals management. West Virginia University Research Corporation, Morgantown, 

WV, 1998. 

EPA. Manual: Wastewater treatment/disposal for small 

communities. EPA/625/R-92/005, EPA, Washington, 

DC, 1992. 

EPA. A plain english guide to the EPA Part 503 Biosolids Rule. EPA/832/R-93/003, EPA, Washington, 

DC, 1994. 

EPA. Introduction to the National Pretreatment 

Program. EPA/833/B-98/002, EPA, Washington, DC, 

1999.

EPA. Regulations on the Disposal of Arsenic Residuals 

from Drinking Water Treatment Plants. EPA/600/R00/025, Office of Research and Development, Washington, DC, 2000. 

EPA. 40 CFR Parts 9, 141, and 142 National Primary 

Drinking Water, Filter Backwash Recycling Rule, 

Final Rule. Washington, DC. EPA, Washington, DC, 

2001.

EPA. National Pollutant Discharge Elimination 

System, State Program Status. EPA, Washington, DC, 

2003.

EPA. A Regulators’ Guide to Management of Radioactive Residuals from Drinking Water Treatment 

Technologies. EPA/816/R-05/004, EPA, Washington, 

DC, 2005. 

Small Systems Research Committee. Research needs 

for small water systems: A survey. Journal of the 

American Water Works Association 89: 101-113 

(1997).

7-5

Chapter 8 

Homeland Security/ 

Emergency Response 

8.1 Background and Directives 

Under Presidential Decision Directive (PDD) 63 - 

Protecting America’s Critical Infrastructures, issued in 

May 1998, EPA was designated as the lead agency for 

the water supply sector. In November 1998, a preliminary plan (National Infrastructure Assurance: Water 

Supply Sector) was drafted. While the preliminary 

plan showed a scheduled completion date of the end 

of 2003 for these activities, the schedule was accelerated in response to the terrorist acts of September 11, 

2001. In October 2001, a Water Protection Task Force 

was established to ensure that activities to protect and 

secure water supply infrastructure were comprehensive 

and were carried out expeditiously. Also, in October 

2001, EPA disseminated information to the water utilities about steps they could take to protect their sources 

of supply and infrastructure, which include pumping 

stations, treatment facilities, and computer systems. 

EPA worked with the Sandia National Laboratory to 

develop training materials for water utilities to help 

them conduct thorough assessments of their vulnerabilities.

The Public Health Security and Bioterrorism Preparedness and Response Act (Bioterrorism Act), passed in 

June 2002 (P. L. 107-188), provided EPA the mandate 

to work in water security. This law, coupled with the 

Homeland Security Presidential Directives (HSPDs) 

7, 8, 9, 10 and EPA’s own strategic plan for homeland 

security, guides the Agency’s research and technical 

support activities to protect the Nation’s water and 

wastewater infrastructure. The Bioterrorism Act of 

2002, HSPDs 7, 8, 9, 10 and EPA’s overall strategic 

plan are briefly discussed below. 

8.1.1 Bioterrorism Act 

The Bioterrorism Act amended the Safe Drinking Water Act and required all public water suppliers serving 

populations greater than 3,300 to complete Vulnerability Assessments (VAs) and to develop or modify 

Emergency Response Plans (ERPs). Smaller systems 

were encouraged, but not required, to follow the same 

planning and management activities. VAs were intended to identify potential threats, assess the critical assets 

of the system, evaluate the likelihood and consequences of an attack, and develop a prioritized set of system 

upgrades to increase security. Once completed, VAs 

were required to be submitted to the EPA according to 

a pre-set schedule based on the size of the utility. The 

deadline for medium and small size systems (serving 

populations between 3,300 and 50,000) was June 30, 

2004. Additionally for these systems, ERPs providing 

details on response, recovery and remediation actions 

in the event of a contamination or flow disruption 

event were to be submitted within 6-months of the 

submittal of VA and no later than December 31, 2004. 

8.1.2 Homeland Security Presidential Directive 

(HSPD)-7 - Critical Infrastructure 

Identification, Prioritization, and 

Protection 

Under this HSPD, EPA is identified as the “SectorSpecific Agency” for drinking water and water treatment systems. The term “Sector-Specific Agency” 

means a federal department or agency responsible 

for infrastructure protection activities in a designated 

critical infrastructure sector or key resources category. 

The Sector-Specific Agencies are required to conduct 

their activities under the various HSPD directives in 

accordance with guidance provided by the Department 

of Homeland Security (DHS) Secretary. Under this 

directive, EPA must: 

• Collaborate with all relevant federal departments 

and agencies, state and local governments, and 

the private sector; 

• Conduct or facilitate vulnerability assessments 

of the sector; and 

• Encourage risk management strategies to protect 

against and mitigate the effects of attacks against 

critical infrastructure and key resources. 

8.1.3 HSPD-8 - National Preparedness 

HSPD-8 directs the federal government agencies and 

departments to be prepared to respond to nationally 

significant terrorist incidents. EPA is identified as an 

agency that provides assistance for first responder preparedness, and has responsibilities under this HSPD. 

8.1.4 HSPD-9 - Defense of United States 

Agriculture and Food 

Under this HSPD, the EPA Administrator is required 

to build upon/expand current drinking water monitoring and surveillance programs. This work requires 

both detection methods as well as laboratory networks 

needed to accomplish this task. 

8.1.5 HSPD-10 - BioDefense for the 21st 

Century 

Under this HSPD, EPA is required to survey Chemical, 

Biological, Radiation and Nuclear laboratory capacity 

and capability. EPA and other agencies are required to 

develop standards, protocols, and capabilities to address the risks of contamination following a biological 

weapons attack. EPA and other agencies are also re8-1
quired to develop strategies, guidelines, and plans for 

decontamination of persons, equipment, and facilities. 

8.1.6 EPA’s Strategic Plan for Homeland 

Security

In September 2002, EPA published a Draft Strategic 

Plan for Homeland Security which describes the expansion of EPA activities under existing programs and 

new initiatives in direct response to potential threats 

and vulnerabilities. The strategic plan (EPA, 2002) is 

organized into four mission-critical areas: 

1. Critical Infrastructure Protection 

2. Preparedness, Response, and Recovery 

3. Communication and Information 

4. Protection of EPA Personnel and Infrastructure. 

To meet the responsibilities specified under the 

aforementioned directives, EPA’s Office of Water 

established the Water Protection Task Force which 

was formally organized as the Water Security Division 

(WSD) in August 2003. Additionally, EPA’s ORD 

officially established the National Homeland Security 

Research Center (NHSRC) in February 2003. 

These organizations work synergistically to provide 

research and technical support to the drinking water 

and wastewater sectors. NHSRC’s Water Security 

Team contributes by conducting applied research and 

then reporting on ways to better secure the Nation’s 

water systems from threats and attacks. The Team is 

producing various products, such as analytical tools 

and procedures, technology evaluations, models and 

methodologies, decontamination techniques, technical resource guides and protocols, and risk assessment 

methods. All of these products are for use by EPA’s 

key water infrastructure customers — water utility 

operators, public health officials, and emergency and 

follow-up responders. Other research programs in NHSRC deal with the protection of buildings and rapid 

risk assessment. WSD provides support to drinking 

water and wastewater systems by preparing vulnerability assessment and emergency response systems 

and tools, providing technical and financial assistance, 

and developing information exchange mechanisms. 

WSD is also charged with supporting best security 

practices, providing security enhancement guidance, 

and incorporating security into the day-to-day operations of the drinking water and wastewater industries. 

