e eoo te or r ter trto Ste ceMany individuals provided insights that helped shape this manual. The...

Project #4350B

Designing Epidemiology Studies for Drinking Water Distribution Systems: A Guidance Manual

About the Water Research Foundation The Water Research Foundation (WRF) is a member-supported, international, 501(c)3 research cooperative that advances the science of water to protect public health and the environment. Governed by utilities, WRF delivers scientifically sound research solutions and knowledge to serve our subscribers in all areas of drinking water, wastewater, stormwater, and reuse. Our subscribers guide our work in almost every way—from planning our research agenda to executing research projects and delivering results. This partnership ensures that our research addresses real-world challenges. Nearly 1,000 water, wastewater, and combined utilities; consulting firms; and manufacturers in North America and abroad contribute subscription payments to support WRF’s work. Additional funding comes from collaborative partnerships with other national and international organizations and the U.S. federal government, allowing for resources to be leveraged, expertise to be shared, and broad-based knowledge to be developed and disseminated. Since 1966, WRF has funded and managed more than 1,500 research studies valued at over $500 million. Our research is conducted under the guidance of experts in a variety of fields. This scientific rigor and third-party credibility is valued by water sector leaders in their decision-making processes. From its headquarters in Denver, Colorado and its Washington, D.C. office, WRF’s staff directs and supports the efforts of more than 500 volunteers who serve on the board of directors and various committees. These volunteers represent many facets of the water industry, and contribute their expertise to select and monitor research studies that benefit the entire One Water community. Research results are disseminated through many channels, including reports, the website, webcasts, workshops, and periodicals. More information about WRF and how to become a subscriber is available at www.WaterRF.org.



Prepared by: Amy E. Kirby, Karen Levy, Ethell Vereen, and Christine L. Moe Emory University School of Public Health, Atlanta, GA 30322

Sponsored by: Water Research Foundation 6666 West Quincy Avenue, Denver, CO 80235-3098

Published by:


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This study was funded by the Water Research Foundation (WRF). WRF assumes no responsibility for the content of the research study reported in this publication or for the opinions or statements of fact expressed in the report. The mention of trade names for commercial products does not represent or imply the approval or endorsement of WRF. This report is presented solely for informational

purposes.

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ALL RIGHTS RESERVED.

No part of this publication may be copied, reproduced, or otherwise utilized without permission.

ISBN 978-1-60573-316-6

Printed in the U.S.A.


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TABLE OF CONTENTS

LIST OF TABLES ......................................................................................................................... ix LIST OF FIGURES ....................................................................................................................... xi FOREWORD ............................................................................................................................... xiii ACKNOWLEDGMENTS ............................................................................................................ xv EXECUTIVE SUMMARY ........................................................................................................ xvii CHAPTER 1: INTRODUCTION TO DRINKING WATER SYSTEMS ...................................... 1

Drinking Water Systems in the United States ..................................................................... 1 Water System Classifications ................................................................................. 2 Drinking Water Supply Sources ............................................................................. 3 Water Treatment ..................................................................................................... 5

Distribution System Features .............................................................................................. 9 Piping ...................................................................................................................... 9 Finished Water Storage Facilities ......................................................................... 10 Fire Hydrants ........................................................................................................ 11 Pumping Stations .................................................................................................. 11 Blow-Off Valves ................................................................................................... 11 Valves ................................................................................................................... 11 Premise Plumbing ................................................................................................. 11

Distribution System Characteristics .................................................................................. 12 Grid Versus Branching System ............................................................................. 12 Water Age ............................................................................................................. 12 Multiple Treatment Plants and Sources ................................................................ 13 Fire Flow Requirements ........................................................................................ 13 Infrastructure Deterioration .................................................................................. 13

Distribution System Management..................................................................................... 14 Hydrant Flushing .................................................................................................. 14 Water Loss Control Programs ............................................................................... 14 Asset Management ................................................................................................ 15 Indicators to Assess Water Quality ....................................................................... 16

U.S. Distribution System and Water Quality Regulations ................................................ 16 Safe Drinking Water Act of 1974 ......................................................................... 17 Total Coliform Rule and Revised Total Coliform Rule........................................ 17 Disinfectants and Disinfection Byproducts Rule .................................................. 17 Surface Water Treatment Rule .............................................................................. 17 Ground Water Rule ............................................................................................... 18 Filter Backwash Recycling Rule ........................................................................... 18 Lead and Copper Rule .......................................................................................... 18 Chemical Phase Rules ........................................................................................... 19


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Radionuclides Rule ............................................................................................... 19 Arsenic Rule.......................................................................................................... 19 Public Notification Rule ....................................................................................... 19

CHAPTER 2: USING AVAILABLE DATA FROM THE DISTRIBUTION SYSTEM ............ 21

Federal Water Quality Regulations ................................................................................... 21 Secondary Drinking Water Regulations ............................................................... 22

Water Monitoring Data ..................................................................................................... 23 Water Quality Monitoring at the Source and Treatment Plant ............................. 23 Distribution System Water Quality Monitoring ................................................... 29

Public Notifications .......................................................................................................... 34 Distribution System Operations ........................................................................................ 34

pH .......................................................................................................................... 34 Temperature .......................................................................................................... 34 Alkalinity .............................................................................................................. 35 Hardness ................................................................................................................ 35 Flushing Programs ................................................................................................ 35 Main Breaks, Repairs, or Replacements ............................................................... 35 Water Pressure ...................................................................................................... 36

Premise Plumbing ............................................................................................................. 37 Customer Complaint Data ................................................................................................. 37 Limitations of the Available Data ..................................................................................... 38

CHAPTER 3: SOURCES OF POTABLE WATER SYSTEM DATA ........................................ 39 Government Entities ......................................................................................................... 39

Federal................................................................................................................... 39 State....................................................................................................................... 41 Consumer Confidence Reports ............................................................................. 42

Utilities .............................................................................................................................. 42 Utility Data Requests ............................................................................................ 42 SCADA/Historian ................................................................................................. 42

Industry Groups ................................................................................................................ 43 AWWA's Waterstats 2002 Water Utility Distribution Database .......................... 43

CHAPTER 4: INTEGRATION OF DISTRIBUTION SYSTEM MODELS INTO PUBLIC

HEALTH RESEARCH ..................................................................................................... 45 Basics of Computer Modeling of Distribution Systems ................................................... 46

Components of a Hydraulic Model ....................................................................... 46 Components of a Water Quality Model ................................................................ 48 Calibrating and Validating a Distribution System Model ..................................... 49

Incorporating Distribution System Models into Public Health Studies ............................ 50 Using Models to Determine Sampling Sites ......................................................... 50 Using Models to Interpret Study Results .............................................................. 51 Using Models to Simulate Distribution System Events ........................................ 51


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CHAPTER 5: EPIDEMIOLOGICAL STUDIES OF DRINKING WATER DISTRIBUTION SYSTEMS AND HEALTH .............................................................................................. 53 Relevant Epidemiological Study Designs ......................................................................... 54

Measures of Effect ................................................................................................ 58 Review of Important Studies of Drinking Water and Health ............................... 58

Conclusions ....................................................................................................................... 63 CHAPTER 6: CONSIDERATIONS FOR PLANNING AND IMPLEMENTING

EPIDEMIOLOGICAL STUDIES OF DRINKING WATER DISTRIBUTION SYSTEMS AND HEALTH .............................................................................................. 65 Why Conduct an Epidemiological Study of Drinking Water Distribution Systems and Health? ........................................................................................................... 65 Considerations and Challenges with Study Design and Implementation ......................... 66

Study Design ......................................................................................................... 66 Study Site .............................................................................................................. 71 Study Population ................................................................................................... 71 Building a Study Team ......................................................................................... 72 Exposure Assessment............................................................................................ 73 Water Monitoring and Sampling Strategy ............................................................ 75 Sample Concentration and Detection Methods ..................................................... 76 Health Outcomes ................................................................................................... 77 Disease Surveillance Data ..................................................................................... 79 Surveys .................................................................................................................. 80 Monitoring Absenteeism ....................................................................................... 80 Monitoring Inquiries to Health Call Centers or Nurse Hotlines ........................... 82

Monitoring Internet Search Volume for Words That Describe Gastrointestinal Symptoms ................................................................................................. 82

Monitoring Sales of Anti-Diarrheal Medications ................................................. 82 Monitoring Illness in Sentinel Families or Institutions......................................... 83 Monitoring Visits to Health Care Providers for Gastrointestinal Illness .............. 83 Monitoring Laboratory Activity and Results ........................................................ 84 Health Outcomes That May Be Associated with Chemical Contaminants .......... 84 Monitoring Death Certificates .............................................................................. 84 Summary of General Strengths and Limitations of Enhanced Surveillance ......... 85 Study Population Sample Size Considerations ..................................................... 85 Pilot Studies .......................................................................................................... 86 Subject Recruitment and Retention ...................................................................... 87 Good Research Practices ....................................................................................... 87 Communication of Study Findings ....................................................................... 88

Future Directions .............................................................................................................. 89 Uncertainty about Future Water Challenges ......................................................... 89

Recommendations ............................................................................................................. 90 APPENDIX A: EXPERT INTERVIEWS .................................................................................... 93 REFERENCES ............................................................................................................................. 97


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ABBREVIATIONS .................................................................................................................... 111


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TABLES

2.1 Contaminants covered by the Secondary Drinking Water Regulations ............................ 22 2.2 Synthetic organic contaminants ........................................................................................ 28 2.3 Volatile organic contaminants .......................................................................................... 28 2.4 Inorganic contaminants ..................................................................................................... 28 6.1 Surveillance approaches for specific health outcomes ..................................................... 81


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FIGURES

1.1 Water treatment plant. ......................................................................................................... 6 4.1 Nodes with an average water age greater than 100 hrs ..................................................... 50 5.1 Classification of epidemiological studies of distribution systems and health .................. 56 6.1 Household intervention trial with distribution system vulnerability assessment and

double-difference analyses ................................................................................................ 68 6.2 Household intervention trial with crossover ..................................................................... 69 6.3 Community intervention trial ............................................................................................ 70


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FOREWORD

The Water Research Foundation (WRF) is a nonprofit corporation dedicated to the development and implementation of scientifically sound research designed to help water utilities respond to regulatory requirements and address high-priority concerns. WRF’s research agenda is developed through a process of consultation with WRF subscribers and other water professionals. WRF’s Board of Directors and other professional volunteers help prioritize and select research projects for funding based upon current and future industry needs, applicability, and past work. WRF sponsors research projects through the Focus Area, Emerging Opportunities, Tailored Collaboration, and Facilitated Research programs, as well as various joint research efforts with organizations such as the U.S. Environmental Protection Agency and the U.S. Bureau of Reclamation.

This publication is a result of a research project fully funded or funded in part by WRF subscribers. WRF’s subscription program provides a cost-effective and collaborative method for funding research in the public interest. The research investment that underpins this report will intrinsically increase in value as the findings are applied in communities throughout the world. WRF research projects are managed closely from their inception to the final report by the staff and a large cadre of volunteers who willingly contribute their time and expertise. WRF provides planning, management, and technical oversight and awards contracts to other institutions such as water utilities, universities, and engineering firms to conduct the research.

A broad spectrum of water issues is addressed by WRF's research agenda, including infrastructure and asset management, rates and utility finance, risk communication, green infrastructure, food waste co-digestion, reuse, alternative water supplies, water loss control, and more. The ultimate purpose of the coordinated effort is to help water suppliers provide a reliable supply of safe and affordable water to consumers. The true benefits of WRF’s research are realized when the results are implemented at the utility level. WRF's staff and Board of Directors are pleased to offer this publication as a contribution toward that end.

Charles M. Murray Robert C. Renner, PE Chair, Board of Directors Chief Executive Officer Water Research Foundation Water Research Foundation


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ACKNOWLEDGMENTS

Many individuals provided insights that helped shape this manual. The authors would like to thank the expert panel who generously offered their time and insights during interviews: Gary Burlingame, Steve Via, Tim Wade, Jack Colford, Kellogg Schwab, and Mark LeChevallier. We also want to thank Dominic Boccelli and Stuart Hooper for their assistance developing and revising Chapter 4. Our Project Manager Maureen Hodgins and our Project Advisory Committee, Tim Wade, Yeongho Lee, and Anne Seely, provided support and advice throughout the writing process. Their unique perspectives were instrumental in developing a broadly applicable manual that accurately represents the challenges and opportunities in the field. The authors would also like to thank Samina Panwhar for her support in producing this manual. The project duration was from 2011 to 2017, yet most of this manual was written from 2013 to 2015.


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EXECUTIVE SUMMARY

OBJECTIVE

Municipal water is a widespread daily environmental exposure for most people in the United States, with municipal water used for showering, cooking, and cleaning, in addition to drinking. As a result, there has been a great deal of research on the quality of municipal drinking water and potential health risks. However, most of the epidemiological or public health research to date has focused on source water quality and treatment processes. In recent years, as multiple barrier approach to ensure safe drinking water has become almost universal, attention has shifted to waterborne disease that may be associated with deficits in water distribution systems and premise plumbing. Waterborne disease outbreaks have been linked to deficiencies in the distribution system (CDC 2013). These outbreaks have highlighted the need to understand better the effects of various drinking water distribution system attributes on water quality and health outcomes. There is limited information about the association between water distribution system and health. This information gap is partially due to the difficulty in designing rigorous epidemiological studies that can distinguish between health risks associated specifically with the distribution system versus with other components of a water supply versus risks that are unrelated to water (such as diarrheal disease from contaminated food).

Water utilities and industry leaders are increasingly recognizing the need for more research on water quality in distribution system, what factors affect water quality in distribution system and what are best practices to ensure that distribution system water is safe. Rigorous studies will require knowledge of environmental epidemiological designs and methods and analytical approaches that can focus on potential specific risks associated with the distribution system compared to other components of a water system. Further, some knowledge of distribution systems is required because water systems may be complex and operations may change over time. Such studies must be of sufficient scale to detect low risks and multiple health effects that may be relevant. Health outcomes that may be related to drinking water (e.g. diarrhea and, to a lesser extent, respiratory infections such as legionellosis) are difficult to quantify because the symptoms are non-specific and testing is rare, which can lead to misclassification of health status. Drinking water and health studies must also take into account temporal and spatial changes in distribution system water quality and consumer behavior (such as household water filters or routine consumption of bottled water). Additionally, distribution system effects on health can be obscured by the potentially larger effects of other water system components, such as source water or premise plumbing. Careful study design is necessary to separate distribution system effects from the effects of upstream or downstream components (such as source water quality, treatment processes, and premise plumbing). Public health researchers, particularly epidemiologists and risk assessment experts, are needed to conceptualize these studies and ensure that they are conducted with appropriate rigor and statistical power. Researchers will benefit from working with the water utility staff and engineers to understand the subject distribution system. The ultimate goal of drinking water and health studies is to identify possible distribution system factors (such as pipe material, water pressure, network configuration, water demand patterns, residual disinfectant concentrations, water residence time, etc.) that may compromise water quality and result in public health risks. A better understanding of the relationship between these distribution system factors and health risks


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will allow water utilities to prioritize their operation and maintenance practices and system monitoring to more efficiently mitigate risk.

In order to work effectively with water sector professionals and develop evidence-based guidance for water utilities to optimize their distribution system and protect public health, public health researchers need a good understanding of the types of water systems that are common in the US, their associated infrastructure, and the regulations that govern these systems. Although primary data collection is likely necessary for distribution system-focused health studies, researchers should consider the range of data already available from utilities, state and federal government agencies, and water industry groups. These data may inform study design, supplement primary data collection, or facilitate interpretation of the results. Additionally, the use of distribution system hydraulic models is strongly recommended in both the design and interpretation of drinking water and health research.

The goal of this manual is to provide public health researchers with appropriate foundational knowledge about municipal water systems and to give practical guidance on how to conduct studies of potential health risks associated with drinking water distribution system in collaboration with water sector professionals.

This research focus was a result of the Water Research Foundation Strategic Initiative on Distribution System Water Quality (WRF n.d.). The larger goal was to fund research to improve our understanding of distribution system water quality. This project falls under the sub-goal of improving how we define and measure multiple barriers to ensure distribution system water quality and was called for in the Expert Workshop report (Hasit et al. 2007). BACKGROUND

The provision of safe drinking water has been identified by the Centers for Disease Control

and Prevention (CDC) as a critical step in controlling infectious disease and one of the top ten public health achievements in the US and globally. In the US, drinking water is provided by approximately 155,000 different public and private entities, with regulatory oversight by the Environmental Protection Agency (EPA) and state and local authorities (EPA 2017c, U. S. Geological Survey 2009). The US Geological Survey (USGS) estimates that domestic water deliveries alone account for 25.6 billion gallons of water per day (U. S. Geological Survey 2009). Most of this water is provided by community water systems and is delivered to the consumer through a network of 1.8 million miles of distribution pipes. Water distribution systems include the federally-regulated network of pipes, storage tanks and associated equipment (pumps, disinfectant boosters, valves) necessary to deliver water from the treatment plant to the customer service lines. Delivery of water from the service lines to the tap is through premise plumbing, which is not under the jurisdiction of the utility or the EPA.

To protect the drinking water quality, water systems use a multiple barrier approach, which provides operational redundancies within the system to prevent contamination. The EPA (2017a) multiple barrier approach includes “assessing and protecting drinking water sources, protecting wells and collection systems, making sure water is treated by qualified operators, ensuring the integrity of the distribution system, and making information available to the public on the quality of their drinking water.” For example, the primary barrier to intrusion is pipe maintenance and leak detection. However, should there be a breach, high system pressure prevents water and soil from entering the pipes. If the pressure is also overcome, the disinfection residual will inactivate any microbial contaminants that enter the system. The final barrier is routine monitoring of water


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quality. In 2013, the American Society of Civil Engineers gave the US drinking water infrastructure a grade of D, largely due to aging DS, where aging implies deteriorating condition (American Society of Civil Engineers 2013). Many systems include pipes that are over 100 years old, and there are 240,000 main breaks recorded annually. It is estimated that over $251 billion is needed to repair the deficiencies in the distribution system alone, which represents 75% of the needed capital investments in US drinking water systems overall. Yet, most utilities operate with very small margins and must prioritize non-emergency repairs and renovations carefully. In the absence of health effects evidence, these decisions are primarily based on operational parameters and may not improve the safety of the delivered water.

Overall, the quality of drinking water in the US is very good and drinking water-related disease outbreaks are rare. Between 2005 and 2010, only 79 outbreaks were linked to drinking water (Brunkard et al. 2011, Yoder et al. 2008). However, contaminants in drinking water may be contributors to endemic rates of gastrointestinal and opportunistic respiratory disease (i.e. baseline levels in the absence of an outbreak), though exact estimates of attribution are not known (Ercumen et al. 2014). Among the outbreaks related to drinking water between 2005 and 2010, 10% were due to deficiencies in the DS. Despite this, most regulations focus on source water quality and treatment processes, and provide limited guidance to water utilities on distribution system operation and maintenance. A recent report from the American Academy of Microbiology highlighted the complex microbial community that exists within distribution system pipes and the lack of information about how that community may be associated with water-borne health risks (Ingerson-Mahar and Reid 2012). The report called for collaboration between water utilities, public health agencies, and microbial ecologists to conduct targeted research that can inform better distribution system operations and monitoring, and ultimately, ensure safer water. APPROACH

The approach for creating this manual is rooted in the authors’ experiences as

epidemiologists and environmental scientists who have conducted studies of drinking water systems. This manual collects the information that we have found valuable in developing our studies and understanding the work of others in the field. Additionally, we interviewed six leaders in the drinking water and health sector to utilize their expertise and insight on the critical needs and major obstacles facing the field. The information shared by these experts – John Colford, Steve Via, Tim Wade, Gary Burlingame, Kellogg Schwab, and Mark LeChevallier – is used throughout the manual to add depth to the content. The focus of this manual is to provide guidance for researchers interested in studying the associations between microbiological water quality in distribution system and public health outcomes. It does not address chemical contaminants and chronic health effects that have been associated with drinking water (such as bladder cancer or arsenic poisoning) or adverse reproductive health outcomes. The project duration was from 2011 to 2017, yet most of this manual was written from 2013 to 2015.

Chapter 1 provides an overview of water systems in the US. The goal of this chapter is to provide public health researchers with the terminology and a basic understanding of water systems to facilitate communication with water sector professionals. Types and sizes of systems, as well as common system components, are described. Operating standards and approaches vary widely and, thus, are not covered in detail. However, general guidelines for operation are included. The federal regulations governing drinking water systems are also reviewed. Common variations in system design and/or operation that can impact health studies are highlighted.


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Chapter 2 summarizes the existing water quality and system performance monitoring data that is available to researchers to guide study development, supplement primary data, and facilitate interpretation of results. All public water systems are subject to EPA oversight, so EPA regulations and monitoring requirements are presented here as a minimal dataset that researchers can expect for any system. For each contaminant, the frequency, location(s), and extent of monitoring are included. In addition to required monitoring data, we discuss operational parameters that may be of use to health researchers. The chapter concludes with a discussion of the limitations of this type of data.

Chapter 3 describes additional data sources that may be of use to public health researchers. These sources include data repositories such as Safe Drinking Water Information System (SDWIS), which records violations of the federal drinking water regulations, and Storage and Retrieval (STORET), which compiles physical, chemical, and biological water quality measures. We also review data request processes such as Freedom of Information Act (FOIA) and utility data requests.

Chapter 4 provides a high-level overview of hydraulic modeling of distribution system networks. All of the experts we interviewed emphasized the importance of integrating hydraulic and water quality models into health studies to improve study design and interpretation of the study findings. The basics of modeling networks and model optimization are covered. Examples of health studies that used hydraulic and/or water quality models are reviewed. After reading this chapter, public health researchers will understand the basic terminology and approaches to support a productive collaboration with water system modelers.

Chapter 5 reviews landmark and more recent epidemiological studies of health effects linked to the DS. Various study designs, strategies for exposure assessment, and health outcome measures are described with examples of how they have been used in previous studies. The strengths and limitations of these approaches are also examined.

Chapter 6 provides recommendations and practical guidance for planning and conducting epidemiological studies of distribution system effects. The information in this chapter is a synthesis of the authors’ experience conducting studies in distribution system and discussing the results with water sector and public health professionals, the expert interviews, and the information in the preceding chapters. Topics include study design issues (i.e. site selection, health outcomes, exposure assessment), alternative approaches to data collection (i.e. pharmaceutical sales monitoring, sentinel populations, social media searches), good research practices, and appropriate communication of study findings to stakeholders. The chapter concludes with projections of future challenges to drinking water quality that will create the need for additional public health research. RECOMMENDATIONS

Developing and implementing a feasible, valid, and relevant study of drinking water

distribution system and health has many challenges. However, with careful study design and effective collaboration between partners, these challenges can be minimized. This manual provides suggestions for all phases of a research study, from inception to dissemination of results. The guidance is broad-ranging but can be summarized into three general recommendations.

1. Know your study site and system. Just as all study populations are unique, each water

system is unique. The details of individual water systems can facilitate a specific study approach, or render a proposed study impractical or invalid. A thorough understanding


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of the study system is necessary for study design, interpretation of study findings, and, importantly, translation of study findings into distribution system management practices.

2. Engage water utility partners but understand their limitations. Utility partners have a wealth of information and skills that can strengthen distribution system health risk studies, and they have the greatest stake in the outcome of such studies. Public health researchers should engage utilities as partners in research, but they must recognize that research is not the primary mission for utilities. Study design, data collection and usage, and results dissemination must all be carried out with consideration of the primary goal of safe drinking water provision to consumers.

3. Choose outcomes carefully and consider all potential confounders. Many of the health outcomes of interest have non-specific symptoms and other causes that are not associated with water. Thus, public health researchers must carefully balance the goal of determining the magnitude of the health risk with not overestimating health effects that are attributable to the DS. Additionally, because water systems are large, complex systems, there will be many related effects that are unlikely to be amenable to experimental control. These confounders must be addressed through careful study design and/or statistical approaches.

In conclusion, there is a critical need for public health research to support the efforts of

water utilities to deliver safe water for all purposes. Our discussion with experts and review of the literature identified a number of important research needs, including risks associated with premise plumbing, the relative risks from specific distribution system deficiencies, the growing risks from non-gastrointestinal pathogens such as Legionella, mycobacteria and Naegleria fowlerii, the need for better approaches for monitoring distribution system and modeling risks, better strategies for sampling, and sensitive, rapid techniques to detect waterborne microbial threats. Future water supply challenges, such as water scarcity, increased reliance on water reuse, deteriorating distribution system infrastructure, and a growing proportion of sensitive subpopulations, can only be addressed by effective collaboration between health researchers and water professionals.


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CHAPTER 1 INTRODUCTION TO DRINKING WATER SYSTEMS

Drinking water systems are highly variable. They may be small or large, ranging from one that serves a small trailer park to one that serves a major metropolitan area. They may be very simple or very complicated in construction and operation. They may use a ground water source, a surface water source, or a combination. They may be regulated or unregulated by Federal and State governments. Drinking water systems are complex and operations may change over time.

In this section1, we provide a focused overview of key elements of the range of US drinking water systems, including water system types, water sources, distribution system features, treatments, and key features regarding premise plumbing relevant to water quality and health effects studies. We summarize terminology specific to the water industry that will help public health experts understand how distribution systems are managed. We summarize US regulations on the distribution system and water quality and provide a brief explanation of their public health relevance. We also briefly describe the typical US approach of disinfectant residuals in the distribution system.

DRINKING WATER SYSTEMS IN THE UNITED STATES

Drinking water systems in the United States can be either public or private. Public water systems, which may be publicly or privately owned, are defined and regulated by the US Environmental Protection Agency (EPA). EPA defines a public water system as a system for the provision to the public of water for human consumption through pipes or other constructed conveyances, if such a system has at least 15 service connections or regularly serves an average of at least 25 individuals daily at least 60 days out of the year. EPA estimates that there are approximately 153,688 active public drinking water systems in the United States (EPA 2011).

Public water systems are further classified as community or non-community systems. The vast majority of the estimated 308 million people in the United States (U.S. Census 2010) are served by 52,873 community water systems (CWS), and the remainder are served by 19,400 non-community water systems or by private wells (EPA 2011). EPA classification of these water systems is based on the number of people they serve, the source of their raw water, and whether the customer base is consistent year-round or varies over the course of the year. An individual system or a private water supply, such as a household well, does not meet the EPA definition of a public water system. These systems typically serve a single family or farm. Approximately 15% of Americans rely on their own private drinking water supply (EPA 2002a), and these supplies are not subject to EPA regulations or standards, although some state and local governments do have regulations or ordinances to protect users of these systems. Special concerns related to private drinking water supplies are not discussed further in this manual, but researchers interested in this area can find more information in the following EPA document (EPA 2016i).

1 The project duration was from 2011 to 2017, yet most of this manual was written from 2013 to 2015.


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Water System Classifications

Water system classification is based on the number and type of population it serves and whether water is supplied year-round or on an as-needed basis (EPA 2011). Based on the size of population it serves, public water systems are divided into the following five categories:

(1) Very Small (25-500 people) (2) Small (501-3,300 people) (3) Medium (3,301-10,000 people) (4) Large (10,001-100,000 people) (5) Very Large (100,001+ people) The drinking water system statistics for each of the water systems are taken from the Safe

Drinking Water Information System/Federal version (SDWIS/FED) (EPA 2016j). SDWIS/FED is the EPA official record of public drinking water systems, their violations of state and EPA regulations, and enforcement actions taken by EPA or states as a result of those violations. EPA maintains the database using information collected and submitted by the states. The data in the following pages are based on information from current, active water systems maintained in SDWIS/FED FY2010 fourth quarter ‘frozen’ data (EPA 2011). Note in the following categories that populations are not summed because some people are served by multiple systems and counted more than once.

Community Water Systems (CWS)

EPA defines a CWS as “A public water system that supplies water to the same population year-round.”

There are 52,789-52,873 CWS in the US and they serve 300.1 -300.2 million people. Most of the CWS population served (92%) is serviced by the 17% of CWS categorized as medium to very large. Conversely, only 9% of the CWS population are serviced by the 83% of CWS classified as very small or small. Most of the CWS population served (70%) are serviced by the 23% of CWS which use surface water. Most CWS (77%) use groundwater but only serve 30% of that population. (EPA 2011)

Non-Transient Non-Community Water System (NTNCWS)

EPA defines a NTNCWS as “A public water system that regularly supplies water to at least 25 of the same people at least six months per year, but not year-round. Some examples are schools, factories, office buildings, and hospitals that have their own water systems.”

There are 19,357-19,400 NTNCWS in the US and they serve 6.4 million people. Most NTNCWS (99%) are classified as very small or small and they serve most of the NTNCWS population (79%). One percent of the NTNCWS are classified as medium to very large and serve a minority of the NTNCWS population (21%). Most NTNCWS (96%) rely on groundwater and serve most of the NTNCWS population (86%). Few NTNCWS (4%) rely on surface water and they serve the minority of the NTNCW population (14%). (EPA 2011)


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Transient Non-Community Water Systems (TNCWS)

A TNCWS is defined as “A public water system that provides water in a place such as a gas station or campground where people do not remain for long periods of time.”

There are 87,493-87,672 TNCWS in the US and they serve 13.1 million people. It should be noted that TNCWS provide water to many people for a short period and most people get their main source of water by another source such as a CWS. All TNCWS are classified as very small or small and they serve the most of the TNCWS population (78%). Few TNCWS (0.001%) are classified as medium to very large and they serve a minority of the TNCWS population (22%). Most TNCWS (97%) rely on groundwater and they serve most of the TNCWS population (80%). Few TNCWS (3%) rely on surface water and serve the minority of the TNCWS population (20%). (EPA 2011)

Drinking Water Supply Sources

Drinking water comes from two major sources: surface water such as lakes, rivers, and reservoirs; and groundwater, which is pumped from underground aquifers (Winter 1999). Sometimes these sources are close to a community, but water can also be transported long distances by canals or pipelines. According to the EPA, more water systems use groundwater rather than surface water as a source, but more people receive their water from a system supplied by surface water (EPA 2011). This is because large metropolitan areas tend to rely on surface water supplies, whereas small, rural areas tend to rely on groundwater. Note also that systems can be supplied by both surface and groundwater and rely on different water sources throughout the year.

Water reuse, or the use of highly treated wastewater effluent, is another water supply source. In the US, water reuse is less than 1% of U.S. water use. Water reuse is used for non-potable (industry or irrigation) and potable uses and some municipal water utilities employ water reuse. In areas where municipal water demand is greater than available, high quality water supplies, communities are considering developing or expanding water reuse. This report does not include water reuse. (National Research Council 2012)

Although most water requires some treatment before use, protecting water at the source is the first critical step in a multi-barrier approach to providing safe drinking water to the public. Protection of source water is largely regulated by the Clean Water Act (CWA). Among other things, the CWA designates all surface waters with specific beneficial uses. How is the water used? Do people swim or boat in it (recreational use)? Do they drink it (public drinking water supply use)? There are water quality standards for each type of beneficial use. These standards are used as a "measuring stick" to indicate if waters meet or do not meet expectations.

Three main categories of water supply sources are used in the United States: surface water, groundwater, and groundwater under the influence of surface water (EPA 2011). To protect the quality of water sources and minimize health risks, states, municipalities, water suppliers, and citizens undertake various efforts that include wellhead protection (WHP), watershed protection, and reservoir management. In addition to the CWA, other federal regulatory approaches have also emerged given the variability of water sources geographically and the variability of potential risks to such sources (point-source and non-point-source contamination). A few of the federal environmental laws that address source water issues include the Safe Drinking Water Act (SDWA) (which encompasses the WHP Program, the Sole Source Aquifer Program, and the Underground Injection Control Program); the Resource Conservation and Recovery Act (RCRA); the


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Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA); and the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) (EPA 1997b).

