United States
Environmental Protection
Agency
Office of Water (4601M)
Office of Ground Water and Drinking Water
Total Coliform Rule Issue Paper
Distribution System Indicators of Drinking Water
Quality
December 2006

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PREPARED FOR:
U.S. Environmental Protection Agency
Office of Ground Water and Drinking Water
Standards and Risk Management Division
1200 Pennsylvania Ave., NW
Washington DC 20004
PREPARED BY:
HDR Engineering, Inc.
The Cadmus Group, Inc.
U.S. EPA Office of Groundwater and Drinking Water
Background and Disclaimer
The USEPA is revising the Total Coliform Rule (TCR) and is considering new possible
distribution system requirements as part of these revisions. As part of this process, the
USEPA is publishing a series of issue papers to present available information on topics
relevant to possible TCR revisions. This paper was developed as part of that effort.
The objectives of the issue papers are to review the available data, information and
research regarding the potential public health risks associated with the distribution
system issues, and where relevant identify areas in which additional research may be
warranted. The issue papers will serve as background material for EPA, expert and
stakeholder discussions. The papers only present available information and do not
represent Agency policy. Some of the papers were prepared by parties outside of EPA;
EPA does not endorse those papers, but is providing them for information and review.
Additional Information
The paper is available at the TCR web site at:
http://www.epa.gov/safewater/disinfection/tcr/index.html
Questions or comments regarding this paper may be directed to TCR@epa.gov.

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Distribution System Indicators of Drinking Water Quality
Draft
December 14, 2006
Prepared for:
Rosemarie Odom, Work Assignment Manager
Environomics contract 68-C-02-042
Work Assignment Number 06
Ken Rotert, Work Assignment Manager
U.S. Environmental Protection Agency
Office of Ground Water and Drinking Water
1200 Pennsylvania Avenue, NW.
Washington, DC 20460
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1	INTRODUCTION	4
2	BACKGROUND	4
2.1 Organization of the Paper	5
3	DEFINITIONS	6
3.1	Distribution System	6
3.2	Indicator	6
4	RATIONALE FOR USE OF INDICATORS	6
4.1	Why Not Monitor Directly for Contaminants?	6
4.2	What Is an Ideal Indicator?	7
5	DISTRIBUTION SYSTEM PROBLEMS	9
5.1	Pathways that Breach Distribution System Integrity	9
5.1.1	Main Breaks, Repairs, and Installation	10
5.1.2	Operation and Maintenance Deficiencies	10
5.1.3	Permeation	11
5.1.4	Finished Covered Storage Tank Deficiencies	11
5.1.5	Cross-connections and Backflow	11
5.1.6	Intrusion	12
5.1.7	Biofilm	12
5.1.8	Corrosion and Leaching	12
5.2	Distribution System Contamination	13
5.2.1	Fecal Contamination	13
5.2.2	Toxic or Carcinogenic Contamination	14
5.3	Public Health Outcome	14
5.3.1 Waterborne Disease Outbreaks and Endemic Illness	14
6	INDICATORS	15
6.1	Microbial Indicators	15
6.1.1	Total Coliforms	15
6.1.2	Thermotolerant (Fecal) Coliforms	18
6.1.3	Escherichia coli	20
6.1.4	Total Heterotrophic Bacteria as Measured by the HPC Method	22
6.1.5	Total Bacteriological Counts and Total Viable Bacterial Counts	24
6.1.6	Pseudomonas and Aeromonas	26
6.1.7	Enterococci and Fecal Streptococci	28
6.1.8	Somatic Coliphage	29
6.1.9	Male-Specific Coliphage 	31
6.1.10	Clostridium perfringens	33
6.1.11	Bacteroides fragilis phages	34
6.2	Chemical Indicators	35
6.2.1	Residual Disinfectant	35
6.2.2	pH	38
6.2.3	Alkalinity	39
6.2.4	Calcium	40
6.2.5	Conductivity	41
6.2.6	Fecal Sterols	42
6.2.7	Caffeine and Pharmaceuticals	43
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6.2.8	Organic Carbon	45
6.2.9	Adenosine Triphosphate (ATP)	47
6.2.10	Endotoxin	48
6.2.11	Iron	49
6.2.12	Ammonia, Nitrate, Nitrite, and Nitrogen	51
6.2.13	Aluminum	52
6.2.14	Chloride	53
6.2.15	Microbially Available Phosphorous	54
6.2.16	Turbidity	55
6.3 Other Indicators	56
6.3.1	Temperature	56
6.3.2	Pressure	57
6.3.3	Sanitary Survey Results	59
6.3.4	Water Loss	62
7	SUMMARY OF INDICATORS BY DISTRIBUTION SYSTEM PROBLEM	63
8	REFERENCES	67
9	APPENDICES	89
9.1 Summary Table of Advantages and Disadvantages for Each Indicator	89
Exhibit 1 Characteristics of the Ideal Microbial Indicator of Fecal Contamination	8
Exhibit 2: Summary of Findings from Craun et al. (1997)	17
Exhibit 3 Microbial Indicators	64
Exhibit 4 Chemical Indicators	65
Exhibit 5 Other Indicators	66
Distribution System Indicators of Drinking Water Quality
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1 Introduction
As discussed in the "TCR and Distribution System Issue Papers Overview," EPA plans
to assess the effectiveness of the current TCR and determine what alternative and/or additional
monitoring strategies are available, and to consider revisions to the TCR with new requirements
for ensuring the integrity of the distribution system. Part of this assessment entails reviewing
available indicators of distribution system water quality and determining whether a potential
indicator can adequately identify the failure of barriers that protect against waterborne disease.
This paper compiles available information on indicators of drinking water quality within
potable water distribution systems. The indicators include microbial and non-microbial
parameters for which sample collection and analyses could be performed to identify existing or
potential problems, as well as other methods or tools that may similarly function as problem
indicators. Distribution-related problems for which indicators are evaluated are based on the
priority issues identified for the Distribution System White Papers developed for the Total
Coliform Review potential revisions (USEPA, 2006). For the purposes of this paper, the
distribution system-related problems for which indicators might be used were divided into three
categories that represent the range or degree of severity associated with problem outcomes
including:
1)	Indicators of Pathways that Breach Distribution System Integrity
2)	Indicators of Distribution System Contamination
3)	Indicators of Public Health Risk
The descriptions of each indicator were compiled by reviewing the primary literature
available in online databases, such as Medline and Biological abstracts; resource materials from
reference books, technical reports, and technical conference proceedings; and additional
documents previously prepared for the U.S. Environmental Protection Agency (EPA).
Many or all of the indicators addressed herein may be useful for purposes other than
distribution system assessment, including the identification of water treatment effectiveness or
source water treatment needs. This paper focuses only on distribution system applications. As
such, topics beyond the scope of this paper include the following: indicator applications for
environmental monitoring of groundwater and surface waters, water quality issues related to
recreational exposure to water, and treatment monitoring at source water treatment facilities or
at the point of entry of the treated water to the distribution system. On some occasions,
however, if information is not available regarding potential use of an indicator in the distribution
system, then the performance of an indicator in source water or during treatment may be
discussed. The discussion includes both regulated and unregulated indicators.
2 Background
Drinking water monitoring based upon tests for coliform bacteria as indicators of fecal
contamination originated approximately 100 years ago (Cox, 1997). At that time, most
waterborne disease outbreaks were caused by pathogenic organisms and could be clearly
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traced to fecal contamination of drinking water. The prevention of gastrointestinal illness from
drinking water exposure meant keeping human fecal material out of water, and the best
available technology for detecting fecal contamination was to monitor drinking water for the
presence of coliform bacteria.
Today, water is treated and piped through elaborate distribution systems. The age and
complexity of distribution systems, coupled with the increased availability and use of chemicals,
has increased the likelihood for contamination events and waterborne disease not related to
source water treatment deficiencies. There is also endemic disease that is suspected to occur
due to contamination of distribution systems (Payment et al., 1991). Monitoring water for
indicators and for other conditions that may provide information on distribution system
deficiencies and integrity problems is an important tool for protecting the public health.
2.1 Organization of the Paper
Section 3 discusses key definitions. Section 4 provides the rationale for using indicators
and an overview of the desired characteristics of an ideal indicator. Section 5 discusses
distribution system problems for which indicators could potentially be used. These problems
serve as the basis for the information compiled for each indicator and how indicators are
subsequently compared.
Section 6 lists all of the indicators addressed in this paper and is organized into types of
indicators in terms of Microbial, Chemical, or Other for convenience. For each indicator the
discussion addresses potential applications of the indicator in terms of the distribution system
problems outlined in section 5. This includes application as: an indicator of pathways that
breach distribution system integrity; an indicator of distribution system contamination; and an
indicator of public health outcome. Many indicators could potentially be used in all three problem
categories, to differing degrees.
Section 7 presents the summary table of indicators grouped by the distribution system
problems that they can potentially help identify. The usefulness of each indicator in the various
applications has been designated as either "strong", "weak", or "not applicable". The rationale
used for selecting these designations is provided in Section 7.
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3 Definitions
3.1	Distribution System
Within the context of this paper, a distribution system is defined as a system of
conveyances that distributes potable water. All pipes, storage tanks, pipe laterals, and
appurtenances that comprise the delivery system are included in this definition.
Appurtenances owned and operated by private customers, such as service lines and
plumbing components, that are typically not considered the responsibility of the public
water system purveyor are also considered in this definition because they are physically
attached to the distribution system and could potentially be a source of contamination,
through, for example, backflow or leaching of contaminants from service lines. These
and similar events may affect the water quality under the purveyor's jurisdiction.
However this paper does not consider indicators that specifically identify problems in
household plumbing.
3.2	Indicator
An "indicator" is a parameter that can be measured and used as a surrogate for
another parameter or condition which either cannot be directly measured or is difficult to
directly measure. Indicators are used in many contexts and the definition for an indicator
may vary based on its use. By definition a contaminant cannot be an indicator of itself.
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.
4 Rationale for Use of Indicators
4.1 Why Not Monitor Directly for Contaminants ?
Many contaminants have been identified as causes of waterborne disease
outbreaks from drinking water exposures. These contaminants can enter the distribution
system from multiple pathways, as presented in Section 5. Waterborne pathogens are
biologically diverse, including bacteria, viruses, and protozoa. While methods for the
detection of some pathogens and microorganisms have been developed, some of the
methods are extremely labor intensive, require long incubation periods, require special
reagents, or are very expensive. Some pathogens and viruses have never been
successfully propagated in the laboratory. Even where the methods are available, few
laboratories have the expertise and the facilities to isolate and identify pathogens
capable of causing waterborne diseases. In addition, monitoring directly for a single
pathogen will only provide information for that specific pathogen and may not provide
information about other potential contaminants, unless the degree of co-occurrence of
the organisms can be determined. The resources and technology needed to monitor for
all potential pathogens is not available for most water systems.
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Similarly, numerous chemical compounds can contaminate distribution systems.
Timely monitoring for each and every chemical compound that could be present in the
distribution system is simply not feasible for most water systems given technical and
resource constraints.
Under certain circumstances, the use of an indicator as a surrogate for the direct
measurement of multiple pathogens or compounds, or as the first-level screening tool to
better focus on specific pathogens, can be an effective and feasible approach.
4.2 What Is an Ideal Indicator?
The characteristics of an ideal indicator vary based on the specific context or
situation that an indicator is measuring. For distribution system water quality and
infrastructure condition, a broad definition of the ideal indicator is not available that
covers both microbial and chemical contamination. However, considerable literature is
available on the characteristics of an ideal indicator for one type of distribution system
contamination - fecal contamination. The following discussion focuses on indicator
attributes for only fecal contamination, but the concepts could also be applied across
other types of contamination or conditions.
The characteristics of the "ideal indicator" for fecal contamination were proposed
by several investigators beginning with Bonde (1962 and 1966) and followed by
Scarpino (1971), Dutka (1973), Cabelli (1977), Barrow (1981), and the NRC (2002).
These characteristics are described in Exhibit 1.
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Exhibit 1 Characteristics of the Ideal Microbial Indicator of Fecal Contamination
Characteristic
Bonde
1966
Scarpino
1971
Dutka
1973
Cabelli
1977
Barrow
1981
NRC
2002
Be present when and where
pathogens are present
X
X
X
X


Be unable to replicate and grow in
the environment
X
X
X

X

Be more resistant to disinfection
than pathogens
X

X
X
X
X
Be easy to isolate and enumerate
X
X
X
X
X

Be applicable to all types of water

X




Not be subject to antibiosis
X





Be absent from sources other than
sewage or be exclusively
associated with sewage



X
X

Occur in greater numbers than
pathogens
X




X
Density of indicator should have a
direct relationship to degree of
fecal contamination

X




Indicator density should correlate
with health hazard from a given
type of pollution



X


Correlated to health risk





X
Similar (or greater) survival
compared to pathogens





X
Similar (or greater) transport
compared to pathogens





X
Specific to a fecal source or
quantifiable as to source of origin





X
Desirable Attributes of Indicator Methods
Specificity to desired target
organism