In addition, WSD works closely with NHSRC in 

delivering research results in a timely and appropriate 

fashion. EPA’s WSWRD provides technical support to 

NHSRC in conducting bench-and pilot-scale research 

at the EPA’s Test and Evaluation (T&E) Facility in 

Cincinnati, Ohio. Assistance is also provided for 

field implementation of technologies to complement 

NHSRC’s research. 

8.2 EPA’s Homeland Security 

and Emergency Response 

Initiatives and Resources 

Many of EPA’s ongoing homeland security and emergency response initiatives and resources are summarized on the EPA website link on water security (EPA, 

2005c). Additionally, the water security resources 

for small systems are summarized at the EPA website 

(EPA, 2005c). The resources available for small water 

systems at this web site include links to: 

• VA Tools 

• Self-Assessment Guide for Drinking Water 

Systems.

• Guide for Wastewater Systems. 

• Security Emergency Managements Systems 

(SEMS) software program developed by the 

National Rural Water Association (NRWA). 

• Automated Security Survey and Evaluation 

Tool developed by New England Water Works 

Association.

• Emergency/Incident Planning 

• ERP Guidance - This document provides 

guidance to small and medium-sized community 

drinking water systems on developing or 

revising their ERPs. 

• Response Protocol Toolbox (RPTB) - This 

document is composed of six interrelated 

modules that provide guidance on planning 

for and responding to both threats and actual 

incidents of intentional contamination of public 

drinking water supplies. 

• Emergency Response Workshops - EPA is 

conducting a series of ongoing nationwide 

workshops for all sizes of water utilities that 

provides instruction on the RPTB and the 

Incident Command System. This workshop also 

includes an enhanced tabletop exercise that will 

test and develop emergency response skills. 

• ERP Enhancement to Vulnerability SelfAssessment Tools Software. 

• Tools & Technical Assistance 

• Security Product Guides - EPA has developed 

these guides to provide information on products 

available to enhance physical and cyber security 

and to present information on monitoring 

protocols.

8-2
• Top Ten List to protect small ground water 

suppliers from contamination events. 

• Water Security Guide - This guide, currently 

under development, will provide security 

guidance to drinking water managers and 

operators of systems serving 3,300 people or 

fewer. The guide is expected to be available in 

Calendar Year 2005. 

As indicated earlier in this chapter, the VAs and ERPs 

have already been completed by most small systems. 

Therefore, the tools and resources related to these topics are not discussed further in this document. 

8.3 Threats and Risks to the Water 

Supply

Smaller PWSs, where source areas are known to occur 

at some significant distance from an actual supply, are 

more likely to be severely threatened (Field, 2002). 

The risk of contamination using chemical, biological 

and/or radiological substances with subsequent consequences must be understood by small system managers to provide appropriate security, employ suitable 

detection systems and develop strategies to deal with 

contamination events. 

8.3.1 Chemical and Radiological 

Contaminants

Chemical contaminants include inorganic, organic, radiological and other chemical warfare compounds that 

have a wide range of impacts on water quality and the 

consumer. For example, the impacts can range from 

a harmless change in color to introduction of highly 

toxic neurotoxins (e.g., Sarin, VX) that would cause 

significant fatalities in the exposed population. 

8.3.2 Biological Contaminants 

According to Providing Safe Drinking Water in Small 

Systems (NSF International World Health Organization, 1999), there is an average of 10 to 15 outbreaks 

of disease from tap water in the U.S. per year, with 

“over 100 types of bacteria, viruses and protozoa that 

can be found in contaminated water.” The book states 

that “in both developed and developing countries water 

quality has continued to deteriorate (Bank, 1992).” 

The book also summarizes that “the potential rise in 

waterborne disease outbreaks may be due to increasing 

susceptible populations, political upheaval and high 

numbers of refugees in developing countries. Natural 

disasters such as flooding and droughts due to climatic 

changes may also be affecting global water quality.” 

8.3.3 Risk Assessment and Mitigation 

Risk assessment was a required element of the federally mandated VAs. Furthermore, small systems were 

encouraged to implement actions that specifically 

addressed the potential threats and vulnerabilities 

identified during the federally mandated vulnerability 

assessments. Some key measures that were recommended include: 

• Routine or around-the-clock monitoring of 

treatment and key supply infrastructure (using 

video surveillance, intrusion detection, alarm 

systems).

• General increase in security procedures such 

as identification for employees and visitors 

with continuing emphasis on security at staff 

meetings.

• Routine inspection of key facilities and 

suspension of public access to these facilities. 

• Routine testing of water quality to ensure that it 

continues to meet or exceed the required federal 

and state standards. 

Along with providing research and technical support, 

WSWRD, NHSRC and WSD encourage information 

sharing and risk communication strategies among key 

water infrastructure customers. This includes making 

use of the Water Information Sharing and Analysis 

Center. Small system operators are encouraged to 

contact (through available state and local channels 

or directly) both WSD and NHSRC periodically for 

resources and technology related inputs that might be 

available to address their needs. 

8.4 Response Protocol Toolbox 

EPA released the “Interim Final Response Protocol 

Toolbox: Planning for and Responding to Contamination Threats to Drinking Water Systems,” in December 

of 2003 (EPA, 2003). The RPTB is composed of six 

interrelated modules, in addition to an overview, which 

focus on different aspects of planning a response to 

contamination threats and incidents. The module titles 

are listed below: 

Overview (EPA-817-D-03-007) 

Module 1 - Water Utility Planning Guide (EPA-817-

D-03-001)

Module 2 - Contamination Threat Management 

Guide (EPA-817-D-03-002) 

Module 3 - Site Characterization and Sampling 

Guide (EPA-817-D-03-003) 

Module 4 - Analytical Guide (EPA-817-D-03-004) 

Module 5 - Public Health Response Guide (EPA817-D-03-005)

8-3
Module 6 - Remediation and Recovery Guide 

(EPA-817-D-03-006) 

These modules provide emergency response planning 

tools that may be adopted voluntarily. The RPTB is 

designed to help the water sector to effectively and 

appropriately respond to intentional contamination 

threats and incidents. EPA produced the RPTB, building on the experience and expertise of several drinking 

water utilities, particularly the Metropolitan Water District of Southern California. The users are encouraged 

to review the overview before using other Modules. 

Since the release of RPTB, EPA received feedback 

and suggestions from several sources concerning improvements in the RPTB. Subsequently, EPA developed RPTB: Response Guidelines (EPA, 2004)- An 

action oriented document (easy to use document for 

field and crisis conditions) to assist drinking water 

utilities, laboratories, emergency responders, state 

drinking water programs, technical assistance providers, and public health and law enforcement officials 

during the management of an ongoing contamination 

threat or incident. The RPTB Response Guidelines 

are not intended to replace the RPTB and do not 

contain the detailed information contained within the 

six complete modules. The RPTB Response Guidelines are to be viewed as the application of the same 

principles contained in the RPTB during an actual 

incident. 