Surface Water

The majority of people in the US (70%) are supplied year-round by CWSs that use surface water (EPA 2011). Surface water is a part of the hydrologic cycle that is constantly replenished through precipitation and diminishes via evaporation and seepage into the ground. Surface water is collected on the ground or in a stream, river, lake, reservoir, or ocean. Because of its exposure to the environment and the potential for contamination, surface water typically requires both filtration and disinfection to reach drinking water quality standards.

Groundwater

Groundwater is the water supply for the majority of public water systems (91%) however, only serves 33% of the population because groundwater is more prevalent in the NTNCWS and TNCWS categories which are numerous yet serve fewer people (EPA 2011). Groundwater is located in aquifers below the ground in pores of rock or soil. Water is extracted by drilling boreholes or wells in the ground. The use of groundwater for public water supply varies state by state, and within states, depending on the availability of surface water and the hydrogeology of the region, which affects the productivity of the aquifer. Many homes also have their own private wells drilled on their property to tap this supply. Normally groundwater is considered to be the most pure source of water because it is naturally filtered as it passes through the layers of rock and sediment in an aquifer. Unfortunately, groundwater can become contaminated by human activity, and the geology of the rocks in the aquifer may have a major impact on the quality of the groundwater. Chemicals and microorganisms can enter the soil and rock, polluting the aquifer and eventually the well. Many times, the technology required to remove these contaminants can be more complicated and expensive than surface water treatments. Studies of groundwater quality in the past two decades have revealed that many aquifers are contaminated and that groundwater requires treatment before it can be a safe drinking water supply (Borchardt et al. 2007, Abbaszadegan et al. 1993).

Groundwater under the Direct Influence of Surface Water

The federal rule (40 CFR 141) defines Groundwater Under the Direct Influence of Surface Water (GWUDI) as:

“Any water beneath the surface of the ground with significant occurrence of insects or other macroorganisms, algae, or large-diameter pathogens such as Giardia lamblia or Cryptosporidium, or significant and relatively rapid shifts in water characteristics such as turbidity, temperature, conductivity, or pH which closely correlate to climatological or surface water conditions (40 CFR 141 definition).”

GWUDI basically means the groundwater source is located close enough to nearby surface water, such as a river or lake, to receive direct surface water recharge (Code of Federal Regulations 2006a). Since a portion of the groundwater source's recharge is from surface water, the groundwater source is considered at risk of contamination from microorganisms and chemicals that are not normally found in pure groundwaters. Public water systems that use GWUDI as a source of their drinking water must comply with the federal Surface Water Treatment Rule


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(SWTR) and the Long Term Enhanced Surface Water Treatment Rule (LT1 and LT2). Information regarding the Surface Water Treatment Rule and LT1 and LT2 is available at (EPA 2016l).

Water Treatment

Water treatment constitutes a variety of processes that can vary based on a number of factors such as the source of water; physical, chemical, and microbiological constituents of raw water; and feasibility of treatment technology.

The most commonly used processes include coagulation (flocculation and sedimentation), filtration, and disinfection. Some water systems also use ion exchange and adsorption. Water utilities select the treatment combination most appropriate to treat the contaminants found in the source water of that particular system. A brief description of these commonly used treatment processes is given below. Figure 1.1 shows a typical water treatment process. Information about a particular local drinking water system may be obtained by contacting the local utility directly. Additional information is available from the EPA, such as the Drinking Water Treatability Database (EPA n.d.).


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Source: Adapted with permission of American Water Works Association from AWWA Drinking Water Week Blue Thumb Kit. Figure 1.1 Water treatment plant: Diagram of the typical treatment process for a conventional water treatment plant from source to end user.

Sedimentation

Some treatment plants have reservoirs to store water after pumping from the surface water source. This initial sedimentation of the source water reduces the turbidity in water thereby lowering the particulate burden on the filters. Lower turbidity level makes the disinfectant more effective which in turn mitigates disinfection byproducts (DBPs).


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Aeration

Aeration is the process of adding air or oxygen to water. Aeration can be used to oxidize substances such as iron and manganese, and it can also be utilized to remove carbon dioxide, taste, and odor causing substances, volatile organic compounds (VOCs), volatile synthetic organic compounds (SOCs), ammonia, trihalomethanes, pesticides, herbicides, and gases such as methane, hydrogen sulfide, and radon (Code of Federal Regulations 1991b). Aeration has not proven to be effective in treating pathogenic organisms like bacteria and viruses (Connecticut Department of Public Health 2009).

Coagulation, Flocculation, and Sedimentation

Flocculation refers to water treatment processes that combine or coagulate small particles into larger particles, which settle out of the water as sediment. The coagulation process involves adding iron or aluminum salts such as aluminum sulfate, ferric sulfate, ferric chloride, or synthetic organic polymers (used alone or in combination with metal salts) to the water. These coagulants with a positive charge neutralize the negatively charged dissolved and suspended particles in the water, forming large masses called ‘flocs.’ The flocculation process includes slow stirring to promote collision between floc particles, which leads to the formation of larger floc aggregates. Settling or sedimentation occurs naturally as flocculated particles settle out of the water to the bottom of the sedimentation tanks.

Softening

Precipitative softening is used to reduce hardness in source water, caused by the presence of multivalent ions such as calcium (Ca2+) and magnesium (Mg2+) (Morales et al. 2000). These minerals can cause scaling of pipes and equipment in drinking water systems. The most common precipitative softening alternatives used by water systems include lime, lime-soda ash, and caustic softening. Lime-soda is used in water with low concentrations of non-carbonate hardness; lime-soda is required in water with high concentration of non-carbonate hardness; and caustic softening is used when the treated water does not contain adequate carbonate hardness to react with lime.

Filtration

Many water treatment facilities use filtration to remove particles from water, including clays and silts, natural organic matter, precipitates from other treatment processes in the facility, iron and manganese, and microorganisms. The effectiveness of the filtration process varies depending on the quality of source water and filter media, but it can improve color and turbidity and can also remove Giardia, Cryptosporidium, bacteria, and viruses. Direct filtration, as defined in federal rule 40 CFR 141.2, is a relatively simple process that bypasses the sedimentation step following coagulation and flocculation processes (National Academy of Sciences 2008). While economically viable, direct filtration is effective only in the systems with high quality source water having low turbidity and constant flows.

Filtration clarifies water and enhances the effectiveness of disinfection. Although filtration is an important process in water treatment there are several other factors that contribute to making water safe for human consumption.


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Membranes

Membrane processes such as reverse osmosis and nanofiltration are suitable for small-scale drinking water treatment systems with a wide variety of contaminants. Membranes may also be a filtration process. These systems, however, are susceptible to producing large volumes of wastewater and the media can become clogged if particle-rich source water is not pre-filtered. Membranes were originally used for desalination processes, but recent improvements in technology have made them popular in removing microorganisms, particulates, and natural organic materials that affect taste and color of water (National Academy of Sciences 2008).

Disinfection

Disinfection is often the last step in water treatment before it enters the distribution system. Disinfection is used to kill potentially hazardous microorganisms in the water. Among the most common disinfectants are chlorine, chloramine, and chlorine dioxide, all of which are effective not only in disinfecting water during the treatment process but also in maintaining disinfection residual in the distribution system. Other disinfection techniques, such as ozonation and ultraviolet radiation, are also used, but neither of these are effective in controlling microbiological contamination in the distribution system because they do not provide a residual (Ngwenya, Ncube, and Parsons 2013).

Chlorine. Chlorine is the most widely used disinfectant in drinking water treatment to control microbial contamination. Chlorine, a powerful oxidant, comes in gaseous or liquid forms and has the lowest production and operating costs and longest use history in water treatment operations (Ngwenya, Ncube, and Parsons 2013). Chlorination in drinking water systems is used at different steps and locations. The efficacy of chlorine must be balanced with the concerns about adverse effects of the disinfection byproducts (trihalomethanes and haloacetic acids) that are formed when chlorine reacts with organic material in the water.

Chloramines. Chloramine (as Cl2) is also used as a disinfectant. It is commonly used as a disinfectants residual in distribution systems. Chloramine is formed by adding ammonia to water containing free chlorine. Monochloramine is the most common form of chlorine-based disinfectant used in public water systems in the US. (Ngwenya, Ncube, and Parsons 2013)

Chlorine Dioxide. Chlorine dioxide, also used as a disinfectant in water supplies, is a highly endothermic compound that can decompose quickly when separated from diluting substances. The Niagara Falls, New York water treatment plant used chlorine dioxide for drinking water treatment in 1944 for phenol elimination from water. Chlorine dioxide is commonly used as a pre-oxidant to oxidize natural particulates in water that result in formation of disinfection byproducts. (Aieta and Berg 1986)

Ozonation. The use of ozone as a disinfectant in drinking water started as early as 1906 in France, and now it is widely used in many parts of Europe. The use of ozonation in North America started in the late 1970s. The Los Angeles plant is the largest ozone production facility in the world.

Ozone to be used as a disinfectant is made onsite by passing oxygen through ultraviolet light. The main advantage of ozonation is that it is effective in inactivating protozoa and other microorganisms and it forms fewer byproducts and leaves no taste in water. However, it is more costly than chlorine disinfection. (Ngwenya, Ncube, and Parsons 2013)

Ultraviolet Light (UV). UV light disinfection involves exposing water to radiation from UV light. Nucleic acids are damaged by UV radiation. Thus, UV-inactivated organisms cannot


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replicate due to damaged genetic material. Research has shown that the optimum UV wavelength range to destroy bacteria is between 250 nm and 270 nm (Lahlou 2000). At shorter wavelengths (e.g.185 nm), UV light is powerful enough to produce ozone, hydroxyl, and other free radicals that destroy bacteria. The U.S. Department of Health, Education, and Welfare set guidelines for UV light disinfection in 1966 (Lahlou 2000). These guidelines require a minimum dose of 16 mWs/cm2 (milliwatt seconds per square centimeter) at all points throughout the water disinfection unit (Lahlou 2000). However, the American National Standards Institute and the National Sanitation Foundation International set the minimum UV light requirement at 38 mWs/cm2 for class A point of use (POU) and point of entry (POE) devices that treat visually clear water (Lahlou 2000).

UV light disinfection does not form any significant disinfection byproducts, nor does it cause any significant increase in assimilable organic carbon (AOC). UV radiation is not suitable for water with high levels of suspended solids, turbidity, color, or soluble organic matter. These materials can react with UV radiation, and reduce disinfection performance (Lahlou 2000). Additionally, turbidity makes it difficult for UV radiation to penetrate water (Lahlou 2000).

Advanced Oxidation. Oxidants, mainly potassium permanganate (KMnO4), are used in water systems primarily to control taste and odor, remove color, control biological growth in treatment plants, and remove iron and manganese. Potassium permanganate may also be effective in controlling the formation of trihalomethanes (THMs) and other disinfection byproducts by oxidizing precursors and reducing the disinfectant demand (Hazen and Sawyer et al. 1992). Although potassium permanganate is an effective oxidant, it is considered as a poor disinfectant, and it is not recommended to maintain a KMnO4 residual in water because of its tendency to give water a pink color. A study conducted at treatment plants in North Carolina showed that pre-treatment of water with permanganate slightly reduced chloroform formation. The study also concluded that pre-oxidation with permanganate did not have any net effect on the chlorine demand of the water. Thus, potassium permanganate is not considered primarily as a disinfectant, but it can be strategically used in the treatment process as an alternative to pre-chlorination at locations where chemical oxidation is also required to control color, taste and odor, and algae (Singer, Borchardt, and Colthurst 1980).

DISTRIBUTION SYSTEM FEATURES

Distribution systems are critically important components of water supply systems. The water distribution system is the infrastructure “including all water utility components for the distribution of finished or potable water by means of gravity storage feed or pumps through distribution pumping networks to customers or other users, including distribution equalizing storage” (AWWA definition; (Mays 1989). It is estimated that water distribution systems span one million miles in the US (Grigg 2005). Distribution systems consist of numerous components, and maintenance and management of those components are a challenge. A brief description of the major components of distribution systems is provided below.

Piping

Piping is the one element that all distribution systems have in common (Murphy, Radder, and Kirmeyer 2005). Distribution system piping includes transmission mains, distribution mains, and service lines. Distribution system piping can vary in size and use, ranging from long, isolated transmission mains to small service lines (Murphy, Radder, and Kirmeyer 2005). The first tier of piping is the transmission mains, pipelines with a typical diameter of 12-60” that carry water from


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treatment facilities to the distribution system (AWWA 2000). The second tier of piping is the distribution mains, pipelines with a typical diameter of 6-10” that convey water from the transmission mains to service lines. The third tier of piping is the service lines that carry water to consumers’ residences.

The type and age of the pipes that make up drinking water distribution systems range from cast iron pipes installed during the late 19th century, to ductile iron pipe, and finally to plastic pipes introduced in the 1970s and beyond (National Research Council 2006). Most water systems and distribution pipes will be reaching the end of their expected life spans in the next 30 years (although actual life spans may be longer depending on utility practices and local conditions). However, some pipe materials tend to degrade prematurely. Galvanized pipe is particularly susceptible to corrosion in certain soils, and unlined cast iron pipe is susceptible to internal corrosion (Murphy, Radder, and Kirmeyer 2005, National Research Council 2006, EPA 2013c). Furthermore, health concerns associated with asbestos during pipe repair make asbestos cement pipe undesirable. Many water suppliers are replacing these types of mains with ductile iron or polyvinyl chloride (PVC) pipe (Murphy, Radder, and Kirmeyer 2005, National Research Council 2006, EPA 2013c).

Pipes in North American transmission mains and distribution systems may be composed of many materials, often with multiple types of pipe in a single distribution system. Common pipe materials include steel, galvanized metal, cast iron, ductile iron, reinforced or pre-stressed concrete, asbestos cement, PVC, lead, polyethylene, and fiberglass (Murphy, Radder, and Kirmeyer 2005). Jesperson (2001) says, “Wooden pipes were common until the early 1800s when the increased pressure required to pump water into rapidly expanding streets began to split the pipes.” Given the inherent nature of some of the materials to react with water and its constituents, such as phosphate, chlorine, and fluoride, the types of pipes used to convey water from the treatment facilities to consumer taps affect the quality of water (Murphy, Radder, and Kirmeyer 2005). It is unknown if these distribution water quality changes pose a public health concern.

As an example, when pipes do not have lining, pipe materials such as cast or ductile iron, asbestos cement or pressurized concrete form cavities on the internal surfaces, creating ideal environments for microorganisms to colonize and thrive (Lahlou 2000). Additionally, some oxidant-resistant microorganisms settle on internal pipe surfaces, producing a complex micro-environment know as a biofilm (Lahlou 2002). While not all biofilm is considered a nuisance and a health hazard, biofilms may provide favorable environments for microorganisms, providing protection from disinfectants for coliform and other bacteria, and they may also interfere with the detection of coliform bacteria.

Finished Water Storage Facilities

Types of finished water storage facilities include below-ground tanks, elevated tanks, ground-level covered reservoirs, and ground-level uncovered reservoirs (AWWA 2000). Storage facilities are generally utilized to equalize water demand, to reduce pressure fluctuations, and to provide reserves for firefighting, power outages, and other emergencies. The Water Industry Database contains data on more than 10,000 finished water storage facilities in the US. Out of the total, 54% are ground level storage facilities, 24% elevated tanks, and 19% below ground and uncovered reservoirs. Steel and concrete are the two primary materials used in constructing these tanks. According to the Water Industry Database, approximately 97% of elevated tanks are steel and 3% concrete, whereas for ground level storage facilities, 74% are steel and 26% concrete. (AWWA 2000)


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Fire Hydrants

Fire hydrants are installed at street intersections and at intermediate points between intersections recommended by the state Insurance Service Office. Two types of hydrants are commonly used in the distribution systems: dry barrel and wet barrel. Wet barrel fire hydrants are the most commonly used pressurized hydrants (AWWA 2000). Dry hydrants are non-pressurized and are installed below the water level of a pond or lake. The total number of hydrants in the US is estimated as 5.65 million (Kirmeyer, Richards, and Smith 1994). The primary purpose of fire hydrants is to deliver high water volumes for firefighting. However, hydrants are also used for flushing, a critical maintenance procedure for the distribution system.

Pumping Stations

To maintain optimum pressure in the water distribution line, pumping stations are located in the distribution system. Booster stations move water from lower pressure zones to higher pressure zones, and lift stations pump water from underground storage tanks to the distribution system (AWWA 2000). In addition, pumping stations can be used as booster chlorination stations and water quality monitoring sites. In some systems, the pumping stations are also equipped with backup power supply to meet fire demands and to operate in case of power failure.

Blow-Off Valves

Blow-off valves are used to flush water mains at places where hydrants are not available (AWWA 2000). Blow-off valves are generally located at low points or dead ends in the distribution system to remove sediments from the water mains. A minimum velocity of 2.5 feet per second (fps) is maintained for proper flushing (Pierson et al. 2001).

Valves

Distribution system valves are designed and installed to isolate sections of the water mains in case of leaks, maintenance activities, or to improve the operation of the system. Gate valves and butterfly valves are the two common types widely used in the water system. Some other valve types used in water distribution systems include globe valves, needle valves, pressure relief valves, air/vacuum valves, and diaphragm valves (Murphy, Radder, and Kirmeyer 2005). Air release valves are typically used at high points in the distribution system, especially where the terrain is hilly with long pipelines.

Premise Plumbing

Premise plumbing includes the portion of the potable water distribution system beyond the property line and in building (e.g. schools, hospitals, private homes). It includes the pipe from the water meter to the building and all plumbing inside the building. Premise plumbing systems typically have about ten times more surface area per unit length than a pipe in the distribution system (Case 2009). These systems are made from a wide range of materials, including in some cases lead lines or other materials not common in the utility distribution system (Case 2009, National Research Council 2006). Additionally, premise plumbing can harbor increased levels of opportunistic pathogens such as Legionella. Premise plumbing may also have a greater frequency of cross connections, reduced levels of secondary disinfectants, increased development of biofilms


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(which can contribute to the loss of disinfectant residual) and high water age, when compared with the utility distribution system. (Case 2009, National Research Council 2006)

DISTRIBUTION SYSTEM CHARACTERISTICS

Grid Versus Branching System

Distribution systems may be classified as grid or branching systems, or a combination of the two. A branching system has numerous terminals or “dead ends" that prevent water from being circulated through the system (Jesperson 2001, National Research Council 2006). This is similar to that of a tree branch, in which smaller pipes branch off larger pipes throughout the service area, such that the water can take only one pathway from the source to the consumer. This kind of pattern requires frequent flushing as water tends to stagnate in dead-end zones making it more susceptible to taste and odor problems. This type of system is most frequently used in rural areas. (Jesperson 2001, National Research Council 2006)

A grid system consists of connected pipe loops throughout the area to be served, and is the most widely used configuration in large municipal areas. In this type of system, there are several pathways that the water can follow from the source to the consumer as it can supply water to any point from at least two directions. It also permits any broken pipe sections to be isolated for repair without disrupting service to large areas of the community. (Jesperson 2001, National Research Council 2006)

Also, by keeping water moving, grid systems reduce some of the problems associated with water stagnation, such as adverse reactions with the pipe walls,; and grid systems increase fire-fighting capability (Jesperson 2001, National Research Council 2006). However, these systems can have dead-ends too; especially in suburban areas like cul-de-sacs (National Research Council 2006). Most systems have a combination of both grid and branched portions.

Water Age

The longer length of time water is in the distribution system the higher potential of adverse effects. In situations with increased water age, the following water quality problems with direct potential for public health impacts related to increased water age are disinfection by-product formation and biodegradation, corrosion control effectiveness, nitrification, and microbial regrowth, recovery, and shielding (AWWA and EESI 2002). Other water quality problems are disinfectant decay, taste and odor, temperature increases, sediment deposition, and color (AWWA and EESI 2002). Low flows in pipes create long travel times, with a resulting loss of disinfectant residual. In addition, longer water residence time can lead to collection of sediments and accumulation of microbes, which can grow and be protected from disinfectants (National Research Council 2006). Furthermore, sediment deposition will result in rougher pipes with reduced hydraulic capacity and increased pumping costs. Long

“A lot of the water quality issues we have in the distribution system boil down to water age, and there are opportunities to reduce water age by things like setting lower expectations for fire flow. But there really is not a very good effort aside from work that the Dutch are doing. And I'm not sure they did it because of water quality issues. … It's a competing risk issue. The Dutch feel like they can use modern firefighting techniques with less water and improve their water age.” - Steve Via


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detention times can also greatly reduce corrosion control effectiveness by impacting phosphate inhibitors and pH management. Greater water age is also correlated with a greater likelihood of an intrusion event. (National Research Council 2006)

Multiple Treatment Plants and Sources

Distributed or decentralized treatment systems refer to those in which a centralized treatment plant is augmented with additional treatment units that are located at various key points throughout the distribution system. Usually, the distributed units provide advanced treatment to meet stringent water quality requirements at consumer endpoints that would otherwise be in violation. Distributed treatment units are located either at the point-of-entry of households or at a more upstream location (National Research Council 2006). For example, booster chlorination units can be located strategically throughout the distribution system to maintain disinfectant residuals (Tryby et al. 1999).

Fire Flow Requirements

In addition to providing drinking water, a primary function of most distribution systems is to provide ample standby fire flow, the standards for which are governed by the National Fire Protection Association (National Fire Protection Association 2016, National Research Council 2006). In all but the largest systems, the flow necessary to fight a major fire is usually the major factor determining the amount of water to be stored, the size of the system’s mains, and the pressure needed (National Research Council 2006).

Fire flow standards require a minimum residual water pressure of 20 pounds per square inch (psi) during flow. It is common to maintain pressures of 60 to 75 psi in industrial and commercial areas and 30 to 50 psi in residential areas. Requirements for fire-fighting purposes should be sufficient to provide water for 10 to 12 hours in large communities and two hours in smaller ones. Fire-fighting reserve volumes are a function of the quantity of water needed per minute and the duration for which it is needed. For example, if 2,750 gallons per minute are needed for 10 hours, total fire-fighting storage would be 1.65 million gallons. (National Fire Protection Association 2016)

Infrastructure Deterioration

Much of the nation’s drinking water infrastructure suffers from deterioration. The rate at which water mains require replacement or rehabilitation varies greatly by pipe material, age of the pipe (assumed to indicate condition or deterioration, yet may be more accurately used to determine manufacturing specifications of the pipe), soil characteristics, weather conditions, and construction methods. Systems that have been unable to rehabilitate or replace mains may have proportionally more aged infrastructure, and therefore a higher level of need (National Research Council 2006, EPA 2013c). The 2011 Drinking Water Infrastructure Needs Survey and Assessment (DWINSA) found widespread infrastructure deterioration in all sizes of water systems (EPA 2013c). Transmission and distribution projects were the largest category of need at $247.5 billion over the next 20 years (64.4 percent of the total need). This category of need increased the most since the 2007 Assessment.


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DISTRIBUTION SYSTEM MANAGEMENT

With the exception of the smallest water systems, most utilities use a Supervisory Control and Data Acquisition (SCADA) system to manage their operations. SCADA is a computerized system used in many industries to monitor and control industrial processes. It is unique in that it accommodates large systems with multiple sites and long distances, making it ideal for water distribution systems. SCADA systems integrate real-time system operation data with diagrams of the system design to provide a visual representation of the system status for operators. Some of the operations that can be performed through a SCADA system are monitoring flowrate, pressure, and chemical intake, turning pumps on or off, and opening and closing valves. These processes can be performed manually, on a set schedule, or in response to real-time data from sensor units such as pressure gauges or water quality probes throughout the water system. Historian software extends and enhances the capabilities of SCADA with improved data storage capacity. Thus, SCADA/Historian is both a real-time operations system and an archiving system for O&M and water quality data.

Hydrant Flushing

Flushing is a critical tool for maintaining water quality in the distribution system. Sediments accumulate in the distribution system over time and mainly consist of minerals that have precipitated out of the water. Regular flushing of the distribution system is performed to remove these sediments (EPA 2003) and to decrease the water age, which affects the water quality in the system (AWWA 2002). Annual flushing is performed in most cases, but more frequent flushing is done in the sections of the distribution system where water velocity is lower resulting in stagnation. Flushing is also conducted in response to water quality problems (e.g. total coliform detection or customer complaints) and when new pipes are installed or main breaks are repaired.

Systems using conventional flushing programs open fire hydrants in the target area, closing them when certain water quality measures are met (e.g. turbidity, color, disinfectant residual). For dead end or oversize pipes, high velocity flushing may not be possible. In these cases, continuous blow-off releases water at a low velocity, which reduces water age but does not remove sediment from the pipe walls. Unidirectional flushing is a refinement of conventional flushing. In this approach, valves are used to isolate individual pipes and pipes are flushed sequentially, moving from the treatment plant into the distribution system. This approach has the advantage of ensuring high velocity scouring to remove sediment and limiting the potential for backflow of dirty water into cleaned pipes. Fire hydrants are most often used for flushing, but flushing valves and service connections can also be used (Pierson et al. 2001). To prevent degradation of surface waters, flushed water is discharged into either sanitary, storm, or combined sewers.

Water Loss Control Programs

It’s hard to find an accurate estimate of water losses throughout the U.S. because the industry recommended best practice for determining water losses were published by AWWA in 2009 and are gradually being adopted across the country. Water Losses are defined as leaks, metering inaccuracies, data handling errors and unauthorized consumption (AWWA 2016b). EPA and AWWA estimate Water Losses to be 14-18% which is about 5.9 billion gallons per day (CNT 2013). The most robust water audit data set to date is from Georgia and it shows that median Water Losses are 58 gallons per service connection per day, with 90% coming from Real Losses (leaks)


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and 10% from Apparent Losses (Sturm et al. 2015). AWWA (2016b) defines Real Losses as the “physical water losses from the pressurized system and the utility’s storage tanks, up to the point of customer consumption” and Apparent Losses are the “losses in customer concumption attributed to inaccuracies associated with customer metering, systematic data handling errors, plus unauthorized consumption.” Real Losses are an economic loss and present a potential public health risk, since leaking pipes are vulnerable to intrusion by contaminants if the water pressure drops. (WRF 2017).

Water audits are essential for assessing the efficiency of a water utility’s resources and operational and financial impacts (AWWA 2016b). A water audit is a thorough examination of a water utility’s data, records, accounts, and procedures regarding the volumes of water that are moved from system input through the distribution system to the customer. The data must segregate the volumes of water reaching customers from the volumes of loss (AWWA 2016b). There are three levels of a water audit and they complement each other and increase in sophistication and level of data. The first level is the top-down water audit, also called a “water balance,” which is an initial desktop assessment of records and identifies revenue and non-revenue water. The second level is the component analysis, which focuses on Water Losses, either Apparent or Real. The third level is the bottom-up audit and is comprised of detailed field measurements to support the top-down audit. Water audit results will help inform the interventions to reduce losses and increase revenue recovery (WRF 2017). Popular intervention activities include leak detection surveys, repairing leaks, pressure management and replacing infrastructure. Pressure management can reduce rapid changes in pressure (water hammer) which can cause leaks or increase leakage volumes. The more detailed collection of water loss information (component analysis) can effectively target areas of water losses where leak detection surveys can be used to identify leak locations. Leak detection surveys are a labor-intensive process because an operator listens for leaks aboveground as they walk the distribution system. Speed of repair activities can reduce leaks. More attention is being paid to water losses than before. More states (now 10) are requiring utilities to submit water audits (NRDC 2017). New technological advances in metering (Advanced Metering Infrastructure) and continuous acoustic sensors are being used in the distribution system to detect leaks and are gradually becoming more widespread.

Asset Management

Asset management is a planning process that ensures that utilities get the most value from every part of the system and have the financial resources to rehabilitate and replace them when necessary (EPA 2003). A drinking water system owner or operator must address current rehabilitation and replacement needs, and also forecast and plan for future needs. Since the system is likely operating with limited resources, the owner/operator must have a process in place for prioritizing such decisions.

Public health research can contribute to asset management in several ways. Public health research of distribution systems might be able to identify vulnerabilities associated with health risks in a system that will aide in prioritizing investments for system rehabilitation, replacement, and maintenance. Public health research can help to evaluate implementation of new regulations, as well as compliance with current policies and may yield insight into physical, chemical, and microbial trends not routinely monitored within a system. A detailed evaluation of the integration of public health research and asset management is beyond the scope of this report; however, inclusion of public health research as part of the overall strategy for asset management can and


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will allow utilities to make informed decisions about the water system’s purpose, structure, functions, and future.

Indicators to Assess Water Quality

An “indicator” is a parameter that can be measured and used as a surrogate for another parameter or condition that either cannot be directly measured or is difficult to directly measure. Indicators usually do not have health effects themselves. In the context of distribution system assessment, an indicator is a surrogate that is used to demonstrate or predict vulnerability to pathways that breach distribution system integrity; distribution system contamination; or the potential for public health risk outcomes (EPA 2006). Waterborne disease outbreaks and endemic illness may occur, but do not always occur, following a contamination event. Likewise, indicators of pathways or indicators of contaminants may not always indicate a vulnerability, contamination, or public health risk (EPA 2006, Wu et al. 2011).

Turbidity, total coliforms, fecal coliform, and Escherichia coli (E. coli), and fecal indicators (Enterococci or coliphage) are a few of the common indicators regulated in drinking water systems (EPA 2006). As with most indicators, turbidity has no direct health effects, is not a direct indicator of health risk, and is not expected to be a consistent indicator of microbiological quality of water. However, it can interfere with disinfection and provide a medium for microbial growth. Coliforms are bacteria that are naturally present in the environment. They are used as an indicator that other, potentially harmful, bacteria may be present, and as an indicator of treatment process efficacy. Fecal coliform and E. coli are bacteria whose presence indicates that water may be contaminated by human or animal wastes. Coliphage are viruses that infect the bacterium E. coli and are used as surrogates for the presence of human enteric viruses and their removal or inactivation by treatment. Enterococci are bacterial indicators of fecal contamination. EPA regulatory indicators in drinking water are described in detail in the Distribution System Indicators of Drinking Water Quality report. (EPA 2006)

U.S. DISTRIBUTION SYSTEM AND WATER QUALITY REGULATIONS

The first federal regulation of drinking water quality was enacted in 1909 when the U.S. Public Health Service set standards for the bacteriological quality of drinking water. Although these standards were applicable to only interstate and international carriers like ships and trains, many small cities also adopted these regulations for their systems. The regulations were refined and upgraded over the years. In 1974, Congress passed the Safe Drinking Water Act (SDWA), which is the backbone of the US drinking water regulations. Additional regulations have been passed to address specific risks within US drinking water systems. In this section, we will give a brief overview of each regulation. More detail on the laws that are applicable to distribution systems can be found in Chapter 2.2 Regulations are subject to change, refer to the federal or state regulations for the latest information.



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Safe Drinking Water Act of 1974

The SDWA is the major rule that regulates drinking water quality in the United States (1974). This law regulates all waters – above ground or underground – that are actually or potentially used for drinking. The SDWA authorizes the EPA to set national health-based standards for drinking water that are protective against naturally occurring and anthropogenic contaminants. As part of the SDWA, EPA established the National Primary Drinking Water Regulations (NPDWR) that set enforceable Maximum Contaminant Levels (MCLs) for a number of microbial and chemical contaminants. It is the responsibility of the EPA, states, and water utilities to work together to meet these standards.

The SDWA has been amended twice. The 1986 amendment expanded the enforcement powers, added regulation of lead plumbing materials, increased monitoring requirements, and changed the filtration and disinfection requirements for certain systems. In 1996, the law was expanded to cover consumer information, operator certification, disinfection byproducts, and economic analysis of regulatory requirements. In addition, the 1996 amendment established the Drinking Water State Revolving Fund to help water systems afford improved infrastructure.

Total Coliform Rule and Revised Total Coliform Rule

The Total Coliform Rule (TCR) was published in 1989 and Revised Total Coliform Rules (RTCR) in 2013 (EPA 2013d). According to EPA (2017d), the purpose of enacting the TCR and RTCR is to “improve public health protection” and total coliforms (“an indicator of other pathogens for drinking water”) are used to determine the “adequacy of water treatment and the integrity of the distribution system.” The monitoring requirements set forth by the TCR and RTCR are complex, requiring collection of samples at both the treatment plant and in the distribution system. The details of this rule are reviewed in Chapter 2. This is the only regulation that cannot be waived by state water authorities.