X
Broad applicability





X
Precision





X
Adequate sensitivity





X
Length of time to get results





X
Quantifiable





X
Measures viability or infectivity





X
Logistical feasibility





X
Adapted from Dufour, 1984.
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5 Distribution System Problems
The distribution system problems discussed in Section 5 are grouped into the following
sequential focus areas:
1)	Pathways that Breach Distribution System Integrity
•	Main Breaks, Repairs and Installation
•	Operation and Maintenance Deficiencies
•	Cross-connections and Backflow
•	Intrusion
•	Permeation
•	Finished Covered Storage Tank Deficiencies
•	Biofilms
•	Corrosion and Leaching
2)	Distribution System Contamination
•	Fecal Contamination
•	Toxic or carcinogenic contamination
3)	Public Health Risk
•	Waterborne disease Outbreaks and Endemic Illness
By evaluating indicators in a sequential manner (e.g., it is possible to have a
breach in distribution system integrity but not cause contamination, and it is also
possible to have a contamination event, but not cause a waterborne disease), the
indicators can be considered with regard to their effectiveness as predictive and/or
forensic tools. The pathways that breach distribution system integrity can generally be
thought of as external (i.e., cross-connection, intrusion, main breaks, etc.) or internal
(i.e., biofilms, corrosion and leaching) pathways. These designations were used in the
summary tables developed in Section 7.
5.1 Pathways that Breach Distribution System Integrity
Integrity of the distribution system refers to: (1) physical integrity- the
maintenance of a physical barrier between the distribution system interior and the
external environment; (2) hydraulic integrity - the maintenance of a desirable water flow,
water pressure, and water age, taking both potable drinking water and fire flow provision
into account; or (3) water quality integrity, which refers to the maintenance of finished
water quality via prevention of internally derived contamination (NRC, 2006). Breaches
of distribution system physical, hydraulic, or water quality integrity may occur through the
pathways listed above.
It is desirable to place boundaries on the degree/severity of breach or water
quality change that should be considered, since it is impractical and unnecessary to
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attempt to indicate every type of change. Therefore, in the following discussion, each
pathway is considered based on a change or breach that at a minimum would require
improvements in operations and maintenance procedures. Minor water quality changes,
such as minor fluctuations in temperature, pH, alkalinity, or disinfectant residual, that are
inherent in daily and seasonal fluctuations associated with a well-operated treatment
plant and distribution system are not considered.
5.1.1	Main Breaks, Repairs, and Installation
Contamination of pipe interiors is not uncommon during installation. Pierson et
al. (2002) surveyed inspectors, engineers, and other distribution workers at three utilities
about potential sources of contamination during the construction or replacement of water
mains. Commonly reported sources of contamination of drinking water and pipe interior
construction identified in Pierson et al. (2002) include the following:
Broken service lines fill trench during installation;
Pipe gets dirty during storage before installation;
Trench dirt gets in pipe during installation; and
Rainwater fills trench during installation.
Besner et al. (2002) summarized contamination concerns during new main
installation and repair or replacement. Inadequate flushing velocities to purge
contaminants from the new pipe, unsanitary conditions during work efforts, and
introduction of contaminated sediment into the pipe that was not subsequently removed
all create feasible contamination scenarios. The potential problem of contamination
during pipe repair or installation is described more fully (including examples) in the paper
titled "New or Repaired Water Mains" (AWWA and EES, 2002).
Water lines (mains and service lines) can be susceptible to contamination if they
experience a break or opening and are in close proximity to sewer lines. This condition
could result in contamination of the water main if the sewer line leaks and the water main
experiences low or negative pressures, such as in the case of an intrusion event.
Pressure reduction or loss can occur in association with main and service line
breaks. The pressure reduction or loss can result in contaminant entry (through
intrusion or backflow). A 2000 American Backflow Prevention Association (ABPA)
survey indicated that 19 percent and 16 percent of pressure loss events within the
distribution system were attributed to main breaks and service line breaks, respectively.
5.1.2	Operation and Maintenance Deficiencies
Flushing and pigging are routine maintenance practices often conducted within
the distribution system to address consumer complaints and to reduce the retention time
of water to improve water quality. Utilities have typically manually flushed water from the
system using fire hydrants or flushing hydrants to control microbial growth (Brandt et al.,
2004). These practices can affect the distribution system water quality in a negative
manner if not conducted properly. Improper flushing can result in moving a contaminant
further into the distribution system.
Stagnant water can occur in dead-end pipes or storage facilities that are over-
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sized or have periods of limited use. Stagnant water provides an opportunity for
suspended particulates to settle into pipe sediments, for biofilm to develop, and for
biologically mediated corrosion to accelerate (Brandt et al., 2004). Long-term water
storage in finished water reservoirs (lasting weeks or several months) can result in
waterborne heterotrophic bacteria growing in sediments, attaching to inner walls, and
spreading a biofilm over surfaces (Geldreich, 1996). Long retention time can also result
in reduction in disinfectant residual and cause the release of ammonia through the decay
of chloramines (Brandt et al., 2004).
Loose deposits are susceptible to entrainment and suspension under normal
hydraulic scenarios, such as flow reversals and velocity changes (Friedman et al.,
2004a). Sudden flow increases (USEPA, 1992) or hydraulic disturbances (USEPA and
CA DHS, 1989) can cause accumulated biofilm, scales, sediment, or tubercles to shear
or slough, resulting in release to the water column. Also, if the distribution system is fed
by multiple sources with varying water quality, the release of biofilms, scales, or
sediments may occur at the interface between the sources.
The magnitude of pressure transients initiated by valve operations can be
reduced by slowing the rate of opening and closing. When a valve is closed slowly, the
rate of change of velocity in the pipeline decreases (Friedman et al., 2004b). The
magnitude of transient in water mains can be as high as 100-ft (43 psi) change in head
for every 1-fps change in velocity (Walski and Lutes, 1994).
5.1.3	Permeation
Permeation of piping materials and nonmetallic joints can be defined as the
passage of contaminants external to the pipe through porous, nonmetallic materials, into
the drinking water (Friedman et al., 2002). The problem of permeation is generally
limited to plastic, nonmetallic pipe. In addition, new PVC pipes exhibit lower permeation
rates than new polyethylene or polybutylene pipes (DWI0772, 1997). More than 100
incidents of drinking water contamination resulting from permeation of subsurface mains
and fittings have been reported in the United States (Glaza and Park, 1992). BTEX and
organic solvents are most common contaminants that permeate plastic pipe (Friedman
et al., 2002).
5.1.4	Finished Covered Storage Tank Deficiencies
Storage tank deficiencies, such as vents without screens, inadequate hatches,
access hatches that are not locked, and physical openings in storage tank roofs, can
result in the entry of contaminants. Coatings on the storage tank interior can also result
in contamination if the coating fails or is not properly cured. Potential public health
issues associated with finished water storage facilities are described in a distribution
system white paper on covered storage (AWWA & EES, 2002c).
5.1.5	Cross-connections and Backflow
A cross-connection is an unprotected connection between a public potable water
system and any other system or source where unintended substances can be potentially
introduced to the potable water supply, such as used water, industrial fluid, or gas (USC-
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FCCCHR, 1993).
Backflow is the "undesirable reversal of flow of water or mixtures of water and
other liquids, gases or other substances into the distribution pipes of the potable supply
of water from any source or sources (USC-FCCCHR, 1993)." In order for a backflow
event to occur, a cross connection and pressure loss that creates a pressure differential
must exist within the distribution system, or the cross connection has created a pressure
gradient in excess of normal distribution system pressure.
From 1971 through 1998, "chemical and microbial contamination from cross-
connections and backsiphonage were responsible for most distribution system related
illnesses. Outbreaks could be traced to backflow prevention devices that were needed
but not installed, had been inappropriately installed, or had been inadequately
maintained" (Craun and Calderon, 2001).
5.1.6	Intrusion
Intrusion can occur when a transient or low pressure event occurs within the
distribution system that results in a lower pressure within the pipe than the pressure
outside the pipe. This pressure gradient can result in contaminants contained in soil and
water surrounding the distribution pipe to be "sucked" into the distribution pipe if external
water pressure exceeds internal pressure (LeChevallier et al., 2002). Friedman et al.
(2004b) demonstrated that transient pressure waves can travel several miles throughout
the distribution system until they are dissipated, thereby increasing the potential for
contamination through leakage points over a wide-spread area.
5.1.7	Biofilms
Biofilms are defined as a complex mixture of microbes, organic, and inorganic
material accumulated amidst a microbially produced organic polymer matrix attached to
the inner surface of the distribution system (USEPA, 2002). Contaminants, including
total coliforms and some pathogens, may attach to or become enmeshed in biofilms on
pipe walls in distribution systems. Many pathogens have been found to survive, if not
grow, in these pipe biofilms where they are protected from disinfectants. Over time,
coliform bacteria may detach or slough from the biofilm, causing persistent total coliform
detections. Pathogens may also be included in the detached material and may result in
waterborne disease. The biofilm can result in total coliform positive detections and other
contamination events if disturbed.
Organisms that have been found in biofilms include bacteria, viruses, protozoa,
invertebrates, algae, and fungi (USEPA, 2002). Less efficient treatment of source water
during runoff or changing water quality conditions may cause a change in the organic
matter of treated water, which in turn may enable increased biofilm growth in the
distribution system (Besner et al., 2002).
5.1.8 Corrosion and Leaching
Corrosion is the gradual deterioration of metal pipe, metal fixtures, cement mortar
lining in pipe, or other substances because of a reaction with the water (AWWA, 1999a).
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Corrosion can be the result of physical actions that erode the coating of a pipe, chemical
dissolution that leaches a pipe's lining or wall material, or electrochemical reactions that
remove metal from the wall of the pipe (AWWA, 2000). Corrosion can result in the
leaching of certain metals, such as lead and copper (AWWA, 2000). Biological growths
within the distribution system can also cause corrosion by providing an environment in
which physical and chemical interaction can occur. Leaching is defined as the
dissolution of metals, solids, and chemicals into drinking water (Symons et al., 2000).
Some of the factors that influence corrosion and leaching are water velocity, pipe
material, and water quality within the distribution system, such as pH, alkalinity,
temperature, chlorine residual, and hardness of the water.
Contaminants from pipe linings, tank coatings, fittings, or other materials can
sometimes leach into the drinking water, causing contamination. Cement-lined pipes
and storage tanks can leach calcium carbonate into the water, which may significantly
increase the alkalinity and pH of the water. This is especially true when the cement-
lined material is new, but also depends on the type of cement used, the contact time
between the water and cement material, and the diameter of the pipe.
5.2 Distribution System Contamination
Contamination problems in the distribution system can occur through the
pathways or breaches in distribution system integrity as described in the previous
section. However, an indication of a pathway does not necessarily indicate the
presence of a specific contaminant, nor does it indicate that contamination has occurred
through that pathway. Hence another way of identifying a distribution system problem is
to look specifically for indicators of contaminants, i.e. contaminants that pose a public
health risk.
5.2.1 Fecal Contamination
Fecal contamination of distribution system water may occur when the distribution
system is compromised such that a pathway has been established for fecal contaminant
entry. Contamination of this type may occur through intrusion, openings in storage
tanks, a broken main, or through a cross connection between a sewage source and
water line. For example, in June, 2001, an employee of the Mauriceville Special Utility
District in Texas inadvertently connected a sewer line to a fresh water line (U.S. Water
News Online, 2001). As a result, sewage contaminated the drinking water supply for
about 20 days before customer complaints about particles in the water prompted the
utility district to conduct sampling. The samples came back positive for fecal coliform
bacteria and resulted in an acute TCR violation.
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5.2.2 Toxic or Carcinogenic Contamination
Toxic or carcinogenic contamination can enter through external pathways that
result in contamination of the distribution system, similar to fecal contaminants. The
events that can lead to this type of contamination include intrusion, openings in storage
tanks, broken mains, permeation, or through a cross connection between a non-potable
source and water line. Examples of toxic and carcinogenic contaminants include
organic compounds (e.g. PCBs, benzene), heavy metals (e.g., lead, mercury, cadmium),
asbestos, and others.
Toxic and carcinogenic contaminants can also manifest within the distribution
system, such as in the case of biofilms, corrosion, and leaching. In addition,
modification to O&M practices or to treatment practices can cause the release of
contaminants in established pipe scales due to changes in pH, alkalinity, or other water
quality parameters. A separate White Paper is currently under development that
addresses accumulation and release of inorganic contaminants in distribution systems.
5.3 Public Health Outcome
Public health outcomes such as 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 public
health outcome.
5.3.1 Waterborne Disease Outbreaks and Endemic Illness
Ingestion of distribution system water containing pathogens, toxins, or
carcinogens can result in illness. In some instances, the illness may go unnoticed by
water system personnel or public health officials, and in other instances, officials may be
unable to link the illness with the water system. The latter scenario can occur when the
affected population believes the illness may have been foodborne, where follow-up
testing of the distribution system could not detect the presence of the contaminant, or
when the number of people affected may not have triggered notice by the public health
community.
However, illnesses may be recognized by local public health officials or others,
and in some instances, reported to the Centers for Disease Control and Prevention
(CDC). CDC's investigation will determine if the contamination event meets the two
criteria for a waterborne disease outbreak. First, a waterborne disease outbreak is
defined as when two or more individuals have experienced a similar illness after
ingestion of water or exposure to water. If water quality data indicate chemical
contamination or laboratory-confirmed primary amebic meningoencephalitis, a
waterborne disease outbreak is defined as when one or more individuals experience
illness. Second, epidemiological evidence must implicate ingested water as the
probable source of illness (CDC, 2004).
There is evidence of significant under-reporting of the number of outbreaks and
illnesses associated with these outbreaks due to inherent limitations in detecting them
and biases in reporting them. For example, most local surveillance systems are
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passive—i.e., the disease reporting is primarily the responsibility of the health care
provider and/or laboratory (Frost et al., 1996). Frost et al. (1996) noted that "health care
providers and laboratories usually receive little encouragement from the health
department to report illnesses, and enforcement of reporting requirements is minimal." In
addition, only a fraction of illness-causing agents are reportable to the CDC. CDC has
identified 52 nationally notifiable diseases that might be waterborne, including
cryptosporidiosis, giardiasis, salmonellosis, typhoid fever, legionellosis and shigellosis.
States, however, are not obligated to include these diseases in their own surveillance
programs. A 1997 survey revealed that approximately 87 percent of state health
departments include 80 percent of the 52 nationally notifiable diseases in their
surveillance programs. Only about one-third of states include over 90 percent of the
diseases (GAO 1999). Some of the pathogens associated with distribution system
contamination are not on CDC's list. Moreover, CDC does not have a comparable list for
toxic chemicals.
6 Indicators
The discussion for each indicator provides background information, identifies
potential distribution system problems that the indicator may demonstrate or predict
vulnerability to, and discusses advantages and disadvantages of the indicator.
Under every indicator, each category of distribution system problems is
considered: Indicators of pathways that breach distributions system integrity; Indicators
of distribution system contamination; Indicators of Public Health Outcome. However, if
information was not readily available for a category, that category was omitted from the
discussion.
6.1 Microbial Indicators
6.1.1 Total Conforms
Background
Total coliforms are defined as gram negative, non sporeforming, facultatively
anaerobic rod-shaped bacteria capable of lactose-fermentation with gas production at
35°C within 48 hours. The group consists of several genera of the family
Enterobacteriaceae, including species Enterobacter, Klebsiella, Citrobacter, and E. coli.
Total coliforms may be of fecal origin, but also survive and grow in the environment
(Flint, 1987; Pommepuy et al., 1992). Total coliforms have been used as an indicator of
drinking water quality since the early 1900s. The rationale for using total coliforms in this
manner is based on their presence in large numbers in the gut of humans and other
warm blooded animals, allowing their detection even after extensive dilution (Stevens et
al., 2001). Although not typically pathogens themselves, they are used to indicate the
potential for pathogenic organisms to be present (52 FR 42226; Nwachuku et al. 2002).
However, where other problems are not evident (e.g., cross-connections or treatment
deficiencies), a persistent coliform problem may indicate biofilm growth problems
(Edberg, 1994; O'Neill and Parry, 1997; Crozes and Cushing, 2000). Investigators have
identified several species of coliforms that can grow in pipe biofilms, including
Distribution System Indicators of Drinking Water Quality
15