8.5 Recommended Procedures for 

Securing Small Systems 

The Association of State Drinking Water Administrators (ASDWA)/NRWA document, titled Security Vulnerability Self-Assessment Guide for Small Drinking 

Water Systems (ASDWA/NRWA, 2002), suggests the 

following: 

• restrict or limit access to the critical components 

of the water system (i.e., a part of the physical 

infrastructure of the system that is essential for 

water flow and/or water quality) to authorized 

personnel only; 

• secure the facility perimeter with a fence; 

• lock all building doors and windows, hatches 

and vents, gates, and other points of entry to 

prevent access by unauthorized personnel, and 

check the locks regularly; 

• assure adequate lighting around the critical 

water system components, which is a good 

deterrent to unauthorized access (motion 

detectors that activate switches that turn lights 

on or trigger alarms also enhance security; 

• post warning signs (tampering, unauthorized 

access, etc.) on all critical components; 

• patrol and inspect critical components; 

• clear the area around critical components of 

any objects that may be used for breaking and 

entering;

• assure that entry points to the water system 

are easily seen (clear fence lines of vegetation, 

including overhanging or nearby trees); 

• consider installing an alarm system that notifies 

the authorities or designated contact when there 

has been a breach of security; 

• record locks and associated keys and to whom 

the keys have been assigned; 

• limit entry codes and/or keys to water system 

personnel only; 

• form a neighborhood watch system; 

• properly seal wellheads; 

• properly install vents and caps to help prevent 

the introduction of a contaminant into the water 

supply;

• properly secure observation/test and abandoned 

wells;

• secure surface water sources, where possible, 

with fences or gates; 

• control the use of hydrants and valves; 

• monitor distribution system for positive 

pressure; 

• implement a backflow prevention program. 

8.6 Infrastructure and Bulk Water 

The DHS developed a document entitled National 

Strategy for the Physical Protection of Critical Infrastructures and Key Assets (DHS, 2003). This Strategy 

document identifies a clear set of national goals, objectives and outlines, and guiding principles that underpin 

the Nation’s efforts to secure the infrastructures and 

assets vital to national security, governance, public 

health and safety, economy, and public confidence. 

This Strategy also provides a unifying organization 

and identifies specific initiatives to drive the near-term 

national protection priorities and inform the resource 

allocation process. Most importantly, it establishes 

a foundation for building and fostering the cooperative environment in which government, industry, and 

private citizens can carry out their respective protection responsibilities effectively and efficiently. The 

8-4
Strategy states the following concerning water: 

“On the supply side, the primary focus of critical infrastructure protection efforts is the Nation’s 170,000 

public water systems. These utilities depend on reservoirs, dams, wells, and aquifers, as well as treatment 

facilities, pumping stations, aqueducts, and transmission pipelines.” The Strategy also states that “in order 

to set priorities among the wide range of protective 

measures that should be taken, the water sector is focusing on the types of infrastructure attacks that could 

result in significant human casualties and property 

damage or widespread economic consequences. In 

general, there are four areas of primary concentration: 

• Physical damage or destruction of critical assets, 

including intentional release of toxic chemicals; 

• Actual or threatened contamination of the water 

supply;

• Cyber attack on information management 

systems or other electronic systems; and 

• Interruption of services from another 

infrastructure. 

The Strategy also states that water infrastructure 

protection initiatives are guided both by the challenges 

that the water sector faces and by recent legislation. 

Additional protection initiatives include efforts to: 

• Identify high-priority vulnerabilities and 

improve site security 

• Improve sector monitoring and analytical 

capabilities 

• Improve sector-wide information exchange and 

coordinate contingency planning 

• Work with other sectors to manage unique risks 

resulting from interdependencies 

The Drinking Water Needs Survey (EPA, 1997) states 

that “community water systems need to invest significant amounts of money in infrastructure improvements 

if they are to continue providing water that is safe 

to drink. Much of the Nation’s drinking water infrastructure suffers from long term neglect and serious 

deterioration. Recent events, including waterborne 

disease outbreaks and extended boil water notices in 

major cities, have focused national attention on the 

dangers associated with contamination of public water 

supplies. Current needs for minimizing health threats 

from microbiological contaminants (those needs associated with the SWTR and the TCR) are especially 

critical. Water systems around the country must make 

immediate investments in infrastructure to protect 

public health and ensure the availability of safe drinking water.” 

8.7 Telemetry 

Small water utilities typically have their customer and 

billing information system computerized (a traditional 

Information Technology-IT system) along with some 

remote components potentially on a Supervisory 

Control and Data Acquisition (SCADA) System (a.k.a. 

telemetry). These IT/SCADA systems are vulnerable 

to attacks which may disrupt the operations of the utility and potentially damage equipment. The Association of State Drinking Water Administrators/National 

Rural Water Association document, titled Security 

Vulnerability Self-Assessment Guide for Small Drinking Water Systems (ASDWA/NRWA, 2002), suggests 

the following: 

• password protect all computer access; 

• install a firewall protection program; 

• consider subscribing to a virus protection update 

program;

• back up computers regularly; 

The U.S. Department of Homeland Security’s website 

(www.dhs.gov) provides information on reporting 

cyber-security incidents. It specifies that individuals 

can report to the United States Computer Emergency 

Readiness Team at www.us-cert.gov and federal agencies/department report to www.us-cert.gov/federal. 

The DHS website also provides information on current 

threats, including the advisory system, advisories, and 

information bulletins. 

Panguluri et al, (2004), provide an overview of a 

utility’s computer system infrastructure along with 

identifying methods for mitigating cyber-attacks. This 

document also has a compilation of sources from 

where common vulnerabilities can be identified. An 

overview of planning for incident response and business continuity is also provided in this document. 

8.8 Early Warning Systems for 

Drinking Water Systems 

According to Online Monitoring for Drinking Water 

Utilities (AWWARF-PROAQUA, 2002) “a water utility’s primary responsibility is to consistently produce 

and distribute water that will satisfy the customer in 

terms of quality and quantity. Water quality in the 

distribution system can significantly deteriorate due to 

bacterial growth, corrosion, and direct contamination. 

Assuring stable, high-quality drinking water depends 

on the utility’s ability to ensure that the water put into 

8-5
the distribution system maintains its quality until it is 

consumed. Online monitoring of a limited number of 

variables can substantially contribute to achieving this 

goal.” 

“Water quality monitoring sensor equipment may be 

used to monitor key elements of water or wastewater 

treatment processes (such as influent water quality, 

treatment processes, or effluent water quality) to identify anomalies that may indicate threats to the system. 

Some sensors, such as sensors using biological organisms or measuring radiological contaminants, measure 

“surrogate” parameters that may indicate problems in 

the system but do not identify sources of contamination directly, while others, particularly chemical monitoring systems measure potential contamination directly. In addition, sensors can provide more accurate 

control of critical components in water and wastewater 

systems and may provide a means of early warning 

so that the potential effects of certain types of attacks 

can be mitigated. One advantage of using chemical 

and biological sensors to monitor for potential threats 

to water and wastewater systems is that many utilities 

already employ sensors to monitor potable water (raw 

or finished) or influent/effluent for SDWA or CWA 

water quality compliance or process control. 

Chemical sensors that can be used to identify potential threats to water and wastewater systems include 

inorganic monitors (e.g. chlorine analyzer), organic 

monitors (e.g. total organic carbon analyzer) and 

toxicity meters. Radiological meters can be used to 

measure concentrations of several different radioactive 

species. Monitors that use biological species can be 

used as sentinels for the presence of contaminants of 

concern, such as toxics. “At the present time, biological monitors are not in widespread use and very few 

biomonitors are used by drinking water utilities in the 

U.S. (EPA, 2005b).” “Proof that the delivered water 

meets the quality requirements must be gained during 

and after the treatment process. For that reason, online 

monitoring of key parameters, in combination with 

other tools, will help the system operator to: 

• Identify areas in the system that are vulnerable 

to water quality deterioration or external 

contaminant sources 

• Take proper preventive or corrective measures to 

improve system integrity 

• Substantially increase the capability of early 

detection methods for regulated parameters 

• Optimize the system in terms of energy 

consumption and water supply patterns 

• Document that some parameters (disinfectant 

residuals, fluoride, etc.) comply with required 

concentrations for a specified period of time 

(e.g., over 95 percent of operation period) 

• Inform customer on water quality (via the 

Internet or other communication systems).” 