Disinfectants and Disinfection Byproducts Rule

Although disinfectants are critical to maintaining a safe water supply, high levels of disinfectants and their byproducts can be potential health hazards. To maintain this balance, EPA published the Disinfectants and Disinfection Byproducts Rules (DBPR), Stages 1 and 2. Stage 1 DBPR, published in 1998, established Maximum Disinfectant Residual Levels (MDRLs) for disinfectants and MCLs for four classes of disinfection byproducts, as well as monitoring regulations for systems using disinfectants other than UV light. In 2006, Stage 2 DBPR required that each monitoring location be reported separately, in contrast to the system-wide average that was required under Stage 1 DBPR. Stage 2 also added a requirement for an operational evaluation to ensure that mitigation actions are effective. Systems using conventional filtration must also document efficient removal of organic carbon, which is a precursor for disinfection byproducts. (Code of Federal Regulations 1998a). Surface Water Treatment Rule

The Surface Water Treatment Rule (SWTR) of 1989 was published to prevent health risks associated with viruses, Legionella, and Giardia lamblia in drinking water. Because these organisms are associated with contaminated surface water, the rule only applies to systems that


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use surface water or GWUDI as a source. The SWTR sets standards for disinfection and filtration in these systems to ensure effective removal of microbial contaminants. (EPA 2016l)

When the Stage 1 DBPR was instituted, there was concern that it could lead to increases in Cryptosporidium, which requires higher disinfectant levels to be inactivated. The Interim Enhanced SWTR (IESWTR) was published in 1998 to address this increased risk. In addition to defining a treatment technique for Cryptosporidium, the IESWTR established turbidity regulations and monitoring guidelines. More generally, the IESWTR prohibited the construction of uncovered finished water storage tanks and required all surface water and GWUDI systems to conduct regular sanitary surveys, regardless of their size. (Code of Federal Regulations 1998b)

The IESWTR only covers utilities that serve > 10,000 people. In 2002, the Long Term 1 Enhanced SWTR (LT1ESWTR) extended the same regulations to small systems using surface water or GWUDI as a source. (Code of Federal Regulations 2002).

As with the Stage 1 DBPR, implementation of the Stage 2 DBPR in 2006 raised concerns about the risk of Cryptosporidium. The Long Term 2 Enhanced SWTR (LT2ESWTR) was published along with the Stage 2 DBPR to provide targeted regulations for systems at high risk of microbial contamination. This rule requires systems to monitor their source water for Cryptosporidium, and based on the results, refine their processing to ensure effective removal or inactivation of the oocysts. (Code of Federal Regulations 2006)

Ground Water Rule

The Ground Water Rule (GWR) was implemented in 2006 to address concerns over fecal contamination of groundwater, particularly as sources for drinking water systems. As opposed to the 1986 Amendment to the SDWA that required all PWSs with groundwater sources to disinfect their water, the 2006 rule establishes a monitoring and compliance framework to identify source waters that are at risk of contamination. In addition to source water monitoring, the GWR also requires verification of the efficacy of treatment techniques and sanitary surveys. (Code of Federal Regulations 2006a)

Filter Backwash Recycling Rule

Released in 2001 by the EPA, the Filter Backwash Recycling Rule (FBRR) regulates the process of recycling wastewater generated by the backwashing of drinking water filters (Code of Federal Regulations 2001b). This rule was developed in response to several outbreaks of cryptosporidiosis where recycled filter backwash at drinking water treatment plants was the presumed cause (Craun et al. 1998). To minimize this risk, the FBRR requires that the backwash water from conventional or direct filtration be returned to the beginning of the filtration system or an alternate location approved by the state. This ensures that any pathogens present in the backwash water will be subjected to the full removal/inactivation efficiency of the entire system. Lead and Copper Rule

Following the 1986 amendment to the SDWA that established regulations for lead in plumbing, EPA published the Lead and Copper Rule (LCR) in 1991 to further limit the presence of these metals in drinking water (Code of Federal Regulations 2000a). The LCR requires water systems to identify locations within the distribution system that are at high risk for lead and copper contamination and monitor these sites regularly. This is the only Federal regulation that requires


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monitoring of premise plumbing. Restrictions on pipe materials and guidelines for limiting the corrosivity of water reduce the leaching of metals from the distribution system infrastructure into the drinking water. The most recent revision of the rule was in 2007. (Code of Federal Regulations 2007).

Long-term revisions to the lead and copper rule are being considered to improve public health. (EPA 2017b).

Chemical Phase Rules

The Chemical Phase Rules are a series of four rules that regulate over 65 chemical contaminants. Phase I was published in 1987 and regulated 8 volatile organic chemicals (VOCs) (Code of Federal Regulations 1987). Phase II, published in 1991, added 10 additional VOCs, 14 synthetic organic chemicals (SOCs), and 8 inorganic chemicals (IOCs) (Code of Federal Regulations 1991a). Six months later, Phase IIB added one SOC and one IOC (Code of Federal Regulations 1991b). In 1992, Phase V added 3 VOCs, 15 SOCs, and 5 IOCs (one was subsequently removed in 1995). (Code of Federal Regulations 1992).

To ease the monitoring burden of these rules, the Standardized Monitoring Framework (SMF) was published in Phase II and implemented in 1993 (Code of Federal Regulations 1991a). The SMF is a concise monitoring schedule that covers all chemical contaminants regulated by the Chemical Phase Rules, the Arsenic Rule, and the Radionuclides Rule. The SMF is discussed in greater detail in Chapter 2.

Radionuclides Rule

The Radionuclides Rule was published in 2000 to reduce the public exposure to radioactivity. The rule sets MCLs for four types of radioactivity: beta/photon emitters, gross alpha particles, radium 226/228, and uranium. (Code of Federal Regulations 2000b).

Arsenic Rule

The NPDWR initially set the MCL for arsenic at 50 ppb. In 2001, EPA published the Arsenic Rule that reduced the MCL to 10 ppb. In response to concerns that the lower MCL would increase cost but not sufficiently reduce risk, EPA convened a meeting of its Scientific Advisory Board to review the Rule. The Board upheld the lower MCL, which became enforceable on Jan. 23, 2006. (Code of Federal Regulations 2001a).

Public Notification Rule

In 2000, the Public Notification Rule was implemented to ensure that consumers were informed about health risks associated with drinking water. Under this rule, systems with regulatory violations are required to inform their customers of the violation and their actions to mitigate the health risk. There are three tiers of notification: immediate, as soon as practical, and annual. The notification tier is dependent upon the level of risk associated with the violation. (Code of Federal Regulations 2000c).


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CHAPTER 2 USING AVAILABLE DATA FROM THE DISTRIBUTION SYSTEM

This chapter3 describes distribution system data commonly available to public health researchers, including distribution system specifications, water quality, and premise plumbing. It is important for public health researchers to understand the quality and reliability of the available data and how it could impact the interpretation of results of health studies on populations served by the water systems.

There is a great wealth of data on drinking water quality available to public health researchers. Water utilities of all sizes and types are required by federal regulations to monitor their systems for a variety of health-related factors. These monitoring activities can provide a ready source of continuous or regularly collected data that is reasonably comparable across utilities. However, generally, these data are collected by utilities to assess internal system management and to meet regulatory requirements, and not to enable public health research. Very little, if any, of these data are collected for research purposes. Therefore, their use in public health studies must be undertaken with care and consideration.

FEDERAL WATER QUALITY REGULATIONS

Regulations are subject to change, refer to the federal or state regulations for the latest information. Drinking water monitoring is driven primarily by the regulations set forth in the federal Safe Drinking Water Act (SDWA) (1974). The SDWA authorizes EPA to institute the National Primary Drinking Water Regulations (NPDWR), which has set standards for 90 chemical, microbiological, radiological, and physical contaminants in drinking water. These contaminants are divided into six broad categories: 1) microorganisms, 2) disinfectants, 3) disinfection byproducts, 4) inorganic chemicals, 5) organic chemicals, and 6) radionuclides. With the exception of disinfectants, each contaminant has a Maximum Contaminant Level Goal (MCLG), Maximum Contaminant Level (MCL), and either a monitoring requirement or a Treatment Technique (TT)


“Utilities collect data for their own purposes, they don't collect it for research. And a lot of the data that is collected is operational in nature and it's got a very short shelf life utility for the system. And if it's in any kind of data storage structure, it's built around that application…. If you're collecting turbidity data out in the distribution system, it's not compliance data. So, you're looking at it for flags. There's no need to invest in storing that data for more than a short period of time. …So, something that's monitored for regulatory purposes, say chlorine, then you've got an added layer of the data will be aggregated at a level that's required by the regulation, either by averaging or extracting a particular data point in some algorithm. But once you've met that compliance objective then you’ve got a lot of data points where storage is not really useful so different utilities are going to have different rules but there's not a lot of data just sitting around for the sake of keeping it close by.” –Steve Via


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requirement. MCLGs are based on known or expected health risks associated with a particular contaminant and are set at a level that should not result in any health impacts. MCLGs take into account sensitive populations such as infants, the elderly, and persons with compromised immune systems. MCLs are the contaminant levels associated with enforcement. Like MCLGs, they are based on health risks, but additionally consider the feasibility of removal or inactivation. Thus, MCLs are always greater than or equal to the MCLG for a contaminant. For contaminants where monitoring is not available or is overly burdensome, a TT is required in place of an MCL. TTs specify the types and efficacies of treatment processes in lieu of specific monitoring. Because disinfectants are intentionally added to drinking water, there are no MCLGs or MCLs for disinfectants. Instead, the regulations establish Maximum Residual Disinfectant Levels (MRDLs) along with monitoring schedules (Code of Federal Regulations 1998a). To limit the burden imposed by monitoring, the Standardized Monitoring Framework (SMF) was implemented in 1993 to synchronize the monitoring schedule for inorganic chemicals, organic chemicals, and radionuclides (Code of Federal Regulations 1991b).

Monitoring associated with NPDWR covers many contaminants and physical properties of interest to public health researchers, but there are limitations. The NPDWR are applicable only to public water supply systems, whether publicly or privately owned. Systems serving at least 25 people or 15 service connections, and operating for a minimum of 60 days per year are considered public water systems and are subject to NPDWR. In the US, there are approximately 160,000 public water systems, serving an estimated 290 million people (Code of Federal Regulations 1992). Small systems serving less than 3,300 people can obtain variances from the state to operate outside of the NPDWR standard. Thus, NPDWR monitoring data disproportionately reflect medium to large public water systems.

The regulations set forth by the NPDWR only document water quality from the source water through the treatment system to the entry point to the distribution system; they do not set standards for contaminants within the distribution system. However, the legislation gives authority to EPA to set additional regulations for water quality in the distribution system. Using this authority, EPA has developed several rules that extend the NPDWR coverage to include monitoring within distribution systems and premise plumbing. These regulations include the Total Coliform Rule, the Lead and Copper Rule, and the Disinfectants and Disinfection By-products Rules, Stages 1 and 2.

Secondary Drinking Water Regulations

In addition to these primary standards, EPA has also established secondary, non-enforceable standards for 15 contaminants that may cause cosmetic or aesthetic effects (Table 2.1) (Code of Federal Regulations 1991b). Since these contaminants are not known to pose any health risks, EPA does not set MCLGs for them. However, as guidance for public water systems, each contaminant in this group does have a secondary MCL (SMCL). The SMCL is based on the feasibility of contaminant removal, good operating procedures and non-health-associated water quality issues (e.g. odor, foaming, etc.). Because SMCLs are not enforceable, there are no federal monitoring requirements.

Table 2.1 Contaminants covered by the Secondary Drinking Water

Regulations Aluminum Manganese Chloride Odor Color pH Copper Silver Corrosivity Sulfate Fluoride Total dissolved solids Foaming agents Zinc Iron


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EPA regularly reviews the NPDWR and develops revised regulations as necessary to address new health concerns, incorporate new techniques, or address issues with feasibility. Researchers should review the EPA drinking water standards website (EPA 2016b) regularly for revisions and proposed changes to the regulations.

States have the authority to grant waivers for any EPA regulation. Waivers are granted on a case-by-case basis. For any contaminant, monitoring can be reduced or eliminated completely. Until the 2013 revision, there were no waivers available for the TCR, but the revised rule sets criteria that states can use to grant reduced monitoring levels. Variances can also be granted by states to allow individual water systems to continue operating despite being in violation of one or more EPA regulations.

States and localities can also leverage additional regulations on water quality (such as enforce a more stringent MCL), extending the contaminants covered, the monitoring frequency, or the monitoring locations. Local building codes may add further restrictions on premise plumbing, though this rarely includes any monitoring. Furthermore, operational water quality monitoring is necessary to optimize treatment plants to achieve expected outcomes. The parameters for operational monitoring provide a timely indication of performance and response time to make necessary adjustments to the treatment processes (World Health Organization 2011a). Additionally, EPA continually considers potential new risks to drinking water quality and maintains a Candidate Contaminant List of compounds that they is review for inclusion in future regulations; water systems may already monitor for some of these compounds (EPA 2013b).

WATER MONITORING DATA

For all contaminants for which EPA sets an MCL or MRDL, there are one or more approved analytical techniques. These techniques have been thoroughly vetted by EPA to ensure that they perform equivalently. A list of approved analytical techniques for each contaminant can be found at (EPA 2016g). Although lab-to-lab differences may still bias results, EPA-mandated monitoring data should be comparable across water systems. This reliability makes monitoring data particularly useful for researchers interested in comparing water systems.

Here, we review the data produced via EPA-mandated or EPA-suggested monitoring in light of its utility in public health research. Researchers can reasonably expect that utilities will have most or all of this data available upon request. Additional monitoring data may be available based on state regulations or utility operating needs. Researchers should discuss the available data with their collaborators at the utility prior to making decisions about study design.

Water Quality Monitoring at the Source and Treatment Plant

Turbidity

Turbidity is a measure of water clarity and can be affected by soil particles, algae, plankton, microbes, and various other substances in water. However, turbidity is a non-specific measure of the scattering of light by particles suspended in water, and as such is influenced by various types of particulates, including silt, clay, and organic matter, that may- or may not have pathogenic properties and can differ in prevalence among water systems (Burlingame, Pickel, and Roman 1998).

Turbidity is often used as an indicator of microbiological contamination. Although some studies have found correlations between turbidity and bacterial or viral pathogen load or infections


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(Johnson et al. 2010, Morris et al. 1996, Tinker et al. 2010), for most pathogens this correlation is not stable and should not be considered predictive. Increased turbidity can cause increased pathogen load by providing nutrients to support bacterial growth and by increasing the disinfectant demand, thereby lowering the disinfection efficacy. Turbidity can also reduce disinfection efficacy because microbes adsorbed to particulates can be partially protected from the effect of disinfection. This can be of particular concern in systems where chlorination is the only treatment applied before water enters the distribution system. Both of these effects can result in high standard plate counts, masking the detection of coliforms (LeChevallier, Evans, and Seidler 1981), though coliform-specific media can partially overcome this limitation. Turbidity can also affect other water parameters. For instance, higher turbidity increases water temperature as the suspended particles absorb more heat. The increased temperature in turn reduces the dissolved oxygen because warm water holds less dissolved oxygen than cold water.

Turbidity in surface water, such as streams and rivers, varies constantly. Dry weather keeps the turbidity stable in the surface water; however, precipitation brings additional suspended particles into water and greatly increases turbidity (World Health Organization 2011a). Turbidity in surface water is also correlated with Giardia and Cryptosporidium contamination (LeChevallier, Norton, and Lee 1991b). Considering the variability of this parameter, real-time remotely operated sensors and data collection systems can provide a robust dataset for water quality surveillance, operation optimization, and public health research.

Turbidity monitoring (to measure filtration performance) is required by the SWTR, which seeks to reduce pathogens in drinking water (EPA 2016l). Monitoring for these pathogens requires high-cost, advanced laboratory techniques. Since frequent monitoring for these organisms is more complex and costly than for many other organisms, a TT combined with turbidity monitoring is mandated. Drinking water treatment systems that use conventional or direct filtration must continuously monitor (at least every 15 min) turbidity in the effluent from every filter. The turbidity value cannot exceed 1 nephelometric turbidity unit (NTU) at any time, and 95% of the samples in any month must be less than or equal to 0.3 NTU. Systems that use slow sand or diatomaceous earth filtration must monitor their combined filter effluents at least every four hours. These measures cannot exceed 5 NTU, and 95% of the samples in a month must be less than or equal to 1 NTU. Systems using any other type of filtration follow a monitoring schedule set by the state and may not exceed 5 NTU in any measure. Unfiltered systems must monitor the turbidity in the source water every four hours, and no measure can exceed 5 NTU.

Total Organic Carbon (TOC), UV at 254 nm

Total Organic Carbon (TOC) is a measure of the organic load in water. Natural sources of TOC include decaying plant and animal matter and microbial contaminants. Synthetic organic compounds, such as detergents, fertilizers, pesticides, and industrial chemicals can also contribute to TOC. With passage of the Safe Drinking Water Act, TOC analysis emerged as a rapid and accurate alternative to the classical, but lengthy, biological oxygen demand (BOD) and chemical oxygen demand (COD) tests traditionally reserved for assessing the pollution potential of wastewaters. TOC is generally removed through enhanced coagulation and enhanced softening techniques. Few studies have specifically addressed the relationship between TOC and health risk (Weinrich et al. 2010); however, there is good reason to expect a correlation. High TOC values due to increased microbial load can present a direct health risk. If natural sources are causing high TOC, they will also increase the disinfectant demand and lower disinfectant efficacy. Many of the synthetic compounds that can cause high TOC measures are known or believed to have direct


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health impacts. Additionally, TOC is known to react with disinfectants to produce disinfection byproducts.

TOC is regulated under the DBPR due to its reactivity with disinfectants; however, it is not a universally mandated water quality measure. Only public water systems where the source is surface water or groundwater under the direct influence of surface water that use conventional filtration treatment are required to monitor TOC and alkalinity, or specific ultraviolet absorbance. The measurement must be taken monthly at each entrance to the distribution system. (Code of Federal Regulations 1998b)

Nitrate/Nitrite

Nitrate (NO3-) and nitrite (NO2

-) are part of the nitrogen cycle and are naturally found in all water sources. Biological and physical processes contribute to the nitrogen load in water. Of concern to public health is the excessive contribution of industrial sources of these compounds. Nitrate is used as fertilizer and is transferred to surface and groundwaters by runoff. Wastewater treatment and leaking sewer and septic systems also return nitrates to water sources. Although nitrate is stable, it is readily converted to nitrite by bacteria. Nitrite can also form within the distribution system when chloramine is used as a disinfectant. In this case, nitrite levels will increase with water residence time within the system (Arber, Speed, and Scully 1985).

The primary public health concern for nitrate and nitrite is methemoglobinemia, which is a loss of oxygen capacity in the blood due to chemical reduction of hemoglobin to methemoglobin. Infants are much more susceptible to nitrate/nitrite toxicity than are adults, and the condition, commonly referred to as “Blue Baby Syndrome,” can be fatal. Reported toxicity levels vary greatly, from 1.5 mg/kg body weight to over 200 mg/kg body weight. Although the specific toxicity level is unclear, cases of drinking-water-associated methemoglobinemia are consistently correlated with exposure to very high nitrate/nitrite levels in water, 100mg/L and higher. Nitrate/nitrite consumption has also been linked to an increased risk of gastric cancer and goiter, but a causative relationship has not been established for these outcomes (World Health Organization 2011b).

Both nitrate and nitrite are regulated under the SDWA, and monitoring regulations are included in the SMF. For nitrate, the MCL and the MCLG are 10 mg/L (as nitrogen, N). Groundwater systems that are reliably and consistently below the MCL and surface water systems that are below ½ MCL for four consecutive quarters must monitor nitrate annually. For systems that are consistently at or above ½ MCL, monitoring must occur quarterly. The MCL and MCLG for nitrite are 1 mg/L (as N). For systems with very low nitrite levels (consistently below ½ MCL), monitoring frequency is determined by the state. For systems with nitrite levels consistently above ½MCL but below the MCL, monitoring must occur annually. If the nitrite level is not consistently below the MCL, the monitoring frequency is increased to quarterly. For both nitrate and nitrite, all monitoring activities occur at the entrance to the distribution system. (EPA 2016b)

Radionuclides

In December 2000, EPA released the Radionuclides Rule to address the cancer risk posed by radioactive compounds in drinking water (Code of Federal Regulations 2000b). As with nitrates, there are natural and industrial sources of radionuclides. The rule divided these compounds into four categories, each with its own MCL and associated monitoring requirements. For all four categories, the MCLG is zero.


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The first three categories (combined radium 226/228, uranium, and alpha particles) include only naturally occurring radionuclides. The levels of these compounds are strongly influenced by the surrounding geology, and levels in source water vary considerably. High levels of radium and alpha particles associated with medical treatments or accidental exposures are known to increase the risk of cancer, but the risk attributable to lower exposures in drinking water is unclear. There is evidence suggesting that uranium in drinking water can result in impaired kidney function, but the association is weak (Kurttio et al. 2002). Despite these uncertainties, EPA has set the MCLs at 5 pCi/L, 15 pCi/L, and 30μg/L for combined radium 226/228, gross alpha particles, and uranium, respectively. For all three categories, utilities are required to initially monitor for four consecutive quarters. If all four measurements are below detection, only one sample per 9-year compliance period is required. If the initial measures are detectable but less than ½ MCL, one sample is required per 6-year compliance period. If the samples are between ½ MCL and MCL, one sample is required every 3 years. If any initial measure is greater than the MCL, quarterly monitoring must continue until four consecutive measures are below the MCL. (Code of Federal Regulations 2000b)

The fourth category, beta particle and photon emitters, includes 168 industrial compounds that have the potential to contaminate water sources through accidental or negligent releases. Long-term consumption of water contaminated with these compounds has been associated with an increased risk of cancer (Lowry and Lowry 1988). The MCL for beta and photon emitters is 4 mrem/yr. Because the potential sources of these compounds are exclusively man-made, only systems deemed to be at risk of contamination are required to monitor. The initial monitoring is quarterly for gross beta particles and yearly for tritium and strontium. If the detected levels are low, defined as the running average minus the naturally occurring potassium 40 (assuming it is less than or equal to 50 pCi/L), then monitoring is required once per 3-year compliance period. If the initial monitoring results do not meet this definition, the initial monitoring schedule must continue and states set further regulations. (Code of Federal Regulations 2000b)

All radionuclide monitoring occurs at the entrance to the distribution system.

Asbestos

Asbestos is a fibrous mineral that is commonly used in insulation materials. Asbestos is a concern in drinking water because it can be combined with cement to form fiber cement, which is a common material for water pipes; asbestos can then leach from pipes into the water. It is also possible for natural sources of asbestos to contaminate water sources. Asbestos can be removed by coagulation and filtration, or direct and diatomite filtration. Corrosion control within the distribution system is also important to prevent contamination from asbestos-containing pipes.

In the late 20th century, it was discovered that inhalation of asbestos leads to lung cancer, mesothelioma, and asbestosis. A cohort study in San Francisco found positive associations between asbestos levels in drinking water and a variety of cancers (Kanarek et al. 1980). However, no association was observed in a case-control study conducted in Washington state (Polissar, Severson, and Boatman 1984). Asbestos has been linked to benign intestinal polyps, a correlation which is supported by animal studies (Corpet, Pirot, and Goubet 1993).

The SDWA-mandated MCL and MCLG for asbestos is 7 million fibers per liter (MFL), but some states have more stringent requirements. According to the SMF, systems that are above the MCL must monitor quarterly at the entrance to the distribution system. Systems at or below


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the MCL must only monitor once in every 9-year compliance period. States have the authority to waive all asbestos monitoring requirements. (Code of Federal Regulations 1991b) Arsenic

In 2001, EPA published the Arsenic and Clarifications to Compliance and New Source Monitoring Final Rule, which reduced the arsenic MCL from 50 g/L to 10 g/L (Code of Federal Regulations 2001a). Arsenic can contaminate water through erosion of natural supplies, agricultural runoff, and industrial discharge. Despite the potential for naturally occurring contamination, the MCLG for arsenic is 0 g/L.

Arsenic exposure is strongly linked to increased risk of cancer. Long-term exposure to arsenic-contaminated drinking water is associated with lung, liver, bladder, and kidney cancer (Jarup 2003, Morales et al. 2000). One study estimated that exposure to one liter of arsenic-contaminated drinking water per day increased the risk of these cancers by 13-fold (Smith et al. 1992).

Systems that use surface water as their source must monitor for arsenic yearly. If the source is groundwater, the monitoring requirement is reduced to once per 3-year compliance period. If a measure is above the MCL, samples must be taken quarterly until the measures are reliably below the MCL. States can issue waivers that reduce the monitoring frequency to once every 9 years. Systems are not eligible for these waivers if any of the most recent three tests were above the MCL. All of these monitoring activities occur at the entrance to the distribution system. (Code of Federal Regulations 2001a).

Organic Chemicals

A total of 53 organic chemicals are regulated under the NPDWR, listed in Tables 2.2 and 2.3. Each of these compounds has a MCL and MCLG, and these values can be found on the EPA website: http://water.epa.gov/drink/contaminants/index.cfm. For monitoring purposes, these compounds are divided in synthetic organic contaminants (SOCs) and volatile organic compounds (VOCs), and their monitoring requirements are part of the SMF.

SOC monitoring is dependent on the size of the service population. For systems serving more than 3,300 people, two quarterly samples taken within one year of a 3-year compliance period are required. If the system serves less than 3,300 customers, it must sample once every three years. In both cases, states can grant a waiver of the monitoring requirements. If a sample is above the trigger level but less than or equal to the MCL, monitoring is increased to every year. If sampling is not reliably below the MCL, monitoring frequency is increased to quarterly. All samples are collected at each entrance to the distribution system. (Code of Federal Regulations 1991b).


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Table 2.2 Synthetic organic contaminants

Alachlor Lindane Di(ethylhexyl)-adipate Hexachlorocyclo-pentadiene Atrazine Methoxychlor Di(ethylhexyl)-phthalate

Carbofuran Toxaphene Dinoseb Oxymal Chlordane Polychlorinated biphenyls

(PCBs) Diquat Picloram

Ethylenedibromide 2,4-dichlorophenoxyacetic acid (2,4-D)

Endothall Simazine

1,2-dibromo-3-chloropropane

2,4,5-trichlorophenoxypropionic acid (2,4,5-TP)

Endrin Dioxin (2,3,7,8-TCDD)

Heptachlor Pentachlorophenol Glyphosate Heptachlor epoxide Benzo(a)pyrene Hexachlorobenzene

VOC monitoring also occurs at the entrance to the distribution system, and the frequency is based

on the source water for the system. Without a waiver, all systems must sample every year. Systems using groundwater sources are eligible for a waiver that will reduce the monitoring frequency to once every six years. Surface water systems can receive a waiver from all monitoring requirements. If a sample is above the trigger level but below the MCL, monitoring frequency remains once per year. If the samples are not reliably below the MCL, the frequency of monitoring increases to quarterly. (Code of Federal Regulations 1991a).

Table 2.3

Volatile organic contaminants Benzene 1,1,1-trichloroethane Styrene 1,2-dichloropropane Carbon tetrachloride 1,1-dichloroethylene Tetrachloroethylene Dichloromethane p-Dichlorobenzene Cis-1,2-dichloroethylene Toluene 1,1,2-trichloroethane Trichloroethylene Ethylbenzene Trans-1,2-

dichloroethylene 1,2,4-trichlorobenzene

Vinyl chloride Monochlorobenzene Xylenes

Inorganic Chemicals

The NPDWR set MCLs and MCLGs for 13 inorganic chemicals (Table 2.4). These values can be found on the EPA website (EPA 2016b). Monitoring requirements for these compounds are included in the SMF, and are dependent on the source water for the system. Groundwater systems must monitor at the entry to the distribution system every 3 years. Surface water systems must monitor every year. For both sources, a waiver can be granted by the state that reduces the monitoring frequency to once every 9 years. For either source, if the detected levels are not reliably at or below the MCL, monitoring frequency must increase to quarterly. (Code of Federal Regulations 1991b).

Fluoride

Fluoride is one of the inorganic contaminants described above; however, it is unique in certain aspects. Unlike most chemical contaminants, fluoride enters a water system primarily by addition at the treatment plant. Beginning in the mid-20th century, widespread fluoridation of the

Table 2.4 Inorganic contaminants

Asbestos Nitrate Beryllium Cadmium Nitrite Cyanide Chromium Selenium Thallium Fluoride Barium Mercury Antimony


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US drinking water supply was undertaken to lower the rate of dental caries. Drinking water fluoridation is recommended by CDC (CDC 2001), but it is voluntary. Although low levels of fluoride are beneficial, high levels can be toxic. The health- related concerns are dental fluorosis, skeletal fluorosis, neurological effects, carcinogenicity, and endocrine disruption. Therefore, EPA has set both a MCL and a SMCL for fluoride. The MCL (4 mg/L) is monitored as described above for inorganic contaminants and is based on health risks. The SMCL (2 mg/L) is not enforceable at the federal level and is meant to prevent cosmetic effects such as skin or tooth discoloration and aesthetic effects such as taste, color, and odor in drinking water. States may have more stringent regulations than EPA. In 2015, the U.S. Public Health Service recommended the optimal level of fluoride was 0.7 mg/L instead of the 1962 recommendation of 0.7 mg/L - 1.2 mg/L. (Code of Federal Regulations 1991b, Cornwell et al. 2015)

Chlorine Dioxide

Chlorine dioxide is another commonly used disinfectant. Both chlorine dioxide and its DBP, chlorite, are toxic, causing anemia and neurological disorders (Couri, Abdel-Rahman, and Bull 1982). Under the Stage 1 DBPR, the MRDL for chlorine dioxide is 0.8 mg/l. Systems using chlorine dioxide must monitor the concentration daily at the entrance to the distribution system. (Code of Federal Regulations 1998a).

Bromate

Bromate is formed when ozone is used to disinfect water, and it reacts with naturally occurring bromide found in source water (von Gunten and Hoigne 1994). The amount of bromate formed during ozonation is influenced by three factors: bromide concentration, ozone concentration, and pH. By using the minimal effective dose of ozone and reducing the operating pH at this treatment stage to approximately 6.5, bromate formation in the water can be controlled (World Health Organization 2011a). Bromate can also be formed in water disinfected with hypochlorite (Weinberg, Delcomyn, and Unnam 2003). There is strong evidence from animal studies that bromate is carcinogenic, particularly to the kidneys (DeAngelo et al. 1998, Kurokawa et al. 1986). These studies spurred the International Agency for Research on Cancer to classify bromate as a Group B carcinogen (possibly carcinogenic to humans) (International Agency for Research on Cancer 2011).

Under the Stage 1 DBPR, bromate is regulated at an annual average of 10 g/L in drinking water. All systems using ozone for disinfection are required to monitor bromate levels monthly at the entrance to the distribution system. Despite evidence that hypochlorite disinfection can also stimulate bromate production, there is no monitoring requirement for systems using this disinfection strategy. (Code of Federal Regulations 1998a).