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Enterobacter cloacae, Klebsiella oxytoca, Citrobacter freundii, and Enterobacter
agglomerans (Geldreich, 1996).
Total coliforms are typically associated with treatment effectiveness, and should
be absent from adequately treated plant effluents (LeChevallier et al., 1991, 1996, 1999;
Craun et al. 1997, 2001). The presence of total coliforms in the distribution system
while possibly due to inadequate treatment, could also be due to cross-connections or
failure to maintain an adequate disinfectant residual (LeChevallier, 1996). Coliforms
present in the distributions system can come from a number of sources, and they can
also grow within the distribution system, in biofilms as discussed below. Simple,
inexpensive analytical methods are available (Rompre et al., 2002).
Total coliforms are usually effectively inactivated by disinfectant residuals
commonly encountered in distribution systems. They show less resistance to
disinfectants than Giardia, Cryptosporidium, and some viruses.
Indicator of Breaches Distribution System Integrity
While coliforms may be used as an indicator of treatment effectiveness, they can
be introduced or grow within the distribution system. As discussed above total coliforms
can indicate distribution system integrity problems such as cross-connections, intrusion,
or presence of biofilms. In some cases, it may be difficult to identify a specific pathway
or breach of distribution system integrity using total coliforms as an indicator.
Total coliforms have been identified as a component of biofilms (Edberg, 1994;
O'Neill and Parry, 1997; Crozes and Cushing, 2000). Environmental conditions in the
distribution system where the water temperature is above 15°C, the pH is neutral, and
AOC concentrations are adequate, favor the colonization of total coliform bacteria on
surfaces within the distribution that may become part of a biofilm (WHO, 2004).
Investigators have identified several species of coliforms that can grow in pipe biofilms,
including Enterobacter cloacae, Klebsiella spp., Citrobacter freundii, and Enterobacter
agglomerans (Geldreich, 1996). LeChevallier et al. (1987) studied distribution system
biofilms at a water utility in New Jersey and found that coliforms moved from the
treatment plant into the distribution system, and were found in increased numbers at
sites corresponding to growth of biofilm. While total coliforms may be an indicator of the
presence of biofilms, they are not uniformly associated with biofilms (LeChevallier, 1987;
Characklis, 1986), nor do they only occur because of the presence of biofilms as
suggested by the multiple potential pathways outlined above.
Indicator of Distribution System Contamination
Some of the total coliform bacteria are capable of growth in environmental
conditions, which may limit their use as indicators of fecal contamination in a water
system. A subset of the total coliform group is the fecal coliform group, which is believed
to serve as better indicators of fecal contamination. E. coli and fecal coliforms are
thought to be good fecal indicators and are part of the total coliform group.
Indicator of Public Health Outcome
Total coliforms may be adequate for predicting a system's vulnerability to
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16

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bacterial pathogens, but may not be sufficient for predicting a system's vulnerability to an
outbreak from other microbial contaminants, such as protozoa and viruses (Nwachuku et
al., 2002).
Craun et al. (1997) reviewed epidemiologic investigative reports of waterborne
disease outbreaks and available data from 1983-1992 (Exhibit 2). The authors
examined the percent of outbreaks where total coliforms are present, depending on the
system type and the type of outbreak. This research finds different rates depending on
the type of system and outbreak. The authors also noted that increased sampling for
coliform organisms, above that required for compliance monitoring, may have occurred
during the outbreaks. In addition, the authors cautioned that the data were limited and
could not rule-out the influence of random error.
Exhibit 2: Summary of Findings from Craun et al. (1997)

Systems with
Total Coliforms
Present During
Outbreak
Investigations
(of 157 outbreaks
with available
information)
Systems with Total Coliforms Present During Outbreak
Investigations Where:
Outbreaks
Attributed
to
Treatment
Inadequacy
Outbreaks
Attributed to
Distribution or
Unknown
Deficiency
Outbreaks
Caused by
Bacteria,
Viruses, or
Unidentified
Agents
Outbreaks
Caused by
Giardia or
Cryptosporidiu
m
Community
52%
48%
63%
64%
35%
Non-
community
87%