(AWAARF, 2002) 

8.9 Disinfection in Distribution 

Systems

Disinfection of drinking water is considered to be 

one of the major public health advances of the 20th 

century. Disinfection ensures that dangerous microbial contaminants are inactivated before they can enter 

the distribution system. The successful application 

of chlorine as a disinfectant was first demonstrated in 

England. In 1908, Jersey City (New Jersey) initiated 

the use of chlorine for water disinfection in the U.S. 

This approach subsequently spread to other locations, 

and soon the rates of common epidemics such as 

typhoid and cholera dramatically dropped in the U.S. 

Today, disinfection is an essential part of drinking 

water treatment. Chlorine gas, hypochlorite, chlorine 

dioxide, and chloramines are most often used because 

they are very effective disinfectants, and residual 

concentrations can be maintained in the water distribution system. Some European countries use ozone 

and chlorine dioxide as oxidizing agents for primary 

disinfection prior to the addition of chlorine or chlorine dioxide for residual disinfection. The Netherlands 

identifies ozone as the primary disinfectant, as well as 

common use of chlorine dioxide but typically uses no 

chlorine or other disinfectant residual in the distribution system (Connell, 1998). 

8.10 Preparedness Assessment 

for Handling Threats 

The NRWA has customized the Standardized Emergency Management Systems/Incident Command System (SEMS/ICS) training for small systems to manage, respond and mitigate real or perceived threats. 

SEMS/ICS is based on the use of commonly accepted 

terminology that clearly describes needs and expectations between response agencies. This terminology 

is based on the established and accepted common 

names for emergency response equipment, organizational units, functions, resources, and facilities. A 

SEMS/ICS response organization is based on the type 

and size of the incident. Modular organization allows 

for the addition and reduction of positions based on 

current and future needs. All SEMS/ICS organizations 

build from the top down as the incident grows. 

SEMS/ICS is made up of five functions: Management; 

Operations; Planning; Logistics; and Finance. These 

8-6
functions may, as the incident grows, be organized 

and staffed into Sections. Initially, the Director of 

Emergency Services may be performing all five functions. Then, as the incident grows, each function may 

be established as a Section with several Units under 

each Section. Only those functional elements that are 

required to meet current objectives will be activated. 

Those functions which are needed but not staffed will 

be the responsibility of the next higher element in 

the organization. Several states mandate the use of 

SEMS/ICS when responding to any of the following 

emergency operations: 

• Single jurisdictional responsibility with multiple 

agency involvement 

• Multiple jurisdictional responsibility with 

multiple agency involvement 

The SEMS/ICS provides an efficient tool for the 

management of emergency operations. SEMS / ICS is 

designed to be adaptable to any emergency or incident. 

The system expands in a rapid and logical manner 

from an initial response to a major incident call-out. 

When organizational needs dictate, the system also 

contracts just as rapidly. SEMS/ICS allows for continuous notification of intelligence from state and local 

level agencies to information and alerts from the Office of Homeland Security, Federal Bureau of Investigation, Environmental Protection Agency, Department 

of Energy, Department of Transportation, U.S. Bureau 

of Reclamation and the Awareness National Security 

Intelligence Reports, as well as the Association of 

Metropolitan Water Agencies and the American Water 

Works Association. 

8.11 Local/State Emergency 

Planning Committees 

Local Emergency Planning Committees (LEPCs) were 

established by the Emergency Planning and Community Right-to-Know Act (EPCRA), which includes 

emergency planning and community right-to-know 

requirements. The purpose of the LEPC includes: 

• Development, training, and testing of the 

hazardous substances emergency response plan 

for the community 

• Development of procedures for regulated 

facilities to provide informational and 

emergency notification to the LEPC 

• Development of procedures for receiving and 

processing requests from the public under 

EPCRA

• Provision for public notification of LEPC 

activities 

A major role for LEPCs is to work with industry and 

the interested public to encourage continuous attention to chemical safety, risk reduction, and accident 

prevention by each local stakeholder. The EPA’s 

Office of Emergency Management (OEM) maintains 

a LEPC database (EPA, 2005a) which contains over 

3,000 listings. This database can be searched by state, 

name address or by zip code. The database is updated 

monthly. In addition, the Local Governments Reimbursement (LGR) Program provides federal funds to 

local governments for costs related to temporary emergency measures conducted in response to releases or 

threatened releases of hazardous substances. The program serves as a “safety net” to provide supplemental 

funding to local governments that do not have funds 

available to pay for these response actions. Eligible 

local governments may submit applications to EPA for 

reimbursement of up to $25,000 per incident. 

On February 18, 1998, EPA published a new LGR 

regulation that simplifies and streamlines the process 

for applicants. EPA has designed the reimbursement 

process to be very straightforward. Local governments obtain and complete a simple LGR application 

form that requires a local government to provide basic 

information about the incident, document its response 

costs by attaching copies of receipts, and certify that 

certain program requirements have been met. An applicant may receive a reimbursement check from the 

federal government in as little as three months after 

EPA receives the application. Local governments can 

take action today to help ensure that they are eligible 

to participate in the LGR program in the future. 

EPA’s LGR Program HelpLine can be reached by calling 800-431-9209 or via e-mail at lgr.epa@epamail. 

epa.gov. 

8.12 Alternative Drinking Water 

Supplies in the Event of an 

Incident

Public water systems may at some time need to utilize 

an alternate source of water. This need may arise due 

to drought, contamination of the primary source, or 

failure at the source (e.g. a dam). Use of an alternate 

source of water can be complex, and will require 

advance approval by the state agencies. Prior to submitting an application for approval, the PWS should 

perform a preliminary evaluation to assess the difficulty of locating pipes to transport water on a temporary 

basis, obtaining right-of-way or access rights, and securing financing to construct temporary or permanent 

structures. If a PWS anticipates the need to utilize 

an alternate source of raw water and the preliminary 

evaluation indicates that the project can be accom8-7
plished, the PWS should proceed by contacting the 

regulating state agency to obtain approval. Typically, 

a state agency will require basic information, such as 

identification of proposed alternate source(s), surface 

and ground, including location and name of source. In 

addition, specific information on each proposed alternate source is usually required, such as estimated days 

of water available and potential sources of contamination within the vicinity of each proposed source (e.g., 

domestic or hazardous waste sites, oil and gas wells, 

abandoned wells, mining operations, discharges from 

sewage treatment plants, industrial discharges). Also, 

depending upon the size and location of the alternative 

source, there may be many other requirements that a 

PWS must meet to be able to utilize that source. Furthermore, alternate sources of raw water must be tested 

(for evaluating the water quality), evaluated against 

available treatment techniques, and finished water 

testing must be performed in order to ascertain that the 

water provided to the public will meet all regulatory 

requirements.

If an alternate source(s) is(are) approved, the results 

of the raw water testing are typically used in part to 

determine the amount of testing necessary for the finished water. Other factors would include the operation 

and maintenance of the treatment plant and the water 

treatment practices in place to remove contaminants if 

they are encountered. Typically, at a minimum, testing 

is required for total coliform bacteria in the treated water. Continued use of the alternate sources will also be 

subject to routine monitoring requirements. In many 

cases it may be more economical and practical to 

contract with a neighboring water supplier and form a 

partnership for sharing raw and/or finished water during emergencies. If such sources are not available, the 

PWS should implement other appropriate emergency 

water conservation measures outlined in their ERP. 

8.13 Key Questions 

• Are information sources adequate for small 

systems? Can information dissemination be 

improved through cooperation with NRWA? 

• Are emergency response procedures/protocol 

adequate? Are small systems satisfied with 

these procedures? 