Distribution System Water Quality Monitoring

Total Coliforms

The strictest EPA water regulations with respect to monitoring and frequency address the presence of fecal indicator bacteria throughout the water system. These bacteria are found in very high numbers in feces of humans and other warm-blooded animals. Similar coliform bacteria can be found throughout the environment, not associated with feces. The sum of these environmental


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coliforms and fecal coliforms (including Escherichia coli) is referred to as total coliforms. Thus, all samples positive for fecal coliform/E. coli will be positive for total coliforms, but the reverse is not necessarily true. Since much of the microbial risk associated with drinking water arises from fecal contamination, systems can monitor total coliforms and fecal coliforms or E. coli as surrogates for total microbial risk. The Total Coliform Rule (TCR) was published in 1989 and became effective in 1990 (the revised Total Coliform Rule is described below). According to EPA (2017d) the goal of the TCR is to “protect public health by ensuring the integrity of the drinking water distribution system and monitoring for the presence of microbial contamination.” The TCR set the MCLG for total coliforms at 0 colony-forming units per 100 mL (cfu/100 mL) and the MCL levels are based on the positive samples test for total coliforms and E. coli or fecal coliforms (EPA 2017). (EPA 2013d). Although quantitative assays are available, many utilities use presence/absence assays. In this case, a positive result should be interpreted at ≥ 1 cfu/100 mL, and a negative result should be interpreted at <1 cfu/100 mL. Since water temperatures and nutrient load in most US waters are rarely high enough to support growth of fecal coliforms/E.coli, detection of these organisms represents incomplete disinfection or intrusion (LeChevallier, Welch, and Smith 1996).

The monitoring schedule for total coliforms is based on the size of the service population. Utilities must collect between 1 and 480 TCR monitoring samples per month from sites throughout the distribution system. These sites must be representative of the entire distribution system and must be approved by the state. Samples must be collected at regular intervals throughout the month, though small groundwater systems (< 4,900 served) can collect all samples on the same day each month. All samples must be tested for total coliforms, and any sample that tests positive for total coliform must be tested for fecal coliforms/E. coli. Many utilities use assay systems such as Colilert (IDEXX Laboratories, Westminster, CO) that test for total coliforms and E. coli simultaneously, in which case both data types are available for every sample. Any total coliform-positive sample triggers repeat testing. Three samples must be collected within 24 hours of the initial positive sample. These samples are collected at the original sample site, an upstream service connection, and a downstream service connection. If any of the repeat samples are positive, a second set of repeat samples must be collected. (EPA 2013d)

Systems collecting fewer than 40 samples per month are considered to have a monthly MCL violation if more than 1 routine or repeat sample is positive for total coliforms. Larger systems collecting at least 40 samples per month have a monthly MCL violation if more than 5% of their total samples (routine + repeat) are total coliform-positive. An acute MCL violation occurs when any system has a fecal coliform/E. coli-positive repeat sample, or a fecal coliform/E. coli-positive routine sample followed by a total coliform-positive repeat sample. (EPA 2013d)

It is not possible to get a waiver from total coliform testing. The only systems eligible for a reduced monitoring schedule are groundwater systems serving fewer than 1,000 customers that have no known sanitary defects. For these systems, monitoring can be reduced to no fewer than one sample per quarter for community systems and one sample per year for non-community systems. (EPA 2013d)

“I think the most pressing issue is that we don't know how to monitor the integrity of the distribution system. We identified the integrity in three different ways: physical integrity, hydraulic integrity, and water quality integrity. But when it really comes to trying to determine when has the integrity been lost, we don't have a lot of good monitors.” - Mark LeChevallier


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Revised Total Coliform Rule: The Revised Total Coliform Rule (RTCR) was published in 2013 and went into effect in 2016 (EPA 2013). The RTCR has a slightly different purpose than the TCR; of “increase public health protection through the reduction of potential pathways of entry for fecal contamination into distribution systems.” (EPA 2013d). It sets the E. coli MCLG to zero and the “MCL is based on the occurrence of a condition that includes routine and repeat samples” (EPA 2017d). EPA (2017d) describes the RTCR key provisions as sets a MLCG and MCL for E. coli, sets a total coliform treatment technique requirement, sets monitoring requirements for total coliforms and E. coli (sample siting plan and schedule), requirements for seasonal systems, requirements for assessments and corrective action based on monitoring results, public notification requirements for violations, and specific language to be included in Consumer Confidence Reports (CCR).

Other Microbial Contaminants

In addition to total coliforms and E. coli, the SDWA sets regulations for four other microbial contaminants: Cryptosporidium, Giardia lamblia, Legionella, and enteric viruses. Cryptosporidium, Giardia, and enteric viruses can cause large outbreaks of infectious diarrhea (Proctor, Blair, and Davis 1998, Moe 2004) and are of particular concern because they are more resistant to disinfection than bacteria (Betancourt and Rose 2004). Inhalation of water contaminated with Legionella can result in severe pneumonia. Legionella is susceptible to disinfection, but it can colonize warm, standing water, which is less likely to be sufficiently disinfected (Buse and Ashbolt 2011). For this reason, Legionella outbreaks are usually associated with premise plumbing. Monitoring for each of these microorganisms is technically challenging and would be overly burdensome for utilities. Therefore, EPA does not establish MCLs for these organisms. Instead, there are TTs that must be used to ensure adequate removal of these microbes. For Cryptosporidium, the appropriate TT is filtration that is known to remove 99% of oocysts. Acceptable TTs for Giardia must remove or inactivate 99.9% of organisms. TOC monitoring (described above) is also used to control the risk of protozoan contaminants. TTs for viruses must remove or inactivate 99.99% of viruses. There is no TT standard for Legionella, as the TT requirements for Cryptosporidium, Giardia, and viruses are sufficient to remove Legionella as well. The MCLG for each of these contaminants is zero. (Code of Federal Regulations 1989).

Heterotrophic plate counts (HPC) are a non-specific measure of total bacterial load in water. HPC has no direct health effects, and thus has no MCLG or MCL (Chowdhury 2012). Despite that, EPA does have approved TTs for reducing HPC. There is no monitoring requirement for HPC, but many utilities will measure it when total coliforms are measured as a surrogate for disinfectant residual.

“We cannot stick with the conventional diarrhea as outcome of concern. … There are airborne issues that come from aerosolization of water. Legionella is a significant problem …[in] distribution and hot water systems mostly inside buildings. … Legionella is a respiratory problem, so in addition to drinking water, misters and sprayers are also of concern. Mycobacterium avium complex (MAC) … is also a potential challenge. Why? It is tough, it hides, it gets in the pipes, it stays in the biofilm, it comes off in slugs and all of a sudden your dose is an important issue as well.” – Kellogg Schwab


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Lead and Copper

At moderate levels, lead can cause anemia by disrupting hemoglobin synthesis. Higher exposures can cause neurological damage, particularly in children, and there is epidemiologic evidence that exposure to lead in childhood can lead to lower IQ (Jarup 2003). Copper is less hazardous due to the body’s efficient homeostasis, but high copper can cause gastrointestinal upset. There is increasing evidence that copper exposure may increase the risk of Alzheimer’s and other neurodegenerative diseases, but a causative link has not been established (Brewer 2010a). In individuals with Wilson’s Disease, copper accumulates in the body and can cause cirrhosis of the liver (Brewer 2010b). These individuals are especially at risk when copper levels in drinking water increase.

Given these health risks, EPA developed the Lead and Copper Rule (LCR) (Code of Federal Regulations 2007). The monitoring framework set forth by the LCR is unlike other EPA regulations because most of the lead and copper in water is from pipes and premise plumbing. The LCR establishes Action Levels (ALs) for each metal: 0.015 mg/L for lead and 1.3 mg/L for copper. Because premise plumbing is a significant source of lead and copper in drinking water, the LCR requires that monitoring samples be drawn at the taps of homes or buildings that are deemed at high risk for contamination. The LCR is the only rule in the regulatory framework that considers premise plumbing.

All systems must collect first-draw tap samples throughout the distribution system every six months. The number of samples required is based on the size of the service population, and it ranges from 5-100. Systems serving more than 50,000 people and smaller systems that exceed the AL, must also monitor a suite of water quality parameters (pH, alkalinity, calcium, conductivity, orthophosphate, silica, and temperature) every six months at the taps and every two weeks at the entry to the distribution system. Waivers can reduce the monitoring frequency to every year, every three years, or every nine years if the system is consistently below the AL. (Code of Federal Regulations 2007).

An AL exceedance is not a violation but can trigger other requirements that include water quality parameter (WQP) monitoring, corrosion control treatment (CCT), source water monitoring and treatment, public education, and lead service line replacement (LSLR). Systems that are above the AL for lead or copper must also monitor the source water to determine the proportion of contamination that is due to the source. Surface water systems must monitor annually, and groundwater systems must monitor every three years. If the source water is found to be a significant contamination source, the system has two years to install source water treatment that will reduce the contamination, as monitored at the entrance to the distribution system. All large systems and medium to small systems that exceed the AL must install corrosion control treatment. To confirm that these systems are effective, tap samples and water quality parameters must be measured for two consecutive 6-month monitoring periods. Finally, the LCR mandates that at least 7% of lead service lines must be replaced annually. Systems may monitor lead in specific lines to determine replacement priorities or apply for a waiver of line replacement (“replaced through testing”). Utilities can discontinue lead serve line replacement when they are under the lead action level for two consecutive 6-month monitoring periods and must recommence if they subsequently exceed it. (Code of Federal Regulations 2007).

Long-term revisions to the lead and copper rule are being considered to improve public health EPA (2017b).


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Chlorine and Chloramine

Chlorine and chloramine are commonly used for disinfection, and one of the benefits of these compounds is that they remain active in the finished water, providing continued protection within the distribution system (Ngwenya, Ncube, and Parsons 2013). These compounds do not pose a significant health hazard at the levels present in drinking water; however, higher levels of disinfectants lead to higher levels of DBPs, which are hazardous. Therefore, EPA sets limits for the MRDL. The MRDL is 4 mg/L for both chlorine and chloramine (Code of Federal Regulations 1998a). Disinfectant residuals must be measured at the same locations and the same schedule as coliform monitoring set forth by the TCR (see above).

Chlorite

Chlorite is a disinfection byproduct formed when chlorine dioxide is used. Typically, 60-70% of chlorine dioxide is converted to chlorite in the treated water, and this reaction is favored in alkaline conditions (World Health Organization 2011a). Animal studies have shown that exposure to chlorite, as well as the related, but not regulated, DBP chlorate, can cause methemoglobinemia and neurodevelopmental disorders (Boorman 1999). A volunteer study with adults found that daily consumption of up to 500 g chlorite for 12 weeks did not have any detectable physiologic effect (World Health Organization 2011a). Epidemiological studies have found a correlation between premature birth and chlorinated drinking water, an effect that is believed to be due to exposure to chlorite and chlorate (Tuthill et al. 1982). Based on the potential risk to infants, EPA regulates chlorite as part of the DBPR. The MCLG for chlorite is 0.8 mg/L and the MCL is 1 mg/L (Code of Federal Regulations 1998a). Chlorite levels are monitored daily at the entrance to the distribution system and monthly within the distribution system.

Total Trihalomethanes and Haloacetic Acids

Chlorine-based disinfection can result in the production of halogenated DBPs: trihalomethanes (THM) and haloacetic acids (HAA). The formation of these DBPs depends on organic load and pH (Liang and Singer 2003). Epidemiologic studies have linked high exposure to THMs and HAAs to increased rates of cancer, specifically bladder cancer (Chowdhury et al. 2011, Lee et al. 2013). Toxic exposure to these compounds can come from ingestion, dermal contact, or inhalation. One study found that the most relevant exposure is through inhalation in the shower (Lee et al. 2013).

EPA regulates five HAAs (dichloroacetic acid, trichloroacetic acid, monochloroacetic acid, bromoacetic acid, and dibromoacetic acid) and four THMs (chloroform, bromodichloromethane, bromoform, and dibromochloromethane). Each compound has its own MCLG; however, they do not have individual MCLs. The Disinfectants and Disinfection Byproduct Rule only considers the running annual average of the sum of the concentrations of the individual compounds. In Stage 1 DBPR, a single average is computed for all monitoring locations in a system (running annual average, RAA); in Stage 2, each location has its own running average for compliance measures (local RAA, LRAA). For HAA5, the MCL is 0.06 mg/l. For Total THM, the MCL is 0.08 mg/L. Under Stage 1, monitoring only occurs at the point in the distribution system with the longest water residence time. The number of monitoring sites in Stage 2 is dependent upon the source water, size of the service population, and the results of an Initial Distribution System Evaluation (IDSE), and


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it ranges from 2 to 20 sites within the distribution system. Small systems must monitor yearly. All other systems must monitor quarterly. (Code of Federal Regulations 1998a)

PUBLIC NOTIFICATIONS

Public notifications records are another data source for assessing water quality. The Public Notification Rule sets three notification tiers. Events that present an immediate health risk fall into Tier 1 and must be reported to the public within 24 hrs. These events include fecal coliform/E. coli-positive samples in the distribution system, nitrate/nitrite levels in excess of the MCL, chlorine dioxide in excess of the MRDL in the distribution system, high turbidity, and known waterborne outbreaks. All other MCL and MRDL violations are considered Tier 2, as are monitoring and compliance violations. Tier 2 events require public notification within 30 days. Tier 3 events include operating under a variance, the availability of monitoring results for unregulated contaminants, and fluoride levels in excess of the SMCL. Tier 3 events require annual notification. (Code of Federal Regulations 2000c)

DISTRIBUTION SYSTEM OPERATIONS

In addition to the EPA-mandated monitoring detailed above, there are many types of data that systems collect for Operations and Maintenance (O&M). Utilities conduct planned activities such as flushing programs and unplanned activities such as main break repairs or replacements to protect the quality of water in the water systems. The frequency and location of monitoring will vary by system, based on their needs, and these can change over time. In this section, factors that are commonly measured for O&M are discussed.

pH

pH generally has no health impact per se, but it is considered as a main operational parameter (Kenny et al. 2009). To achieve effective disinfection with chlorine in the distribution system, the pH of water should be lower than 8. However, acidic pH (7 or lower) is associated with corrosion of distribution pipes. Another important effect of pH is on the formation and distribution of disinfection byproducts. Lower pH favors the formation of HAAs, and reduces the formation of THMs. Conversely, a higher pH leads to higher concentrations of THMs and reduced concentrations of HAAs (World Health Organization 2011a). Bromate formation during ozonation is also strongly influenced by pH. To limit bromate formation, the pH is reduced to 6.5 prior to disinfection and raised to neutral or above after disinfection to prevent corrosion (von Gunten and Hoigne 1994). Out of range pH can also contribute to poor taste (low pH) or a slippery feel (high pH), both of which can increase customer dissatisfaction. Under the National Secondary Drinking Water Regulations, EPA recommends maintaining water pH between 6.5 and 8.5 (Code of Federal Regulations 2002). Due to its importance in operations and customer satisfaction and ease of measurement, most water systems will monitor pH within the treatment plant frequently.

Temperature

High water temperatures contribute to taste, odor, color, and corrosion problems in finished water. More importantly, higher temperatures also enhance the growth of microorganisms (LeChevallier, Welch, and Smith 1996). Although this occurs without posing any public health risk in most cases, microbial regrowth is an issue in distribution systems carrying water over long


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distances in warm climates. Warmer water temperatures increase the rate of disinfectant decay (Sohn et al. 2004), which combined with high levels of biodegradable organic carbon can allow growth of Legionella, Vibrio cholerae, Naegleria fowleri, Acanthamoeba, and other organisms in surface water and in distribution systems (Berry, Xi, and Raskin 2006). However, water temperature and nutrient levels in most US waters are generally not high enough to support the growth of fecal coliforms/E.coli. Increased turbidity can also lead to higher water temperatures. Service lines and premise plumbing are generally more prone to higher water temperature (National Research Council 2006).

Alkalinity

Alkalinity is the capacity of water to neutralize an acid solution, and it is measured as mg/L CaCO3. Low alkalinity can cause internal pipe corrosion and subsequent release of metals such as iron, lead, and copper in water (National Research Council 2006). Low alkalinity also reduces the pH of water.

Hardness

Like alkalinity, hardness also causes corrosion of the pipes (Hammer 1975). Hard water contains high levels of dissolved minerals, such as magnesium, calcium, iron, and aluminum, however, hardness is measured as the sum of only magnesium and calcium. Hardness can cause a number of nuisance issues: mineral buildup on plumbing fixtures, decreased efficiency of electric water heaters, poor detergent performance, alkali taste to water, etc. Hardness is of particular concern to industrial water customers, as it can result in scaling and damage to equipment.

Flushing Programs

Flushing programs are used to minimize water age and remove sediments in pipes. Generally, utilities perform flushing annually; however, more frequent flushing may be used to manage localized water quality issues. Although flushing is performed to protect water quality in the distribution system, it can have negative consequences. The sudden release of large water volumes can cause changes in flow through the distribution system, affecting both the magnitude of flow and the direction. The opening and closing of valves and high-volume demand can result in pressure drops in other areas of the distribution system, which can lead to intrusion and contamination. A poor flushing can degrade water quality by scouring sediments, tubercles, and scales from the interior pipe walls but not fully removing them from the pipe (Pierson et al. 2001, Nilsson et al. 2008).

Each utility employs its customized flushing programs based on the nature and size of the distribution system. Information on the flushing operation, schedule, and duration of each flushing event can be obtained from the utility.

Main Breaks, Repairs, or Replacements

Aging (really, deteriorating) water infrastructure in the US has become vulnerable to main breaks and leaks. A Midwestern water utility that kept a diligent record of its main breaks reported a steep rise in the main breaks from approximately 250 breaks per year in 1970 to approximately 2,200 breaks per year in 1989 (National Research Council 2006). Main breaks and leaks not only incur hefty expenses, they can potentially affect the water quality in the pipes due to pressure loss,


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contaminant intrusion, and other operational issues (Nygard et al. 2007). Utilities may opt to replace deteriorating infrastructure before breaks can occur. In theory, pipe replacement presents less risk than a break, but poor practices, such as lack of disinfection and poor flushing, can leave contaminants in new pipes.

There are multiple sources of main break, repair, and replacement data. Utilities have records of main breaks and leaks repairs and possibly water audits (see Chapter 1, Water Loss Control Programs). They may also have a prospective plan for line replacement. Another source is the American Water Works Association water industry database (see Chapter 3 for more details).

Water Pressure

Distribution systems strive to maintain constant positive pressure in the water lines to prevent any contaminants from entering the system and ensure adequate pressure at customers’ taps. Although water pressure in the distribution system is not regulated by EPA, it is recommended to maintain a system-wide pressure between 20 and 80 psi (World Health Organization 2011a, Yang et al. 2011).

States can (and many do) require distribution systems to maintain pressures of at least 20 psi at ground level in all locations, and under all flow conditions. The “Recommended Standards for Water Works” by the Ten State Standards suggests that normal operating pressures be greater than 35 psi and ideally between 60 and 80 psi. Real world distribution systems can see pressures outside the recommended ranges (below 35 psi or greater than 100 psi), especially in hilly areas. In a utility survey, most utilities responded that they had regulatory requirements related to low pressure, such as 95% had to maintain 20 psi during fire flow, 21 % had to maintain positive pressure during emergency conditions, and 71% had to maintain pressure of 0-20 psi. However, less utilities had requirements related to high pressures, for example, 56% did not have a requirement of maximum high pressure delivered to customers and 67% lacked maximum pressure requirements. LeChevallier et al. (2014).

Building codes may also contain pressure requirements for plumbing. There are two widely adopted plumbing codes in the US (the International Plumbing Code and the Uniform Plumbing Code) and local jurisdictions can enact additional codes. According to (National Research Council 2006), the Uniform Plumbing Code sets a maximum water pressure of 80 psi at service connections, and requires the installation of a pressure reducing device if this pressure is exceeded.

Low-pressure events/areas increase the possibility of water contamination through intrusion or backflow from a non-potable source (i.e. a cross connection). High-pressure events/areas can lead to damaged fixtures and equipment.

Pressure transients in the distribution system can affect water quality. Pressure transient events are generally more frequent and severe at the pump stations and control valves, in high elevation areas, and at locations farther from overhead storage tank (Boulos et al. 2005). The major cause of low or negative pressure is associated with power outage or pump failure. However, due to the transient nature of these events, it has been a challenge to collect conclusive data to see whether these events pose a substantial risk to water quality in the distribution system (LeChevallier et al. 2003).

Pressure in the distribution system is monitored by the utility at various points ensure optimal operation to minimize extreme pressures that can potentially affect the water quality or the integrity of the water infrastructure. Large utilities often employ automated pressure loggers that log pressure frequently and generate large, longitudinal datasets. Some states may require utilities to submit pressure monitoring information.


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PREMISE PLUMBING

Premise plumbing is the piping associated with buildings (public or private) and is connected with the distribution system via service lines. Water quality in premise plumbing is not regulated by EPA with the exception of the LCR, which requires utilities to collect samples at the tap of at-risk connections. Any water quality risk that exists in the distribution system can be present in premise plumbing; however, these problems can be magnified due to the additional challenges associated with premise plumbing (National Research Council 2006). One of major risk factors is the high surface area of piping/tubing to water volume ratio, which increases the contact time of water in the plumbing and consequently increases the water quality risk. Water age can be a challenge due to inconsistent use of all areas of premise plumbing. This, in turn, leads to difficulty maintaining a sufficient disinfectant residual, which could allow microbial regrowth in the water or colonization of fixtures (Buse and Ashbolt 2011, Schoen and Ashbolt 2011, Yoder et al. 2012). Other factors that contribute to greater risk in premise plumbing include extreme temperatures and the wide variety of plumbing materials that could potentially react with water constituents such as disinfectants.

Very little data is available on premise plumbing. Monitoring records associated with the LCR will give some insight into the presence and extent of high-risk premise plumbing. Utilities may also have a limited dataset on cross connections and backflow issues. Installation records for backflow preventers, which stop intrusion in premise plumbing from contaminating a main, can identify locations with premise plumbing issues.

CUSTOMER COMPLAINT DATA

Any community water system will be subject to customer complaints. These complaints will cover a very broad range of issues from water quality (e.g. color, clarity, taste, odor) to delivery issues (e.g. pressure) to break and leak reports. Many water utilities keep records of customer complaints about water and collect information on the type of complaint (taste, odor, turbidity) and the location of the customer filing the complaint. Whenever possible, water utilities should try to send a team to collect water samples from the household with the complaint and analyze the water for chlorine residual, turbidity, and coliforms. Utilities may also collect a water sample from a nearby hydrant for comparison and isolation of the problem from the premise plumbing. Customer complaint records can also provide useful geographic information about water quality problems by adding GIS information to a database for tracking customer complaints. Customer complaints can provide an early indication of significant problems with water quality. One of the first indications of the 1993 outbreak of cryptosporidiosis in Milwaukee, Wisconsin, was customer complaints about water turbidity (MacKenzie et al. 1995). In a retrospective study of the outbreak, there was a correlation in time and magnitude between customer complaints and illness, suggesting that customer complaints could serve as a surrogate for risk (Proctor, Blair, and Davis 1998). However, it is unclear if this would extend to other drinking water risks. In contrast, a recent study of customer perceptions of water quality and water service in rural Alabama found no association between customer reports of intermittent service, low water pressure and poor taste, odor or color, and measured quality of household tap water samples (total and free chlorine, pH, turbidity and presence of total coliforms and E. coli). The authors concluded that consumer-reported water quality data were of limited utility in predicting potential microbial risks associated with small rural water supplies (Wedgworth et al. 2014).


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LIMITATIONS OF THE AVAILABLE DATA

Although the data types listed above represent a valuable resource to public health researchers interested in water distribution systems, there are limitations to their use. It is important to remember that these data are collected to meet regulatory requirements or for O&M, not for research. As a result, the data will often require some data manipulation and cleaning before it can be useful in a health study. Older datasets may still be kept as hard-copy paper records, which are subject to physical degradation or loss, as well as transcription errors. Even electronic datasets can have large pieces of missing data, which could be due to equipment malfunctions or file corruption.

Even systems with modern, continuous datalogging systems may not have data that is research-ready. It is not unusual to find, for example, that the pressure monitoring system is completely separate from the flushing program, each with a unique file type, data setup, and access point. Merging such datasets for analysis can be time-consuming, and should be considered when planning the study design. The file formats used for data storage by the water utilities may be incompatible with a health study’s analysis plan. For example, longitudinal pressure data may be stored as a series of daily reports instead of one file. Thus, a year’s worth of data could be 365 separate files.

The use of geocoding and GIS analysis in health research has grown considerably in the past decade. Many utilities have begun geocoding their data; however, this should not be assumed. Even if data acquisition has switched to geocoded databases, the archived datasets may not be compatible. Databases with street addresses, such as billing information, should be carefully reviewed for accuracy.

Perhaps the greatest limitation of these data is their collection frequency. With the exception of total coliforms, most contaminants of interest to public health are measured very infrequently. This low-resolution exposure data is difficult to compare to higher resolution health measures, such as emergency department discharges or cancer registries.


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CHAPTER 3 SOURCES OF POTABLE WATER SYSTEM DATA

The quality of public health research on drinking water depends in part on the type and quality of available data. This is particularly true when third party datasets are used for analysis. Several sources of drinking water data are available from government entities, utilities, industry groups, and non-profit organizations. In this chapter4, we describe the availability, accessibility, accuracy, and completeness of data and databases maintained by government agencies, utilities, and industry groups that may be useful for epidemiological studies of drinking water and health. We discuss ways in which utility data can be obtained and in what formats they are available.

A brief description of each source is provided below.

GOVERNMENT ENTITIES

Federal

EPA is the federal agency that collects water quality data relevant to public health research. In particular, they maintain six datasets that are publicly available and of interest to public health researchers. Each of these data systems is reviewed below, with an emphasis on the type of data included and limitations of each system. Additional datasets are maintained exclusively for the use of EPA water system employees. These datasets are not covered here.

The United States Geological Survey (USGS) also maintains databases of water quality data. However, fitting with their mission, these data cover natural water sources only, such as rivers, lakes, and streams. Since these databases do not contain any data on treated drinking water, they will not be covered in detail in this manual. Interested researchers can access tutorials covering all of the USGS water databases at (U. S. Geological Survey 2016).

Safe Drinking Water Information System/Federal

The Safe Drinking Water Information System/Federal (SDWIS/FED) tracks federal drinking water violations. All public water systems must be registered with SDWIS/FED, and data is submitted to the federal government by the states. Each water system is assigned an ID number, and the following characteristics of the system are recorded: the size of service population, the type of system (transient, non-transient, residential), the operational timeframe (year-round or seasonal), and the type of source water. States must report all violations of federal regulations to SDWIS/FED, including MCL exceedances, public notification failures, and monitoring violations. For all reported violations, enforcement and follow up actions are also reported to SDWIS/FED. The results of data reliability studies performed by EPA are also found in this database. This publicly available dataset does not contain details of the violations beyond the type and date reported, nor does it allow export of the data in an analysis-ready format. (EPA 2016j)

Sampling results for regulated contaminants are only included in the SDWIS/FED database when the level exceeds the MCL. In contrast, all sampling results for unregulated contaminants are reported. However, the testing for these unregulated agents is inconsistent across systems, so



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the sampling results available in this database must be analyzed with care. Missing results for regulated contaminants can mean that the level was just below the MCL, the contaminant was undetectable, the test was not required for that system, or the system had been granted a waiver. Each of these options has unique implications for analysis. Likewise, results for unregulated contaminants must be analyzed carefully because the frequency, location, and analysis methods vary by system. (EPA 2016j) There is also concern among utilities that this data contributed to this database is not complete and correction of errors does not occur in a timely manner.

SDWIS/FED data can be retrieved as annual reports, through Envirofacts queries, or MS Excel PivotTables. Directions for accessing SDWIS/FED data can be found at (EPA 2016j). Access to the full database can be requested through the EPA.

Storage and Retrieval Data Warehouse

The STORET (short for STOrage and RETrieval) Data Warehouse is a repository for data on physical, chemical, and biological water quality measures, as well as biomonitoring data from animals and plants (EPA 2013a). The data in STORET is submitted by water resource management groups throughout the US, and the repository is updated weekly. Submission to STORET is not required for water utilities, thus datasets may not be complete. Although EPA does not screen submitted data for validity, they do require significant documentation of each submission. This metadata includes the date and type of collection, the reason for testing, the lab performing the analysis, and documentation of laboratory quality assurance and quality control results. This level of documentation makes the STORET database a valuable resource for researchers interested in water quality. Public health researchers have used the data available in STORET for risk assessment studies related to drinking water and surface waters (Staples, Parkerton, and Peterson 2000, Wilson and Weng 2010).

STORET data is divided into two databases. Data collected since 1998 is submitted to the active STORET Data Warehouse. The STORET Legacy Data Center contains data prior to 1998, dating back to the early 20th century. Both databases allow users to submit data queries based on type of water tested, the ID or location of the sampling station, sample criteria (i.e. continuous vs. grab, depth, etc.), and result criteria (i.e. average, maximum, etc.). The current Data Warehouse can also be queried by the intent of the sampling activity and the analyte or organism measured. (EPA 2013a)

STORET queries, for both the modern and the Legacy databases, can be submitted at (EPA 2016k).

National Contaminant Occurrence Database

The National Contaminant Occurrence Database (NCOD) contains sampling results for regulated and unregulated contaminants. The focus of this dataset is on finished drinking water quality; most samples are collected at the entry point to the distribution system. However, there are some source water sample results in the unregulated contaminant data. Like STORET, the strength of this dataset is that it contains actual test results with numeric values, allowing for more complex correlation studies. (EPA 2016h)

The regulated contaminant database is managed by EPA as a data source for policy recommendations, and has been confirmed to be valid and complete. In contrast, the unregulated contaminant database contains results of testing that is voluntary on the part of the water system. The EPA does not use the unregulated contaminant dataset for analysis, only surveillance. In light


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of this, extra care should be taken when using the data on unregulated contaminants for public health studies. (EPA 2016h)

NCOD datasets can be downloaded at (EPA 2016h).

Information Collection Rule

The Information Collection Rule data is available to the public and contains disinfection byproducts and microbials occurrence data at the national, state and utility levels and was collected to support the development of national drinking water standards. Between July 1997 and December 1998, EPA collected water samples from water systems across the country and tested them for microbial contamination and the levels of disinfection byproducts. Depending on the analyte or organism, the samples were collected at the source, the treatment plant, or within the distribution system. The purpose of this study was to assess drinking water quality at the national level, thus results may not be representative at the regional or local level. (EPA 2016f)

The results of this study can be found using an ICR Query (EPA 2016f). The database can be queried by analyte, organism, state, or water system.

Enforcement and Compliance History Online

The Enforcement and Compliance History Online (ECHO) web database houses all discharge permits filed with the EPA. The available data in ECHO include the facility holding the permit, inspection reports, violations, enforcement actions and penalties. These data are available for the most recent three years. Although this system does not contain any data on water quality within the distribution system, researchers may use it as a source of water quality data for the watershed of interest. (EPA 2016c)

Directions for accessing ECHO, generating reports, and downloading the ECHO widget can be found at (EPA 2016c).

Freedom of Information Act

Under the Freedom of Information Act (FOIA), the public has the right to request records from Federal agencies, including EPA. FOIA requests to EPA can be submitted online at (EPA 2016e). Through this online resource, researchers can submit requests, track the status of requests, search the database of requests submitted by others, and generate instant reports from the information requested. If a request falls under any of the nine exemptions listed in the Act, the agencies are allowed to withhold information.

State

Unlike the federal government, states are not required to maintain publicly available databases on water quality. Many states use SDWIS/STATE to maintain their drinking water databases. SDWIS/STATE is a software program designed and distributed by EPA to facilitate the management of water quality data at the state level. The database consists of a detailed water system inventory, site visit information, sample schedules, sample analytical results, compliance determination, rule violation management, and enforcement action taking. Through this system, EPA also assists states to report water quality information to their consumers (EPA 1997a). Unlike SDWIS/FED, SDWIS/STATE databases are not publicly available. Access to these databases must be negotiated with each state water authority. (EPA 1997a)


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Consumer Confidence Reports

The Consumer Confidence Report (CCR) Rule requires public water systems to publish annual water quality reports (EPA 2016a). These reports are in addition to any public notifications that are required under the Public Notification Rule. All community water systems that operate year-round must provide a CCR by July 1 each year. Although much of the CCR’s mandated contents are educational information on risks associated with drinking water, there are some components that may be of use to public health researchers. The susceptibility of the source water to contamination, as determined by a source water assessment, must be included, along with directions for acquiring a copy of the assessment itself. Any regulated contaminants that were detected in the water system in the past year must be reported with the level (or range) of contamination and the MCL. Systems must also provide a report of their compliance with all applicable rules. Individual states may have additional requirements for the CCR.