CD
O
>.o
o-

Individual
(nonpublic)
93%


93%

All Systems
73%




Note: Shaded boxes indicate data not provided
In a comparison of TCR violations for water systems that had or had not reported
an outbreak during 1991-1998, Nwachuku et al. (2002) concluded that when all
etiologies were considered for community water system outbreaks, the outbreak
systems were more likely than non-outbreak comparison systems (p<0.05) to have
reported an MCL violation in the 3-and 12-month periods before the outbreak. Although
the focus of the paper was on the TCR, the authors also concluded that their analyses,
along with disinfection information, showed that coliform bacteria and the TCR are
insufficient to assess an increased risk of waterborne disease outbreaks from Giardia
and Cryptosporidium and may be insufficient for some viruses (Nwachuku et al., 2002
The research concluded that current, routine monitoring under the TCR was not
adequate to predict waterborne outbreak vulnerability, and that additional monitoring in
combination with an additional indicator may be more reliable.
Advantages
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Total coliform densities are much greater than the density of fecal indicators
(Payment et al., 1985). Total coliform bacteria are useful in assessing treatment
effectiveness and breaches in the distribution system as well as a water system's
vulnerability to fecal contamination, as stated above (Craun and Calderon, 2001).
Detection methods for total coliform bacteria are simple and inexpensive, and
laboratories are familiar with these methods (Rompre et al., 2002).
Disadvantages
It cannot easily be determined if total coliforms are of fecal or environmental
origin. They are not ideal indicators because they are more sensitive to disinfection than
some pathogens.
Total coliforms are not good indicators of specific contamination pathways. They
are not uniformly associated with biofilms nor is their presence exclusive to biofilms.
Total coliforms can also be present due to a number of pathways such as treatment
breakthrough, cross-connections and intrusion.
Total coliforms do not appear to be good indicators of vulnerability to waterborne
outbreaks, without investing in additional monitoring beyond current TCR requirements,
and possibly in conjunction with another indicator.
High levels of heterotrophic bacteria can interfere with total coliform analysis in
lactose-based culture methods, whereby method interference can occur when the HPC
densities exceeded 500 cfu/mL (Geldreich et al., 1972). Experimental studies have also
shown that high levels of HPC bacteria can out-compete coliform organisms for low
levels of nutrients (LeChevallier and McFeters, 1985).
6.1.2 Thermotolerant (Fecal) Coliforms
Background
Thermotolerant coliforms are now the preferred designation for the group of
bacteria previously referred to as fecal coliforms (WHO, 1996). This group of organisms,
which are distinguished from other members of the total coliform group by their ability to
ferment lactose at a specified elevated temperature, includes thermotolerant strains of
the genera Klebsiella, Escherichia, Enterobacter and Citrobacter (WHO, 2004). In
drinking water, E. coli typically comprises the majority of the thermotolerant coliforms
isolated. For example, Warren et al. (1978) determined that 96.96% of a single
thermotolerant coliform sample was E. coli, 2.32% was E. cloacae, 0.66% was K.
pneumoniae, and 0.33% was C. freundii.
The presence of thermotolerant coliform bacteria is thought to correlate with the
presence of enteric pathogens in the environment (Bulson et al., 1984). In general,
thermotolerant coliform bacteria are relatively reliable as indicators for disease-causing
bacteria, and slightly less effective in determining the presence of viral and protozoan
pathogens compared to bacteria (Reynolds et al., 2003).
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Because environmental strains of certain organisms are included in the
thermotolerant coliform group and growth within distribution systems has been reported
in biofilms (Fass et al., 1997), their presence cannot explicitly be related to fecal matter.
Indicator of Breaches of Distribution System Integrity
Thermotolerant coliforms in the distribution system may originate from sources
outside the distribution system, which could indicate that a pathway exists for fecal
contamination of distribution system water due to cross-connection or distribution system
intrusion. However thermotolerant Klebsiella and other coliforms are capable of growth
in biofilms and may serve as an indicator of biofilm growth (Fass et al., 1996). The
multiple pathways and sources for thermotolerant coliforms suggest difficulty using these
organisms alone to indicate a particular pathway or source of contamination, and hence
a targeted remedial action. The density of thermotolerant coliforms is lower than the level
of total coliforms since thermotolerant coliforms are a subset of the total coliform group.
While thermotolerant coliforms are a more specific fecal indicator, the lower density of
thermotolerant coliforms in distribution system water relative to total coliforms may mean
that they are a less sensitive fecal indicator.
Indicator of Distribution System Contamination
Thermotolerant coliforms are more closely linked to fecal contamination than total
coliforms. However, the presence of thermotolerant coliforms can not be explicitly
related to fecal matter.
Indicator of Public Health Outcome
Thermotolerant coliform bacteria are relatively reliable indicators of disease
causing bacteria (Reynolds et al., 2003).
Advantages
Analytical methods are simple, reliable, inexpensive, and produce results within
48 hours. Laboratories are familiar with the test methods (APHA, 1995). In comparison
with E. coli, thermotolerant coliforms are typically found in greater densities and are
therefore easier to detect than E. coli (Davis et al., 2005). With respect to total coliforms,
thermotolerant coliforms are a more specific indicator of fecal contamination than total
coliforms (Cabelli, 1977). Most thermotolerant samples are associated with recent fecal
contamination.
Disadvantages
Some environmental strains of Klebsiella and other strains of total coliforms are
detected using analytical methods for thermotolerant coliforms making this indicator less
reliable than E. coli for determining the presence of fecal contamination (WHO, 2004).
Pseudomonas spp. are antagonistic to fecal indicator organisms, and their presence in
distribution water may affect performance of compliance monitoring tests for fecal
coliforms and E. coli (Wernicke and Dott, 1987).
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E. coli is normally present in a fecal coliform-positive sample; therefore, the
disadvantages of using E. coli would apply. That is, they may die out more quickly than
some waterborne pathogens due to succumbing to environmental factors or to
inactivation by disinfectants, and have been reported to grow in the environment in
tropical waters and soils.
In comparison with total coliforms, thermotolerant coliforms are found in water at
a lower density than total coliforms and are thus harder to detect.
Thermotolerant coliforms could be present in the distribution system due to
various pathways and contamination events or growth in biofilms. It may be difficult to
determine the source based only on this indicator.
The presence and detection of fecal coliforms in the distribution system
constitutes an acute violation of the TCR (40 CFR § 141.63 (b)).
6.1.3 Escherichia coli
Background
Escherichia coli is a member of the family Enterobacteriaceae and is included in
the total coliform and fecal coliform group of bacteria. E. coli are abundant in human
and animal feces and thus can be found in sewage and wastewater treatment effluent.
E. coli have been used as indicators of fecal water contamination for over 50 years
(Schubert and Mann, 1968; Weber-Schutt, 1964). The presence of E. coli in water is
strong evidence of human or animal fecal contamination, which suggests that enteric
pathogens may also be present. E. coli has replaced thermotolerant (fecal) coliform
bacteria as the principal fecal indicator for water and wastewater (WHO, 1993), although
fecal coliform monitoring is still required under the Surface Water Treatment Rule and is
still allowed under the TCR. Although traditionally believed to have a relatively short
survival time in the environment in temperate climates, E. coli is correlated with point
source pollution of inadequately treated wastewater, septic tanks, and livestock
discharge. Recently, E. coli has been reported to grow in soils and water in tropical
climates (Solo-Gabriel et al., 2000).
Indicator Breaches of Distribution System Integrity
E. coli may be used to indicate that distribution system water is vulnerable to
fecal contamination due to a variety of pathways, including distribution system intrusion,
contaminated storage, or cross-connections. However evidence suggests that E. coli
may potentially also survive and grow in distribution system biofilms. Further information
about whether a sudden occurrence of E. coli may be more likely due to a contamination
event versus from biofilm growth could be useful in characterizing E. coli as an indicator.
Fass et al. (1996) injected two nonpathogenic strains of E. coli into a pilot
distribution system with a biofilm at 20° C and noted the E. coli grew slightly before
eventually dying out.
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Several studies have shown that E. coli can survive in biofilms in distribution
systems (Olson, 1982; LeChevallier, 1987). Another study by Camper et al. (2003)
found that environmental isolates of E. coli removed from a New Haven, Connecticut
drinking water system as well as an enterotoxigenic E. coli. strain experienced growth
under conditions representative of municipal drinking water systems. In model
distribution system biofilms, exposed to either hypochlorous acid or monochloramine, E.
coli cells were able to survive at least 10 days in distribution system biofilms, even under
high levels of disinfection (Williams et al., 2003).
Indicator of Distribution System Contamination
The presence of E. coli in distribution system water is strong evidence of human
or animal fecal contamination, which suggests that enteric pathogens may also be
present. E. coli have the same resistance to environmental factors as other enteric
bacteria. However, E. coli are more sensitive to environmental factors than viruses and
cysts or oocysts of pathogenic protozoa. While E. coli is a more specific fecal indicator
than total coliforms or thermotolerant coliforms, the low density of E. coli in distribution
system water relative to total and thermotolerant coliforms may mean that it is a less
sensitive fecal indicator.
Indicator of Public Health Outcome
Several studies have found that the concentration of E. coli in drinking water
significantly correlates with the presence of gastrointestinal illnesses. For example, Moe
et al. (1991) examined the effectiveness of indicator bacteria in predicting
gastrointestinal disease in individuals less than 2 years old in the Philippines. E. coli and
enterococci were found to be more reliable predictors of the risk of gastrointestinal
disease compared to thermotolerant coliforms or fecal streptococci. Raina et al. (1999)
also found a significant association between E. coli in well-water of rural Canada, and
gastrointestinal illness in family members. Similarly, Strauss et al. (2001) determined
that the odds ratio to contract a Gl illness for individuals exposed to E. coli was 1.52
compared to those who were exposed to E. coli levels below current U.S. and Canadian
standards. Total coliforms had an odds ratio of only 0.39. Further, Noble et al. (2004)
determined that E. coli survives longer than enterococci in sunlight exposed sewage and
run-off. In addition, Strauss et al. (2001) hypothesized that E. coli is a more reliable
predictor than thermotolerant coliforms since E. coli is a more specific measure for fecal
contamination than the general category of thermotolerant coliforms, which is comprised
of multiple species.
To determine the potential for using E. coli as an indicator of water quality, many
studies examined the association between E. coli in recreational waters and the
prevalence of Gl illnesses. For example, Wade et al. (2003) conducted a systematic
review of over 25 peer-reviewed and governmental studies that examined the
relationship between E. coli, enterococci and other bacterial indicators with Gl illness.
Their research demonstrated that in freshwater, E. coli was the most consistent
predicator of Gl illness, whereby a log unit increase in E. coli was associated with a 2.12
increase in relative risk for contracting a Gl illness. Likewise, an earlier review of peer-
reviewed literature indicated that E. coli best correlates with health outcomes in
freshwater (Pruss, 1998). These results parallel EPA's recommendations in 1986, which
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suggest that E. coli should be used as an indicator of water quality in fresh recreational
waters (USEPA, 1986).
Advantages
Analytical methods are simple, reliable, inexpensive and produce results within
24 to 48 hours (Brenner et al., 1993). E. coli is closely associated with recent fecal
contamination and is found in high concentrations in sewage and septage. (Cabelli,
1977; WHO, 1994) E. coli is extremely sensitive to disinfection and its presence would
indicate a major deficiency in the distribution system (Noble et al., 2004; WHO, 2004).
Disadvantages
The density in water of E. coli is less than that of total coliforms. E. coli may be
more sensitive to environmental factors or to inactivation by disinfectants than some
waterborne pathogens. Since E. coli can be inactivated through disinfection, fecal
contamination that enters the distribution system may not be detected if E. coli is the
only indicator used (WHO, 2004). However in the event of a sewage contamination, the
loss in disinfectant residual (LeChevallier, 1999) could be an alternative indicator.
Pseudomonas spp. and other HPC bacteria may interfere with the methods used for
fecal coliforms and E. coli (Wernicke and Dott, 1987).
6.1.4 Heterotrophic Bacteria as Measured by the HPC Method
Background
Heterotrophic bacteria are a broad class of organisms that use organic nutrients
for growth. The group includes harmless environmental bacteria, virtually all pathogenic
bacteria, and opportunistic pathogens (bacteria that cause a disease in a comprised host
but that are unlikely to cause a disease in an uncompromised host). Opportunistic
pathogens include strains of Pseudomonas aeruginosa, Acinetobacter spp., Aeromonas
spp., Klebsiella pneumoniae, and others. However, these opportunistic pathogens are
not detected with the media used for HPC determination (WHO, 2002).
The number of heterotrophic bacteria recovered from a water sample will depend
on the procedures and isolation medium used, and on the interaction among the
developing colonies (APHA, 1995). The population of these bacteria is often measured
by the Heterotrophic Plate Count (HPC) procedure (Standard Method 9215), previously
referred to as the standard plate count procedure. Other methods of measuring
heterotrophic bacteria would include total bacteriological count, total viable bacterial
count, adenosine triphosphate, and endotoxin. These methods and their use as
indicators in drinking water are discussed in other sections of this document.
The range of heterotrophic bacteria usually measured in drinking water is <0.2
CFU/ml to 10,000 CFU/ml or higher (Allen et al., 2002). No validated epidemiological
evidence links consumption of high levels of heterotrophic bacteria in drinking water to
increased health risks (Leclerc, 2002).
Measurements of heterotrophic bacteria may be useful in managing distribution
Distribution System Indicators of Drinking Water Quality
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system water quality for the following (Reasoner, 1990):
•	Monitoring the efficiency of the treatment process
•	Evaluating changes in finished water quality and distribution system
cleanliness
•	Assessing bacterial growth in the distribution system
•	Measuring bacterial growth contributed by treated drinking water
•	Comparing bacterial populations in the distribution system before and after
treatment process changes (e.g., type of disinfectant, disinfectant
concentrations or level of filtration).
Indicator of Breaches of Distribution System Integrity
HPC measurements provide an indication of general water quality within the
distribution system (WHO, 2003a). An increase in HPC can be an indication of
treatment breakthrough, contamination introduced post-treatment during main breaks,
repairs, and installation or through intrusion, microbial growth within the distribution
system, or the presence of deposits and biofilms (WHO, 2004). An increase in HPC
bacteria may also be due to nitrifying distribution conditions for chloraminated systems
(AWWA and EES, 2002d).
HPC measurements can be used to assess microbial growth on materials used
in water distribution systems and for determining the extent of growth in distribution
water. Growth of heterotrophic bacteria associated microorganisms can occur as
biofilms, and is typically reflected in water samples as higher HPC values (WHO, 2002).
LeChevallier et al. (1987) studied distribution system biofilms at a water utility in New
Jersey and found that HPC moved from the treatment plant into the distribution system,
and were found in increased numbers at sites corresponding to growth of biofilm.
Biotyping of coliforms and heterotrophic plate counts were used to detect and monitor
locations with biofilm growth. Where biofilm can be ruled out as the cause, elevated
counts of heterotrophic microorganisms can be used to indicate distribution system
integrity problems of a nonfecal nature.
Heterotrophic bacteria levels respond to conditions in the distribution system that
include stagnation, loss of residual disinfectant, high levels of AOC in the water, higher
water temperature, and availability of particular nutrients. They are also useful for
determining changes in water quality in the distribution system. Carter et al. (2000)
found correlations between HPC counts using R2A agar and pH, conductivity,
temperature, and disinfectant residual in the distribution system.
While total coliform tests are useful in identifying a problem and perhaps in
localizing a problem within the distribution system, the use of HPC and other methods is
necessary to characterize contamination and biofilm occurrences (Edberg, 1994).
Indicator of Distribution System Contamination
Wth respect to being an indicator of fecal contamination, WHO (2003a)
concluded that in situations where fecal contamination is not present, HPC levels do not
correlate to health effects to the general population. EPA (1996) concluded that
because increased levels of HPC do not correlate to an increased likelihood of fecal
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contamination, heterotrophic bacteria are not reliable indicators.
Indicator of Public Health Outcome
Current research suggests that heterotrophic bacteria are not appropriate
indicators for waterborne disease outbreaks or endemic illness risks (WHO 2002, 2003a,
Allen et al., 2004). The World Health Organization expert meeting on the role of
heterotrophic measurements in drinking water quality and safety concluded that there is
no evidence of an association with gastro-intestinal infection through the waterborne
route among the general population and heterotrophic bacteria (WHO, 2003a). Allen et
al. (2004) examined 11 health studies and determined that there was no evidence to
support health-based regulations of HPC concentrations. Pavlov et al. (2004) concluded
that heterotrophic bacteria health risks were confined to a small percentage of the
population, such as the very young, very old, AIDS patients, and patients on therapy for
organ transplantation or cancer treatment.
Advantages
Heterotrophic microorganisms are a general indicator of microbial water quality