8.14 References 

ASDWA/NRWA. Security vulnerability self-assessment guide for small drinking water systems. http://

www.doh.wa.gov/ehp/dw/Security/Security_Vulnerability.pdf. 2002. 

AWWARF-PROAQUA, Online monitoring for drinking water utilities. American Water Works Association, 

Denver, CO. 2002. 

World Bank. World Development Report: Development and the Environment. Oxford University Press, 

New York, NY, 1992. 

Connell, G.F. European water disinfection practices 

parallel U.S. treatment methods. http://www.clo2. 

com/reading/waternews/european.html. 1998. 

DHS. National strategy for the physical protection of 

critical infrastructures and key assets. http://www.dhs. 

gov/interweb/assetlibrary/Physical_Strategy.pdf. 2003. 

EPA. Drinking water infrastructure needs survey, first 

report to congress. Washington, DC http://www.epa. 

gov/safewater/needssurvey/pdfs/1997/report_needssurvey_1997_cover.pdf, 1997. 

EPA. Strategic plan for homeland security. http://www. 

epa.gov/epahome/downloads/epa_homeland_security_strategic_plan.pdf. 2002. 

EPA. Interim final response protocol toolbox: Planning for and responding to contamination threats to 

drinking water systems. Washington, DC http://cfpub. 

epa.gov/safewater/watersecurity/home.cfm?program_ 

id=8#response_toolbox, 2003. 

EPA. Response protocol toolbox: Response guidelines. 

Washington, DC http://www.epa.gov/safewater/watersecurity/pubs/rptb_response_guidelines.pdf, 2004. 

EPA. Local emergency planning committee database. 

Accessed: August 5, 2005. Last Update: April 2005. 

http://www.epa.gov/ceppo/lepclist.htm. 2005a. 

EPA. Sensors for monitoring chemical, biological, 

and radiological contamination. Accessed: August 5, 

2005. Last Update: March 8, 2005. http://www.epa. 

gov/watersecurity/guide/chemicalbiologicalandradiologicalsensoroverview.html. 2005b. 

EPA. Water security. Accessed: August 5, 2005. Last 

Update: June 24, 2005. http://cfpub.epa.gov/safewater/ 

watersecurity/index.cfm. 2005c. 

Field, M., Development of a counterterrorism preparedness tool for evaluation risks to Karstic spring 

water. in US Geological Survey Karst Interest Group 

Proceedings, Shepherdstown, WV. 2002. 

8-8
NSF International World Health Organization, Providing safe drinking water in small systems: Technology, 

Operations, and Economics. Lewis Publishers, Boca 

Raton, FL. 1999. 

Panguluri, S., W.R. Phillips, and R.M. Clark, Cyber 

Threats and IT/SCADA System Vulnerability. in Mays 

L., editor. Water Supply Systems Security. McGraw 

Hill, New York, NY. 2004. 

8-9

Chapter 9 

Remote Monitoring 

and Control 

9.1 Introduction

Drinking water regulations require all conventional 

drinking water treatment system operators to provide 

water quality monitoring to ensure that good quality 

water is provided to the consumers (EPA, 1996). Most 

treatment systems/technologies can be equipped with 

sensors and operating devices that can be monitored 

from remote locations. Remote monitoring and control technology can be used to improve monitoring/reporting and reduce operation and maintenance (O&M) 

costs. Remote monitoring and control technologies or 

remote telemetry systems are also known as Supervisory Control and Data Acquisition (SCADA) systems. 

A SCADA system consists of three key components: 

monitoring/control device(s) (e.g., a sensor/analyzer 

that measures and reports the desired parameter, a variable frequency drive pump the speed of which can be 

controlled remotely), data transmission equipment/media (e.g., phone, wire and radio), and data collection 

and processing unit (typically a central computer that 

analyzes the reported parameter value and programmatically decides what controls, are warranted based 

on the reported value). For example, when a tank level 

sensor reports that a remote reservoir is full, this information is processed by the SCADA central computer 

which instructs the associated pump to shut down. For 

small packaged treatment systems, such equipment 

could easily double the purchase cost. However, operational payback can be quickly realized through lower 

use of chemicals, low residue generation (disposal), 

and increased reliability. Also, the cost of subsequent 

networking of multiple package plant sites or water 

quality monitoring devices is also decreased after the 

initial cost for installing the basic SCADA equipment has been incurred. It has been demonstrated 

that various remote monitoring technologies are being 

appropriately designed for small systems and these 

will ultimately produce a better quality of drinking 

water, accommodate the resources of small systems, 

increase the confidence level of the customer, operator and regulator, and comply with the monitoring and 

reporting guidelines. 

SCADA systems are not always used to their fullest 

potential by small systems due to complex operating 

systems and control (software and hardware) that usually require specially trained computer programmers 

or technicians and costly service agreements. In the 

last few years, SCADA vendors have changed the way 

they design and fabricate their systems, thus making 

them more accessible and affordable to small drinking 

water treatment operators. 

9.2 Rationale for Online Monitoring 

The application of SCADA to operate, monitor, 

and control small systems from a central location is 

believed to be one mechanism that can reduce violations of MCLs as well as Monitoring/Reporting (M/R) 

violations. Through the application of SCADA, EPA 

has demonstrated that filters could be operated more 

efficiently for particle removal, disinfectant doses 

altered in real-time in response to varying raw water 

conditions, and routine maintenance and chemical 

re-supply can be scheduled more efficiently. Small 

independent systems could contract with an off-site 

O&M firm or join with other small system communities or utilities to either work out schedules to monitor 

via SCADA or hire an O&M services provider, while 

maintaining ownership. This type of approach would 

provide the small system the economies-of-scale that 

the medium and larger systems have in purchasing 

supplies, equipment, and power. 

EPA has been evaluating a variety of “small” SCADA 

systems that would allow a single qualified/certified 

operator to monitor and control the operation of several small treatment systems from a central location. 

The use of a SCADA system results in optimum utilization of time for onsite inspections and maintenance, 

thus allowing the operator to visit only the problematic 

systems/sites and better schedule the maintenance of 

these systems. The expected results from an appropriately designed and successfully deployed SCADA 

system are (Panguluri et al., 2005a): 

• enhanced security and control, 

• improved water quality, 

• regulatory compliance, and 

• reduced overall maintenance costs 

9.3 Selection and Implementation 

of Supervisory Control and 

Data Acquisition (SCADA) 

Systems

It is important to understand the treatment system 

operation, location and other environmental factors 

when engineering and designing a SCADA system 

for remote operation and maintenance. The treatment 

system operation, location and site-specific factors (the 

site-specific factors are discussed later in this section) 

will determine the need and the basic design of the 

SCADA system. These factors will also help to deter9-1
mine if the system will complement the needs of the 

treatment system and the utility services. Retrofitting 

a treatment system for remote operations can be cost 

prohibitive; many of the small treatment systems currently in use were not originally designed for remote 

operations. Rural areas have little or no electronic 

hardware to communicate with a SCADA system. 

Thus, the cost of upgrading the treatment system for 

remote operations could be significant. Therefore, it is 

essential that the treatment system be fairly amenable 

to automation. Table 9.1 identifies the current amenability of small package plant treatment technologies to 

SCADA. 

Many of these treatment technologies are available as 

package plants with some degree of automation designed specifically for small systems. The membrane 

technologies are extremely amenable to automation 

and remote control and also provide efficient removal 

for a wide range of drinking water contaminants. 