CCRs must be publicly available. EPA encourages water systems to post their CCRs online; however smaller systems may use alternate distribution methods, such as printing it in the newspaper or mailing it to customers. A search tool is available on the EPA website (EPA 2016a) that provides links to electronic CCRs and contact information for water systems that do not post their CCRs on the web.

UTILITIES

Utility Data Requests

Utilities collect water quality data for regulatory compliance and for optimizing system operations. As discussed in Chapter 2, utilities collect system operation data such as pressure, flow, flushing frequency, and main breaks, as well as physical, chemical, and biological water quality data. Some utilities may also keep a record of customer reports or queries about water quality problems. The compliance data from the utilities are public and available through quarterly and annual reports submitted to regulatory agencies. The data that are used to guide and improve system operations are not public, but they can be requested from the utilities for the purpose of research. The non-public utility data may be considered confidential business information so an agreement on data publicity may be required. A general approach for research institutions is to develop and agree on a mutual data sharing agreement by which the utilities can share data but may also request research data and findings from the institution it is collaborating with. If managed properly, this arrangement of data sharing can potentially lead to benefits for both parties. Research institutions will have access to restricted data to refine their studies, and utilities will benefit from research outcomes that may assist them in improving their operations. An example of this is the use of hydraulic model data provided by water utilities in the City of Atlanta to estimate water residence times that was used in epidemiological analyses by Tinker et al. (Tinker et al. 2009).

SCADA/Historian

Most public water systems use SCADA to manage their operations. In addition to real-time operations, SCADA systems function as data archives, particularly when paired with Historian software. Archived data may include scheduled and unscheduled operations (e.g. flushing, valve operations), remote sensor data (e.g. pressure, flowrate, TOC, etc.), and system layout and features. Researchers can request access to SCADA records through the utilities. Because the data archived


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by SCADA is not under regulatory authority, there is great variation in the type and quality of data across systems.

INDUSTRY GROUPS

AWWA's Waterstats 2002 Water Utility Distribution Database

AWWA has compiled an extensive database with information on water distribution systems in the U.S. and Canada. It includes information on 337 small, medium, and large drinking water utilities that were surveyed in 2002 and 2003. The data includes water system characteristics such as utility information, pipe material, valves, fire hydrants and flushing, finished water storage facilities, water conveyance, corrosion control, customer metering, customer service lines, water supply auditing, leakage management, and infrastructure. This database was created to assisting decision makers in utilizing best practices and managing water distribution systems more efficiently. This database is available as a CD-ROM from the AWWA store (AWWA 2016a).

“The Partnership for Safe Water has now, in place, a distribution system optimization program. The Partnership for Safe Water was originally designed to have the water industry develop a response to Cryptosporidium; a best practice for control during treatment. It's been running for over twenty years on filtration plants. Now they've developed a newer program for distribution systems with a standardized way of collecting and reporting data on pressure and chlorine residual, and other aspects of the water distribution system. … They have been agreed upon by a group of utilities to say that these are the right data to collect, this is the way to collect it and report it; now utilities are signing up to be part of this program so there will be a learning phase. But the point is that good data will be available to support other studies.” – Gary Burlingame


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CHAPTER 4 INTEGRATION OF DISTRIBUTION SYSTEM MODELS INTO PUBLIC

HEALTH RESEARCH

Computer models of drinking water distribution systems have become a critical tool for operating and maintaining water distribution systems. Utilities use hydraulic models for a variety of purposes, including determining production needs under a variety of conditions, assessing their fire flow capability, identifying pressure zones, and identifying vulnerabilities within the system. These hydraulic models can be extended to allow estimation of many water quality measures associated with public health, such as water age, disinfectant residuals, and concentrations of disinfection byproducts. However, public health research has been slow to embrace the utility of these models in informing study design and interpretation. Properly incorporated models can identify optimal sampling locations and times, facilitate comparisons of hypotheses, and assist researchers in interpreting study results.5

This chapter includes a brief introduction to the basic concepts and terminology of

distribution system models. This is not intended as a primer for developing models, but rather will give the reader sufficient understanding to work effectively with modelers and incorporate modeling results into their studies. To that end, specific issues researchers may encounter when incorporating models will be discussed. Finally, examples of public health studies that illustrate the use of water models will be reviewed. Unless noted otherwise, the information in this chapter is derived from the AWWA publication Computer Modeling of Water Distribution Systems (AWWA 2012) and Comprehensive Water Distribution Systems Analysis Handbook by Boulos, Lansey, and Karney (Boulos et al. 2004).


“I think whenever you're going to do something in the distribution system, it needs to be tied to hydraulics models. How it can be used to support planning, design and implementation are critical. … The exact measure in water quality parameters and indicators depends on the nature of the contamination and the nature of the risk you're trying to understand. That's why I advocate model it, understand it, understand exposure, and then once you have a really good understanding of the model and what drives the model, then you can design the monitoring program around that. But we almost always do it the reverse.” – Mark LeChevallier “Hydraulic and water quality models should be used to support planning design implementation. I personally wouldn't go in and do a study if I couldn't get a water quality model running first.” – Steve Via


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BASICS OF COMPUTER MODELING OF DISTRIBUTION SYSTEMS

All computer modeling of distribution systems begins with a hydraulic model. In its simplest form, a hydraulic model defines the water inflows and outflows of a distribution system and the paths that the water will take through the system. Hydraulic models can be static, capturing a snapshot of the distribution system in time, or dynamic, modeling the change in the system over time. Water pressure, or head, is the key parameter of interest in hydraulic models, as it is the driver of water movement through the system.

Water quality models are built upon hydraulic models and allow the tracking of discrete units of water through the distribution system. Any compound carried in the water can be followed through the system, both temporally and spatially. The models also account for mixing of water at pipe junctions. This quality can be used to assess the extent of water mixing within the distribution system when there are multiple sources. Further, reaction kinetics can be assigned to the compound of interest and linked to the underlying hydraulic model. This linkage allows simulations of formation and decay as the compounds move through the distribution system. Because transport is an integral component of water quality models, these models are usually focused on change in the system over time.

To encourage the use of computer models, EPA released the EPANET software package. This software is designed specifically to model hydraulics and water quality in piped water systems. The Multi-Species Extension (EPANET-MSX) allows complex water quality models, following multiple reactions simultaneously. EPANET and EPANET-MSX can be downloaded free of charge at (EPA 2016d). Other extensions and plugins are available that allow EPANET to interface with commonly used GIS and drafting programs, such as ArcGIS and CAD.

Creating an accurate network model of the distribution system is a major project for any utility. Data on the distribution system facilities, operations and demand must be collected, often from many sources, and checked for accuracy and completeness. Converting this data into a functioning network model requires a specialized skill set. Large utilities may have a dedicated modeler on staff to build and maintain their models, but many utilities will contract with an outside company to build the model. It is reasonable to expect that most utilities will have a hydraulic model, but policies on sharing these models will vary. Not only is a distribution system model a large investment of time and resources, the network map contains potentially sensitive information and public release beyond the utility may present a potential security risk for the utility. Some utilities will release the model in its entirety to researchers. Other utilities may want to be more engaged in the project and will only release the results of a model simulation. Public health researchers should be sensitive to the utility’s needs when requesting and working with these models, and presenting the results of their studies.

Components of a Hydraulic Model

Hydraulic models have three components: infrastructure and facilities, operations data, and water demand. Infrastructure includes all of the unchanging mechanical components of the distribution system and is a constant in the model, while operations data and water demand are

“One aspect is building the model. The additional aspect, which is very important, is keeping the model continually updated, and that's a big effort. Lots of systems might build a model and then not keep it updated, and then you have to wonder, when it's time to use it, how reliable is it going to be?”– Gary Burlingame


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variable. Nodes are points within the system where water can enter or leave the system and can be thought of as the “sampling points” within the model. All output data from the model will be reported in relation to a specific node or nodes.

The system infrastructure and facilities are represented as a scale diagram of the mechanical components of the distribution system. The network of pipes is represented as a series of path lengths connected by nodes. Each section of pipe is assigned a physical length, diameter, and roughness factor. The roughness factor is an estimate of the flow characteristics through a pipe, and it can be estimated from the pipe diameter, material, and age. There are no changes in parameter values across the length of a pipe section, only at nodes joining two different pipes. ‘All pipes’ models have a representation for every physical pipe in the distribution system, regardless of how small or short or whether it is a dead-end. In contrast, ‘skeletonized’ models remove the pipes considered non-essential for the desired analysis, often the smaller service lines. Although all pipes models are necessary to get detailed information on the entire service population, they also have increased uncertainty and are more difficult to calibrate than skeletonized models. Pumps, valves, storage tanks, and reservoirs are also represented in the network model, along with parameters defining their hydraulic capacities.

Because most distribution systems are at least partially dependent on gravity for water transport, the elevation of system components must be included in the network model. Each node is assigned an elevation, as are all pumps, valves, tanks, and reservoirs. Pipe elevations are inferred from the elevation of the nodes at each end of the segment. Thus, it is possible that long lengths of pipe may have high or low points that are not represented in the network model.

Operations data are the variables which are under the control of the facility operator, such as pump speed, valve position (i.e. open or closed), flow rate through a pipe, water level in a storage tank, and water pressure. These variables can be programmed to respond automatically to changes in the model, mimicking the control logic and set points in a SCADA, system or the modeler can adjust each variable independently. The values assigned to these variables should be within the range seen in normal operations of the system being modeled.

To accurately model water flow through a distribution system, the model must include data on the volume of water flowing into the system (production) and water leaving the system (demand). Production data is readily available from the utility and is simply the volume of water entering the distribution system from the treatment facility. Demand data is less clear cut, and there are many approaches to allocating demand across a model. In all models, each node is assigned a demand profile that describes the pattern of water loss from the system at that point. The simplest approach is to equally allocate demand across every node. However, demand varies by customer type (i.e. residential, commercial, industrial), time of day (diurnal variation), time of year (seasonal variation), and population density, among other variables. Demand allocation schemes have been developed to address each of these issues, and the level of detail varies greatly. In some cases, demand is assigned in blocks, with all of the nodes in a block having equal demand allocations. In the most detailed models, every node has a unique demand profile; however, this approach is only practical for small networks. The choice of demand profile and allocation is dependent upon the research question for which the model is being used, the available data describing the distribution system being modeled, and the acceptable level of complexity in the model itself.

There are two types of hydraulic simulations: steady state and extended period. Steady state models are static representations of a distribution system after all inputs or changes have stopped. Although an actual distribution system will never reach steady state, these models can be useful for determining flow rates, system capacity and water pressures. Extended-period simulations


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model the behavior of the system over time, generally one or two days. These simulations link a series of steady state simulations each representing a discrete time period, with the output from the first simulation serving as the input for the next. A less common type of hydraulic model is a transient model, which simulates very rapid changes in pressure within the system. The time range on transient models is a few seconds to a few minutes.

Components of a Water Quality Model

Water quality models are built upon a hydraulic model, as described above. The model itself is a series of linear equations describing fluid transport or chemical or biological reactions. For steady state solutions of water quality models, these equations are applied to the initial values at each node, and the results are presented for each node. For extended period simulations, the water in each pipe is divided into segments, and the model equations are applied to each segment individually. At each time step, the segment of water with the values calculated by the model is advanced through the pipe system according to the results of the underlying hydraulic model. The resulting conditions are used as the input for the next time step. The time scale of water quality models is generally a few minutes to a few days, depending on the speed of the reaction of interest and the underlying hydraulic model.

Water quality models are based on four assumptions. 1) A segment of water and any substances dissolved or suspended within it moves through

the pipes as a discrete unit. There is no mixing along the length of a pipe, nor is there any dispersion of solutes. This property is called advective transport.

2) When two water flows merge, such as at a pipe junction, the water mixes completely and instantaneously. The outflow from a pipe junction is simply the average of the inflows weighted by their flowrates.

3) The contents of storage tanks are completely mixed. The concentrations of a given compound within the tanks can change due to inflow or reactions within the tank, but there are no gradients within the tank. More advanced models will divide the tank contents into compartments, with each compartment completely mixed and allowing exchange between the compartments to simulate dispersion.

4) Chemical and biological reactions can occur as a substance moves through a pipe or within storage tanks. The parameters and kinetics of the reactions are dictated by the substance being modeled and whether the reaction occurs in the bulk liquid or along the interface with the wall. Models can simulate the formation of compounds (e.g. THMs), the decay of compounds (e.g. chlorine residual), the reaction of contaminants (e.g. chlorine and TOC reacting to generate HAAs), as well as the growth or inactivation of microbial contaminants. Conservative compounds are those that do not undergo any reactions.

These assumptions are necessary to limit the mathematical complexity of the model, but

they also limit the applicability of the model results. For example, models of intrusion events cannot simulate the longitudinal dispersion of the contaminants. In this case, the duration of risk may be underestimated and the concentration of the contaminant may be overestimated. Likewise, instantaneous mixing can complicate interpretations of water age. Assuming the flowrates are equivalent, the merging of a 50-hr flow with a 100-hr flow results in a 75-hr flow. Whether or not this is an accurate representation of the risks associated with water age is unknown.


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Calibrating and Validating a Distribution System Model

Once the model is built, it must be calibrated and validated to ensure that the model results represent the behavior of the distribution system as accurately as possible. Calibration is an iterative process of assessing the model results for reasonableness, making adjustments to the model design and/or input parameters, and repeating the simulation. The goal of this process is to refine the model such that input and output parameters are as close as possible to the actual values measured in the distribution system. The results of the calibrated model are compared to operational data and distribution system field tests, such as tracer studies and disinfectant residuals. The model is validated if the model results approximate the available data. There are no general guidelines for determining a reasonable value for an input parameter, nor an acceptable variation from the field data. The degree of accuracy required in a model is determined by the modeler and the intended purpose of the model.

There are many parameters that can impact the validity of a distribution system model, but they generally fall into one of four categories: model skeletonization, network infrastructure, demand allocation, and reaction kinetics. Even in a properly calibrated and validated model, these factors can and do impact the accuracy of model simulations. Public health researchers should consider the potential impact of each of these limitations on their study when choosing a model and when interpreting the results of the model.

The degree of model skeletonization will always influence the validity of model results. A highly skeletonized model is by definition missing a substantial amount of the data in the distribution system. This is especially important if the researcher is interested in distribution system effects at the household level, where there may be many feet of pipe between the point of interest and the modeled network. Alternatively, all pipes models can be difficult to calibrate given the increased level of noise in the system. These models may be less stable or less accurate than a skeletonized model. Thus, an all pipes model prediction at the household level may have so much uncertainty that it is not possible to document a public health effect.

Errors in distribution system infrastructure are common causes of model calibration and validation issues. It is unlikely that the utility will have completely accurate records of their facilities, including pipe materials, diameter, age, and condition. Since these parameters are required for the model, assumptions are often made to facilitate model construction. Common errors are missing or extra pipes, previously unknown cross connections between systems, incorrect roughness factors, valves in the incorrect position, and incorrect pump settings. Because it is difficult to assess many of these features in the field, especially pipe characteristics, modeling can be used to identify errors in the utility’s infrastructure documentation. Researchers should consider the potential impact of infrastructure errors whenever a model is employed; however, such errors are more likely when the distribution system is very old and documentation may be incomplete, or the model is old (> 5 years) and does not capture recent changes to the system.

Unrealistic demand allocation can result in invalid model results. In order to build a model, assumptions must be made about location, magnitude, and timing of water demand. Even in very detailed models with unique demand profiles for each node, the node demand may be a composite of multiple customers at that node. Models must also account for loss, a demand for which there is typically little to no data for comparison. Since loss due to leaks is related to intrusion risk (Kirmeyer et al. 2001), inaccurate allocation of this demand will result in uncertainty in the model’s predictions. Public health researchers should review the demand allocation used in their model to ensure that it is reasonable for their study question and study population. For example, it may be acceptable to equally distribute demand in a model of a small, primarily residential


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distribution system. However, a study of household health effects in a distribution system with many industrial consumers would benefit from a model with block allocation by customer type.

In water quality models, the equations specifying reaction conditions must represent the actual kinetics as closely as possible. Reaction kinetics are based on laboratory studies examining the processes under controlled conditions (for example, (Gallard and von Gunten 2002, LeChevallier, Evans, and Seidler 1981, Wan et al. 2013, Wang et al. 2013). However, these controlled conditions rarely, if ever, exist in the distribution system. Additionally, there can be interactions between components of different reactions that are not modeled. For example, a model may account for chlorine decay due to interaction with organic compounds and the inactivation of bacteria due to chlorine, but not the increase in organic compounds due to bacterial metabolism. As a result of these inaccuracies, the results of water quality models are often interpreted in terms of relative value and trends across the distribution system instead of specific values.

INCORPORATING DISTRIBUTION SYSTEM MODELS INTO PUBLIC HEALTH STUDIES

All of the experts interviewed for this manual agreed that computer models can greatly improve the quality of studies of health effects related to water distribution systems. Since most health impacts from distribution systems are small, rare, and/or transient, it can be difficult to capture the effects in a study that is limited in scale, both temporally and spatially. Modeling can increase the chance that a researcher will be able to document these events by identifying locations and times that such events are most likely to occur. Models can also be used to interpret study results by providing additional data on characteristics that are difficult to measure, such as water age. Finally, models can allow virtual experiments on a system-wide scale that would otherwise be impossible. Examples of each of these uses are described below.

Using Models to Determine Sampling Sites

Identifying appropriate sample collection locations and times for a health effects study should be based on data about the exposure of interest. For drinking water distribution systems, each exposure event is unique and risk is highly skewed with most exposures presenting very little risk and only a few exposures presenting significant risk. Thus, collecting samples from the distribution system to assess risk parameters has been equated to searching for a needle in a

Figure 4.1. Nodes with an average water age greater than 100 hrs. Output from a utility distribution system model used to estimate water age. Only nodes with average water ages greater than 100 hrs are shown as a heat map, with red indicating the nodes with the highest water ages. Circles indicate significant spatial clustering.


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haystack. Well-calibrated models can be used to identify areas that are most at risk for loss of water quality. By focusing on these areas, public health researchers can reduce both the number of samples necessary to see an effect and the variability in their results. The EPA developed the Threat Ensemble Vulnerability Assessment – Sensor Placement Optimization Tool (TEVA – SPOT) for water utilities to “optimize the number and location of contamination detection sensors so that economic and/or public health consequences are minimized (EPA 2017e).

As part of the research study that accompanies this manual, Kirby et al. (2017) used a water quality model to identify regions of the distribution system with high water age (e.g. long residence time). The goal of the study is to assess the microbial water quality in segments of the distribution system that are vulnerable to loss of water quality. The utility’s distribution system model was used to determine water age throughout the system. Nodes with water ages greater than 100 hours were mapped (Fig. 4.1) and sampling points nearest these nodes were identified. The final selection of a sampling site for microbial analysis was based on the proximity to a high water age node and the availability of facilities for the sampling equipment. Although the nodes with the highest water ages tended to be most distant from the point of entry, distance alone was not a good predictor of water age. Without a model, the risk of misclassification in sample site selection (e.g. selecting a site for increased water age that actually had moderate or low water age) would have been substantial. Although using a model does not eliminate the possibility of misclassification, it reduces it considerably.

Using Models to Interpret Study Results

Even in a carefully designed distribution system study, there are many variables influencing the results. The complex interactions within the system can lead to results that are difficult to interpret. Computer models can be used to better understand such complicated datasets. Additional data from the model results, such as chlorine residuals or water age, may provide insight into the underlying phenomena. Models can also be used to test possible study interpretations to examine whether they make sense within the distribution system framework.

Tinker et al. (Tinker et al. 2009) analyzed the spatial distribution of emergency department discharges for gastrointestinal illness. The frequency of discharges was compared to water age estimated from distribution system models. With the added data from the models, a meaningful correlation could be found between the distribution of discharges and the water distribution system. Zip codes with increased average water age also had higher rates of gastrointestinal illness. Further, the models did not predict lower chlorine residuals in the zip codes with the highest water age, supporting the hypothesis that the risk attributable to increased water age is due to an increased risk of intrusion, not loss of disinfectant residual.

Using Models to Simulate Distribution System Events

Experimental studies in drinking water distribution systems are technically challenging, if not impossible. Barriers include consumer safety, consumer perceptions of risk, and the sensitivity of the analysis at large scale. Computer models of distribution systems provide a method to perform these experiments. Although these studies require an experienced and dedicated modeler, they are presented here to demonstrate the capabilities of model simulations.


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Teunis et al. (Teunis et al. 2010) used a combination of several models to estimate the risk

of illness associated with a transient intrusion event. The study was based on a hydraulic model for an existing distribution system. The average size of pipe leaks (e.g. pore diameter) was calculated by equally distributing water loss across all nodes and determining the pore size necessary to account for the loss. A surge model was used to simulate pressure transients in the distribution system and identify nodes at risk for pressure loss and intrusion. This information was then used as input into a water quality model. To simulate an intrusion, the nodes susceptible to intrusion had an initial positive concentration of virus representing the intrusion, while all other nodes had a virus concentration of zero. Virus transport was simulated over a 24-hr period, with and without system-wide chlorination. The final virus concentration at all nodes was used in a quantitative microbial risk assessment to determine the risk of illness associated with water consumption from each node. Somewhat surprisingly, the study suggests that the duration of the intrusion event, not the input virus concentration, is the primary determinant of health risk. This study was extended in Yang et al. (Yang et al. 2011) to further define the parameters influencing the health risk associated with intrusion.

Utilities are increasingly concerned with protecting their drinking water systems from potential biological or chemical attacks. Since this scenario cannot be tested in an actual distribution system, Nilsson et al. (Nilsson, Buchberger, and Clark 2005) used computer models to simulate an attack and assess the efficacy of different responses. In this case, the attack was simulated by using a model of a chlorine booster system to inject the contaminant at a single node over the course of the first 6 hrs in a 55-hr simulation. To account for the variability in water demand, a program called PRPsym was used to generate stochastic water use profiles for each node in the system. For each scenario, the models were run 1,000 times and the results were averaged. The study found that, during the early phase of the attack, the contaminant accumulated in a storage tank. The effect of the attack could be reduced by half simply by placing a sensor in the tank and setting it such that a trigger cued the tank to fill completely and not release, acting as a sink for the contaminant.

“We now have in Philadelphia an all-pipes hydraulic model. All of our pipes are in the model. It helps our engineers understand the system. Though, it's not necessarily telling you what's really happening. It's telling you what would be expected to happen. So, we went back and looked at all of our total coliform repeat sampling sites. If we were to have a positive sample, we would go five upstream, five downstream, and collect repeat samples. We found that some repeat locations were not even in the upstream or downstream flow of the water. Some downstream were instead upstream. And this might depend on the time of day. Even in Philadelphia it wasn't until we had this hydraulic model that we could go back and better understand where water is flowing in our system and how that works at night time and day time and on weekends.…So there's still a lot that water utilities have to learn about their systems.” – Gary Burlingame


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CHAPTER 5 EPIDEMIOLOGICAL STUDIES OF DRINKING WATER DISTRIBUTION

SYSTEMS AND HEALTH

Epidemiologic studies can play an important role in ensuring the safety of drinking water in distribution systems by increasing our knowledge of the risk factors that lead to water contamination after treatment. 6 Drinking water can become contaminated with a variety of hazardous agents: enteric microbial pathogens from human or animal fecal contamination (e.g., noroviruses, E. coli O157:H7, Cryptosporidium), aquatic microorganisms that can cause harmful infections in humans (e.g., non-tuberculous mycobacteria, Legionella), toxins from aquatic microorganisms (such as cyanobacteria), and several classes of chemical contaminants (organic chemicals such as benzene, polychlorinated biphenyls, and various pesticides; inorganic chemicals such as arsenic and nitrates; metals such as lead and copper; disinfection byproducts such as trihalomethanes; and radioactive compounds) (National Research Council 2006). Understanding how these contaminants enter or persist in the water distribution system and the public health impact of these events can lead to better policies and practices to prevent threats to water quality and health.

Contamination of the water distribution system can result from intrusion of microbes as a result of pressure loss or leaks caused by maintenance work or mains breaks and/or from formation of biofilms in pipes. Human exposure to contaminants in drinking water can occur through ingestion of contaminated water, inhalation of droplets containing respiratory pathogens (such as Legionella or Mycobacterium), or volatilization of chemicals such as disinfection byproducts (Jo, Weisel, and Lioy 1990, Shepherd, Corsi, and Kemp 1996).

The Waterborne Disease and Outbreak Surveillance System (CDC 2016e) collects and reports data related to occurrences and causes of waterborne disease outbreaks associated with drinking water, recreational water, and other nonrecreational waters. This is the primary source of data on the magnitude, scope and health effects of epidemic waterborne disease in the United States. Recent data from this surveillance system reports on outbreaks between 2009-2010 and includes 33 outbreaks (in 17 states) associated with drinking water that caused 1,040 illnesses, 85 hospitalizations (8.2% of cases), and nine deaths. Of the 33 drinking water-associated outbreaks (both acute GI illness and acute respiratory illness); 19 (57.6%) outbreaks were associated with Legionella, six (18.2%) with other bacteria, three (9.1%) with parasites, two (6.1%) with viruses, two (6.1%) with both bacteria and parasites; one (3.0%) with a chemical. Premise plumbing was associated with 19 (57.6%) outbreaks (all Legionella outbreaks), and distribution system deficiencies accounted for five outbreaks (15.1%; three in unchlorinated systems and two resulting from cross connections between potable and non-potable water pipes) (CDC 2013). Identification of the deficiencies implicated in drinking water outbreaks and efforts to correct these deficiencies may prevent future outbreaks and illness.

Outbreaks of waterborne disease represent only the disease events that impact a large enough number of people at once to be detectable by public health agencies and do not represent the endemic burden of waterborne disease in the population. This endemic disease can be evaluated through epidemiological studies. The public health burden resulting from contamination of water



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in the distribution system has been considered significant enough to require research studies for further evaluation of the risk. Several studies have focused on the link between waterborne disease and the drinking water distribution system.

RELEVANT EPIDEMIOLOGICAL STUDY DESIGNS

Both epidemiological studies and risk assessment have been used to characterize the human health risks associated with drinking water distribution system. Here we focus on epidemiological studies that collect empirical data on the relationship between exposures and disease in actual populations. Epidemiological studies can be descriptive, using population surveys or systematic disease surveillance (monitoring) to describe disease patterns by various factors such as age, seasonality, and geographic location; correlational (also called “ecologic”), using population level data on disease rates to look for correlations with exposures; or analytical (experimental or observational), using individual-level data to test a formal hypothesis about the association between exposure and disease (National Research Council 2006).

Analytical studies may be experimental, such as a randomized controlled trial where disease rates are compared between groups of individuals who drink water directly from the distribution system versus others who drink water from another source, such as bottled water or water treated with a filter. In randomized controlled trials, the participants are randomly assigned to a specific drinking water group, and bottled water or a water treatment device is usually provided by the study in order to control the quality of the water ingested by the comparison group. The random assignment helps ensure that other “confounding” factors that may contribute to risk of illness (such as immune status or diet) will be evenly distributed between the experimental groups. Randomized controlled trials are considered to be the strongest research design to examine the causal relationship between water quality interventions and health outcomes because they are prospective in nature and control for the many confounding factors that may affect risk of illness. One concern about using this design for studies of drinking water is that the study participants are often aware if they are in the group that is drinking tap water directly from the distribution system or in the group that is drinking water that receives some additional treatment, and this awareness may bias their report of health effects. Some investigators have sought to mitigate this bias by “blinding” study participants to their exposure status, for example, by placing water filters in all the study households, but half of the filters are actively providing water treatment and others are visibly identical “sham” devices that do not affect water quality (Colford et al. 2005). Another approach to reduce bias in health outcome measures can be to use objective measures of health outcomes, such as measuring change over time in antibody titers to specific enteric pathogens, rather than subjective, self-reported symptoms of gastrointestinal disease. Other disadvantages of randomized control trials are that they are more expensive than observational studies, and it can be challenging to recruit normal, healthy subjects who are willing to participate in a study that may require a change in their lifestyle and keeping records of their health and relevant exposure behaviors (such as travel). Careful sample size estimations are necessary to ensure that the study has sufficient statistical power to detect what may be very small differences in health effects between the group that drinks distribution system water and the comparison group.

One design variation of a randomized controlled trial that has been used in studies of distribution water (e.g., Colford et al. 2005, Lambertini et al. 2012) has been the case-crossover design where mid-way through a trial with a longitudinal cohort, the assigned water group for the participants is switched and those that were drinking tap water without additional treatment in the first half of the study start drinking tap water with additional treatment or bottled water, while


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those who were drinking water with additional treatment start drinking tap water directly from the distribution system. One advantage of the crossover design is that the possible effect of confounders (other risk factors for disease or exposure) is reduced because each participant serves as his or her own control. In a non-crossover study, even though the participants are randomized to the different water groups, it is still possible that some factors that may contribute to risk of disease or risk of exposure may not be equally distributed across the different groups. Another advantage is that crossover designs are statistically efficient and so require fewer subjects than non-crossover designs.

Analytical studies may also be observational, in which groups with different exposures are compared, such as groups who drink water from two different water utilities. Observational analytical studies may be further divided by study design: cross-sectional studies examine exposure and disease rates in individuals during a single period of time; cohort studies follow two groups with different exposures over a period of time and compare their rates of disease; case-control studies compare exposure in groups with and without disease.

Time-series studies are another type of observational design that has been used to examine variation in water quality over time in relation to variation in disease occurrence. In these studies, repeated measures of water quality characteristics, such as turbidity or chlorine residual, are compared to trends in health outcomes, such as emergency department visits for acute gastrointestinal illness (Schwartz, Levin, and Goldstein 2000, Schwartz, Levin, and Hodge 1997, Tinker et al. 2010) or anti-diarrheal drug sales (Beaudeau et al. 1999), in order to determine if there are temporal associations between water quality and health outcomes in the population that is served by the water system. Several time-series studies have reported significant positive associations between water quality measures and healthcare (or medication) utilization for gastrointestinal illness (Beaudeau et al. 1999, Schwartz, Levin, and Goldstein 2000, Schwartz, Levin, and Hodge 1997, Tinker et al. 2010). These studies have the advantage of being relatively low cost because they analyze existing data sets, they can examine multiple water quality parameters and multiple health outcomes, and they consider the temporal order of events (i.e. does a rise in emergency department visits for gastrointestinal illness follow a spike in water turbidity or a drop in chlorine residual in distribution system water). However, time-series studies provide population-level results and cannot consider the effect of individual drinking water habits or other behaviors that may modify the strength of the association between water quality and health outcomes. Time-series studies rely on data that was not originally collected for the purpose of epidemiological research and may not be ideally suited for the analyses, and these also need to consider the many factors that impact the lag time between the measurement of the water quality parameter and the reported health outcome of interest.

Further discussion of the advantages and challenges associated with these different study designs is provided in Chapter 6 of this manual.

A number of epidemiological studies have investigated the association of acute gastrointestinal illness with drinking tap water. Acute gastrointestinal illness is the most commonly studied health outcome in epidemiological studies of drinking water because of concern about the potential presence of enteric pathogens from fecal contamination of drinking water supplies or distribution systems. A few studies have examined specific enteric infections, such as endemic cryptosporidiosis, campylobacteriosis or giardiasis (reviewed in (Craun and Calderon 2006)). The advantages and disadvantages of measuring gastrointestinal illness and other possible health outcomes are discussed in Chapter 6. Epidemiological studies of drinking water and health have been conducted across a range of diverse locations, with major differences in source water


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conditions, treatment approaches, populations served, and age and condition of the distribution system. Two recent meta-analyses have reviewed studies of drinking water and acute gastrointestinal illness (Ercumen et al. 2014, Murphy et al. 2014). Their findings, conclusions, and recommendations are summarized below.