conditions. They are also effective indicators of bacterial growth (WHO, 2002). The
Standard HPC method is simple, inexpensive, and produces results within 48 hours
(Exner et al., 2003).
Disadvantages
In the report entitled "Heterotrophic Plate Count Measurement in Drinking Water
Safety Management," the WHO concluded there is no evidence that heterotrophic
bacteria counts alone directly relate to health risk either from epidemiological studies or
from correlation and occurrence of waterborne pathogens (WHO, 2002).
High measurements of heterotrophic bacteria can be indicative of a range of
issues, and cannot be used to determine if the problem is of fecal origin.
HPC measurements can lead to unreliable results. For example, the population
of microorganisms recovered in an HPC test will differ significantly depending upon the
type of test used, the location of the sample, the season the sample was taken, and the
number of consecutive samples taken at a single area (WHO, 2002).
Standard HPC methods are insensitive to waterborne bacteria.
6.1.5 Total Bacteriological Counts and Total Viable Bacterial Counts
Background
Total bacterial counts reveal the number and variety of bacterial populations
present in a sample. This measurement enables enumeration of those populations that
will not grow on artificial media, and comprises the full number of viable, viable but non-
culturable, and nonviable organisms present in a water sample. Total bacterial counts
are conducted microscopically using fluorescent dyes such as acridine orange, which
stains nucleic acids (APHA, 1995). More complex techniques can be used to discern
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serotype and genetic content information (WHO OECD, 2003b). Total bacterial counts
are less specific than total coliforms and would produce a higher hit rate than total
coliform sampling.
A viable cell is one that can divide and form offspring (Madigan, 2006).
Measurement of total viable bacterial counts is based on the ability of the organisms to
grow using specific culture methods, although staining techniques are sometimes used.
Viable counts have been used as a measure of water quality since bacteriological
methods permitting enumeration of microorganisms were first introduced in the late
1800s. These methods have been referred to by a variety of names, including total
bacterial count, total plate count, colony count, standard plate count, total viable count,
and heterotrophic plate count (HPC). Slight variations in the methods and medium will
affect the organisms recovered from the water sample; some procedures use low
nutrient agar to target recovery of stressed organisms while others may contain
ingredients that support growth of bacteria that have virulence factors related to their
ability to cause waterborne disease.
Total bacterial counts are less specific than HPC in terms of medium and
incubation conditions. Total viable counts will have similar applications, advantages,
and disadvantages as do results obtained using the HPC method.
Indicator of Breaches of Distribution System Integrity
Elevated bacterial counts can potentially be used to indicate distribution system
integrity problems of a nonspecific nature including intrusion, loss of disinfectant
residual, stagnation, and an increase in nutrient levels in the water.
Total viable counts are useful for determining changes in water quality during
water storage and distribution (Carter et al., 2000), and can be used to assess microbial
growth on materials used in water distribution systems and for determining the extent of
growth in distribution water. Viable heterotrophic bacteria levels respond to stagnation,
loss of residual disinfectant, high levels of AOC in the water, higher water temperature,
and availability of nutrients (Reasoner, 1990).
As with heterotrophic bacteria, total viable counts and total bacterial counts can
be used to detect and monitor biofilm growth in the distribution system.
Advantages
Total bacterial counts, whether based on culture methods or direct counts,
provide basic information on the numbers of bacteria in water. OECD WHO (2003b)
notes that although actual bacterial counts are of limited value, significant changes in
viable counts normally found at particular locations may warn of significant problems.
The methods for viable counts that rely on culture methods are relatively simple
to perform, are inexpensive, and are familiar to laboratory personnel (Gunasekera et al.,
2000). Total bacterial counts capture bacteria that will not grow on artificial media.
Disadvantages
Total bacterial counts, whether viable or nonviable, are nonspecific and do not
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provide an index of fecal contamination or waterborne disease outbreaks. As noted in
the HPC discussion, the WHO report, "Heterotrophic Plate Count Measurement in
Drinking Water Safety Management," concluded there is no evidence that heterotrophic
bacteria counts alone directly relate to health risk either from epidemiological studies or
from correlation and occurrence of waterborne pathogens (WHO, 2002). Total counts
cannot distinguish viable and nonviable cells and is a microscopic method which is
tedious and time-consuming (Gunasekera et al., 2000).
6.1.6 Pseudomonas and Aeromonas
Background
Pseudomonas and Aeromonas spp. are Gram-negative, rod-shaped, oxidase
positive, non-spore forming bacteria that occur naturally in the environment. P.
aeruginosa is commonly found in feces, soil, water, and sewage (OECD WHO, 2003b).
Aeromonas is not associated with fecal pollution, but is capable of growth in distribution
mains and storage tanks. Pseudomonads and Aeromonas spp. have been isolated from
biofilms (van der Kooij and Hijnen, 1988) and are able to grow in low nutrient conditions
(Ribas et al., 2000).
The Dutch standard for Aeromonas levels is 20 cfu/100 ml_ in finished water and
200 cfu/100 ml_ in distribution water (van der Kooij, 1988).
Indicator of Breaches of Distribution System Integrity
Aeromonas and Pseudomonas have been proposed as indicators of distribution
system integrity because they are common environmental organisms (WHO, 1996).
Further, the presence of Aeromonas spp. in water distribution systems suggests
inadequate chlorine residuals or the potential for biofilms (Stelzer et al., 1992). The
growth of these microorganisms in the water distribution system is often most favorable
when there is a low concentration of biodegradable dissolved organic carbon (BDOC).
Pseudomonas has been proposed as an indicator of bacterial growth since it has a
greater affinity with some of the components of the BDOC than other bacteria (van der
Kooij et al. 1982).
Pseudomonas and Aeromonas have been recovered from biofilms. In Barcelona,
Spain, both Pseudomonas and Aeromonas were considered useful potential indicators
of bacterial growth, although Pseudomonas was deemed a better indicator (Ribas et al.,
2000). Stelzer et al. (1992) came to a similar conclusion after analyzing the drinking
water supply in Germany.
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Indicator of Distribution System Contamination
P. aeruginosa is not an indicator of fecal contamination since it is not always
present in feces and sewage and may multiply in the environment (OECD WHO, 2003b).
There have been mixed findings as to whether Aeromonas indicates fecal
contamination. In Cameroon, Nola et al. (1998) found that Aeromonas hydrophila in well
water was strongly correlated with the density of fecal bacteria. However, in Italy,
Legnani et al. (1988) did not find a correlation between the concentration of Aeromonas
spp. and fecal indicator organisms. Aeromonas is easily reduced though treatment, but
high levels can still be found in the distribution system as a result of regrowth (OECD
WHO, 2003b).
While not an indicator of fecal contamination, the presence of P. aeruginosa may
be one of the factors taken into account in assessing bacterial contamination in general
as its presence may signify a deterioration in bacteriological quality (OECD WHO,
2003b).
Indicator of Public Health Outcome
In Mexico, De Victorica and Galvan (2001) documented an outbreak of E. coli
and P. aeruginosa, where there was a primary infection by E. coli and a secondary
infection by P. aeruginosa in 5 children. De Victoria and Galvan (2001) concluded that P.
aeruginosa should be used as an indicator of waterborne diseases.
Although no major outbreak has been documented with direct links to public
water supplies, increased Aeromonas occurrences were reported from the Netherlands
and Australian water supplies in which warmer months were correlated with increased
Aeromonas associated gastroenteritis (Burke et al., 1984; van der Kooij, 1988b)
(Havelaar et al., 1990). Other workers from Cairo, Egypt, have claimed that the
domestic water supply was responsible for increased gastroenteritis cases, based on the
fact that 90 % of their water supplies tested positive for Aeromonas (Ghanem et al.,
1993).
Some Aeromonas species are considered opportunistic pathogens and may
cause Gl illness. For example, Aeromonas hydrophila can produce cytotoxins and
enterotoxins associated with acute gastroenteritis (Fernandez et al., 2000). In Auckland,
New Zealand, Simmons et al. (2001) determined that households that reported at least
one case of gastrointestinal symptoms in the month prior to sampling were significantly
more likely to have water samples containing Aeromonas spp., with an odds ratio of
3.22.
Advantages
Pseudomonas and Aeromonas may be useful in indicating an inadequate
chlorine residual or the presence of biofilm growth. They are both detectable by simple,
inexpensive methods that can be applied in a basic bacteriological laboratory (OECD
WHO, 2003b).
Disadvantages
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Pseudomonas and Aeromonas capture a smaller variety of biofilm bacteria
compared to other potential indicators. Also, because of the motility and growth of
Pseudomonas on certain growth media, they may interfere with the recovery of other
organisms.
6.1.7 Enterococci and Fecal Streptococci
Background
Hardie and Whiley (1997) published a classification and overview of the genera
Streptococcus and Enterococcus. They describe the organisms as Gram-positive, non-
spore forming, spherical or ovoid cells which are typically arranged in pairs or chains and
are widely distributed, mainly on mucosal surfaces of humans and animals. Some are
also found in soil, dairy products and other foods, and on plants. Enterococci are
typically found in the intestinal tract and feces of humans and other animals, they
generally do not grow in the environment except in tropical climates, and they have been
shown to survive longer than E. coli (Hardina and Fujioka, 1991; McFeters etal., 1974).
For these reasons, WHO generally regards them as specific indices of fecal pollution
from warm blooded animals (OECD WHO, 2003b). The predominant intestinal
enterococci are E. faecalis, E. faecium, E. durans, and E. hirae. Some species such as
S. pyogenes and S. pneumoniae are human pathogens.
Althaus et al. (1982) studied the species of fecal streptococci using differential
and selective media and found that some species were characteristically isolated from a
particular source. S. faecalis predominates in human waste, while S. faecium and S.
durans were isolated specifically from sewage and wastewater. Selection of culture
media and methods determines to a great extent which species are isolated. Fecal
streptococci do not grow in water (Brezenski, 1973; Geldreich, 1973), and they survive
longer in winter than in summer (Cohen and Shuval, 1973; Van Donsel et al., 1967).
Sinton et al. (1993a; 1993b) published reviews of fecal streptococci as pollution
indicators.
Indicators of Breaches of Distribution System Integrity
The presence of enterococci indicates a contamination pathway exists for fecal
material to enter the distribution system. Fecal streptococci are more resistant to stress
and chlorination than E. coli and the other coliform bacteria (OECD WHO, 2003b). They
are also highly resistant to drying and thus may be valuable for routine control after new
water mains are laid or distribution systems are repaired (OECD WHO, 2003b).
Indicators of Contamination
Enterococci, E. coli, total coliforms, fecal coliforms, P. aeruginosa, and A.
hydrophila were studied as water quality indicators (Miescier and Cabelli, 1982). Among
these, enterococci best satisfied the requirement for a fecal indicator. Enterococci
survive secondary sewage treatment better than E. coli, they do not generally multiply in
the environment, and they are consistently associated with fecal wastes for humans and
animals. In a study by Pinto et al. (1999), the majority of enterococci (84 percent)
isolated from a variety of polluted water sources were true fecal species.
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Indicators of Waterborne Outbreaks or Endemic Disease
Zmirou et al. (1987) conducted an epidemiological study that examined the
effectiveness of indicator monitoring at preventing human disease from treated drinking
water. Heterotrophic plant count, total coliforms, thermotolerant coliforms, and fecal
streptococci monitoring results were examined, together with the number of cases of
acute gastrointestinal disease in 52 French villages. A log linear model identified fecal
streptococci as the best predictor of human disease, and the association between
monitoring results and human gastrointestinal disease was stronger when both fecal
streptococci and thermotolerant coliforms were positive. Heterotrophic plate counts and
total coliforms made no independent contribution to the ability to predict disease risk;
however any level of indicator bacteria above zero was associated with increased rates
of gastrointestinal disease.
Advantages
Standardized methods are available, are relatively easy to use, and provide rapid
results (USEPA, 1996). Fecal streptococci and enterococci are present in wastewater
and known polluted water; the organisms are generally absent from pure, unpolluted
waters having no contact with human and animal life (the exception being growth in soil
and on plants in tropical climates (Hardina and Fujioka, 1991)).
Disadvantages
As an indicator of treatment effectiveness and distribution system integrity,
enterococci and fecal streptococci are present in lower numbers than total coliforms.
They are also not as good a fecal indicator when pathogenic protozoa are present.
Pathogenic protozoa such as Giardia and Cryptosporidium are more resistant to
environmental stress and disinfection than enterococci and fecal streptococci.
6.1.8 Somatic Coliphage
Background
Bacteriophages are viruses that infect bacteria, and those that infect E. coli are
called coliphages. Somatic coliphages are viruses that infect host cells through the
outer cell membrane. The host bacterium and its density, temperature, pH, and other
variables affect the incidence, survival, and behavior of phage in different water
environments (Stevens et al., 2001). The impacts of these variables affect the
consistency of data and comparisons of bacteriophages in water environments.
Coliphages have been proposed as virus surrogates for water disinfection and
treatment studies. The theory behind the use of coliphage as an indicator of water
quality is based on the premise that these viruses will behave more like human enteric
viruses than do bacterial indicators. In addition, they have also been proposed as
sewage indicators because of their constant presence in feces, sewage, and polluted
waters.
Indicator of Breaches of Distribution System Integrity
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The presence of somatic coliphage may not be a useful indicator of a distribution
system integrity problem, even when the problem involves the introduction of fecal
contamination. LeChevallier et al. (2006) measured the presence of somatic coliphage
in the distribution system, finding that of nearly 400 samples, the only samples
containing somatic coliphage were attributed to a contaminated control sample rather
than a breach in the distribution system. These distribution system samples were
collected during a period corresponding to an unusual number of main breaks,
potentially resulting in distribution system contamination.
Indicator of Distribution System Contamination
Due to their high numbers in sewage and sewage-contaminated waters, somatic
coliphage may be relatively good indicators of fecal contamination (Hilton and Stotzky,
1973; Havelaar et al., 1991). Somatic coliphage can indicate both animal and human
fecal matter (Havelaar et al., 1993). However, other studies have indicated that somatic
coliphage are not a reliable indicator of fecal contamination. Leclerc et al. (2000)
indicate in a literature review that somatic coliphage may not be specific to E. coli and
may multiply in the environment. Leclerc et al. (2000) also indicate that it is possible to
find somatic coliphages without the presence of fecal contamination. Reali et al. (1991)
reviewed the phage literature and reported that most investigators found no correlation
between the density of fecal coliform bacteria and the presence of coliphage. Further,
LeChevallier et al. (2006) detected a coliphage serotype that was not associated with
human fecal contamination, and suggests that more research is needed to determine
whether coliphages are an appropriate indicator of distribution system contamination.
Indicator of Public Health Risk
Leclerc et al. (2000) indicates that somatic coliphage may be found in conditions
unrelated to presence of a health risk. Enteric viruses have been detected in treated
drinking water that was negative for bacteriophages (Grabow et al., 2000). In one recent
study, 41.2% of pathogen positive samples occurred with no detectable levels of somatic
coliphage, while 47.1% of pathogen positive samples contained >25 PFU/100ml, thus
indicating no significant correlation between pathogens and somatic coliphages (Lipp et
al., 2001). Ho et al. (2003) also found no statistical association between somatic
coliphage and human pathogenic viruses in the 68 samples tested.
Advantages
Standardized methods are available for somatic coliphage that allow easy and
rapid detection in environmental samples (Grabow, 1996). Somatic coliphage are also
typically present in high numbers in sewage and sewage contaminated waters (Grabow,
1996). In addition, there are circumstances when coliphages may survive in the water
environment when indicator bacteria do not (Leclerc et al., 2000). Lastly, coliphages are
more resistant to chloramination than to free chlorine, which may therefore make them
particularly well suited for use as indicators in chloraminated systems (LeChevallier et
al., 2006).
Disadvantages
There is no direct correlation between numbers of phages and viruses in human
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feces (USEPA, 2000b). Enteric viruses have been detected in water environments in
the absence of coliphages, and some coliphages may replicate in water environments
(Stevens et al., 2001; Havelaar et al., 1991). Not all infected individuals shed somatic
coliphage (Deborde, 1998). The analytical method is more complicated and expensive
than traditional bacterial indicators and is not widely used. As indicated above, Leclerc
et al. (2000) suggests that somatic coliphage can be found in conditions without
presence of fecal contamination or a health risk.
6.1.9 Male-Specific Coliphage
Background
Male-specific coliphages are also referred to as F+ or F-specific coliphage and
are viruses that infect E. coli through the F-pilus of male strains. The F-pilus allows for
transfer of nucleic acid from one bacterium to another. These phage adsorb to F-pili as
the first stage of infection and some are relatively resistant to disinfectants. F-specific
RNA coliphage exist in four serogroups identified I, II, III, and IV. Groups II and III
predominate in humans while Groups I and IV are found in animals (Hsu et al., 1995).
According to LeChevallier et al. (2006), Male-specific coliphages infect only E. coli.
However, LeClerc, et al., (2000) disagree, indicating that they may attack and multiply in
other coliforms and Enterobacteriaceae.