Federal regulations require all small PWS operators to 

provide monitoring to assure quality of the treatment 

processes. Constant remote monitoring of the water 

quality has the potential to provide savings in costs 

of time and travel for O&M. It has been determined 

that remote telemetry can support regulatory reporting 

guidelines by providing real-time continuous monitoring of the water quality and reporting the information 

electronically. However, current guidelines are not 

available on how to interpret the online data. For example, if the data shows that for a period of 5-minutes 

(in a particular month) the measured chlorine levels 

Table 9.1 Amenability of treatment 

technologies to remote monitoring used for 

small water (EPA, 2003). 

Technology 

Amenability for 

Automation/Remote 

Monitoring & Control* 

Air Stripping 

Oxidation/Filtration 

Ion Exchange 

Activated Alumina 

4 – 5 

1 - 2 

3 - 4 

1 – 2 

Coagulation/Filtration 

Dissolved Air Flotation 

Diatomaceous Earth Filtration 

Slow Sand Filtration 

Bag and Cartridge Filtration 

1 – 2 

1 - 2 

3 - 4 

3 - 4 

3 – 4 

Disinfection 

Corrosion Control 

Membrane Filtration Systems 

Reverse Osmosis/Nanofiltration 

Electrodialysis Systems 

Adsorption 

Lime Softening 

4 – 5 

3 - 4 

3 - 4 

4 - 5 

4 - 5 

3 - 4 

1 – 2 

*A rating scale of one to five (1 to 5) is employed with one (1) being 

unacceptable or poor and five (5) being superior or acceptable. 

were below the regulated levels does that constitute a 

violation? Additionally, states do not have a mechanism to accept large quantities of data There is need 

for developing guidance on how to interpret the online 

monitoring data both from compliance and security 

perspectives. 

Long-term real-time remote monitoring can provide 

data that can be used to significantly enhance treatment system operation and reduce system downtime. 

Real-time remote monitoring (Clark et al., 2004; EPA, 

2003; Haught, 1998; Haught and Panguluri, 1998) has 

the following advantages: 

• Can lead to improved customer satisfaction, 

improved consumer relations and other health 

benefits.

• Can be used to satisfy regulatory recordkeeping 

and reporting requirements. 

• Can reduce labor costs (associated with time and 

travel) for small system operators. 

• Provides the capability to instantly alert 

operators of undesirable water quality and/or 

other changes in treatment system(s). 

• Reduces downtime and increases repair 

efficiency; troubleshooting can be performed 

remotely. 

• Can identify monitored parameter trends and 

adjust operating parameters accordingly. 

• Can provide an attractive alternative to fixed 

sampling and operation and maintenance 

schedules.

The following questions must be addressed before 

purchasing a SCADA System (Clark et al., 2004; EPA, 

2003; Haught, 1998; Haught and Panguluri, 1998): 

• Does the water treatment system justify the 

requirement for a SCADA system (is it remotely 

located)?

• Is the treatment system amenable (can water 

quality instrumentation and operational 

controls “send and receive” data in real-time) to 

automation?

• What types of communication media can be 

used (phone, radio, cellular, etc.)? See Figure 

9.1

• How much automation and control is available 

on the treatment system? 

• What type of SCADA system is needed (is the 

goal to monitor, control or both)? 

9-2
Remote Communication 

Location Media

Satellite

OR

Cellular Network 

OR 

Radio (RF) Communication 

OR 

Telephone Line 

OR

Direct Wire 

Central

Office

• How many parameters are going to be monitored 

and/or controlled? 

• What are the specific regulatory monitoring and 

reporting requirements? 

Figure 9.1 shows the possible schematic layout of a 

remote monitoring network. 

9.4 Fundamentals of SCADA 

As discussed previously, the three key components 

of SCADA are: monitoring/control device(s), data 

transmission equipment/media, and data collection and 

processing unit. This equipment is briefly discussed in 

the following sub-sections of this report. 

9.4.1 Monitoring Equipment 

In general, monitors can be categorized by the types of 

parameters (contaminants, agents, characteristics) that 

the monitor is used to measure. For establishing water 

quality, the monitors are designed to measure one or 

more parameters that represent physical, chemical and/ 

or biological characteristics of the system. The online 

remote monitoring devices are fairly complex devices 

that are designed to automatically measure, record, 

and display specific physical, chemical or biological 

parameters. Online monitoring equipment can be the 

most expensive component of a SCADA system. The 

sensors used in a SCADA system may vary widely, 

depending upon the parameters that need to be monitored. The cost for these devices can range from $ 300 

to $ 85,000. The costs associated with maintenance 

and calibration of the monitoring equipment should be 

considered when planning the acquisition and implementation of a SCADA network. The basic types of 

monitoring devices that may be employed in a water 

distribution system for monitoring water quality are 

discussed below. 

9.4.1.1 Physical Monitors 

Physical monitors are used to measure physical 

characteristics of the water. They include a variety 

of instruments that measure various characteristics, 

such as flow, velocity, water level, pressure and other 

intrinsic physical characteristics of water. Examples 

of intrinsic physical characteristics include: turbidity, 

color, conductivity, hardness, alkalinity, radioactivity, 

temperature and oxidation-reduction potential. In general, physical monitors tend to be relatively inexpensive, quite durable, and readily available. 

9.4.1.2 Chemical Monitors 

Chemical monitors are used to detect and measure 

inorganic or organic chemicals that may be present in 

the water. A wide range of chemicals may be of interest and a large variety of technologies can be used. A 

specific technology or multiple technologies must be 

properly selected for a particular chemical or group of 

chemicals. Examples of chemical monitors include: 

Chlorine analyzer, nitrate sensor, Total Organic CarFigure 9.1 Possible layout of remote monitoring system (EPA, 2003). 

9-3
bon (TOC) analyzer, etc. Typically, the same general 

type of technology may be available for either automated online monitoring capability or for manual grab 

sample analysis. 

9.4.1.3 Biological Monitors 

Biological monitors (biomonitors) include bio-sensors 

and bio-sentinels. Bio-sensors detect the presence of 

biological species of concern, such as some forms of 

algae or pathogens. The general operating principles 

of bio-sensors may include: photometry, enzymatic 

and/or some form of bio-chemical reaction. The 

bio-sentinels use biological organisms as sentinels to 

determine the likely presence of toxicity in a water 

sample. In general, bio-sentinels cannot be used to 

identify the presence of a specific toxic contaminant 

– rather only that there is some form of toxic contaminant present. Most bio-sentinels operate by observing the behavior of selected organisms. Examples of 

such organisms include: fish, mussels, daphnia and 

algae. When the sentinel organism senses the presence of toxic contaminant(s), the organism reacts in 

some manner. The bio-sentinel instruments respond 

to these reactions and note that some form of event is 

occurring. 

While bio-sensors can be directly applied in distribution systems, the bio-sentinels are typically used 

in source waters. This is because most organisms 

are sensitive to the presence of chlorine (or other 

disinfectants) in the water. Therefore, if a bio-sentinel is proposed to be used for distribution system 

monitoring, the water must be de-chlorinated prior to 

entering the bio-sentinel instrument. Also, the biosentinels require a protected housing environment 

along with some sort of nutritional supply to keep 

the sentinel organism alive and healthy. The use of 

bio-monitors is ideally more suitable for security 

issues. 

9.4.2 Control Equipment 

Control equipment such as switches and controllers 

are used widely in SCADA systems. Cost of the control units such as pumps or shut-off valves are generally less expensive (Panguluri et al., 2005a) compared 

to the monitoring equipment. 

9.4.3 Data Collection and Processing Unit(s) 

Depending upon the system design requirements, 

there can be more than one central data collection 

and processing unit. The SCADA system can be designed in a way such that the field SCADA units are 

“dumb” units that simply collect and transmit data 

to the central station for analysis and action. Alternatively, field SCADA units can be “smart” and be 

automated to perform some of the control decisions 

locally and interact with the central station as necessary for additional analysis and support. 