The systematic review and meta-analysis by Ercumen et al. focuses specifically on studies of water distribution system and gastrointestinal illness (Ercumen et al. 2014). The investigators included 20 studies in the review and 14 studies in the meta-analysis. Studies were categorized using the scheme illustrated in Figure 5.1.

The first basis of classification was whether or not the study included point-of-use

(POU) treatment of the tap water or whether there was a recognized deficiency in the distribution system. Distribution system deficiencies were further categorized by breach of physical integrity (cross connections, leaks, age-related pipe deterioration), hydraulic integrity (pressure loss), or water quality integrity (lack of adequate disinfection residual). The studies with POU treatment were sub-classified on the basis of whether there was evidence of malfunction in the distribution system.

The authors identified a total of six studies that included POU treatment; five of these studies were in countries classified as high-income economies (World Bank 2016, Colford et al. 2002, Colford et al. 2005, Hellard et al. 2001, Payment et al. 1991a, Payment et al. 1997). Three of these studies were “blinded” (those conducted by Hellard and Colford), meaning that the study participants were not aware of whether the water treatment device in their household was functional or a visibly identical “sham” device that did not affect water quality. Gastrointestinal symptoms were self-reported through diaries. The two nonblinded studies conducted in one water system in Canada showed a significantly increased risk of gastrointestinal illness in the households that drank tap water with no additional treatment. The three blinded studies were conducted in three different cities, and none of them showed an association between risk of gastrointestinal illness and tap water consumption.

Six studies assessed loss of physical pipe integrity, and three of these were in high-income countries (D'Argenio et al. 1995, Nygard et al. 2007, Tinker et al. 2009). In the latter three studies, reported physical integrity measures were cross-connections, pipe breaks, and water residence time in the pipes. Gastrointestinal illness was assessed from medical databases or self-reported symptoms. Residence in areas where there were reported cross connections, main breaks or longer

Source: Ercumen et al. 2014. Figure 5.1 Classification of epidemiological studies of distributionsystems and health


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water residence time was associated with higher risk of gastrointestinal illness. The study participants were unlikely to be aware of exposure to cross connections or water residence time.

Nine studies examined the relationship between gastrointestinal illness and loss of hydraulic pipe integrity; five of these were in high-income countries (Fewtrell et al. 1997, Huang et al. 2011, Hunter et al. 2005, Nygard et al. 2007). Data on water outage was obtained either from the water utility or was self-reported by the study participants. The experience of a water outage or pressure loss was presumably evident to the study participants, so they were not considered blinded to their exposure status. All of these studies indicated that there was an increased risk of gastrointestinal illness among the groups that experienced water outages compared to those who did not.

Three studies looked at the effects of low or nondetectable chlorine residuals in the distribution system – despite chlorination at the water treatment facility (Egorov et al. 2002, Semenza et al. 1998, Mohanty et al. 2002). Only one of these studies was in a country with a high-income economy (Russia) where the water system was somewhat similar to those in the US (Egorov et al. 2002). Using a cross-sectional design, the Egorov study reported a significantly increased risk of self-reported gastrointestinal illness in areas of the distribution system with the greatest decline in free chlorine residual and greater distance from the water treatment plant.

Despite differences in study designs, locations, and water systems, the analyses of these published reports indicates increased health risk associated with tap water from distribution systems with deficiencies or challenged source waters. The authors caution that there was evidence of publication bias (studies that showed no health effect may not have been published) and health outcome reporting bias in nonblinded studies. The authors also comment on the complexity of water distribution systems, the multiple risk factors that could compromise water quality at the point of use, and the many challenges of conducting these types of epidemiological studies. Key recommendations for future studies were to 1) Blind study participants to exposure status or using objective health outcome measures that minimize recall bias; 2) Collect more detailed information on the water system, especially at the point of use; 3) Measure microbiological water quality at the water treatment facility and at the point of consumption to differentiate between treatment plant deficiencies and post-treatment contamination in the distribution system.

The systematic review by Murphy et al. had a larger scope than the study by Ercumen et al. and included: studies of methodology to calculate waterborne disease burden estimates; studies to estimate waterborne disease burden; quantitative microbial risk assessments; waterborne disease outbreak investigations; randomized control trials; and studies of endemic waterborne disease (Murphy et al. 2014). This review did not include any additional studies of water distribution systems that were not reviewed by Ercumen et al. (Ercumen et al. 2014). However, the authors did point out key data needs for studies of water distribution systems and health, including the following:

‐ Robust studies that quantify health risks due to distribution system operation and failure ‐ Studies that examine risks associated with different system characteristics or events

(e.g. pipe materials, pipe age, system size, disinfectant residual, loss of pressure) ‐ Studies that examine health effects in vulnerable populations ‐ Studies that examine water quality changes (and pathogen detection) after specific

distribution system events ‐ Studies that characterize the condition of drinking water distribution systems ‐ Studies that characterize distribution system residence times and water age


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Some of the more important and larger studies of water and gastrointestinal illness are discussed in more detail below. Only studies that were conducted in the US and other high-income economy countries (as defined by the World Bank) are included in this review because these are of greatest relevance to the audience of this guidance manual. Studies of water and health in low- and middle-income countries are not included in this manual because the water systems and health risks in these countries are often very different from those in the US, and epidemiologic studies in these contexts may focus on different priorities. It is important to note that there are very few studies that were specifically designed to examine the contribution of the drinking water distribution system to illness.

Measures of Effect

The risk of disease attributable to drinking water exposure is based on comparing the disease rates between groups exposed to different types/qualities of drinking water. Epidemiological studies usually report the ratio of disease rates in “exposed” versus “unexposed” populations. In the studies reviewed below, the “exposed” populations are those who drink tap water without additional household-level treatment, or drink tap water in an area affected by pressure drops, or main breaks, or longer water residence time. If the point estimate and 95% confidence interval (CI) for that ratio are above or below 1.0, this suggests that the exposure is either a significant risk factor or protective factor, depending on the direction. If the 95% CI crosses unity, then the result is usually considered non-significant. We report a variety of these ratios in the review of the epidemiological literature below, depending on the methods used by the study authors.

Review of Important Studies of Drinking Water and Health

The following studies were chosen to illustrate the range of approaches that has been used to examine the relationship between drinking water and endemic health outcomes in high-income economy countries. Several of these studies are considered landmark studies because they were the first of their kind (such as the studies by Payment and colleagues in Laval, Montreal) or the first to test improved study design modifications (such as the blinded studies and crossover designs by Colford and colleagues) and were highly influential in the scientific community. It is important to note that these studies were conducted in different locations with different types of water sources and distribution systems, and many of these studies did not find any significant health risk associated with drinking water.

Household Intervention Studies

Several researchers have conducted intervention studies that introduce an in-home water treatment device to some households but not others in order to evaluate the impact of consumption of tap water on the development of gastrointestinal illness. In these studies, households who drink tap water are potentially exposed both to contaminants in the source water that were not removed during treatment as well as contaminants that entered the distribution system after treatment. The households with the point-of-use treatment should be protected from both source water and distribution system contaminants.

Laval, Montreal (1988-89 and 1993-94). Two studies were conducted by Pierre Payment and colleagues in Laval, a suburb of Montreal. The first examined the impact of reverse osmosis


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filters installed in 299 households for a period of 15 months compared to a control group of 207 households with no device. The group with the filters experienced annual incidence of gastrointestinal illness of 0.50, versus 0.76 in the group without the filters. The authors concluded that 35% of reported illness was attributable to drinking tap water (Payment et al. 1991b). In a follow-up study, the researchers used a randomized prospective study design, comparing 1400 families for 16 months assigned to one of four groups: 1) tap water, 2) tap water from a continuously purged tap, 3) bottled water from the treatment plant, and 4) purified bottled water (treated with reverse osmosis or spring water). The water treatment plant produced water that met or exceeded North American regulations for drinking water quality. However, the source water for the treatment plant was a river with significant contamination from human sewage discharges. The study found an excess of gastrointestinal illness associated with tap water of 14% in the tap water group (17% for children ages 2-5) and 19% in the group with tap water from a continuously purged tap (40% for children ages 2-5). These risks were partly associated with the drinking water distribution system (Payment et al. 1997). The participants were not blinded to treatment group in either of these studies, raising concerns of bias.

Melbourne, Australia (1997-99). Hellard et al. conducted a double-blinded, randomized, controlled trial in Melbourne, Australia, a city that draws drinking water from a surface water source in a protected forest catchment, and the water received minimal water treatment (chlorination only) (Hellard et al. 2001). A total of 600 households received either sham filters or real water filters designed to remove viruses, bacteria, and protozoa. The researchers observed a total of 2,669 cases of highly credible gastroenteritis over a 68-week period (0.80 cases/person/year). There was no difference in self-reported gastrointestinal illness in the control versus treatment group (ratio of 0.99, 95% CI: 0.85-1.15). There was also no difference in the frequency of pathogens detected in fecal samples from the control versus treatment group.

Contra Costa County, CA and Davenport, Iowa (1999, 2000-02). Colford et al. first conducted a small, four-month pilot study of 236 participants in 77 houses in Contra Costa County, CA, to show that participants could be effectively blinded to a sham device vs. a functional water filtration device that included UV light (Colford et al. 2002). The water source in this study was the San Joaquin River that received agricultural and industrial runoff and pathogens. The water treatment plant used standard conventional treatment, however a new ozonation plant was brought online during the study period. The researchers showed that study participants could successfully be blinded to their group assignment, but no difference was observed in gastrointestinal illness between the two groups (Incidence Rate Ratio=1.32, 95% CI: 0.75, 2.33; Attributable Risk=0.24, 95% CI: -0.33, 0.57).

The researchers then conducted a crossover study in Davenport, IA, in which they randomly assigned 229 households to a sham device group and 227 households to a treatment device group receiving a ceramic water treatment filter with UV light (Colford et al. 2005). The water source in Davenport was the Mississippi River – a challenged source with evidence of fecal contamination. However, the water utility was recognized for its excellence, and the conventionally-treated finished water consistently met all state and federal standards for one year prior to the study and during the study period. The study groups used the assigned devices for six months, and then switched to the opposite device for another six months. No difference was observed in rates of gastrointestinal illness between the two groups (Risk Ratio=0.98, 95% CI: 0.86, 1.10).

Sonoma, CA (2001-05). Colford et al. also conducted a randomized, triple-blinded, crossover trial in 714 households of 988 adults age 55 and over in Sonoma County, CA, using


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functional vs. sham water filtration units with UV light for six months each (Colford et al. 2009). The water source in this community were 50-60 foot deep wells, built adjacent to the Russian River, that collected water that had infiltrated through the sand bed beneath the river. The water received chlorine disinfection and met US standards. In this study, reductions of approximately 15% in population- and individual-level measures of gastrointestinal illness were associated with the use of the functional device. This study suggests that drinking tap water may be a risk for sensitive sub-populations.

Community Intervention Studies

In contrast to the household intervention studies reviewed above where a sub-set of the population in the area receive water with additional treatment in their household, in community intervention studies, all the residents of the community receive the water with additional treatment. The advantages and limitations of community intervention trials have been reviewed by Calderon and Craun (2006) and include: 1) Environmental modifications of the water supply may be easier to realize than large-scale changes in behavior. Study participants can drink the intervention water both at home and where they work or go to school. In household intervention studies, investigators ask study participants to take bottles of their household water with them to work or school and not drink other water, but compliance with this request is difficult to measure or enforce. 2) Changing water quality on a community-wide scale allows examination of the reduction in primary waterborne disease as well as associated secondary infections – thus capturing the total impact of the intervention on community health; 3) Community-intervention studies can be logistically simpler and less expensive on a per-subject basis. The major limitation of community-intervention studies is identifying an appropriate comparison group because it is usually not possible to identify and randomize identical communities to intervention and control groups. Some studies have examined the change in health effects before and after a community-level water treatment intervention (see Calderon and Craun 2006), but community health may be affected by other temporal trends that are not related to the change in water treatment. Other studies have attempted to randomize groups of communities with similar socio-economic status, etc. but it is difficult to control for community-level variation in illness.

La Crosse, Wisconsin (2006-2007). Lambertini et al. describe a two-year study of 14 small community water systems that used untreated groundwater (Lambertini et al. 2012). Ultraviolet (UV) light disinfection was installed at the wellhead of the water systems for one year and turned off for the other year using a cross-over design. Water samples were collected monthly at wells and households during four 12-week periods and tested for viruses. Because UV treatment was used, there was no residual disinfectant in the distribution system. Self-reported acute gastrointestinal illness was measured prospectively in 621 households in the 14 communities during four 12-week surveillance periods in the spring and autumn. A Monte Carlo risk assessment approach was used to estimate acute gastrointestinal illness risk from the distribution system. The authors reported that acute gastrointestinal illness risk from the distribution system ranged from 0.001 to 0.1047 episodes per person-year and represented 1.6 to 67.8% of risk related to drinking water exposure.

Observational Studies

Many observational studies have examined the relationship between distribution system events or characteristics and gastrointestinal illness. In these studies, comparisons are made


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between disease rates under different exposure scenarios. United Kingdom (2001-02). Hunter et al. found a strong association between self-reported

diarrhea and low-pressure events at the tap, as observed by consumers, in a postal questionnaire-based case-control study (Odds Ratio (OR) = 12.5, 95% CI: 2.5-44.7) (Hunter et al. 2005). This study was not designed to examine this reported relationship but rather was a study of risk factors associated with cryptosporidiosis. The analysis was performed because of the surprisingly high rate of diarrheal disease (6.6%) in the previous two weeks reported by control subjects.

Norway (2003-07). Nygard et al. conducted a cohort study in Norway in which they compared 600 exposed versus 600 unexposed households after episodes of mains breaks or maintenance work on the water distribution system (Nygard et al. 2007). The researchers found an elevated rate of gastrointestinal illness in the exposed group in the one-week period after such episodes (Exposed Group: 12.7%, Unexposed Group: 8.0%, RR=1.58, 95% CI: 1.1-2.3). The researchers concluded that 37% of gastrointestinal illness in their study region was attributable to these events, which presumably led to pressure drops in the distribution system.

Atlanta, GA (1993-2004). Researchers in Atlanta, GA, used a large dataset of over 3 million emergency department visits, 164,937 of which were for gastrointestinal illness, to examine associations with the drinking water distribution system for two water utilities in metro Atlanta (Tinker et al. 2009). Tinker et al. reported a modest increased risk of gastrointestinal illness for individuals living in the zip-codes with the longest water residence times, as measured by a hydraulic model, compared with zip-codes with intermediate water residence times, after controlling for confounding factors such as patient age and markers of socioeconomic status (OR for Utility 1=1.07, 95% CI: 1.03-1.10; OR for Utility 2=1.05, 95% CI: 1.02-1.08). In additional analyses, Levy et al. examined the association between emergency department visits for gastrointestinal illness and estimated water residence time at the nearest distribution system node to the patients’ residential address (Levy et al. 2016). Comparing long water residence time (>90th percentile) with intermediate water residence time, there was a modest increased risk for gastrointestinal illness (OR=1.07, 95% CI: 1.02-1.13) for one utility that had a substantially longer average water residence time (56 hours). The other water utility had a mean water residence time of around 16 hours and no increased risk of gastrointestinal illness was observed. When the investigators examined 12-hour increments of water residence time, exposures to water with >48 hours of residence time were associated with increased risk of gastrointestinal illness, and exposures to water with >96 hours of residence time had the strongest associations with illness. However, due to small sample sizes at these long times, these associations were not statistically significant. The investigators recommended that water utilities aim to reduce water residence time in the distribution system to <2-3 days and consider adding booster disinfection to areas with long water residence times to minimize risk of gastrointestinal illness from water consumption.

The authors also observed a modest association between raw water turbidity and emergency department visits for gastrointestinal illness using a time-series study design (Tinker et al. 2010).

La Crosse, Wisconsin (2001-02). Borchardt et al. sampled tap water of 14 Wisconsin communities supplied by non-disinfected groundwater for human enteric viruses and examined their relationship with self-reported acute gastrointestinal illness in the community during four 12-week periods (Borchardt et al. 2012). The authors found a positive association between communities and time periods with the highest virus detection and acute gastrointestinal illness and estimated the fraction of gastrointestinal illness attributable to viruses in tap water between 6-22%.


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Gothenburg, Sweden (2007-2010). Malm et al. examined a database of 110,622 contacts to a health call center data in Gothenburg, Sweden, 13-14% of which were for gastrointestinal symptoms, to investigate if calls for gastrointestinal symptoms increased at times of risk of impaired water quality due to disturbances at water works or the distribution network as compared with the number of calls during control periods in the same area (Malm et al. 2013). The researchers examined eight periods of disturbances in the water works (e.g. short stops of chlorine dosing), six periods of large disturbances in the distribution network (e.g. pumping station failure or pipe breaks with major consequences), and 818 pipe break and leak repairs over a three-year period. They found no statistically significant increase in calls due to gastrointestinal illness during or after disturbances at the water works or in the distribution network.

Alabama (2010). CDC researchers examined the health impacts of an event in which approximately 18,000 residents of two predominantly rural counties in Alabama lost access to municipal water for up to 12 days after below-freezing temperatures led to breaks in water mains and residential water pipes and caused widespread systemic mechanical failures. A survey of 1,283 residents in 470 households revealed a significantly higher prevalence of acute gastrointestinal illness among residents of households that lost both water service and water pressure (adjusted odds ratio (AOR) = 2.6), that lost water service for ≥7 days (AOR = 2.4), and that lost water pressure for ≥7 days (AOR = 3.5). They also observed significant dose-response relationships between increased duration of lost water service or pressure and illness (Etheridge et al. 2011).

These results must be interpreted with caution, however, because loss of water affects sanitation, hand hygiene, and food hygiene – all of which are well-accepted risk factors for acute gastrointestinal illness. This investigation began approximately 6 weeks after the onset of the water emergency, and all the information on periods of water loss, pressure loss, and dates of illness were self-reported and subject to recall bias. In addition, there was very limited evidence about the role of distribution system water quality as a risk factor for gastrointestinal illness during this event. No water samples were collected and analyzed to examine whether water quality was compromised.

Cherepovets, Russia (1998-99). Egorov and colleagues carried out several studies of the distribution system and health in the Russian city of Cherepovets (Egorov et al. 2002). Egorov reports on the results of a cross-sectional study to examine how the decline of residual chlorine concentrations in the distribution system affects gastrointestinal illness. The researchers conducted water quality monitoring and surveys with 2069 study participants. An interquartile range variability in free residual chlorine decline (0.22 mg/l) was associated with self-reported gastrointestinal illness after controlling for socioeconomic, hygienic, and demographic factors (RR=1.42, 95% CI: 1.05-1.91). Egorov also reported on a study of 367 individuals from 100 randomly selected families in which an interquartile range of increase in finished water turbidity of 0.8 Nephelometric Turbidity Units (NTU) was associated with significantly increased self-reported gastrointestinal illness (RR=1.57 95% CI: 1.16-1.86) (Egorov et al. 2003).

Taiwan (2004-2006). Huang et al. report the use of a national health insurance database to examine medical visits for gastrointestinal illness, eye, and skin infections (based on ICD-9 codes) during 10-day time periods before, with, and after water outages reported by the Taiwan Water Corporation (Huang et al. 2011). The dates of the outages, locations affected, and reasons for the outages were provided by the water utility. The investigators observed an increase in healthcare utilization during, and in the 10 days following, water outages. The RR for medical visits for gastrointestinal illness was 1.31 (95% CI: 1.26-1.37), visits related to skin problems (RR=1.36;


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95% CI: 1.30-1.42) and visits related to eye problems (RR=1.34, 95%CI 1.26-1.44). This study is unusual in that it examined a range of health outcomes, and all of them were significantly elevated

Vancouver, Canada (1995-2003). Teschke et al. conducted a retrospective cohort study using a large universal health insurance database in a mixed rural and urban community near Vancouver to examine associations between physician visits and hospitalizations for gastrointestinal illness (Teschke et al. 2010). Water supply chlorination was associated with reduced incidence of physician visits for gastrointestinal illness (OR: 0.92; 95%CI 0.85-1.0). Two water systems with the highest proportions of surface water were associated with increased incidence of physician visits (OR: 1.45 and 1.57; 95% CI 1.28-1.64 and 1.39-1.78).

East Anglia and Herefordshire, England (2008-2010). Risebro et al. conducted a prospective cohort study of 611 individuals served by small private water supplies (Risebro et al. 2012). Participants recorded gastrointestinal symptoms for 12 weeks in daily health diaries. Microbiological water quality was measured at the household water tap in samples collected at the time of recruitment and 12 weeks post-recruitment. Coliforms, E. coli, or enterococci were detected in 48% of 268 water supplies and 38% of 536 water samples. Overall, there was no association between incidence of gastrointestinal symptoms and detection of a bacterial indicator in the water supply. However, children under 10 years who drank from a water supply with enterococci contamination had a RR of 4.8 (95%CI: 1.5, 15.3). In older age groups, the elevated risk of gastrointestinal illness was not statistically significant.

Mid-Atlantic Region, United States (2005-2006 City B; 2011-2013 City A). Shortridge and Guikema report an observational study of the weekly number of pipe breaks and weekly internet search volume for “diarrhea” and “vomiting” in two large cities in the mid-Atlantic region of the United States (Shortridge and Guikema 2014). Internet search volume measures the number of searches for the term of interest compared to total number of searches during the week by residents of the metro area. Data on the weekly number of distribution system pipe breaks in each city was provided by the water utilities. For City A, the number of weekly pipe breaks ranged from 3-79 and in City B from 3-56. Using various multiple regression models, the investigators observed that pipe breaks were an important and positively-correlated predictor of internet search volume related to gastrointestinal illness terms.

CONCLUSIONS

These studies showed a range of epidemiological approaches to examine the relationship between drinking water quality and potential endemic health effects. Most of these studies focus on gastrointestinal symptoms. Few studies specifically address the role of the water distribution system or premise plumbing. It is important to note that these studies were conducted in different locations with different types of water sources and distribution systems, and many of these studies did not find any significant health risk associated with drinking water. Yet, data from waterborne disease outbreak investigations indicate that premise plumbing and distribution system deficiencies continue to contribute to epidemic waterborne disease (CDC 2016e), and the role of these deficiencies for endemic health outcomes should be further explored.


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CHAPTER 6 CONSIDERATIONS FOR PLANNING AND IMPLEMENTING

EPIDEMIOLOGICAL STUDIES OF DRINKING WATER DISTRIBUTION SYSTEMS AND HEALTH

This chapter 7 provides practical advice on what to consider when planning and implementing epidemiological studies of drinking water distribution systems and health. Much of the guidance in this chapter was derived from interviews with six internationally recognized experts from the US water industry and academia. Information on the experts and the interview guide is provided in Appendix A. Relevant quotes from the experts are included throughout the chapter. Additional guidance is based on the authors’ experience and reviews of the scientific literature.

WHY CONDUCT AN EPIDEMIOLOGICAL STUDY OF DRINKING WATER DISTRIBUTION SYSTEMS AND HEALTH?

Given the number and range of previous epidemiology studies reviewed in Chapter 5, the reader may wonder if there is a need for further studies. While other types of research can examine changes in distribution system water quality, risk factors for distribution system integrity, and other important questions, only epidemiological studies can actually measure the association between distribution system water and health in the population. Although the level of risk from drinking water distribution systems may be very low, because this exposure is so widespread, it is important to understand what factors drive this risk and how it can be better prevented. Epidemiological studies can address these questions. However, it is important to acknowledge that epidemiological studies can be better designed and implemented if there is supporting research, such as risk assessment and risk modeling, to inform the planning of the epidemiology study.

The epidemiology research team must first decide what is the goal for the study. Our

discussions with experts identified a number of critical research needs that could be addressed by epidemiological studies:


“I think we only have a handful of epidemiological studies, and I think they're all really important. So, I think investment in epidemiological studies is a good investment because it tests the reality… it is like when you develop a budget and you want to go on vacation, you put a little bit aside each month so that eventually after a year or two, you have enough money to go on vacation. I think it's the same thing with epidemiological studies, something you might not want to be spending on every day on your normal budget, but I think it's important to put some aside so periodically we can launch these larger more expensive, but well designed, [studies] to test our understanding.” - Mark LeChevallier


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‐ Determine attributable risk from distribution system deficiencies and different distribution system components

‐ Examine health risks from Legionella in distribution systems and premise plumbing. Legionella in premise plumbing contributed to about 27% of the deficiencies reported in drinking water outbreaks from 2001-2006 (Craun et al. 2010). Legionella is the third most common etiologic agent of reported outbreaks associated with drinking water and water not intended for drinking since 1971 (Craun et al. 2010).

‐ Examine health risks from mycobacteria in distribution systems and premise plumbing ‐ Examine and compare health risks from biofilms associated with new plumbing

materials compared to traditional plumbing materials ‐ Evaluate the impact of new premise plumbing designs to mitigate health risks –

especially in hospitals and other settings with vulnerable sub-populations ‐ Examine health risks from virus exfiltration from sewer lines into water mains in areas

of the distribution system where water mains are near sewer lines ‐ Examine the prevalence of cross-connections and the associated health impact ‐ Examine risk mitigation strategies for main break response and repairs ‐ Examine health risks from distribution systems in small water systems with fewer

resources and capacity ‐ Develop better ways to measure the public health quality of water, develop better ways

to measure health effects and more sensitive measures of health endpoints

CONSIDERATIONS AND CHALLENGES WITH STUDY DESIGN AND IMPLEMENTATION

Study Design

The choice of an appropriate epidemiological study design depends on the research question and the available budget. Any epidemiological study should start with a causal model that diagrams the exposures of interest, relevant health outcomes, and other behavioral, social, and demographic, or environmental factors that affect exposure or the health outcome. Examples of causal models for waterborne diseases are presented elsewhere (Craun, Calderon, and Wade 2006, Eisenberg et al. 2007). Once the causal model has been described, then decisions about specific study questions and study design can be more strategic. Every type of study design has strengths and limitations. Intervention studies (like randomized controlled trials) are usually the most rigorous study design, but also the most costly. Several experts commented on the value of observational studies to generate hypotheses. These types of studies are usually the first step in describing the research problem, but as discussed in Chapter 5, they are limited in their ability to test specific hypotheses. Also, there are many confounding factors (related to human behavior, social and demographic factors, and culture) that must be considered in epidemiological studies of drinking water

“…if money was not an issue in a future study, … I would have a control arm, I would have a parallel arm going the whole length of the study, and I would have a crossover arm as a third arm. So that I can take part of the control, the control will be very large, I would cross part of the control over to the cross over and the rest of the control would be large enough to make the comparisons to the parallel so I can really tease out what’s going on.” – Jack Colford


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and health. Based on the evidence from observational studies, it is possible to design better experimental studies that can test specific hypotheses.

Some experts advise only using randomized controlled trials to examine the most critical research questions. The tremendous advantage of randomized, controlled trials is that this study design controls for the effects of the many confounding factors that are related to water quality and risk of disease. For example, an observational study of gastrointestinal illness in different parts of a city where the distribution system is of better or lower quality may be confounded by socio-economic differences in the different neighborhoods that may affect drinking water behavior, illness rates, and measurement of illness rates. A randomized controlled trial can also be designed to evaluate risks associated with specific components of a water system – such as the distribution system. Another advantage of the randomized controlled trial design is that the research team can to some extent control the drinking water exposure of the different study groups by providing a water treatment intervention to one group and not to the other group. The success of this approach requires good compliance by study participants to drink the water assigned to their study group and not water from other sources (e.g. bottled water) or water that has either received additional treatment or by-passed the treatment device provided by the study. Randomized controlled trials may perform one analysis (intention-to-treat analysis) that assumes that all the participants recruited into the study stayed in the study for the whole study period and only consumed the water assigned to their study group and another analysis (per-protocol analysis) that only includes the study participants that actually completed the study and reported high compliance with the study protocol by only drinking the water assigned to their study group (see (Colford et al. 2005)) and compare the results of these two analyses.

Estimation of attributable risk of a health outcome due specifically to distribution system water exposure (ingestion, contact, or inhalation) and not other exposures requires comparing rates of the health outcome between groups who are “equivalent” to each other in every respect except for their distribution system water exposure. Choosing appropriate comparison groups is a key consideration for studies that are not randomized controlled trials.

Three possible design approaches to specifically examine potential health risks associated with the drinking water distribution system are illustrated in the figures below along with a summary of their strengths and limitations (Figures 6.1, 6.2 and 6.3). Using multiple study designs to address a specific research question gives more information about the plausibility of the results. For example, the studies by Nygard et al. (Nygard et al. 2007) and Malm et al. (Malm et al. 2013) used different approaches for measuring self-reported gastrointestinal illness in Norway and Sweden, respectively, and the studies came to different conclusions about the association between water main breaks or repairs and risk of self-reported gastrointestinal illness. There is also value in replicate studies of the same research question in different locations, with different study populations and different types of water systems as demonstrated by the trials of household water treatment devices in Laval, Canada; Davenport, Iowa; Sonoma, California; and Sydney, Australia.


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Source: Adapted National Research Council 2006 with permission from the National Academy of Sciences, Courtesy of the National Academies Press. Figure 6.1 Household intervention trial with distribution system vulnerability assessment and double-difference analyses.

B Most vulnerable distribution

system areas

Water Treatment Plant

A Least vulnerable distribution

system areas

Tap Water HH

Bottled water HH

vs.

Tap Water HH

Bottled water HH

vs.

vs. A B

HH = Household, Δ = difference in health outcomes between bottled water vs. tap water HHs

Strengths and Limitations

• In each geographic area, study participants are randomized to either the bottled water group or the tap water group

• Study participants are not blinded to the type of water (bottled vs. tap) they are drinking, but they are blinded to the distribution system vulnerability classification of their neighborhood

• This design first measures the difference in health outcomes over time between the study participants who drink bottled water vs. those who drink tap water (e.g. ΔA, ΔB). The study then compares the difference of the difference (ΔA vs. ΔB) to examine how the difference in the incidence of health outcomes compares between the study participants in the least vulnerable areas of the distribution system and the most vulnerable areas. This “double-difference” methodology controls for lack of blinding and is used in economic studies and program evaluations to assess the impact of a specific intervention (Maluccio and Flores 2005)

• Requires a pre-study vulnerability assessment of the drinking water distribution system using existing data on water quality (coliforms, chlorine residual), pipe age and breaks, loss of water pressure, estimated water residence time, etc. to identify geographic areas of the distribution system that are vulnerable to water quality degradation.

• Assumes that geographic areas in the distribution system are accurately characterized as “most vulnerable” and “least vulnerable”

• Requires recruiting adequate sample size in specific geographic areas • Assumes that study participants comply with the drinking water assigned to their study group • Study participants may drink different water at school and work


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Source: Adapted National Research Council 2006 with permission from the National Academy of Sciences, Courtesy of the National Academies Press. Figure 6.2 Household intervention trial with crossover


• Randomized Controlled Trial. Potential confounding factors are randomly distributed between the four study groups

• Investigators control water exposure: one study group receives purified bottled water, one study group receives finished water bottled directly at the treatment plant, and one group receives bottled tap water from the most vulnerable part of the distribution system.

• Study participants can be recruited throughout the city and are blinded to the type of bottled water they are drinking

• Comparison of participants drinking purified bottled water vs. bottled treatment plant water indicates risk from the treated source water. Comparison of participants drinking bottled treatment plant water vs. bottled distribution system water indicates risk from the water distribution system. Comparison of participants drinking purified bottled water vs. bottled distribution system water indicates risk from both the water source and the distribution system

• Cross-over design allows greater efficiency in sample size • Requires a pre-study vulnerability assessment of the drinking water distribution system using

existing data on water quality (coliforms, chlorine residual), pipe age and breaks, loss of water pressure, estimated water residence time, etc. to identify geographic areas of the distribution system that are vulnerable to water quality degradation.

• Assumes that study participants comply with the drinking water assigned to their study group • Study participants may drink different water at school and work • Bottled distribution system water may not capture temporal changes in distribution system water

quality that are associated with health risks. Distribution system water would need to be bottled frequently and may require bottling composite samples over time from multiple areas classified as “vulnerable”

• Bottled water quality may change during storage time—this would need to be measured.