F-specific phage meet the criteria for pollution indicators by being detectable
when pathogens are present, occurring in higher numbers than the pathogen and they
are more resistant to environmental influences than pathogens (Lewis, 1995). Woody
and Cliver (1995) determined the minimum temperature for replication of F-RNA phage
to be 25 degrees C. F-specific RNA phage occur at 106/L in sewage (Turner and Lewis,
1995).
Indicator of Breaches of Distribution System Integrity
The presences of male-specific coliphage may be used to indicate a distribution
system integrity problem. LeChevallier et al. (2006) detected male-specific coliphage in
5.6 % of 393 distribution system samples. Of those samples that were positive for the
presence of male-specific coliphage, more than 77% of the samples were collected
within 72 hours of a main break event in the distribution system. Additionally, in the
week before a positive coliphage result, between 2 and 13 main breaks occurred,
suggesting that the contamination may have come from multiple locations. These
results suggest that male-specific coliphage may be effective indicators of distribution
system integrity, and main breaks in particular.
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Indicator of Distribution System Contamination
Due to their high numbers in sewage and sewage-contaminated waters, male-
specific coliphage may be used to indicate the fecal contamination of distribution
systems. Type III F-specific coliphage were found to correlate reliably with the release
of human fecal contamination, but more research is necessary to be able to track the
contamination back to its source (Brion, 2002). All of the isolated coliphage in
LeChevallier et al. (2006) were determined to be serogroup I, which is not associated
with human fecal pollution; the authors suggest that more studies are necessary to
assess whether male-specific coliphage are potential indicators for human fecal
contamination of distribution systems.
Indicator of Public Health Risk
Havelaar et al. (1993) found male-specific coliphages were highly correlated with
entero- and enteric viruses in multiple environments, including chlorinated effluent
waters and UV-irradiated effluent waters.
Advantages
Standardized methods are available for their recovery from drinking water and
they have a narrow host range compared with somatic coliphage. F-RNA phage may
be good surrogates for enteroviruses because they are of similar size and type (Handzel
et al., 1993). Male-specific coliphage are somewhat resistant to disinfectants, and
because they are relatively hardier and persist longer, they more closely mirror the
behavior of enteric viruses than do bacterial indicators (Havelaar et al., 1990, 1991,
1993; Sobsey et al., 1995). LeChevallier et al. (2006) points out that coliphages may be
a better indicator for chloraminated systems than chlorinated systems due to greater
resistance to chloramination.
Male-specific coliphage correlate better with presence of pathogens in human
feces than somatic coliphage, since somatic coliphage may amplify in the environment
(USEPA, 2000b; Havelaar et al., 1991). According to Leclerc et al. (2002),
bacteriophage levels, including male-specific coliphage, may also be sensitive to
temperature conditions (Leclerc et al., 2000) and bacteriophages may be unlikely to
reproduce at the temperatures seen in potable distribution system water.
Disadvantages
Enteric viruses have been detected in water environments in the absence of
coliphages (Stevens et al., 2001). A small percentage of people shed male-specific
coliphage and they are typically shed in fewer numbers than somatic coliphage. It has
been reported that only 3% of humans carry these phages in their E. coli (Leclerc et al.,
2000).
With respect to using bacteriophages in general as an indicator of enteric
viruses, Leclerc et al. (2000) point out the following concerns:
•	Production of reproducible results
•	Sample volume
•	Lack of clear correlation between levels of male-specific bacteriophages in
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human feces and that of sewage.
• Methods for enumerating male-specific phages are not accessible, due to
complexity, amount of time required, and lack of reproducibility.
Male-specific bacteriophages may not be specific to E. coli. and may multiply in
Enterobacteriaceae, a microbe associated with vegetation and biofilms, and other
members of the total coliform group (Leclerc et al., 2000).
6.1.10 Clostridium perfringens
Background
Clostridium spp. are sulfite-reducing, anaerobic, spore-forming bacteria that
inhabit the intestinal tracts of humans and animals and are present in sewage and in soil
or water that has been fecally contaminated. Clostridium perfringens is exclusively of
fecal origin and has been recommended by several investigators as a sensitive indicator
of sewage pollution of ambient waters (Emerson and Cabelli, 1982; Sorensen et al.,
1989; Hill et al., 1993).
Payment and Franco (1993) studied C. perfringens as an indicator of treatment
efficacy of drinking water for virus removal. Statistically significant correlation was found
between C. perfringens counts and those of enteric viruses, Giardia cysts, and
Cryptosporidium oocysts. WHO (2003b) does not recommend Clostridia for distribution
system routine monitoring because, due to their length of survival they may be detected
long after (and far from) the pollution event, leading to possible false alarms.
Indicator of Breaches of Distribution System Integrity
As for other indicators of fecal pollution, the presence of C. perfringens may be
used to indicate a distribution system integrity problem, but their presence must be
interpreted with caution due to the environmental longevity and resistance of spores.
Also, concentrations are much lower than total coliforms and heterotrophic bacteria
counts.
Indicator of Distribution System Contamination
As is the case with indicating distribution system integrity problems, C.
perfringens, may be used to indicate the fecal contamination of distribution systems due
to their high numbers in sewage and sewage-contaminated waters, but their presence
must be interpreted with caution due to the environmental longevity and resistance of
spores. Fujioka and Shizumura (1985) suggested that levels of C. perfringens above 50
CFU/100ml were indicative of human fecal pollution. However, there is some concern
that C. perfringens may not be present in every instance of fecal contamination (USEPA,
1996).
Advantages
C. perfringens is a definitive fecal indicator and standardized methods are
available for its rapid and reliable recovery from water. C. perfringens was found to
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correlate statistically with concentrations of enteric viruses and presence of Giardia cysts
in filtered drinking water (Payment and Franco, 1993).
Disadvantages
Because their spores persist for long periods in the environment, C. perfringens
can result in false positives and may be less suitable as an indicator of recent fecal
contamination. The analytical method requires anaerobic incubation, making the
method somewhat more complex than coliform methods.
6.1.11 Bacteroides fragilis phages
Background
Bacteroides represent the most abundant bacteria in the gut. Bacteroides are
obligate anaerobes of human fecal origin that cannot multiply in the aqueous
environment and that die off relatively quickly because oxygen kills them. Bacteriophage
of Bacteroides fragilis are viruses that infect B. fragilis and two in particular may be
useful as drinking water quality indicators. The phage to B. fragilis HSP40 are found
only in human feces and have not been isolated from feces of animals (Havelaar et al.,
1991; WHO, 2003c, WHO 2004). However, B. fragilis RY2056 phage are more
numerous and are not human-specific (Puig et al., 1999).
B. fragilis phage have been determined to be relatively resistant to environmental
conditions. Bosch et al. (1989) reported that B. fragilis phage were more resistant to
chlorine than E. coli or polioviruses. According to WHO (2004), one phage in the group
B. fragilis HSP40, B40-8, has been found to be more resistant to chlorine disinfection
than polio virus Type 1, Simian rotavirus SA11, coliphage f2, E. coli, and streptococcus
faecalis. This phage is considered to be typical of the B. fragilis HSP40 group.
Jofre et al. (1995) evaluated somatic coliphage, F-specific coliphage and B.
fragilis phage as indicators of treatment efficacy in drinking water treatment plants. They
reported B. fragilis phage were not as numerous as coliphage in raw water but they were
present in higher numbers than enteroviruses, and they were more resistant to treatment
than coliphage, making them better indicators for enteric virus removal in drinking water
treatment. However, due to these low numbers, it is possible that the absence of B.
fragilis phage does not confirm the absence of contamination. WHO 2004 recommends
using the B. fragilis phage in laboratory investigations, pilot trials, and possibly validation
testing. WHO guidelines (2004) recommend against B. fragilis phage for operational or
surveillance monitoring.
Indicator of Breaches of Distribution System Integrity
Information is lacking regarding whether the B. fragilis phage can reliably be
used as an indicator that distribution system integrity has been breached.
Indicator of Distribution System Contamination
Recently, bacteriophage of B. fragilis have received attention as indicators of
human fecal contamination. B. fragilis HSP40 phage had been detected in waters
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receiving human fecal discharges at concentrations up to 5.3x10s PFU/100 mL (Tartera
et al., 1989). B. fragilis phage are present in lower numbers than coliphage, but their
presence is a reliable indication of human fecal contamination as it is unlikely that the
host organism occurs naturally in the environment (Jofre et al., 1986; Tartera and Jofre,
1987; Araujo et al., 1997).
B. fragilis phages were also found to be reliable indicators of enterovius (Gantzer
at al., 1998). More studies are needed to determine whether the B. fragilis phage is also
an indicator of human fecal and enteric virus contamination (Leclerc et al. 2000). .
Advantages
Bacteroides fragilis phage does not grow in the environment, is predictive of very
recent human fecal contamination, and is shed in very high numbers in stools. In
addition, B. fragilis phages seem to be specific indicators of human fecal contamination
as they do not occur naturally in the environment, whereas somatic coliphages and
male-specific phages may be indicative of either human or animal fecal contamination
(Gantzer et al., 1998). B. fragilis phages are the most persistent of the phage indicators
and their size and survival rate in the environment are most similar to those of
enteroviruses (Contreras-Coll, et al., 2002; Gantzer et al., 1998). Bacteroides fragilis
HSP40 phage does not replicate in the environment and is an indicator of human fecal
pollution.
Disadvantages
Complex analytical methods are required for recovery of Bacteroides and B.
fragilis phage (Contreras-Coll, et al., 2002). The concentration of B. fragilis phage in
water is significantly less than coliphage. The absence of B. fragilis phage does not
provide evidence of the absence of fecal contamination.
6.2 Chemical Indicators
6.2.1 Residual Disinfectant
Background
Two federal regulations specify requirements regarding disinfectant residuals in
distribution systems. The SWTR requires surface water systems and systems that use
ground water under the direct influence of surface water to maintain detectable
disinfectant residuals throughout their distribution systems (40 CFR Section 141.72).
These systems are required to monitor their disinfectant residuals at the same locations
where coliform samples are collected for compliance with the TCR. The Stage 1
Disinfectants/Disinfection Byproducts Rule requires water systems that disinfect to
comply with a Maximum Residual Disinfectant Level (MRDL) of 4.0 mg/L as a running
annual average in their distribution systems if they are maintaining a residual using
either chlorine or chloramines. The required monitoring for MRDL compliance is the
same as the required monitoring for SWTR compliance.
Additional information on the effectiveness of disinfectant residuals as indicators
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of contamination is provided in a white paper currently under development entitled "The
Effectiveness of Disinfectant Residuals".
Indicator of Breaches of Distribution System Integrity
A decrease in disinfectant residual in the distribution system can indicate a
contamination problem linked to distribution system integrity. Haas (1999) contended
that in some cases, reductions in the disinfectant residual can signify the existence of a
contamination problem in the distribution system, including problems resulting from
cross-connections and backflow. An EPA Water Protection Task Force (USEPA, 2001)
recently suggested that water systems increase the frequency and locations of
disinfectant residual monitoring in their distribution systems to ensure proper residuals at
all points in the system and to establish a baseline and normal fluctuation from the
baseline. The Task Force stated that strategically placed residual monitors are an
effective way to alert the system to an unexpected increase in disinfectant demand and,
possibly, a breach or contamination of the distribution system.
Disinfectant residuals are likely to be overwhelmed by large contamination
episodes such as a substantial sewage backflow event (LeChevallier, 1999). But other
breaches of distribution system integrity, such as those associated with pressure
transients, can result in smaller amounts of contamination that may not exert a
significant disinfectant demand.
Long hydraulic residence times in storage tanks, while not a breach in distribution
system integrity, can have a detrimental impact on water quality (USEPA, 2004a).
Gauthier et al. (2000) attributed one storage tank's long turnover rate, which ranged from
5.6 to 7.6 days, as the likely reason for periodic losses in disinfectant residual in the
surrounding distribution system.
Biofilms can exert a chlorine demand that reduces the level of disinfectant in the
water (Berger et al., 2000). Increased chlorine demand may signal growth of biofilms in
portions of the distribution system, and a corresponding reduction in chlorine residual
can serve as an indicator of potential biofilm problems.
The kinetics of most chloramine reactions are slower than the kinetics of chlorine
reactions (Faust and Aly, 1998). Chlorine that is bound to an ammonia structure in a
chloramine compound is less available to react with other chemicals in the water than
are its free chlorine counterparts, hypochlorous acid and hypochlorite ion (Hazen and
Sawyer, 1992). As a result, chloramines are less likely to display as much variability in
their concentrations as chlorine. This accounts for why Snead et al. (1980) stated that
chloramine residuals do not show the sensitivity that chlorine residuals do, and therefore
are not as effective indicators of distribution system contamination.
Indicator of Distribution System Contamination
Snead et al. (1980) suggested using disinfectant residual as an indicator of distribution
system contamination. A sudden change in residual, whether an increase or a
decrease, may signal a mechanical failure of the feed system. A decrease may indicate
that contamination of the system has occurred as the result of a main break, backflow
event, or some other form of distribution system upset that exerted an increased
disinfectant demand. The authors clarify that chlorine residual can serve as an effective
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indicator of distribution system upset for water systems that do not usually have trouble
maintaining a residual and do not normally see substantial fluctuations in chlorine
demand. They also note that combined chlorine residuals do not function as well in this
role, since they are slower to react with contaminants entering the distribution system
water.
Denver Water successfully used on-line chlorine residual monitoring in the
distribution system to identify the impact of runoff after a forest fire on finished water
quality (Kirmeyer et al., 2002a). High dissolved manganese levels in silt washed into a
reservoir after the fire, and exerted a chlorine demand in the distribution system.
Chlorine residuals continued to decrease as the water moved further through the
distribution system.
Indicator of Public Health Outcome
Craun and Calderon (2001) estimated that 14.6 percent of waterborne disease
outbreaks that occurred from 1971 to 1998 in community water systems were due to
inadequate or interrupted disinfection of ground water. They also estimate that 21.4
percent of the outbreaks during the same time period were due to inadequate
disinfection of unfiltered surface water. The authors do not distinguish between
outbreaks where primary disinfection of the source was inadequate and those where
residual disinfection in the distribution system was inadequate. Therefore, one cannot
conclude from these results whether the absence of a disinfectant residual indicated the
waterborne disease outbreaks.
The use of disinfectant residual monitoring as an indicator of waterborne disease,
has not been entirely reliable, especially when the disease has resulted from
contamination due to treatment breakthrough. The clearest examples of this were the
Cryptosporidium outbreaks in Georgia (Hayes et al., 1989), Oregon (Leland et al., 1993),
and Milwaukee (MacKenzie et al., 1994), during which chlorine residuals were
maintained throughout the distribution systems that were delivering the contaminated
water. Thus, the contamination events did not pose a noticeable disinfectant demand
within the distribution system.
While evidence exists supporting the role a disinfectant residual can play in
preventing waterborne disease, no documented cases could be found where a reduction
in disinfectant residual alerted water system operators or health officials to a waterborne
disease outbreak.
Advantages
There are numerous advantages to using disinfectant residual as an indicator of
distribution system contamination. Analysis is inexpensive, EPA-approved analytical
methods exist, and the results can be reviewed immediately if the system possesses a
colorimeter, digital chlorine analyzer, or on-line chlorine analyzer within the distribution
system.
Shifts in the disinfectant residual can indicate a wide range of potential issues
regarding distribution system contamination, such as cross-connections (Haas, 1999),
backflow events (Haas, 1999), and long hydraulic residence times in storage tanks
(Gauthier et al. 2000). Changes in the disinfectant residual can also indicate biofilm
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growth and a vulnerability to waterborne disease outbreaks (Berger et al., 2000).
Disadvantages
Some contamination events can occur over a period of seconds, minutes, or
hours, the effectiveness of disinfectant residual measurements as indicators of
contamination may depend on the frequency of the residual measurements. Grab
sampling may not occur frequently enough for residual measurements to show increases
in disinfectant demand resulting from certain types of short-term contamination events.
In order to use disinfectant residual as an indicator of altered water quality, an
historical record is necessary to establish the range of residual values that would
represent normal functions (in absence of contamination events or breaches of the
distribution system), referred to as the baseline. New water systems and systems that
have changed their source or treatment method need time to develop such a residual
record and historical understanding. Because no documented cases could be found
where a reduction in disinfectant residual alerted water system operators or health
officials to a waterborne disease outbreak, disinfectant residual may be an unreliable
indicator. It also does not identify any single contaminant pathway.
6.2.2 pH
Background