9.4.4 Communication Media and Field Wiring 

Depending upon availability, cost, user preference, and 

the relative location of the sensors to the data acquisition system, the communication media can be either 

wired (e.g., direct, phone line) or wireless (e.g., radio, 

cellular). In field environments, distributed input/output is typically employed. A remote data acquisition 

hardware unit employed at the field location performs 

the appropriate signal conditioning and transmits the 

data to a central hub (Clark et al., 2004; EPA, 2003; 

Haught, 1998; Haught and Panguluri, 1998; Pollack et 

al., 1999). More recently, mesh or grid computing systems are used in remote locations to add redundancy 

in cases of link failures. The field wiring between the 

sensor and the remote data acquisition hardware unit is 

typically direct wire. 

Typically, direct wire and phone line (including cellular) communication media are the most inexpensive. 

The primary limitations associated with selecting 

the communication media include installation and 

operating costs, which can vary between $200 (for a 

simple telephone or cellular modem) to several hundred dollars for a satellite-based system per location. 

Ongoing monthly operating costs can range from $25 

for a phone line to approximately $200 per month for 

satellite-based services within the U. S (per monitored 

location). The overall costs for individual SCADA 

components are summarized in Table 9.2 (EPA, 2003). 

For a small system, it is expected that (except for the 

sensor instrumentation) the actual costs will be on the 

lower side of the presented ranges in Table 9.2. 

9.5 Remote Telemetry Applications 

for Small Systems 

Over the years, EPA has funded several remote 

monitoring applications in the field. The very first 

field implementation for a small system was in West 

Virginia and the most recent implementation was in 

Puerto Rico. A brief summary of these case studies is 

presented in this section. 

9.5.1 West Virginia Remote Monitoring Case 

Study 

In May 1991, EPA provided funding to support a 

research project titled “Alternative Low Maintenance 

Technologies for Small Water Systems in Rural Communities” (Goodrich et al., 1993). This project involved the installation of a small drinking water treatment package plant in a rural location in West Virginia. 

The primary objective of this study was to evaluate 

the cost-effectiveness of package plant technology in 

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Table 9.2 Cost estimates of SCADA system components (Updated from EPA, 2003). 

SCADA System Component Component Option Range of Costs, $ 

Hardware Main Computer 

SCADA Unit 

1,000 – 3,500 

500 – 30,000 

Software Operating System 

Telemetry System 

Data Collection & Loggers 

250 – 750a

500 – 30,000b

250 – 8,000 

Communication Medium Telephone 

Cellular

Radio

Satellite

75 – 125c

250 – 500d

200 – 3,500e

200 – 700f

Instrumentation Valves 

Switch

Sensor

25 – 1,500g

25 – 300g

350 – 85,000h

aOperating system software is usually included in the purchase price of a computer. 

bSCADA software is usually included in the purchase price of the hardware. 

cMonthly service charges are estimated. 

dActivation, roaming, and monthly service are estimated and included. 

eUpdated: Equipment cost + transmission cost unlicensed frequency ($0), other vary by radio frequency. 

f

Updated: Starband satellite system monthly cost ~ $200, dish and installation ~ $500. 

gCost per valve and/or switch. 

hCost per individual sensor or sensor system. 

removing microbiological contaminants. The secondary objectives of this project included: remote monitoring and automation of the system to minimize the 

O&M costs, assessment of the community’s acceptance of such a system, ability to pay, and the effect of 

the distribution system on water quality at the tap. The 

following is a brief summary of the overall project. 

The treatment system was located in rural Coalwood 

(McDowell County), WV, approximately 12 miles 

from the McDowell County Public Services Division 

office in Appalachian Mountain terrain. Prior to 1994, 

an aerator combined with a slow sand filter was being 

used for water treatment at this site. This combined 

unit had been operational for over 30 years and needed 

substantial repairs. The water flowed by gravity from 

an abandoned coal mine to an aerator built over a 

six-foot diameter slow sand filter. A hypochlorinator provided disinfection to the treated water, and 

the water flowed by gravity through the distribution 

system to the consumer. The volume of water from 

the mine was considered sufficient for the small rural 

community. 

Based on a review of existing technology, EPA determined that a packaged ultrafiltration (UF) system 

would be ideally suited for this location. In 1992, a UF 

unit was purchased and installed at this site. In 1996, 

EPA developed, installed, and tested a remote monitoring system at the site. The system used commercially 

available hardware along with proprietary EPA-developed software. The software was not user-friendly and 

the overall cost of ownership was very high. Therefore, 

in 1998, EPA updated the SCADA system with a scalable commercially available off-the-shelf user-friendly 

SCADA system. The total cost (including instrumentation, technical support, training, and set-up) was about 

$33,000. After the success of this project in 2000, 

EPA installed similar SCADA systems at Bartley and 

Berwind sites in McDowell County, WV, for remote 

monitoring of the water quality. 

9.5.2 Puerto Rico Remote Monitoring Case 

Study 

For small system operators, depending upon surface 

water sources, various environmental factors heavily 

impact system operations. For example, in tropical areas, storm events can be followed by extreme turbidity 

swings in surface waters (especially during the rainy 

season). While the turbidity increase may be shortlived, the high solids loading following a storm event 

can overwhelm the treatment capacity of the system. 

Frequent occurrence of these events may lead to high 

maintenance costs or, at worst, premature equipment 

failure. Thus, knowledge of the watershed and source 

water conditions prior to the influx of high-turbidity 

water to a treatment system is expected to provide an 

operational advantage. Online remote monitoring of 

smaller systems located in remote areas has the potential to solve these operational issues and enhance the 

quality of water delivered to the consumer. 

In early 2005, EPA funded the field implementation 

of a web-based remote monitoring system in San 

German, Puerto Rico. An overview of the treatment 

system is presented in Figure 9.2 (Panguluri et al., 

2005b).

The system-specific challenges included: 

• Topography - Steep mountainous region with 

dense vegetative cover and significant distance 

between system components 

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Source 

Water 

618m 

Concrete 

Dam 

807m 

720m 

698m 

217m 

[0.38 miles] [0.13 miles] 

Horizontal-Flow 

Gravel Prefilter 

Slow Sand 

Filter 

Distribution 

Tank 

Source 

Water Quality Sonde 

Automatic 

Control Valve 

Distribution 

Water Quality 

Sonde 

Chlorination 

System 

Radio 

Data 

Transmitter 

Data 

Logger 

Data Acquisition 

System 

Radio Receiver 

& Cell Antenna 

Parameters Turbidity 

Temperature 

Conductivity 

Salinity 

Stream Depth 

Battery Voltage 

Data Processing Center 

& Remote Monitoring 

via Internet 

Parameters Turbidity 

Temperature 

Conductivity 

Salinity 

Figure 9.2 Schematic layout of the small 

sytstem in San German, Puerto Rico 

(Panguluri et al., 2005b). 

• Source Variability - 200 inches of rain/year 

results in flooding events and source water 

turbidity swings, lack of water under drought 

conditions

• Other - Lack of electric power and vandalism 

Phase 1 of the implementation was completed in 

April 2005. In this phase, a solar powered real-time 

web-based remote monitoring system was installed 

at the source water (dam) location and at the distribution system location. The monitoring systems at both 

locations are equipped with sensors (multi-parameter 

sondes) that monitor various water quality parameters 

(e.g., pH, temperature, and turbidity),. During periods 

of high-turbidity (>25 NTU) at the source water (dam) 

location, the system is designed to close an automatic 

control valve to protect the horizontal-flow gravel prefilter (HFGP). The source water monitoring location 

has a built-in option for weather monitoring. In Phase 

2 of this implementation, EPA plans to install weather 

sensors and evaluate alternative water treatment technologies.