Purified Bottled Water

Bottled TP Water

Bottled DS Water


A B C D

Study Period 1

Study Period 2

Study Group

Bottled TPWater

Bottled DS Water



TP = Water Treatment Plant, DS = Drinking Water Distribution System

Monitor Health Outcomes: Study Period 1 and Study Period 2


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Figure 6.3 Community intervention trial


• Everyone in the community is exposed to the drinking water intervention both at home and at work • Does not require study participants to change their drinking water behavior. • Measuring health outcomes before the intervention captures potential risks associated with both the

water source and the distribution system. Measuring health outcomes after the intervention captures potential risks associated only with the drinking water distribution system. Risk assessment based on measurements of household water quality is used to estimate risks of gastrointestinal illness attributed to the distribution system (see Lambertini et al., 2012).

• Less expensive than a household intervention study. • Some study participants may not drink tap water • Requires careful monitoring of microbiological water quality at the taps of study participants • Assumes that additional treatment at the water source eliminates waterborne disease risks associated

with the source water and that any remaining waterborne disease is associated with distribution system water quality.

• Temporal changes unrelated to water quality may impact the community during the study period and affect the comparison of health outcomes before and after the intervention.


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Study Site

Choosing an appropriate study site depends on the nature of the research question. In most situations, the research question will drive the selection of the study site that has the right set of exposure and population conditions to examine the question. For example, studies of the risk associated with distribution system in small water systems, may require a region where there are many small systems in close proximity to each other to make the logistics of implementing the study more feasible and less expensive. Studies of tap water need to be in locations that do not have taste and odor problems that may drive a high proportion of residents to drink bottled water or install household water treatment devices to mitigate taste and odor problems. Observational studies need locations where there is a range of exposure conditions that may provide an opportunity to compare health outcomes at the extreme ends of exposure—such as short vs. long water age.

In some situations, a potential study site may have a specific environmental hazard that needs to be evaluated for its possible health impact, or a site may be the target of a planned infrastructure intervention—such as the addition of a water treatment process or extensive renovation of the distribution system network. In these situations, the researcher may be able to examine the impact of the intervention on water quality and health outcomes. The timing of such studies needs to allow sufficient data collection before and after the intervention and consider the effect of seasonality and other temporal trends on exposure and outcomes.

Finally, there are outbreak situations where a cluster of cases is recognized in a specific location within a short period of time (if an acute health outcome), and the investigator must determine 1) if the cases are linked to a common water exposure, 2) the risk factors that contributed to the outbreak, and 3) how to control the outbreak as quickly as possible. Outbreak investigations are a special type of epidemiological activity, and guidance for how to conduct these investigations and assistance is available from state health departments and the US CDC (see CDC 2016b).

Study Population

Previous studies of waterborne disease and outbreak investigations indicate that different subpopulations (young children, elderly, immunocompromised) have different susceptibilities to

“My next point is the need for replication. We tend to go out and do these big studies and that's kind of the end of the day. Maybe another study gets done by another group, but maybe not. Then, the instruments change and it's sort of hard to compare them so there really hasn't been rigorous replication of any of the findings that we believe in.” – Jack Colford

“I think probably the most interesting ones [i.e. drinking water epidemiological studies] are where there are natural experiments, and we attempted to do this in City X, Massachusetts where they had a very poor treatment plant that was actually required to upgrade, and we collected some health data and water quality data before and then after the improvement. So, I think taking advantage of these kinds of natural experiments is a really effective way [of] trying to [look] where you are going to have a good chance of observing a health effect … [associated with] a major change in water quality.” – Tim Wade


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infection, risks of severe illness, and likelihoods that their illnesses will be recognized and reported. It seems prudent for studies of drinking water and health to include a high proportion of young children and the elderly in the study population. Previous studies of endemic waterborne disease by Payment et al. in Canada (Payment et al. 1991a, Payment et al. 1997), Borchardt et al. in Wisconsin (Borchardt et al. 2012), and Risebro et al. in the United Kingdom (Risebro et al. 2012) indicate that children are at greater risk of endemic waterborne illness, and one trial by Colford et al. among older adults in California suggested that they may significantly benefit from a household water treatment intervention (Colford et al. 2009). Studies of endemic waterborne disease among HIV-infected patients in California by Eisenberg et al. (Eisenberg et al. 2002) and Colford et al. (Colford et al. 2005) suggest that HIV-infected patients may benefit from always drinking boiled water (cross-sectional observational study) or tap water with additional household treatment (blinded randomized controlled trial). The results of these two studies showed large estimates of effect, but these had borderline significance, probably because of sample size. Recruiting sufficient numbers of HIV-infected patients or other immunocompromised subpopulations into epidemiological studies of waterborne disease may be extremely challenging.

Understanding the drinking water habits of the proposed study population is critical. In addition, understanding where members of the study population spend their time on a daily basis may be an important consideration for exposure assessment. If the study design compares exposure to water in different geographic regions of the distribution system, then study populations who live and work, or go to school, in two or more different areas of a city may be misclassified in terms of their primary exposure, and this greatly reduces the power of the study to detect a difference in health outcomes between the “exposed” and comparison populations. Very young or elderly populations may spend more time near their residences. “Sentinel populations” that are relatively confined to a single geographic location (prison, long-term care facilities, residential college/university campuses) may provide valuable exposure information because the majority of water that they drink may be tap water at one specific geographic location, but these populations may also be impacted by other risk factors for gastrointestinal illness and other diseases because of their living situations.

Building a Study Team

Because waterborne diseases and water distribution systems are complex, epidemiological studies in this field really require a strong, multi-disciplinary study team that includes water engineers, water utility operators and field personnel, hydraulic modelers, laboratory scientists (including environmental microbiologists and possibly clinical microbiologists), epidemiologists, risk assessors, public health authorities, biostatisticians, and communications specialists. Some team members with cross-disciplinary training are helpful in order to facilitate communications across disciplines. It is also critical to develop good working relationships with the relevant

“…a good epidemiological study connects us to our health professionals, and gives us both a reason to work more closely together. As you know, our health agencies are pulled in many directions on things other than drinking water. We need something solid, like Cryptosporidium in the 1990s, in order to bring them to the table to think about drinking water and to work with us on drinking water issues. When you have a solid epidemiological study, I think that is some of the ammunition we need to engage them and to divert some of their resources to work with us even more.” – Gary Burlingame


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stakeholders – the water utility, local and state health departments, and possibly municipal authorities who may use the findings of the study to guide decisions about future investments in distribution system infrastructure. It is helpful to have a written memorandum of understanding about data sharing and dissemination of results that is signed by the relevant parties. Memoranda of Understanding between the collaborating groups should address the right to publish, to review manuscripts before journal submission, possible legal concerns if violations of water quality standards are identified, etc. Some epidemiology studies may take years to complete, and water utility commissioners, health authorities and elected officials or political appointees may change by the time the final study reports are complete and ready to be shared.

Long-term collaborations between researchers and water utilities can have multiple benefits as technologies advance and information needs change.

Exposure Assessment

For studies of water distribution system and health, there are many angles to considering exposure – from certain characteristics of the distribution system (or parts of the distribution system) to actually measuring various water quality parameters. Deciding what are the relevant exposures and how to measure them depends on the research question and study design. For observational studies, where the investigator does not control the exposure conditions, it is critical to characterize the range and variability of exposure experienced by the study population as thoroughly as possible. For intervention trials, where the investigator can control deliberate changes in exposure, it is still important to carefully measure water quality to see if the intervention actually had the anticipated effect. For both types of studies, investigators always need to consider consumer behavior because drinking water habits are influenced by personal preferences, cultural norms, trust in public systems and authorities, and perceptions of risk. Members of the study population may choose to drink alternate water sources, such as bottled water, or use household water treatment devices that will change the quality of water they consume. These behaviors may cause misclassification of drinking water exposure and lead to a conservative bias of the results of the study towards the null (i.e. no difference in health outcomes between “exposed” and comparison group), as well as greatly reduce the power of the study to detect a difference in health outcomes.

“…there are some professors that…really made a go of it in the drinking water community because they've developed and maintained a relationship with one or more utilities. It's not just a one way street with the researcher observing whatever data they can extract, it's a long term relationship that goes on for years if not decades and maybe that's easier to do in the engineering side than it is on the public health side. …all of those folks have utilities that they've maintained relationships for years. And with that lengthy relationship there's more trust and more ability to talk through things because you're not…learning something for the first time, …you've already got a working knowledge of what's going on and it's not recreating the wheel every time you walk in…just like anything else… relationship building is a big part of the process and you [need to] know where to go inside a utility organization…. You have to know who in the utility actually is focused on a particular topic and…has relevant data.” – Steve Via


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For study designs that compare different exposure scenarios, there are a number of options, depending on the research question:

‐ Any distribution system

water vs. no distribution system water (study population who drink bottled water or well water)

‐ Any distribution system water vs. distribution system water with a point-of-use water treatment device

‐ Distribution system waters with different types of residual disinfectants (free chlorine vs. chloramine)

‐ Distribution system water in “more vulnerable” locations vs. distribution system water in “less vulnerable” locations of the system – with vulnerability classification based on any number of the following risk factors: longer water age, clusters of historic main breaks, low pressure areas, older pipe network, areas impacted by storage tanks or stagnant/dead end zones, areas with more customer complaints, lower chlorine residuals, higher turbidity, higher TOC, etc.

Study participant awareness of their exposure status and their perception of risk may be an

issue in some exposure scenarios or study designs, and this may affect the participant’s responses to queries about their health status or the frequency with which they report adverse health events. Some randomized, controlled water treatment intervention trials have tried to ‘blind’ study participants (and sometimes also the study staff who collect and analyze the health outcome data) about their exposure status in order to reduce possible disease reporting bias. Other trials have not done this, and it has raised concern about the validity of the study findings.

For studies that opt to measure microbiological water quality, there are challenging decisions about which microorganisms to test for, sampling strategy (location, frequency, criteria for when and where to collect a sample, and sample volume), and analytical techniques.

Strategic choice of the most valuable microbes to test for depends on the research question. Indicator organisms and water quality monitoring are reviewed in Chapter 2. Although total coliforms may be a useful process indicator, they are not considered relevant for health risks. Heterotrophic plate count bacteria are also not valuable indicators of health risk, although some may argue that the concentrations of these microbes may reflect biofilm sloughing and possible risks from opportunistic pathogens. There is increasing concern about biofilms in the distribution system and premise plumbing and the possibility that pathogens in biofilm may be protected from the effects of residual disinfection. Biofilm bacteria that may indicate post-treatment bacterial regrowth, and could be monitored in distribution system water, include aeromonas, pseudomonas, mycobacteria, and Legionella. Although these organisms are generally considered opportunistic pathogens, currently, there is very limited understanding of the human health risks associated with specific concentrations of these organisms in the distribution system or premise plumbing, so it may be challenging to interpret the health implications of these exposures. To examine fecal

“Selective monitoring based on standard 9-5 sample collection and then testing is not necessarily going to capture what's going on with water in an event. So, I would say that the worst is a one grab sample and then extrapolating out. The second worst is using indicators that are not relevant. I'll say this upfront… using total coliforms as a marker of what's going on in distribution systems, I don’t think is an adequate way of doing it…. same with heterotrophic plate counts [HPC bacteria]. It has its place, but it's really not telling you, for human health, what's going on.” – Kellogg Schwab


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contamination in the distribution system, some experts advocate measuring common human enteric viruses in distribution system water because they may be infiltrating the distribution system network via intrusion, and they are persistent (Lambertini et al. 2012). Because of their high infectivity, even low levels of enteric viruses (like norovirus) in distribution system water pose a risk to consumers (Teunis et al. 2010). Methods to detect viruses in drinking water require concentration from large sample volumes and highly sensitive detection assays (PCR or tissue culture) and are more challenging to perform than assays for fecal indicator bacteria like E. coli. In our experience, it is difficult to achieve norovirus detection limits below the median infectious dose (18 virus particles, (Teunis et al. 2008)) which can result in false negative results.

Water Monitoring and Sampling Strategy

Unfortunately, it is not possible to continuously monitor water quality from the treatment facility to the customer tap. Investigators need to develop a logical sampling strategy (location, frequency, criteria for when and where to collect a sample) to assess exposures that are relevant for the research objectives of the study. This sampling strategy can be guided by: 1) data from routine distribution system monitoring for compliance purposes (discussed in Chapter 2); 2) hydraulic models of the distribution system that can predict water age at different locations and where contamination introduced at specific points in the system would move; and 3) risk models of the distribution system that predict locations in the distribution system that may be at greater or lesser risk of degraded water quality because of specific physical and chemical characteristics, i.e. water age, pipe age, pipe materials, history of main breaks, altitude and pressure, history of pressure loss, presence of water storage tanks, presence of stagnant zone and dead ends, turbidity, chlorine residual, temperature, etc. Chapter 4 of this manual discusses the types and uses of models in epidemiologic studies in greater detail. Several of the experts we interviewed encouraged the use of models to plan the strategy for exposure assessment and any related water sample collection.

“The most important thing to appreciate is that sensor technology is not at the level of reliability that we want it to be…If you have all these sensors out there, then you've got to develop an event detection system that collects all that data that is generated every five minutes or more from multiple sensors - thousands of data points. It needs to be able to wake you up at 2AM in the morning and say with "high reliability, this happened in the system". Thus, event detection systems are very complicated. Water quality in the distribution system does change. It changes with source water conditions, it changes with time of year and water temperature, it changes for different reasons. The event detection system has to learn that there's been a change in the water quality baseline, adapt to that change, and using that change, determine if an alert needs to be triggered when something beeps. It’s not easy to do, but we're doing that. We're bringing [on line] the contaminant warning system we've developed -what we call a “dashboard.” The dashboard brings together, on the computer, in one place, our online water quality monitoring data, our customer complaint data, any alerts from the public health department, and any water security alert that says someone could have broken into one of the storage tanks or reservoirs or treatment plants. It brings all that together in one place so that 24/7 we can go on a laptop and see what's going on in our system.” – Gary Burlingame


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Several experts commented on the need for a much better system for monitoring the distribution system. Routine distribution system monitoring data (described in Chapter 2) may have limited utility for health studies. However, it is possible that this data could at least identify areas of uncertainty where the research study should do more targeted sampling and analyses. One expert commented that some water utilities may design their compliance sampling in a way as to make it unlikely to detect problems that would require reporting and follow-up actions. However, health researchers may want to ensure that they capture information on water quality conditions in the locations of greatest risk as well as comparison locations with low risk.

Real-time monitoring of water quality in the distribution system is clearly a goal for the water industry and is currently being developed. This would be a valuable tool for more accurate exposure assessment in epidemiological studies. However, our experts cautioned that the technology is not fully developed yet and will require training time in each distribution system in order for the analyses of the sensor data to recognize meaningful changes that require notification.

Sample Concentration and Detection Methods

Although compliance samples are typically 100 – 1000 mL, for research purposes, large volume samples provide greater sensitivity. This sensitivity may be necessary if the analytical targets are pathogens. Recently developed ultrafiltration methods offer an economical and relatively straightforward way to simultaneously concentrate viruses, bacteria, and protozoa from water (Liu et al. 2012, Cope et al. 2015). Volumes of 100 to 1000 liters can be concentrated on site using a portable ultrafiltration set up, or large sample volumes can be transported back to the laboratory for concentration. The concentrate from the ultrafiltration procedure can be effectively used in conjunction with secondary concentration techniques and multiple analytical techniques (e.g., selective culture, microscopy, molecular detection) to enable sensitive detection of pathogens and microbial indicators in large-volume water samples (Liu et al. 2012).

There are several advanced analytical methods to detect and quantify microorganisms in water samples (or concentrates of water samples) that may be useful for drinking water epidemiology studies. However, there are still limitations with the sensitivity of some of these methods that were developed for clinical diagnostic purposes and may not detect low levels of organisms in environmental samples. For some organisms, culture methods can be highly sensitive and provide information about viability. For organisms that are difficult to culture, or for which standard culture methods have not been developed (e.g. noroviruses), molecular detection methods, like real-time polymerase chain reaction (PCR), are very sensitive and specific. Limitations to these methods include the need for more sophisticated (and expensive) lab equipment, trained personnel, lack of information about viability, and the potential for false negative results due to inhibitors in environmental matrices. Microarrays, multiplex PCR, LuminexTm, BioFireTm and other platforms/methods that allow simultaneous molecular amplification and detection of multiple target organisms are increasingly used for clinical diagnostic purposes. These methods are rapid and designed to handle a large number of samples. However, they currently have limited application to environmental samples because of insufficient sensitivity. Further developments to these methods and environmental concentration methods may enable rapid, sensitive detection of a suite of microorganisms in water that would be valuable for epidemiological studies. Several experts mentioned that the ultimate goal would be sensitive real-time monitoring for bioterrorist agents and other microbial targets using in-line sensors or microchips in the distribution system that feed data back via telemetry and alert water utilities and health authorities about unusual changes in water quality or hazardous situations.


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Health Outcomes

Information on relevant health outcomes for epidemiological studies of endemic waterborne diseases comes from investigations of waterborne disease outbreaks. Outbreaks associated with drinking water typically focus on intestinal disease outcomes (acute gastrointestinal illness) associated with water ingestion. However, distribution system water is also used for bathing and showering, so health outcomes associated with water dermal contact (rashes), water immersion (ear infections and eye irritation), and inhalation of drinking water aerosols (respiratory illness, flu-like illness, pneumonia) are also relevant for studies of endemic waterborne diseases associated with water distribution systems. Many of these health outcomes have multiple causes and multiple transmission routes (such as via fecal-contaminated food and person-to-person transmission via fecal-contaminated hands). This makes it challenging to determine the proportion of cases that are associated with distribution system water (attributable risk). Some of these health outcomes, especially diarrhea and other gastrointestinal symptoms, are very general and non-specific; for instance, diarrhea could be due to Cryptosporidium from drinking unfiltered surface water, or norovirus from drinking treated distribution system water impacted by sewage intrusion, or Salmonella from eating under-cooked chicken, or Giardia from playing with a puppy, or a non-infectious cause such as irritable bowel syndrome. Non-specific health outcomes reduce the statistical power of the study because a water quality intervention is likely to have no effect on some health outcomes like irritable bowel syndrome. By contrast, other health outcomes are extremely specific, such as serological markers for hepatitis A infection, but the transmission route for the infection may still be unknown, and drinking water may represent only a small proportion of the total attributable exposure.

Another important characteristic of many infectious disease outcomes is seasonality, and this needs to be considered when planning an epidemiological study. Bacterial and viral agents of waterborne disease may have different seasonal peaks, and the survival and potential replication of these agents in the aquatic environment are usually associated with temperature and nutrient levels. Peaks in endemic infections may occur because of seasonal differences in exposure behavior as well as seasonal changes in the dominance of a specific transmission route (e.g. swimming) for some infections. For example, although norovirus infections occur all year round, they have a winter peak, and norovirus outbreaks also tend to occur in winter (Matthews et al. 2012). Longitudinal epidemiological studies with infectious disease outcomes are often conducted for at least one year in order to capture seasonal differences in infection. Cross-over designs need to ensure that seasonal differences in health outcomes are accounted for when planning the time each study group is followed with and without a water quality intervention. Community intervention designs that compare health outcomes before and after a community-level water intervention also need to consider the timing of the data collection periods. Cross-sectional study designs need to consider whether data collection spans or misses potential seasonal peaks in the infections of interest.

Many studies and outbreak investigations rely on self-reported symptoms to determine if someone meets the case definition for having diarrhea or acute gastrointestinal illness. These reported cases are usually not confirmed by a medical care provider or laboratory testing of a clinical specimen (stool or sera). Self-reporting of illness or symptoms may be done by health diaries, telephone surveys, or more recently by using cell phone apps, internet surveys or other web-based reporting platforms. Remote reporting methods can save considerable time and expense for the study staff who are responsible for collecting this data. However, these various methods


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involve different degrees of time investment and competency by the study participant and will vary in reliability.

There is considerable debate in the research community about the utility and reliability of self-reported diarrhea or acute gastrointestinal illness as a health outcome for studies of drinking water (Schmidt et al. 2011). Case definitions and study participant interpretation of diarrhea vary, and recall can be quite poor. Despite these shortcomings, acute gastrointestinal illness is the most frequently used health outcome in drinking water studies. Many studies try to capture the severity of the illness by recording whether the case sought medical care or was hospitalized, and/or was absent from work or school.

Examining health outcomes associated with Legionella or mycobacteria in the distribution system or premise plumbing is also complicated by the non-specific symptoms caused by these organisms. While Legionella can cause severe pneumonia, cough, and fever (Legionnaire’s Disease) mainly in elderly and immunocompromised populations, it also causes the much less specific Pontiac Fever that presents as a flu-like illness (fever, chills, malaise) without pneumonia. This latter infection is much more common in the general population and is rarely associated with hospitalization. Epidemic and sporadic cases of Legionnaire’s Disease can be diagnosed by a urine antigen assay. However, Pontiac Fever cases are typically diagnosed on the basis of symptoms, outbreak circumstances and environmental detection of Legionella. There are rare reports of the detection of legionella antibodies in Pontiac Fever cases in outbreaks (Edelstein 2007), but generally there is no routine diagnostic test for this disease or a reliable way to identify sporadic cases.

Non-tuberculous mycobacteria (NTM), also referred to as Pathogenic Environmental Mycobacteria or Mycobacterium avium Complex (MAC), cause a range of non-specific symptoms. Common clinical syndromes include pulmonary infection, lymph node infection, ear infection and skin and soft tissue infection. These infections are increasing in the US (Pedley et al. 2004, EPA 2002b), but the attributable risk from water and distribution system exposures is not known and has been identified as an important research need. High prevalence of NTM infections has been reported in HIV-infected patients (EPA 2002b). Waterborne NTM have been associated with hospital outbreaks, particularly wound infections. Because NTM diseases are not reportable, there is limited understanding of the burden of disease associated these organisms.

Seroprevalence surveys that collect and test sera from a specific population can indicate both symptomatic and asymptomatic infections from specific pathogens. The advantage of this approach for epidemiological studies is twofold: 1) These assays increase the specificity of the measure of health outcome (and potentially increase the statistical power of the study), and 2)

“Diarrhea is … nonspecific, a whole bunch of other things cause diarrhea. On the other hand, it may be the best we have.” – Tim Wade

“Diarrhea because we've always done it …another big issue is the need for outcomes different from diarrhea. Diarrhea is so variable, and its variability creates a lot of statistical noise that requires much larger sample sizes than might be necessary… if you had a reliable serologic or stool marker or some other measure of disease.” – Jack Colford

“…should we be using diarrhea as an outcome? I don't think that necessarily we should be…. We cannot stick with conventional diarrhea as the only outcome of concern. We need better biomarkers that get away from subjective self reporting” – Kellogg Schwab


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These assays may allow researchers to establish a firmer link with exposure by focusing on specific infections rather than non-specific symptoms. Frost et al. used serological markers of Cryptosporidium infection to examine risks associated with drinking water systems (Frost et al. 2005). New methods have been developed to detect antibodies to enteric pathogens in saliva samples (Griffin et al. 2011, Griffin et al. 2015, Moe et al. 2004) and also in fingerstick blood samples blotted on filter paper (Lammie et al. 2012). Because of the relative ease of collecting saliva and fingerstick blood samples and the ability to detect infections that may have occurred months or years before sample collection, these methods may be useful for future drinking water epidemiology studies. Further development work is needed to extend these assay methods to additional enteric pathogens and move them into platforms that enable high sample throughput.

Disease Surveillance Data

Various forms of disease surveillance systems have been used in studies of drinking water

and health. While passive surveillance systems are usually too slow and insensitive to detect waterborne disease outbreaks, they may be valuable for observational studies of endemic disease that may be associated with water systems. Table 6.1 categorizes health outcomes by level of severity and indicates various surveillance approaches for collecting information on these outcomes. Mild to moderate disease outcomes may result in absenteeism from work or school, self-treatment with anti-diarrheal medications, or calls to health care providers (e.g. health call centers or nurse hotlines). These outcomes can be detected by monitoring the following indicators: absenteeism from sentinel institutions (such as schools), sales of anti-diarrheal medications, nurse hotline calls to large health care facilities, and gastrointestinal illness in sentinel populations (such as nursing homes and within families). Clinical cases of infection may result in visits to health care providers, laboratory-confirmed infections, hospitalizations, or mortality. Sources of information on these outcomes include: automated patient visit records at large health care facilities, hospital emergency department visits, hospital admissions and discharge records, clinical laboratory records of confirmed infections, and death certificates listing underlying and contributing causes of death. Some of these surveillance approaches may provide a relatively rapid means of detecting an outbreak of disease (discussed in more detail below). However, it is important to remember that these surveillance approaches cannot distinguish between waterborne infections and infections transmitted via food or other routes. Only epidemiological studies that compare health outcomes in populations exposed to different water sources can determine the proportion of illness or infection that can be attributed to waterborne transmission.

In the US, there are several specific notifiable diseases that are required to be reported by medical practices and laboratories to state health departments and the Centers for Disease Control and Prevention (CDC) (Adams et al. 2014). Of these reportable diseases, only legionellosis, giardiasis, cryptosporidiosis, cholera, hepatitis A infection, salmonellosis, shigellosis, shiga-toxin producing E. coli (e.g. E. coli O157:H7), and typhoid fever can be waterborne, and all of these diseases are not exclusively transmitted via water. Sporadic cases of acute gastrointestinal illness

“…we need to have good disease surveillance data, because if we don't have the disease surveillance data, and it's not high quality, then it's hard to take the first step to try to reduce the disease. Our water systems can support whatever needs to be supported to make sure we have a high quality and reliable disease surveillance system…” – Gary Burlingame


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are not reportable; however, clusters of acute gastrointestinal illness may be reported through the CDC National Outbreak Reporting System (NORS) (CDC 2016d).

Some communities have developed “enhanced surveillance” systems that can be used to supplement the passive notifiable diseases systems described above in order to provide additional information about disease trends in the community and serve as an early warning system for possible outbreaks. The Waterborne Disease Risk Assessment Program of the New York City Department of Environmental Protection and Department of Health and Mental Hygiene is an excellent example of this type of innovative initiative (New York City Department of Environmental Protection 2016). Various supplemental surveillance approaches, and their strengths and limitations, are described in the following subsections.

Surveys

Community surveys can be used to collect information on specific infections or health outcomes without incurring high study costs. Telephone surveys have been used in outbreak investigations and studies of endemic waterborne disease to collect data on gastrointestinal illness (Nygard et al. 2007). There is evidence that community surveys of self-reported diarrhea can overestimate the size of an outbreak (Hunter, Syed, and Naumova 2001). The logistics of conducting telephone surveys in the US may be more challenging now that many telephone customers have caller ID and may not answer a call from a number that they do not recognize. It may be helpful to conduct telephone survey calls from a trusted, credible local institution (e.g. local university or medical center) that community members recognize and may be more likely to answer.

Monitoring Absenteeism

Increased absenteeism, from school or work, is often the first indication of an outbreak in a community. Absenteeism can be monitored using telephone or computer-based systems in schools and sentinel workplaces (factories or government offices with large numbers of employees who must check in and check out on a daily basis). This type of monitoring can provide early notification of outbreaks without great expense; however, this type of system cannot conclusively demonstrate that an outbreak is waterborne. With this surveillance approach, it is possible to examine whether a peak of absenteeism at one institution also occurs simultaneously at other institutions in different areas using the same water supply. If so, the outbreak is more likely to be waterborne. A critical aspect of this approach is that it requires the cooperation of participating institutions that are able to accurately track absenteeism in a stable population of students or workers.


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Table 6.1 Surveillance approaches for specific health outcomes

Health outcome Outcomes that could be detected in a surveillance system

Possible surveillance approaches

Asymptomatic infection

Immune response in infected case Possible secondary transmission to

contacts

Serological surveys

Mild infection Absent from school or work Self-treatment with anti-diarrheal

medications Telephone consultation with health

care providers

Telephone surveys of illness in sentinel households Telephone-based or computer-based reporting system of

absenteeism from sentinel schools, factories, or workplaces Monitoring anti-diarrheal medication sales at sentinel pharmacies Monitoring telephone calls to health care providers (“nurse hotline

calls”) Moderate infection Absent from school or work

Self-treatment with anti-diarrheal medication

Seeks medical care

Monitoring medical records from sentinel health care providers. Monitoring hospital emergency room visits records Monitoring hospital laboratory records of school testing and/or

pathogen detection. Severe infection Absent from school or work

Seeks medical care Hospitalization

Monitoring medical records from sentinel health care providers Monitoring hospital emergency room visits records Monitoring hospital admissions and discharge records Monitoring hospital laboratory records of stool testing and/or

pathogen detection Death Death Monitoring death certificates

Survey of households to identify household members who dies of diarrheal disease

Source: Funari et al. 2011


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Monitoring Inquiries to Health Call Centers or Nurse Hotlines

Mild cases of illness may lead to telephone calls seeking advice from a local health center or HMO nurse hotline instead of physically visiting a health care provider. This behavior may be to avoid the expense of a doctor’s visit or simply to determine if the symptoms justify seeking medical attention. Some health care providers have “nurse hotlines,” where a patient first speaks to a nurse on the telephone to describe his or her illness, and the nurse decides whether the patient needs to be seen by a physician. For some health care systems, it may be possible to monitor these types of inquiries and use this as an inexpensive and timely method of disease surveillance. Nurses are usually required to keep records of all telephone inquiries, including information on the patient and the symptoms. This type of surveillance approach clearly requires time and cooperation of health care facilities that maintain these types of call centers. An advantage of this approach is that it can collect information on specific symptoms and may capture mild illnesses that would not be seen at a medical facility. Limitations of this approach are that it is based on self-reported symptoms, and there is no indication of whether the symptoms are associated with water quality. Malm et al. used information from health care call centers in Gothenburg, Sweden to collect information on gastrointestinal symptoms from different geographic regions of the city and examine the association with disturbances in the municipal water treatment facility or distribution system (Malm et al. 2013).

Monitoring Internet Search Volume for Words That Describe Gastrointestinal Symptoms

Examining Internet search volume for inquiries about gastrointestinal symptoms is a new strategy for monitoring health outcomes and was used in a recent study of pipe breaks in two large US cities. The investigators were able to collect information on weekly Internet search volume by city for terms related to vomiting and diarrhea through the Google Trends website. In both cities, there was a clear positive relationship between pipe breaks and Internet search volume (number of searches for the term of interest relative to the total number of searches in that week from the metro area) (Shortridge and Guikema 2014).

Desai et al (2012) describe a norovirus disease surveillance system that used Google Internet query share (IQS) data on search terms related to gastrointestinal illness. The Google Insights for Search allowed the investigators to track relevant Internet search queries (“norovirus,” ‘vomiting,” “diarrhea,” “nausea,” “abdominal pain,” “stomach virus,” “food poisoning,” “gastroenteritis,” “Norwalk virus,” and “rotavirus”) in specific geographic regions over specific time intervals. The investigators compared the results of this rapid and economical surveillance approach to: 1) CDC norovirus outbreak surveillance data from 30 states, and 2) syndromic surveillance data from hospital emergency departments in the Boston area. The IQS data showed a strong correlation with national (R2=0.70) and regional (R2=0.74) norovirus surveillance data and demonstrated the utility of this approach for rapid identification of increased norovirus activity across the US and in specific geographic regions. (Desai et al. 2012).