Monitoring for pH is one of the most common tests conducted for water (Addy et
al. 2004). In its Response Protocol Toolbox: Planning for and Responding to Drinking
Water Contamination Threats and Incidents (USEPA, 2003), EPA recommends pH
monitoring to establish baseline water quality in the distribution system. In well-buffered
waters, pH should remain fairly constant throughout the distribution system, as long as
the water has come into equilibrium with the pipes and there are no significant corrosion
problems (AWWA, 1999a).
The Lead and Copper Rule (LCR) requires monitoring of pH as part of water
quality parameter monitoring in the event the lead or copper action level is exceeded (40
CFR Section 141.87). As part of the corrosion control treatment plan, pH must also be
monitored and a minimum pH of 7.0 must be maintained within the distribution system
(40 CFR Section 141.82(f)).
Indicator of Breaches of Distribution System Integrity
Changes in the pH can be a direct result of distribution system contamination.
Distribution systems have been contaminated with sodium hydroxide as a result of
unprotected cross-connections. One case involved backflow following a pressure
reduction due to a main break. During the main break, a truck driver was filling a tanker
containing sodium hydroxide with water (AWWA PNWS, 1995).
Low pH in soft water may be indicative of the leaching of some metals and
organic chemicals from pipes such as lead, arsenic, and cadmium (USEPA, 2004b). In
cement-lined pipes or tanks, an increase in pH over time can be indicative of leaching
(Kirmeyer et al., 2002b).
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An increase or decrease in the pH of the distributed water will affect corrosion
and can therefore be an indicator of potential corrosion problems. Corrosion control
efforts may be less effective due to decreases in pH. The pH of water in the distribution
system is an important factor in nitrification activity (Harrington et al., 2003). First, a
reduction of total alkalinity may accompany nitrification because a significant amount of
bicarbonate is consumed in the conversion of ammonia to nitrite. While reduction in
alkalinity does not impose a direct public health impact, reductions in alkalinity can
cause reductions in buffering capacity, which can impact pH stability and corrosivity of
the water toward lead and copper. Thus pH as an indicator can be used along with
alkalinity as an indicator of nitrification.
A reduction in pH can be an indication of problematic biofilm growth. For
example, a decrease in pH can result from growth of sulfur-reducing bacteria such as
Thiobacillus. These bacteria generate hydrogen ions which lowers the pH (AWWA,
1995). A growth in nitrifying bacteria may also decrease the pH by oxidizing ammonium
to nitrate and other nitrogen compounds (Schock, 1999).
Indicator of Distribution System Contamination
After establishing a baseline for the pH of the water, a change in pH can be an
indication of some contamination events (Kirmeyer et al., 2002b).
Advantages
pH is a commonly-monitored parameter, although monitoring is not necessarily required
under all circumstances. The concept of pH is understood by most operators of
distribution systems, and equipment is often already available. The pH can be
monitored using on-line monitoring equipment, by doing grab samples in the field, and in
a water treatment plant laboratory, allowing for almost immediate results.
Disadvantages
A change in pH does not indicate what specific type of contamination event may
have occurred. The change in pH may be minimized by highly buffered water. The
equipment needed to measure pH must be routinely maintained and calibrated. If not
already available, continuous monitoring equipment may be relatively expensive,
depending upon the number of sites monitored.
6.2.3 Alkalinity
Background
Alkalinity, composed mostly of carbonate and bicarbonate ions, is a measure of the
ability of a water to neutralize acids and bases (AWWA, 1999a).The LCR requires
monitoring of alkalinity as part of water quality parameter monitoring in the event the
lead or copper action level is exceeded (40 CFR 141.87).
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Indicator of Breaches of Distribution System Integrity
Alkalinity can be used to evaluate pipe replacement or storage tank coating
rehabilitation needs (Kirmeyer et al., 2002b). Cement-lined pipes and storage tanks can
leach calcium carbonate into the water, which may significantly increase the alkalinity of
the water. This is especially true when the cement-lined material is new, but also
depends on the type of cement used, the contact time between the water and cement
material, and the diameter of the pipe (Friedman et al., 2002).
Alkalinity can be used as an indicator to determine the corrosivity of water in the
distribution system. For example, leaching from metal pipes most commonly occurs in
low alkalinity waters. In addition, a reduction in alkalinity results in a reduction of the
buffering capacity of the water. Without buffering, the pH can more easily fluctuate,
which may lead to corrosive conditions.
Advantages
The method for analyzing alkalinity is well established. Alkalinity testing is
inexpensive and analytical results can be obtained quickly. Water system operators can
perform testing on-site.
Disadvantages
A change in alkalinity does not indicate presence of specific contaminants, but it
does indicate there has been a water quality change that may be associated with or
cause an increase in corrosion or biofilm occurrences (e.g., pH). In addition, current
monitoring for alkalinity under existing rules such as the LCR is limited in its scope in
terms of both frequency and location. Using alkalinity as an indicator would require the
establishment of a baseline condition first, and may require more frequent samples that
are more broadly representative of potential problem areas in the distribution system.
6.2.4 Calcium
Background
Water hardness is attributed to the presence of calcium and magnesium ions.
Hard water is generally less corrosive than soft water due to increased concentrations of
calcium in the hard water. Depending on the water's pH and alkalinity concentration,
calcium will combine with carbonate alkalinity to form a protective coating on the pipe
wall that can retard corrosion (AWWA 2000). Waters low in calcium (soft waters), pH
and alkalinity can result in corrosive conditions affecting cement-lined pipes and storage
tanks. Rather than calcium concentration itself, an increase or decrease in calcium
concentration may indicate potential for contamination to be released in the distribution
system. The LCR requires monitoring of calcium as part of water quality parameter
monitoring in the event the lead or copper action level is exceeded (40 CFR Section
141.87).
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Indicator of Breaches of Distribution System Integrity
Increased concentrations of calcium in the distribution system can be an
indication of corrosion in cement-lined pipe or storage tanks. Cement-lined pipes and
storage tanks can leach calcium carbonate into the water. This is especially true when
the cement-lined material is new, but also depends on the type of cement used, the
contact time between the water and cement material, and the diameter of the pipe.
Monitoring must be conducted in the finished water in order to observe changes in
calcium levels.
Waters that have very low ion content (soft waters) are aggressive to calcium
hydroxide contained in hydrated cements (ACIPCO, 2002). Calcium hydroxide will also
leach from cement-mortar linings exposed to soft waters (Friedman et al., 2002). The
extent of leaching increases with, among other factors, the residence time in the pipe
and is inversely proportional to the pipe diameter. A decrease in calcium levels could
indicate the potential for increased scale formation and reduced flow.
Advantages
The methods for analyzing calcium are well established. Calcium testing is both
inexpensive and analytical results can be obtained quickly (Skipton et al., 2004).
Disadvantages
Calcium is not a specific indicator for contaminants. Detection of increased
levels of calcium above finished water levels may indicate corrosion of cement-lined
pipes or it could also indicate resolubilization of calcium carbonate pipe coating,
developed as part of a corrosion control strategy. More information and other indicators
would be necessary to identify the specific problem.
6.2.5 Conductivity
Background
Conductivity, or specific conductance, is a measure of the ability of water to carry
an electric current (APHA, 1995). This ability depends on the concentration, mobility,
and valence of ions in the water as well as on water temperature. In general, water
containing substantial concentrations of inorganic compounds has higher conductivity.
Water containing organic molecules that do not dissociate well will have lower
conductivity. The conductivity of potable water in the United States usually falls within
the range of 50 to 1500 ^mhos/cm (APHA, 1995), which is the typical range of
fluctuation within systems.
Conductivity can be analyzed by the water system (if the system possesses the
necessary equipment) or analyzed by a laboratory for about $10 (Energy Laboratories,
2003).
The LCR requires monitoring of conductivity as part of water quality parameter
monitoring in the event the lead or copper action level is exceeded (40 CFR Section
141.87).
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Indicator of Breaches of Distribution System Integrity
Kirmeyer et al. (2001) list conductivity as one of the test parameters for water
systems to watch, because a sudden increase or decrease in conductivity often
accompanies a distribution system pathway breach or contamination event.
Conductivity will remain fairly constant throughout a distribution system as long
as the water is in equilibrium with the pipe material. Conductivity may vary more if there
are corrosion problems (USEPA, 2003). Thus changes in conductivity may indicate
corrosion problems.
Indicator of Distribution System Contamination
Conductivity is one of the water quality parameters that EPA recommends water
systems consider for establishing a baseline for their distribution systems' water quality
for security purposes (USEPA, 2003). By doing so, systems will then know what is
typical for their water, and any excursions outside the normal range of measurements
can serve as an indicator of a potential contamination threat.
Advantages
Conductivity measurements can be made frequently at low cost. Measurements
can be made using continuous on-line meters, or with portable instruments. If the
system possesses the necessary instruments, conductivity results can be obtained
immediately.
Disadvantages
Conductivity provides an estimate of the ionic strength of water. It does not
provide specific information about the composition of the ions or microbial contaminants
in the water. Additional water chemistry analysis needs to be performed for a water
system to follow up on a sudden shift in conductivity.
6.2.6 Fecal Sterols
Background
Fecal sterols are metabolites of cholesterol that are found in the gut and feces of
humans and animals. Coprostanol is a fecal sterol that is commonly found in domestic
wastewater. A study by Leeming et al. (1996) showed that coprostanol constitutes
approximately 60 percent of the total sterols found in human feces. The researchers
also found coprostanol in cat and pig feces, but at concentrations approximately 10
times lower than in human feces. Fecal sterols other than coprostanol were found to be
predominant in other animals including cows, horses, and sheep. Thus, coprostanol
could be used to distinguish between fecal contamination from humans and animals
(Leeming et al., 1996). A Standard Method or EPA Method does not exist for the
analysis of fecal sterols. Detection of fecal sterols at the levels present in wastewaters
requires gas chromatography-mass spectrometry. The detection limit of the gas
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chromatography-mass spectrometry method for detecting fecal sterols is estimated to be
10 to 50 nanograms per liter when a 1-liter sample is analyzed (Gomez et al., 1998).
Indicator of Distribution System Contamination
Coprostanol was first studied as an indicator of fecal pollution by Kirchmer
(1971). A comprehensive review of coprostanol as an indicator of fecal pollution was
published by Walker et al. (1982). Since then, papers on fecal sterols as indicators of
sewage and sewage sludge in coastal waters (Chan et al., 1998; Eaganhouse et al.
1988), discuss the relationship between fecal sterols and fecal indicator bacteria
(Leeming and Nichols, 1996; Nichols et al., 1993), and the use of fecal sterols to
determine the source of fecal pollution (Leeming et al., 1996), have focused attention on
this chemical alternative to microbial fecal indicators. No published studies examining
the presence of fecal sterols in treated drinking water have been identified.
Isobe et al. (2004) found a parallel logarithmic correlation between E. coli and
coprostanol for measuring fecal contamination of surface water; however the method
has not been applied to distribution system monitoring because the method may not be
sensitive enough to detect the low levels of coprostanol in drinking water (Gomez et al.,
1998).
No information or studies were identified specifically on fecal sterols as potential
indicators in drinking water systems.
Advantages
An advantage of using fecal sterols as an indicator is that they may allow
differentiation between human sewage pollution and fecal contamination from animals.
Disadvantages
The gas chromatography-mass spectrometry analytical method is expensive,
complex, and many drinking water treatment facilities do not have the necessary
equipment or training to run the analysis. Fecal sterols do not indicate non-fecal
contamination. It is not known if fecal sterols are present in source water or how
effectively they are removed in water treatment processes. Thus, it would be difficult to
establish a baseline for making a distinction between source or distribution system
contamination, such as through a cross-connection.
6.2.7 Caffeine and Pharmaceuticals
Background
Caffeine and pharmaceuticals are discharged into the aqueous environment in
wastewater, and they serve as source tracking indicators of human sewage pollution.
Their presence in groundwater suggests a possibility of septic or sewage contamination.
Their concentration in treated drinking water seldom exceeds the detection limit of
available analytical methods (Kolpin et al., 2002). A Standard Method or EPA Method
does not currently exist for caffeine or pharmaceuticals.
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Kolpin et al. (2002) conducted a national survey of pharmaceuticals, hormones,
and other organic wastewater contaminants (OWCs) in 139 streams in 30 states during
1999-2000. The selection of sampling sites was biased toward streams susceptible to
contamination (i.e., downstream of intense urbanization and livestock production).
OWCs were prevalent during this study, as they were found in 80 percent of the streams
sampled. The compounds detected represent a wide range of residential, industrial, and
agricultural origins and uses. The most frequently detected compounds were
coprostanol (fecal steroid), cholesterol (plant and animal steroid), N,N-diethyltoluamide
(insect repellant), caffeine (stimulant), triclosan (antimicrobial disinfectant), tri(2-
chloroethyl), phosphate (fire retardant), and 4-nonylphenol (nonionic detergent
metabolite). Measured concentrations for this study were generally low and rarely
exceeded drinking water guidelines, drinking-water health advisories or aquatic-life
criteria.
Indicator of Distribution System Contamination
Caffeine and pharmaceuticals are excreted in urine and are present in sewage
effluents as a marker of human sewage pollution (Standley et al., 2000; Siegener and
Chen, 2002). Buerge et al. (2003) reported caffeine concentrations ranging between 7-
73 fu.g/L in wastewater influents, and concentrations of 0.03-9.5 ^g/L in effluents of
wastewater treatment plants, which amounts to 81-99 percent removal. Ambient
concentrations of caffeine in lakes and rivers ranged from 6-250 nanograms (ng)/L.
Remote mountain lakes contained < 2 ng/L caffeine, suggesting caffeine may be useful
as a marker of human impact upon the environment (Buerge et al., 2003).
Weigel et al. (2002) surveyed the occurrence of drugs and personal care
products as pollutants in the North Sea. Analyses were conducted for clofibric acid
(reduces cholesterol levels in blood), diclofenac (anti-inflammatory), ibuprofen (anti-
inflammatory), ketoprofen (anti-inflammatory), propyphenazone (pain reliever), caffeine,
and N,N-diethyl-3-toluamide (DEET) (insect repellant). Clofibric acid, caffeine, and
DEET were present throughout the North Sea in concentrations of up to 1.3, 16 and 1.1
ng/L, respectively. Diclofenac and ibuprofen were found in the estuary of the river Elbe
(6.2 and 0.6 ng/L, respectively) but in none of the marine samples. Ketoprofen was
below the detection limit in all samples.
Few studies were identified linking caffeine to drinking water. Seiler et al. (1999)
surveyed groundwater from private and public wells, together with monitoring wells
around Reno, NV for nitrate, caffeine, and pharmaceuticals to evaluate their presence
and relationship to wastewater contamination. Results of this study indicate that these
compounds can be used as indicators of recharge from domestic wastewater, although
their usefulness is limited because caffeine is reactive and can break down in the
environment and the presence of prescription pharmaceuticals is unpredictable.
Caffeine was detected in ground water samples at concentrations up to 0.23 ^g/L (Seiler
et al. 1999). The human pharmaceuticals chlorpropamide, phensuximide, and
carbamazepine also were detected in some samples.
Advantages
The concentration of caffeine in treated drinking water seldom exceeds the
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detection limit of available analytical methods (Kolpin et al., 2002), whereas the
concentration in wastewater is typically much higher, thus a wastewater contamination
event may result in a significantly higher level, that is detectable over baseline. Since
most pharmaceuticals are not naturally occurring, the presence of pharmaceuticals is a
clear link to human-caused pollution.
Disadvantages
Detection of caffeine at the levels present in source waters and wastewaters
requires liquid chromatography-mass spectrometry. Detection of pharmaceuticals
requires liquid chromatography-mass spectrometry. These are expensive and complex
methods and many drinking water treatment facilities do not have the necessary
equipment or training to run the analysis. Analysis of a single sample for caffeine by an
independent laboratory may cost as much as $435 with a 7 to 14 day turnaround
(Source Molecular Corporation, 2002).
Another disadvantage of caffeine and pharmaceuticals as indicators is that
caffeine is reactive and can break down in the environment and the presence of
prescription pharmaceuticals is unpredictable. Soil microbes easily degrade caffeine.
Some plants have significant levels of caffeine, which could confuse results (Hagedorn,
2004).
An additional disadvantage is that it may be difficult to distinguish between
presence of caffeine and pharmaceuticals from source water that may or may not be
removed by treatment, or whether their presence is related to a distribution system
pathway.
6.2.8 Organic Carbon
Background
Most organic carbon in water comes from decaying plant materials present in
source waters, and it is present in several measurable forms, including the following:
Total Organic Carbon (TOC) is total organic carbon in mg/L measured using
heat, oxygen, ultraviolet irradiation, chemical oxidants, or combinations of these oxidants
that convert organic carbon to carbon dioxide, rounded to two significant figures (40 CFR
Section 141.2). Most of the organic carbon in drinking water is in the form of dissolved
organic carbon (Symons et al., 2000). Typical levels of TOC in drinking water derived