The equipment installed at the project site during 

Phase 1 include: met-tower (without sensors), solar 

panels, storage batteries, water quality/level sensors 

(sondes), SCADA units (controller and controlled 

units) and an automatic control valve. The controller 

Table 9.3 Puerto Rico remote monitoring 

system component costs (Panguluri et al., 

2005b).

Monitoring System Component Total Cost, $ 

Towers, antenna, solar panel, and batteries $3,000

YSI Sondes (2 units) $6,000

Automated control valve $2,000

Two SCADA units (one equipped with radio 

and other with radio and cellular access) $7,000

Website hosting, data warehousing, and 

digital cellular service $300/month

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and controlled SCADA units communicate using radio 

frequency and data is transmitted to a central location 

via a cellular access at the master location to a central 

web-site for operator or user access. Table 9.3 shows 

the costs for system components. 

Prior to the installation of the remote monitoring 

equipment several repairs to the treatment system 

were performed. The repairs included: cleaning and 

replacing of the sand filter and gravel filter. The 

overall Phase 1 installation and repair cost (excluding 

the equipment costs shown in Table 9-3) was approximately $30,000. 

9.6 General Security Issues with 

Remote Monitoring 

Because SCADA systems can provide automatic 

control of a system, system security is an important 

consideration. The primary security vulnerabilities 

for SCADA systems are the communication links, the 

computer software, and power sources for the various 

system components. A brief discussion about security 

considerations for communications and software are 

provided in Chapter 8 of this document. Protection of 

power sources for individual system components will 

be dependent on the power sources used in the system. 

However, security can be improved by ensuring that 

there are backup power systems for emergency situations.

9.7 Contamination Warning 

Systems

EPA’s WSWRD is providing technical support to 

NHSRC at the T&E Facility to research and develop 

monitoring systems that measure relatively standard 

parameters, such as TOC, pH, turbidity, conductivity, 

chlorine, oxidation-reduction potential and temperature. For both water quality- and security-related 

monitoring, the instrument response time is critical. 

Therefore, online monitors are typically used in these 

types of applications. The parameters monitored may 

vary widely depending upon the type of process and 

security monitoring. Currently, WSWRD is assisting 

in the development of a database repository based on 

bench-and-pilot-scale experiments that reveal how 

these traditional parameters, if monitored online, can 

serve as triggers for contamination events. This measured information can then be automatically analyzed 

to determine (1) whether there is an indication of 

unusual contamination in the sample; and (2) what 

the likely contaminant is based on the water quality 

signature of these parameters. The interpretation of 

online data is currently an important research topic 

and a number of companies are offering data mining software or analytical engines to help identify a 

contamination event. 

The American Society of Civil Engineers (ASCE), 

in concert with other leading organizations, entered 

into a cooperative agreement with the EPA to develop 

standards documents and guidance aimed at enhancing the physical security of the Nation’s water, and 

wastewater/storm water systems. Under this agreement, ASCE is leading the effort to develop guidelines for designing an online contaminant monitoring 

system (OCMS). The Interim Voluntary Guidelines 

for Designing an OCMS were published in December 2004. This document provides comprehensive 

information on several topics including: rationale for 

OCMS and system design basics, selection and siting 

of instruments, data analysis and use of distribution 

system models. 

9.8 Key Questions 

• What is the current status of Remote Telemetry 

usage?

• What types of SCADA systems can small 

systems afford, operate, and maintain? 

• If affordable, what parameters can currently be 

monitored and is there room for improvement? 

• What is the purpose: Security or water quality? 

• What are the main maintenance issues for online monitoring systems? 

9.9 References 

Clark, R., S. Panguluri, and R. Haught, 2004. Remote 

Monitoring and Network Models: Their Potential for 

Protecting US Water Supplies. in Mays L., editor. 

Water Supply Systems Security. McGraw Hill, New 

York, NY. 

EPA. Drinking water regulations and health advisories. 

EPA-822-B-96-002, Office of Water, Washington, DC, 

1996.

EPA. Small drinking water systems handbook: A guide 

to packaged filtration and disinfection technologies 

with remote monitoring and control tools. EPA/600/R03/041, National Risk Management Research Laboratory, Cincinnati, OH, 2003. 

Goodrich, J., J. Adams, and B. Lykins. Ultrafiltration 

membrane application for small systems. National 

Risk Management Research Laboratory, Cincinnati, 

OH, 1993. 

9-7
Haught, R., 1998. The use of remote telemetry to 

complement the operations and maintenance of a small 

treatment system. in AWWA Annual Conference, Dallas, TX. 

Haught, R., and S. Panguluri, 1998. Selection and 

management of remote telemetry systems for monitoring and operation of small drinking water treatment plants. in Proceedings of the First International 

Symposium on Safe Drinking Water in Small Systems, 

Washington, DC. 

Panguluri, S., R. Haught, C. Patterson, E. Krishnan, 

and J. Hall, 2005a. Real-time remote monitoring of 

drinking water quality. in Proceedings of ASCE World 

Water and Environment Resources Conference, Anchorage, AK. 

Panguluri, S., R. Haught, C. Patterson, R. Krishnan, R. 

Sinha, and J. Hall, 2005b. EPA small system initiatives: Real-time remote monitoring of small drinking water systems. in Improved monitoring for safe 

and secure water supplies: An integrated approach to 

emerging information technologies, University of Illinois, Urbana IL. 

Pollack, A., A. Chen, R. Haught, and J. Goodrich, 

1999. Options for remote monitoring and control of 

small drinking water facilities. Battelle Press, Columbus, OH. 

9-8 
Chapter 10 

Summary 

10.1 Introduction

The challenges facing small drinking water treatment 

systems are numerous. Research at EPA must focus 

resources on the most pressing issues that apply to as 

many systems as possible. The sheer number of small 

systems and the degrees to which they vary make this 

a difficult task. Research in treatment technology 

and monitoring/reporting must be sensitive to cost 

restrictions which tend to play a much greater role 

in small systems compared to large systems (serving greater than 10,000 people). Furthermore, future 

research must be adaptable to upcoming challenges. 

These factors result in the fact that this Small System 

Research Strategy Document must be considered as 

a “living document”; one that has the capability of 

being flexible to meet new challenges. While searching for breakthroughs in the latest technologies, future 

work must always consider applicable, affordable 

technologies. This document attempts to assess the 

current status of small systems with the primary goal 

of informing decision-makers so that resources can be 

brought to bear on the most pressing issues concerning small systems. It will be crucial to consider input 

from small systems personnel and the public at every 

stage.

10.2 Memorandum of 

Understanding (MOU) with 

the National Rural Water 

Association (NRWA) 

In an effort to focus resources where they are most 

needed, EPA-WSWRD will work with the NRWA 

through a MOU. The NRWA offers an enormous 

amount of resources concerning access at the grass 

roots level with small systems across the country. It is 

hoped that through cooperation with NRWA, WSWRD 

will be able to provide research results to meet the 

most pressing needs for small systems. 

10.3 Chapter-Specific Key 

Questions

At the ends of the chapters in this document, a list of 

key questions is presented. These questions are meant 

to stimulate research in subjects that are of importance 

to small systems in the United States. The questions 

will also serve in the prioritization of research in EPAORD. We hope to work closely with the NRWA in 

discussing and prioritizing future areas of research to 

improve technical support to small systems. We also 

hope that these key questions will be useful to other 

organizations as they move forward with research to 

support small systems. 

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