Monitoring Sales of Anti-Diarrheal Medications

Increased sales of anti-diarrheal medications have been observed to be an early indication of outbreaks of diarrheal disease (Sacks et al. 1986). Monitoring sales of anti-diarrheal medications has also been used as an indicator of community gastrointestinal illness in studies of water quality and disease (Beaudeau et al. 1999). This surveillance approach involves developing a network of


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pharmacies that agree to keep records on the sale of anti-diarrheal medications and then setting up a system to routinely collect this information from the pharmacies. Again, this is a relatively easy and inexpensive method to collect information on incidence of gastroenteritis in the community and could be set up as an electronic reporting system. This approach also captures mild cases of illness in individuals that may not seek medical care and could be designed to collect information on a frequent (weekly) basis in order to rapidly detect rises in incidence of gastrointestinal illness. However, this surveillance system requires the cooperation of a large number of pharmacies, and those participating must have accurate bookkeeping of sales of specific medications. It is important to note that some peaks in sales may not be associated with illness but may be due to discount sales or new advertisements.

Monitoring Illness in Sentinel Families or Institutions

Another surveillance approach is to routinely collect illness/symptom data from houses of sentinel families who agree to keep track of episodes of gastrointestinal illness. Data can be collected in health diaries followed by periodic household interviews by community health workers or telephone interviews. This system can also be used to routinely collect illness/symptom data from institutions with sentinel populations (such as prisons, long-term care facilities, residences for the elderly, residences for students at colleges and universities) that agree to record episodes of gastrointestinal illness. This surveillance approach can detect mild illnesses, could be designed to collect information on a frequent basis, and could possibly be set up as an electronic reporting system. Clearly, this system requires cooperation and time from a large number of families and institutions to record data. The data is based on self-reported illness/symptoms and thus may have low accuracy. Also, some institutions (for example, nursing homes) may have high background illness rates because of susceptible populations and multiple disease transmission routes within the institutions. However, if disease peaks are detected, it would be possible to examine whether a peak of illness at one institution also occurs simultaneously at other institutions in different areas using the same water supply. If so, then the outbreak is more likely to be waterborne.

Monitoring Visits to Health Care Providers for Gastrointestinal Illness

Depending on the health care system in the region, it may be possible to design surveillance systems that routinely collect information from patient records at various medical providers (including community clinics, HMO facilities, hospital emergency departments, and hospital admissions) for patients with gastrointestinal illness. This surveillance approach would capture moderate to severe cases of illness and could be set up as an electronic reporting system. However, this system again requires the cooperation and time of a large number of health care providers and does not indicate whether the gastrointestinal illness is waterborne. The system could be designed to collect data from specific locations, based on patient zip code or street address, and it could target sentinel health care providers who are interested in providing surveillance data as well as providers with automated patient visit records. A large electronic database of emergency department visits for all the hospitals in a large metropolitan area was used to collect information on gastrointestinal illness (based on ICD-9 codes) by patient home zip code and date in studies of drinking water turbidity and water residence time in the distribution system (Tinker et al. 2009, 2010).


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Insurance claims can be another source of data on medical visits by purpose, patient location, and date. Huang et al. reported using a National Health Insurance database in Taiwan to collect information on types of services and diagnoses (based on ICD-9 codes), date, and patient demographic data and calculated incidence of specific medical services for time periods and locations affected by municipal water outages (Huang et al. 2011).

Monitoring Laboratory Activity and Results

Clinical laboratories can provide valuable information for surveillance purposes. For tracking diarrhea rates in a community, information can be collected on the total numbers of stool samples submitted for microbial analyses on a weekly or monthly basis. Data on cases of gastrointestinal illness should be stratified by inpatients and outpatients in order to roughly differentiate between nosocomial infections and community-acquired gastroenteritis. Even without the etiologic results, information on the number of stool samples submitted for microbial analyses could be useful to detect sudden changes in incidence of gastrointestinal illness. In addition, laboratory-confirmed infections of enteric pathogens can be routinely monitored. In many regions, hospital and clinic laboratories, private medical laboratories, and government public health labs are already required to record and report the detection of specific enteric pathogens (Giardia, V. cholerae, etc.). Laboratory-based active surveillance and electronic reporting offers a rapid method to detect confirmed infections that cause moderate to severe symptoms and prompt the subject to seek medical care. This surveillance approach is very specific for target infections. However, the sensitivity of this type of surveillance may be poor if healthcare providers do not request stool specimens or individuals do not provide specimens.

Health Outcomes That May Be Associated with Chemical Contaminants

Although the focus of this manual is guidance for studies of acute health outcomes that may be associated with drinking water distribution systems, it is important to mention that it is also possible to collect information on health outcomes that may be associated with exposure to disinfection byproducts or chemical contaminants in the distribution system. Data on adverse reproductive health outcomes (such as miscarriages, stillbirths, premature births, low birthweight, and birth defects) can be abstracted from birth certificates, death certificates, birth defects registries and other information systems maintained by several organizations, including the CDC National Center for Health Statistics (CDC 2016a), CDC National Center on Birth Defects and Developmental Disabilities (CDC 2016c), and the March of Dimes (March of Dimes 2016). Data on cancers associated with disinfection byproducts, such as bladder cancer, can be obtained from state and national tumor registries such as those maintained by the National Cancer Institute (National Cancer Institute 2016).

Monitoring Death Certificates

Death certificates are an important source of information for surveillance of many diseases. Information from death certificates is also a fundamental source for official mortality statistics that are used to support epidemiological and statistical research other than to better define the mortality impact for particular events. Death certificate data are generally analyzed by examining the “underlying cause of death” – the disease or injury that initiated the events resulting in death. For each death, the underlying cause is selected from an array of conditions reported in the medical


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certification section of the death certificate. This section provides a format for entering the cause of death sequentially.

For waterborne disease surveillance, it is possible to set up a system to routinely check death certificates for deaths associated with enteric pathogens. However, the data in death certificates are of variable quality, and some death certificates may only record immediate cause of death and not underlying causes of death. Other limitations of this approach are that many enteric infections may be undiagnosed and not recorded in death certificates, and there is usually no evidence relating to whether mortality from an enteric infection was linked to waterborne transmission. Another consideration is that for most regions in the US, mortality from waterborne disease is an infrequent event, and it is not worthwhile setting up a surveillance system for such a rare event.

Summary of General Strengths and Limitations of Enhanced Surveillance

These alternative surveillance approaches can provide valuable information on changes in disease rates over time. Some of the more sensitive methods may be able to show the effect of new water quality regulations or implementation of new treatment processes. Some of these systems can provide real-time information to alert health authorities to the occurrence of a waterborne disease outbreak and enable rapid investigation and control. It is important to remember that surveillance data for gastrointestinal illness does not indicate if the illness was waterborne, and most enteric pathogens can be transmitted via food or person-to-person contact as well as water. In order to determine the proportion of enteric illness in a community that is due to contamination of the water supply, problems with water treatment, or deficiencies with the distribution system or premise plumbing, it is necessary to conduct epidemiologic studies or evaluations of water supply interventions.

Study Population Sample Size Considerations

For any epidemiological study, sample size is an important decision that affects the cost and logistics of conducting the study and the likelihood that the study will have the power to adequately address the research objectives. Sample size calculations depend on the study design, the target health outcome, the prevalence of the outcome, the difference you want to be able to detect between the exposed vs. unexposed groups, and the planned statistical analyses approaches. Less specific health outcomes require larger sample sizes because a certain proportion of the cases will be due to other transmission routes or other causes. Note that non-differential (i.e. random) misclassification of disease will reduce the differences between the population drinking clean water and the population drinking water with contamination problems and bias the study results toward the null. Rare health outcomes require larger sample sizes and possibly longer study duration (depending on the study design) in order to capture a sufficient number of cases for comparison. Studies of endemic self-reported gastrointestinal illness in Canada, the United States, the United Kingdom, and Australia report incidence rates that range from 0.7 to 3.5 episodes per person per year (Colford et al. 2009, National Research Council 2006, Risebro et al. 2012). Randomized controlled trials of household water treatment devices in Canada, the US, and Australia have included approximately 450 to 1100 households with a total of about 1300 to 5200 individuals (Murphy et al. 2014). The sample sizes in observational studies vary considerably based on design and data sources. Some studies that use databases of hospital emergency department visits or health insurance claims over multiple years have sample sizes of one million


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records or more. Mining big data sources like these can increase the power of a study, but the trade-off is that there is the potential for bias. Studies that use databases designed for other purposes need to be very carefully designed, and the results need to be interpreted with caution.

Pilot Studies

Pilot studies are extremely important for testing methods and assumptions prior to

undertaking a larger and more expensive study. Colford et al. used a pilot study to determine whether it was possible to “blind” study participants to the status of the water treatment device (sham or functional) intervention installed in their home in case knowledge of this status affected the frequency of self-reported gastrointestinal symptoms (Colford et al. 2002). Pilot studies can be used to test recruitment methods for study participants (i.e. Will community members in a candidate study site agree to participate in the study if you guarantee to deliver bottled water to their home for free for 12 months?), participant compliance with study procedures (i.e. Will someone really use a cell phone app to report gastrointestinal symptoms every week?), or to understand consumer behavior in a candidate study site (i.e. Does 90% of the community really drink the tap water – as the water utility staff assert?).

“…from my experience [it] is just the inestimable value of pilot studies. People who haven't done this work never seem to understand how expensive it could be to pilot the work, and really go through the study in a very small scale, but the lessons learned in terms of how to do the design and the recruitment and the analysis, the whole nine yards… but it is incalculable how much value is added… by doing pilot studies of whatever it is one is going to do. [This] requires on the part of funders some patience to do a pilot that could take a year or two years, and to do a full study, that could take, another couple of years. Most funders don't have the vision to be in the game for four or five or six years, so that's another sort of broader problem.” – Jack Colford

“The best ways [for recruitment and retention] are when you partner closely with people in the community. … for our western studies, we partnered with the water utility and they put our fliers in with their [billing] material. In this area, [people] trusted the utility so that was very effective…. It really helps when people are interested in the issues… In our beach [study] sites, people were concerned about the beach water quality so they wanted to help participate... And, obviously, you have to do all of those things just to make it … easy on them, [and] they have to get paid for their time.” – Tim Wade

“What worked for us was reimbursement. The attrition in a study really threatens the validity of the study. So, to me this is an important line item. The other comment I would make here is to have intermittent incentives, not just a [recruitment] incentive because if you stay in this study for two years or a year, then you're going to get paid, but there's some sort of regular reinforcement. The behavioral economists are good with this stuff.” – Jack Colford


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Subject Recruitment and Retention

One of the greatest challenges for epidemiological studies of drinking water and health is recruitment and retention of study subjects. Because these are usually studies of healthy populations (as opposed to clinical trials of drug treatments for ill patients), there is often less incentive to participate in the study. Also, many studies request the participants to routinely report symptoms, risk factor behavior and other information over a period of time – which can be time consuming for a family. Careful recruitment strategies, clear and compelling communication materials, strong community partnerships (and perhaps celebrity community champions), and strategic use of economic incentives throughout the study period are essential for subject recruitment and retention. Investigators in Australia reported that regular communications (via a study newsletter), family activities, contests and raffles were helpful in retaining study participants (Hellard et al. 2001). In our experience, telephone and mail recruitment were not successful strategies for recruitment of healthy adult participants; however, strategic use of social media has been very effective for study recruitment.

The local reputation of the research organization is also important for subject recruitment. Local research organizations will usually have a hometown advantage if they are perceived as a trusted member of the community – especially research organizations that are also healthcare providers. Research organizations working in communities in other states generally do not have name recognition and need to partner with trusted local organizations in order to gain entry into the community and successfully recruit study subjects.

When planning study recruitment, it is critical for investigators to understand the local drinking water context and water issues that have received attention in the media. Have there been local media reports about problems with the water system that may have influenced the population to use alternative drinking water supplies? Has there been aggressive marketing of household water treatment devices or bottled water delivery services in the area? Have there been reports of scandals associated with water or wastewater facility construction projects or operation and maintenance? Have there been any waterborne disease outbreaks associated with the municipal water supply? Any concerns about the impact of chemical spills or hydro-fracking, etc. on the water system? All of these factors may influence the interest and willingness of the local population to participate in an epidemiological study about water and health.

Good Research Practices

Study investigators need to be aware of the best practices for human subjects research, including ethical review, protecting confidentiality, appropriate collection and handling of clinical specimens, appropriate collection and handling of environmental specimens, use of standard laboratory quality control and quality assurance procedures, use of data management quality control and quality assurance procedures, etc. There are many sources of guidance for these practices, and most research institutions ensure investigator compliance as part of the research

“[Recruiting for studies in towns with small systems:] …we’re going to get everybody involved. I think you get some grassroots organizers in the community and get locals to enroll people and go to the churches and the community centers and appeal to people's public civil pride that we need to do this, that kind of stuff, maybe an entirely different approach to enrollment than what we've done before.” – Mark LeChevallier


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funding agreement.

Communication of Study Findings

Both during the study and after the study is complete, it is critical to communicate with the water utility and local health authorities about the study activities and findings. One expert commented on the publication bias that favors the publication of studies that show an association between drinking water and health effects, and the tendency to exaggerate small health risks. We recommend working closely with the utility and local health authorities to appropriately study results so that they are framed in the appropriate context. For example, in one of our studies, we observed that customers receiving water from one treatment facility had slightly higher rates of acute gastrointestinal illness compared to customers who received water from other treatment facilities in the area. Discussions with our collaborators at the water utility explained that this increased rate of acute gastrointestinal illness was probably due to a short period of construction at the treatment facility when the operations were not representative of normal conditions. This likely explanation was not something we would have learned from just looking at the data we had from the water utility.

Communicating the results to the scientific community and to the public, when appropriate, should be a joint study team activity with the researchers, water utility authorities and health authorities, and should be guided by advice from communication specialists. Health investigators should understand that from a utility perspective even an announcement about the intent to conduct a water and health study in a community will raise concern about the safety of the water supply – no matter how protected the source water or advanced the treatment methodologies. It is possible that any research finding will make more work for the water utility in terms of damage control. It is important that studies that show no association between health outcomes and a community water system are published and appropriately communicated to the public. Studies that do show health risks associated with a community water system should be carefully communicated to the public

“…need for people working in drinking water research to sort of adhere to kind of broad field standards whether it's the CONSORT* guidelines for trials or Newcastle-Ottawa** kind of guidelines for observational studies. In every design, there's a kind of consensus guidelines on what constitutes as proper data collection, reporting and so forth. It was nice if those were done ahead of time. …Pre-registration of trials that are done in the field would be helpful. Just as we insist on drug trials being pre-registered before they're done, so that negative results can't be buried, but that people can find out that the trials were conducted. I think registering these [water] trials to clinical trials.gov or other mechanisms would be very helpful.” – Jack Colford

*CONSORT = Consolidated Standards of Reporting Trials. See (CONSORT Group 2010)

** standards for assessing the quality of non-randomized studies based on three broad criteria: the selection of the study groups; the comparability of the groups; and the ascertainment of either the exposure or outcome of interest for case-control or cohort studies respectively. See http://www.ohri.ca/programs/clinical_epidemiology/oxford.asp


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along with an action plan of how the water utility and health authorities will follow up to mitigate the risk, who may be at greatest risk, and appropriate measures the public can take to protect themselves. Good risk communication should put health risks in perspective in ways that the public can easily understand – such as the risk of contracting an Ebola infection in the United States vs. the risk of having an automobile accident when texting while driving.

For a water utility, information on the magnitude of the health risk (if any) associated with the water distribution system is not as valuable as information on the specific factors that drive the risk. Policy-relevant findings are those that provide guidance on where and how to invest in distribution system infrastructure improvements and how improve system operation and maintenance practices (such as main break repairs) in order to mitigate health risk. FUTURE DIRECTIONS

Uncertainty about Future Water Challenges

Although there are many uncertainties about the challenges that water systems will need to face in the future, there are some trends that are likely to continue. In most cities in the US, distribution system infrastructure is aging (really, deteriorating) faster than it is being replaced (EPA 2009). This will result in greater loss of physical integrity, opportunities for intrusion, and more frequent main breaks.

Looking at the trends in waterborne disease outbreaks, there was no statistically significant change in the proportion of outbreaks attributed to distribution system deficiencies in public water systems between 1971 and 2006 (Craun et al. 2010). However, there was a significant increase in the proportion of outbreaks associated with premise plumbing deficiencies (excluding legionella outbreaks) during this time period, changing from less than 10% during 1971-1994 to over 20% during 1995-2006 (Craun et al. 2010). Although premise plumbing is beyond the jurisdiction of water utilities, several experts mentioned premise plumbing as a topic of concern that requires greater attention by the research community to develop effective prevention measures.

In addition, the US population is aging (Shrestha and Heisler 2011). There is a growing number of immunocompromised people in the US – due to age, chemotherapy, and other health conditions, and these subpopulations are more vulnerable to waterborne diseases. Measures to ensure that drinking water supplies are safe for these growing subpopulations will require continued investment in infrastructure and research.

“I think one of the most important ones [challenges] is water reuse and how we are going to manage reused water and how we are going to assure the safety of reused water.… coping with emerging contaminants, extreme events from climate change, population and demographic shifts.” – Tim Wade

“…as you move to more challenged waters are we looking at the right level of treatment? …are we treating too little, or are we treating too much? …What treatment is being provided seems to be mostly driven by public perception as opposed to any kind of risk analysis…adequacy of supply—you can put it in terms of climate change and you could think about it in terms of drought or any number of frames, but it's all about maintaining a safe and reliable water supply.”– Steve Via


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Climate change may bring drought and water scarcity in some regions and drive faster development of water reuse strategies. Direct potable water reuse, once considered an extreme solution (Water Science and Technology Board 1998) is now being contemplated and planned by more communities (Tchobanoglous et al. 2011). How this practice will affect water treatment processes, monitoring requirements, the ecosystem of water distribution systems that include reclaimed water, and public health is unknown and will require careful research.

Clearly, there will be a need for well-trained scientists and improved research tools to deal with these challenges and make evidence-based recommendations for water system design, operation and maintenance, regulations, and safety plans. Building research capacity for the future requires investment now. Several experts voiced concern about the inadequacy of funding for water and health research – not only to tackle current information needs but also to provide opportunities to train PhD-level scientists for the future. Effective researchers in this complex field will need cross-disciplinary training in order to understand water treatment processes, water distribution systems, epidemiologic research methods, lab methods for environmental microbiology, and clinical microbiology so that they can effectively lead a multi-disciplinary team of scientists to design and implement these studies. Attracting the best researchers will require significantly increased funding, but this investment for the future will surely provide quantum benefits for what can be more fundamental to public health than safe water.

RECOMMENDATIONS

Developing and implementing a feasible, valid, and relevant study of drinking water distribution systems and health has many challenges. However, with careful study design and effective collaboration between partners, these challenges can be minimized. This manual provides suggestions for all phases of a research study, from inception to dissemination of results. The guidance is broad-ranging but can be summarized into three general recommendations:

1. Know your study site and system. Just as all study populations are unique, each water

system is unique. The details of individual water systems can facilitate a specific study approach, or render a proposed study impractical or invalid. A thorough understanding of the study system is necessary for study design, interpretation of study findings, and, importantly, translation of study findings into distribution system management practices.

2. Engage water utility partners but understand their limitations. Utility partners have a wealth of information and skills that can contribute to a stronger study of the distribution system and health, and the utility has the greatest stake in the outcome of such studies. Public health researchers should engage utilities as partners in research, but they must recognize that research is not the primary mission for utilities. Study

“The economic value of what we have [i.e. research knowledge] is totally disconnected, from the trillion dollar water and wastewater infrastructure and treatment systems. So, we're talking about one percent of a trillion dollars, right? That’s what we would like to have. A billion bucks…, a billion bucks to do the research, in a trillion dollar enterprise. Sounds reasonable to me.” – Kellogg Schwab


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design, data collection and usage, and results dissemination must all be carried out with consideration of the primary goal of safe drinking water provision to consumers.

3. Choose outcomes carefully and consider all potential confounders. Many of the health outcomes of interest have non-specific symptoms and other causes that are not associated with water. Thus, public health researchers must carefully balance the goal of determining the magnitude of the health risk with not overestimating health effects that are attributable to the distribution system. Additionally, because water systems are large, complex systems, there will be many related effects that are unlikely to be amenable to experimental control. These confounders must be addressed through careful study design and/or statistical approaches.

In conclusion, there is a critical need for public health research to support the efforts of

water utilities to deliver safe water for all purposes. Our discussion with experts and review of the literature identified several important research needs, including risks associated with premise plumbing, the relative risks from specific distribution system deficiencies, the growing risks from non-gastrointestinal pathogens such as Legionella, mycobacteria and Naegleria fowlerii, the need for better approaches for monitoring distribution systems and modeling risks, better strategies for water sampling, and sensitive, rapid techniques to detect waterborne microbial threats. Future water supply challenges, such as water scarcity, increased reliance on water reuse, deteriorating distribution system infrastructure, and a growing proportion of sensitive subpopulations, can only be addressed by effective collaboration between health researchers and water professionals.


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APPENDIX A EXPERT INTERVIEWS

In formulating this manual, we sought the advice of six experts in the field of drinking water distribution systems and public health studies of drinking water. All the experts received the same list of questions in advance (see below) and were interviewed by telephone for one to two hours by two or more of the authors of this report. 8 All the interviews were recorded and transcribed. These discussions were invaluable for formulating the considerations and recommendations in Chapter 6 and well as providing additional insights into the material presented in the preceding chapters.

EXPERT PANEL

Dr. Kellogg Schwab is a Professor in the Department of Environmental Health Sciences at the Johns Hopkins University (JHU) Bloomberg School of Public Health and Director of the JHU Water Institute. In collaboration with the CDC and state health laboratories, Dr. Schwab has investigated numerous waterborne and foodborne outbreaks of viral gastroenteritis. Applying classical and molecular diagnostic tools, he has developed and participated in multiple research projects designed to evaluate the public health impacts of improving water access and potable water quality and the effectiveness of point-of-use water treatment. Dr. Schwab obtained both a Master of Science (1990) and a Ph.D. (1995) from the University of North Carolina at Chapel Hill School of Public Health. He then did a postdoctoral fellowship in the Department of Molecular Virology at Baylor College of Medicine in Houston, Texas prior to joining the Bloomberg School of Public Health at Johns Hopkins University in 1999.

Dr. Timothy J. Wade is an Epidemiologist with the United States Environmental Protection

Agency (EPA), in the Office of Research and Development at the Human Studies Division in Chapel Hill, North Carolina. He received a Master of Public Health degree in Epidemiology and Biostatistics in 1998 from the University of California, Berkeley, and a Ph.D. degree in Epidemiology in 2002, also from the University of California at Berkeley. His research focuses on quantifying and measuring the health effects of waterborne contaminants. Dr. Wade also holds an adjunct appointment in the Epidemiology Department at the University of North Carolina at Chapel Hill.

Dr. John M. (Jack) Colford is a Professor of Epidemiology at the University of California,

Berkeley, School of Public Health. He is a graduate of the Johns Hopkins School of Medicine (MD 1985) and the UC Berkeley School of Public Health (PhD, Epidemiology, 1996). He completed a residency in Internal Medicine and a fellowship in Infectious Diseases at the University of California, San Francisco and served as Chief Medical Resident at Stanford University Hospital. At UC Berkeley Dr. Colford teaches advanced courses on epidemiologic methods and he has also taught epidemiology methods courses for more than a decade each summer at the University of Michigan and the University of Zurich, Switzerland. He has authored more than 65 peer-reviewed scientific publications, including numerous articles on the health effects of waterborne diseases.



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He is the Principal Investigator of four triple-blinded, randomized controlled trials of drinking water and health effects funded by the National Institutes of Health, the Centers for Disease Control, the Environmental Protection Agency, and the state of California. Additionally, he is the Principal Investigator of numerous observational epidemiology studies of the health effects associated with drinking water and recreational water in the United States, Bolivia, Guatemala, and India.

Dr. Mark LeChevallier is the Director of Innovation & Environmental Stewardship for

American Water in Voorhees, NJ. He received his Bachelor of Science and Master of Science degrees in Microbiology from Oregon State University in 1978 and 1980 and his Ph.D. in Microbiology in 1985 from Montana State University. Dr. LeChevallier is also known around the industry for his talent for making complex scientific concepts more easily understandable to the general public. Dr. LeChevallier has been dedicated to advancing the science of water for more than 30 years through participation in national research foundations, including conducting nearly $5.9 million of research on the topic of water reuse and planning. He has also served as principal investigator or co-investigator on over 80 research grants totaling over $36 million. Additionally, he has served on a variety of professional committees at the local and national level, including several for American Water Works Association (AWWA) and EPA.

Mr. Steve Via is Director of Federal Relations for the American Water Works Association

(AWWA) working in AWWA’s Washington, D.C., office. AWWA is an international, nonprofit, scientific and educational society dedicated to the improvement of water quality and supply. Steve’s primary responsibilities at AWWA are working with federal agencies on the development of regulations that affect the drinking water community and communicating regulatory requirements to the water sector. His work includes both federal policy and individual rulemakings under SDWA, CERCLA, CAA, CWA, FIFRA, NEPA, RCRA, TSCA, and other statutes. Over his 18-year tenure with AWWA, Steve has been involved in the national science policy and risk management discussions surrounding disinfection by-products, pathogens, and a variety of emerging contaminants.

Mr. Gary A. Burlingame is director of Philadelphia Water's Bureau of Laboratory Services

(BLS). BLS is an accredited, full-service environmental and materials analysis laboratory. Mr. Burlingame provides operator workshops through PA-AWWA on such topics as waterborne diseases, water quality, and water contamination response. He has been active in the Water Research Foundation, in supporting AWWA on various committees, on EPA technical workgroups, and on the National Academies, National Research Council’s Committee on Public Water Distribution Systems: Assessing and Reducing Risks. Mr. Burlingame's book, Taste at the Tap, was published in 2009 by AWWA. He was also technical editor for AWWA's book, Diagnosing Taste and Odor Problems Field Guide (2011). Mr. Burlingame has been well published in AWWA's Opflow, and in 2001 he won the Opflow Publications Award. In 2000, Mr. Burlingame won The Golden Spigot Award from AWWA. The award is given to one AWWA member annually in recognition of exemplary service to AWWA in providing creative, visionary, and motivational leadership in achieving its mission and goals. Mr. Burlingame’s educational background includes a Bachelor and a Master of Science degree in Environmental Science from Drexel University, and he is board certified by AAEES as an environmental scientist.


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QUESTIONS SENT TO THE EXPERT PANEL

1. Big Picture Questions The interview will begin by reading the following “big picture” questions, to orient

the interviewee to the major issues of interest. The respondent will have a chance to answer these questions immediately or to return to them after the more specific questions are asked. ‐ What are the general issues around water supply systems as a whole and drinking water

distribution systems in particular that are important for public health research? ‐ In your opinion, what are the most pressing issues around water supply and water

quality in the US with respect to protecting the public’s health? ‐ What are some areas of water and health research important to water utilities?

2. Relevant Studies ‐ What are the most important studies to date on water distribution systems and health

outcomes? ‐ Are there any recent and/or ongoing studies that focus on distribution system water

quality and health that you know about that are not on the list that we sent you?

3. Study Design ‐ How do you think that analytical epidemiological studies have been and can be helpful

in understanding drinking water quality in distribution systems and associated health effects?

‐ What study designs are most feasible and cost-effective for investigating the relationship between water supply systems and health outcomes?

‐ What confounders should be considered in study design, data collection and analyses? 4. Health Outcomes ‐ What health outcomes are most relevant to study with respect to water systems? ‐ What approaches for measuring health outcomes should be considered? ‐ What are the best sources of health outcome data? 5. Target Study Populations ‐ What range of sample size (number of households and number of persons) is needed

for studies of water distribution systems and health, considering target health outcome and study design?

‐ Based on prior studies and health data, how significant are the health impacts on children compared to adults?

‐ What other vulnerable groups should be included in these studies? ‐ What are logical comparison groups for these studies? ‐ What are the best practices for recruiting these study populations? ‐ What are best practices for retaining the study population over time? 6. Exposure Assessment and Water Quality Indicators ‐ What approaches best capture the quality and quantity of drinking water that the study

population is exposed to over time?


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‐ How can water sampling be used most strategically in epidemiologic studies of drinking water quality and health?

7. Water Quality Indicators ‐ What indicators of water quality are most critical to study? ‐ What microbiological analyses (viruses, bacteria, and protozoa) are most relevant for

public health? ‐ What are the challenges encountered by researchers in studying those indicators? ‐ What emerging water quality indicators look promising and are relevant to health? ‐ What are best practices for sampling to address issues of variability in measurement of

indicator organisms (e.g., how many replicate samples are needed? how often do you need to sample to get reliable results? what time of day to sample?)

‐ What volumes of water should be sampled? ‐ Where should water be sampled in the distribution system? Primary and secondary

sampling locations? ‐ When should water be sampled? e.g., Seasonal effects? Sampling triggered by a change

in a water quality parameter? ‐ At what locations in the distribution systems and/or treatment plants should these

indicators be monitored? ‐ What are the potential applications of in-line monitoring of water quality parameters in

epidemiologic studies of water and health? 8. Hydraulic and Water Quality Models ‐ How can hydraulic and water quality models be used to support planning, design and

implementation of water and health studies? ‐ What are the important parameters required to develop and validate these models? ‐ What are some of the challenges in acquiring data from water utilities and/or other

sources to develop these models? How can health researchers minimize potential conflicts with water utilities and work collaboratively with them?

‐ What types of hydraulic models are the most useful?

9. Consumer Behavior ‐ What consumer behavior needs to be considered in studies of drinking water quality

and health? ‐ What are best practices for collecting data on consumer drinking water behavior?


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ABBREVIATIONS

AGI acute gastrointestinal illness AL action level AOC assimilable organic carbon AOR adjusted odds ratio AWWA American Water Works Association BLS Bureau of Laboratory Services CAD computer-aided design CCR Consumer Confidence Report CDC Centers for Disease Control and Prevention CERCLA Comprehensive Environmental Response, Compensation, and

Liability Act CFR Code of Federal Regulations cfu colony forming unit CI confidence interval CONSORT Consolidated Standards of Reporting Trials CWS community water systems DBPR Disinfectants and Disinfection Byproducts Rules DRINK Drinking Water Research Information Network DS distribution system ECHO Enforcement and Compliance History Online EPA United States Environmental Protection Agency FBRR Filter Backwash Recycling Rule FIFRA Federal Insecticide, Fungicide, and Rodenticide Act FOIA Freedom of Information Act fps feet per second GI gastrointestinal GIS geographical information system GWR Ground Water Rule GWUDI Groundwater Under the Direct Influence of Surface Water HPC heterotrophic plate counts ICR Information Collection Rule IESWTR Interim Enhanced Surface Water Treatment Rule LCR Lead and Copper Rule LT1ESWTR, LT1 Long Term 1 Enhanced Surface Water Treatment Rule LT2ESWTR, LT2 Long Term Enhanced Surface Water Treatment Rule 2


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MAC Mycobacterium avium Complex MCL Maximum Contaminant Level MCLG Maximum Contaminant Level Goal MFL million fibers per liter MRDL Maximum Residual Disinfectant Level NCOD National Contaminant Occurrence Database NIEHS National Institute for Environmental Health Science NORS National Outbreak Reporting System NPDWR National Primary Drinking Water Regulations NTM non-tuberculous mycobacteria NTNCWS Non-Transient Non-Community Water System NTU nephelometric turbidity unit O&M Operations and Maintenance OR odds ratio POE point of entry POU point of use Psi pounds per square inch RAA running annual average RCRA Resource Conservation and Recovery Act RR Risk Ratio SCADA Supervisory Control and Data Acquisition SDWIS Safe Drinking Water Information System SMF Standardized Monitoring Framework SOC synthetic organic contaminants STORET STOrage and RETrieval SWTR Surface Water Treatment Rule TEVA Threat Ensemble Vulnerability Assessment TEVA-SPOT Threat Ensemble Vulnerability Assessment Sensor Placement

Optimization TOC total organic carbon TT treatment technique USGS United States Geological Survey UV Ultraviolet Light VOC volatile organic contaminants WTP Water Treatment Plant


e eoo te or r ter trto Ste ceMany individuals provided insights that helped shape this manual. The...

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Transcript of e eoo te or r ter trto Ste ceMany individuals provided insights that helped shape this manual. The...