from surface source waters range from 1-20 mg/L, while ground water has a range of
0.1-2 mg/L. From the standpoint of measuring nutrients that can stimulate bacterial
growth in the distribution system, total organic carbon is not as applicable as AOC
and/or BDOC (LeChevallier, 1991).
Dissolved Organic Carbon (DOC) is the portion of organic carbon in water that
passes through a 0.45-micron pore-diameter filter (Symons, et al., 2000).
Biodegradable Organic Carbon (BDOC) is a measure of the fraction of the
organic carbon in water that can be mineralized by heterotrophic microorganisms (Huck,
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1990). Kirmeyer et al. (2002b) present a cost for BDOC analysis of $200. There is
currently no Standard Method for BDOC.
Assimilable Organic Carbon (AOC) is a measure of the fraction of dissolved
organic material in the water that can be used as a carbon and energy source by
microorganisms (Symons et al., 2000). LeChevallier (2001) reported AOC levels in
North American drinking water from 0.020 to 0.214 mg/L. The analytical costs for AOC
at a laboratory can be as high as $450 (Hoosier Microbiological Laboratory, 2001,
Muncie, Indiana) and only a few laboratories were located that were capable of
performing this analysis. Standard Method 9217B can be used to analyze AOC
concentrations in a water sample. Camper et al. (2000) recommended that utilities
monitor both AOC and BDOC because both types of compounds can be consumed by
microorganisms.
Indicator of Breaches of Distribution System Integrity
The use of nonmicrobial indicators, such as AOC and BDOC, provides a means
of characterizing the potential for microbial growth. The level of AOC entering the
distribution system and within the distribution system may control the rate and extent of
biofilm development (USEPA, 2002). AOC was first proposed as a means of
determining the nutrient potential of water (van der Kooij et al., 1984). Van der Kooij
(1992) related the presence of AOC with growth of bacteria in distribution system water.
AOC increased with increasing distance from the treatment plant and the number of
heterotrophic bacteria was directly related to temperature and AOC. Coliform growth
typically requires AOC concentrations greater than 0.05 mg/L (LeChevallier, 1991; Volk
and Joret, 1994).
Limiting the amount of AOC in water has been shown to control the growth of
biofilms in the distribution system (Schellart, 1986; van der Kooij, 1992). From a study of
20 types of drinking water, van der Kooij (1992) concluded that AOC concentrations less
than 0.01 mg/L of carbon in drinking water entering the distribution system prevent the
growth of heterotrophic bacteria.
LeChevallier (2001) reported that among North American drinking water systems,
those systems with AOC levels above 0.100 mg/L had 19 times more coliform positive
samples than systems with AOC levels below 0.099 mg/L. However, no single factor
was determined to be responsible for all coliform occurrences.
Because of the technical problems associated with the AOC method, some
investigators prefer a test for BDOC (Huck, 1990). DOC and BDOC analyses are
primarily research tools for understanding the metabolic activity occurring in biofilms.
Advantages
An advantage of using AOC and BDOC as an indicator of biofilms is that AOC
and BDOC are nutrients for biofilms and have been clearly linked to biofilm growth.
Several studies have shown that limiting AOC in treated drinking water limits biofilm
growth in the distribution system (Schellart 1986; van der Kooij 1992).
Disadvantages
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LeChevallier (2001) concluded that AOC alone may not be an accurate predictor
of microbial growth. The cost for AOC analysis is expensive, unless the system has the
ability to perform the analysis at its own laboratory. Like the microbial methods, a
disadvantage of both the BDOC and AOC tests is that the tests typically require a
minimum of 2 or 3 days to obtain results and can take up to 4 weeks.
6.2.9 Adenosine Triphosphate (ATP)
Background
ATP is found in all living microbial cells. It serves as a major energy source
within a cell to drive a number of biological processes including protein synthesis,
photosynthesis and muscle contraction (Columbia Encyclopedia, 2001). By supplying
an energy source, ATP aids organisms in sustaining life. Therefore, the presence of
ATP in the distribution system suggests biological activity.
ATP measures metabolic activity of living cells making it a potential microbial
indicator. Boe-Hansen et al. (2003) found ATP measurement to be rapid and easy to
perform while investigating biofilm growth in a model distribution system. It has a high
sensitivity for biomass measurements under low nutrient conditions. There is a highly
significant correlation between ATP and Acridine Orange Direct Count (AODC) data
(Boe-Hansen et al., 2003). Use of ATP as an indicator of metabolic activity of the
biomass in samples or on surfaces is already being performed, particularly in the food
industry (Tanaka et al., 1997).
The concentration of ATP, and subsequent change in microbial growth, will vary
depending upon the conditions of the water system, such as the treatment type. For
example, Chu et al. (2003) determined that average biofilm growth rates were 325 pg
ATP/cm2 for chlorine-free water, 159 pg ATP/cm2 for low-chlorine water, and 118 pg
ATP/cm2 for high chlorine water. In the Netherlands, Magic-Knezev and van der Kooij
(2004) showed that ATP concentrations ranged from 25 to 5000 ng ATP/ cm3 and varied
depending upon the long run filter time and type of filter. Pipe material can also influence
biofilm activity, and therefore, the amount of ATP. For example, mean biofilm activity
was lowest in glass pipes (136 pg ATP/cm2), and higher in cement (212 pg ATP/cm2),
MDPE (302 pg ATP/cm2), and PVC pipes (509 pg ATP/cm2; Hallam et al. 2001).
In France a new ATP extraction and titration system of bacterial ATP was used
during 2001 to test the Paris drinking water. Delahaye et. al (2003) found a linear
relationship between log (ATP) and log (HPC-R2A/ml). Furthermore, there was a slight
change in the microbiological quality in the Paris network, which was related to the
distance traveled from the production location to the site, as well as to a reservoir effect.
Indicator of Breaches of Distribution System Integrity
ATP can be used as an indicator to estimate biomass in the distribution system.
Boe-Hansen et al. (2003) selected total microscopic counts AODC HPC, and ATP as
indicators of biomass in a model distribution system to measure total biomass, viable
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biomass, and metabolically active biomass, respectively. Based on the study, they
recommended the combination of AODC and ATP as the preferred method of
quantitatively estimating biofilm biomass. A standardized method for analyzing ATP in
water exists (ASTM D4012-81), but it is not EPA approved.
In the Netherlands, ATP measurements are currently being monitored and used
to assess biofilm concentrations in the distribution system, to determine the biofilm
growth rate of treated water, and to use as a general indicator of microbial growth (van
der Kooij et al., 2003).
In biofilms, the concentration of ATP has been directly correlated with the
concentration of Candida albicans (Jin et al., 2004), Legionella pneumophila (Kuiper et
al, 2004), and Pseudomonas fluorescens (Simoes et al., 2005). ATP was used as an
indicator to determine that Streptococcus faecalis and Escherichia coli could survive and
remain physiologically active in petroleum-contaminated tropical marine waters (Santo
Domingo et al., 1989).
Indicator of Distribution System Contamination
Since ATP is used to monitor general levels of bacterial growth, ATP can not be
directly correlated to the activity of microbes of fecal origin.
Advantages
ATP has been used successfully in some model and actual distribution systems
as a general indicator of biofilms and microbial growth.
Disadvantages
The bioassay method for measuring ATP is a complex method. Rapid, easy
methods have been developed for use in the food industry, but their applicability to
treated drinking water is not known. There is no EPA approved method for measuring
ATP. There is limited application for ATP testing at temperatures less than 10° C or for
stressed cells. Interpretation of ATP data may be problematic because the amount of
ATP is related to the nutritional state of the organisms, and it is important to ensure that
the ATP results correlate with AODC data (Boe-Hansen et al., 2003).
6.2.10 Endotoxin
Background
Endotoxin is the cell wall lipopolysaccharide (LPS) of Gram-negative bacteria.
Gram-negative bacteria such as Pseudomonas and Aeromonas can enter the
distribution system and contribute to biofilm formation, which can subsequently protect
microbes from disinfection (AWWA, 1999b).
Indicator of Breaches of Distribution System Integrity
Endotoxin could indicate intrusion, backflow, or other events if the intruding
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matter contains Gram-negative bacteria.
Endotoxin can be used as an indicator for determining the presence of Gram-
negative bacteria in the distribution system in suspension or biofilm. However,
endotoxin is not a good indicator of biofilm microbial populations, nor of fecal
contamination alone, since endotoxin measurements do not discriminate between biofilm
and suspension.
•	Haas et al. (1983) attempted to use the limulus amoebocyte lysate (LAL)
spectrophotometric assay for Gram-negative bacterial endotoxins as a
measure of water quality, but was unable to correlate endotoxin results with
HPC tests. They concluded that the LAL test held little promise for assessing
drinking water quality as there was no relationship between endotoxin results
and HPC tests.
•	Korsholm and Sogaard (1987) compared HPC to endotoxin concentrations in
229 unchlorinated drinking water samples and found that counts on R2A
medium were weakly correlated with LPS concentrations. Use of endotoxin
detecting assays to detect trace contamination from Gram-negative bacteria
is sensitive but not sufficiently specific for use in drinking water monitoring
Korsholm and Sogaard (1987).
Advantages
There is a standardized method available for analyzing endotoxin (ASTM E2250-
02). The test method is highly sensitive (Korsholm and Sogaard, 1987). An endotoxin
test kit is commercially available for water operators to perform on-site testing.
Disadvantages
There is limited specificity when using endotoxin as an indicator as it only detects
Gram-negative bacteria. There is poor correlation between endotoxin measurements
and HPCs.
6.2.11 Iron
Background
Metals accumulated in distribution systems, such as iron, can be released to the
flowing water during hydraulic disturbances or change in water quality (Reiber et al.,
1997a). Metal solubility is strongly affected by the water's alkalinity, pH, and hardness.
Iron is oxidized and reduced by various bacteria, causing corrosion and fouling of
pipes. The genera Gallionella and Leptothrix are particularly associated with "red water"
and fouling of domestic water systems (Geldreich, 1996). "Red water" is generally
caused by iron corrosion and is common in old unlined cast iron mains or under
turbulent conditions (Kirmeyer et al., 2002b). The accumulation of iron in the distribution
system can be a result of oxidation and settling of iron (Kirmeyer et al., 2002b).
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Iron entering water as a result of corrosion frequently deposits into scales that
line pipe walls. These scales provide a location for numerous compounds and corrosion
byproducts to accumulate (McNeill and Edwards, 2001). Scale dissolution can return
metals into the water either as soluble species or attached to scale particles that have
detached from the pipe surface.
The secondary MCL for iron is 0.3 mg/L. Approved methods for iron analysis
include EPA Methods 200.7 and 200.9 and Standard Methods 3120B, 3111B, and
3113B.
Indicator of Breaches of Distribution System Integrity
An increase in iron concentrations over time can indicate that corrosion has
taken place, and may have affected the structural integrity of the pipe. This can help the
system to determine pipe replacement frequency (Kirmeyer et al., 2002b).
Iron can also be monitored at dead ends and if an increase in historical iron levels is
noted, the system may use this as a tool to determine flushing frequency (Kirmeyer et
al., 2002b). If sequestering is practiced, an increase in iron concentration may indicate
that the sequestering agent is not properly working (USEPA, 2004b).
Corrosion can result in the release of contaminants, such as iron, into the
distribution system. Unlined cast iron mains have shown to be a source of iron in the
distribution system under corrosive water conditions (Friedman et al., 2004a). Iron
deposits have shown an increase when the time between flushing of the water mains
increases (Friedman et al., 2004a). Iron can also be released from cast iron pipe by
aggressive waters (USEPA, 2004b). In some instances, the increase of iron
concentrations over time may be indicative of long retention times that allow oxidized
iron to settle.
Low flow conditions favor the release of soluble iron from pipe walls (Brandt et
al., 2004). The addition of chlorine to previously unchlorinated ground water can affect
the composition and stability of scales on pipe, resulting in the release of particulate iron.
This condition occurred in Fremont, Nebraska, where iron levels greater than 300 mg/L
were obtained when the system initiated chlorination (Reiber et al., 1997b). The release
of iron was related to the oxidation by chlorine of ferrous iron bearing corrosion scales in
the distribution system.
Flushing of 8-inch mains in Newport News, Virginia, indicated unlined cast iron
pipe produced significantly more iron when flushed as compared to lined ductile iron
pipe within the same distribution system that received the same finished water
(Friedman et al., 2004a). This study indicates corrosion of unlined cast iron pipe
provides a significant (91-times more) contribution of iron-rich deposits when compared
to lined ductile iron pipe.
Advantages
Iron is a frequent product of corrosion in iron pipes. The presence of high
concentrations of iron compared to finished water levels would indicate corrosion and
increased concentrations could signify release. The cost of an iron analysis is relatively
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inexpensive at about $10 per sample. EPA Method 200.8 will also detect the presence
of other metals.
Disadvantages
Corrosion byproducts can migrate throughout the distribution system, making it
difficult to directly relate the measurement of iron in a sample to a specific problem
location (Friedman et al., 2004a)
6.2.12 Ammonia, Nitrate, Nitrite, and Nitrogen
Background
Chloramination is the practice of adding ammonia and chlorine to form
chloramines, a more stable disinfectant than free chlorine. Where chloramination is
practiced, ammonia may be detected in the distribution system. The ammonia can be
attributed to residual ammonia that is added as part of the chloramination process, or to
ammonia that is released as part of the decay of chloramines (Harrington, 2003). In
some cases, ammonia may be naturally-occurring. In the presence of ammonia,
nitrifying bacteria may begin the process of nitrification by using ammonia as an energy
source. Ammonia-oxidizing bacteria (AOB) of the genus Nitrosomonas can oxidize
ammonia to nitrites. Nitrites may then be oxidized to nitrates by bacteria of the genus
Nitrobacter as the final step in the nitrification process. Where ammonia is found in the
distribution system, concentrations of nitrite and nitrate may increase as nitrification
occurs in the distribution system.
Indicator of Pathways that Breach Distribution System Integrity
Nitrites may indicate the decomposition of chloramine residual, which has been
associated with an increase in heterotrophic bacteria (Harrington, 2003). Measurement
of nitrite and nitrate above background levels can indicate a nitrification event. In
addition to measuring nitrate, nitrification is often indirectly identified by one or more
symptoms including (Wlczak et al., 1996):
•	Loss of chloramine residual
•	Increase in water temperature
•	Decrease in dissolved oxygen
•	Drop in pH (emphasis added) and alkalinity
•	Increase in HPC population
Monitoring for ammonia in the distribution system can indicate the disinfection
efficiency of the chloramination process. Monitoring for these nutrients for optimization
of the chloramination process could also serve as an indicator of corrosion and acute
cross-connection risks (i.e., sewage and fertilizer wastes) if a sudden increase was
noted for these contaminants.
Advantages
Ammonia, nitrites, and nitrates are relatively easy to sample and analyze.
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Disadvantages
Analysis costs are modest, depending upon the desired detection level (Energy
Laboratories, 2003). However, the expenses associated with labor and analysis costs
could become significant over time if optimization of the chloramination process requires
continuous monitoring.
6.2.13 Aluminum
Background
Aggressive, soft, and poorly buffered (i.e., low alkalinity) water promotes
aluminum leaching from cement materials. These are the same water quality conditions
that are conducive to leaching of lead and copper. Aluminum has a secondary MCL
between 0.05 mg/L and 0.2 mg/L (40 CFR Section 143.3). Aluminum can be present in
the distribution system as a result of chemical feed practices, such as adding alum as a
coagulant, or as a result of leaching from pipe materials.
Indicator of Breaches of Distribution System Integrity
An increase in aluminum can be an indicator of corrosive conditions created by
problematic biofilms, e.g., sulfur-reducing bacteria and nitrifying bacteria.
An increase in aluminum concentrations within the distribution system can also
be an indicator of leaching. Aluminum has been reported to leach from the cement-
mortar lining of distribution pipe.
In a study by Berend and Trouwborst (1999), the installation of 7,200 feet of
cement-mortar lined ductile iron pipe caused aluminum levels in a water supply to
increase from 5 |jg/L to 690 |jg/L over the course of 2 months. More than 2 years later,
aluminum continued to leach from the lining and produce water with over 100 |jg/L of
aluminum. The water that was being distributed by the pipes in the study was
aggressive (maximum Langelier Index between -0.5 and -1.5), soft (hardness 15-20
mg/L as CaC03), of low alkalinity (no data), and high pH (8.5 to 9.5). The extent of
leaching is also strongly related to the contact time between the water and the cement-
mortar lining. In the study by Berend and Trouwborst (1999), the average contact time
was 2.3 days.
Advantages
Sampling and analysis for aluminum are relatively straightforward and
inexpensive (Energy Laboratories, 2003). Sampling in areas of pipe with cement-mortar
lining may easily identify leaching of aluminum when compared with aluminum levels in
samples taken from the entry point(s).
Disadvantages
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Detection of elevated aluminum levels would not identify the source of corrosive
conditions per se. Further investigation to identify the cause of corrosive conditions
would likely be necessary. If aluminum salts are used as a coagulant in the treatment
process, aluminum may also have to be monitored after treatment to establish
background levels following treatment. Alum floe may also accumulate in distribution
system sediments, further confounding the use of aluminum as an indicator of leaching
(NRC, 2006).
6.2.14 Chloride
Background
Chloride is present in agricultural, industrial, and domestic wastewaters that are
discharged to surface waters. Home water softeners contribute a significant amount of
chlorides as a result of the regeneration process. Human excreta are another significant
source of chlorides with an average of about 6 grams of chloride per person per day
(Metcalf and Eddy, 1991). The secondary MCL for chloride is 250 mg/L. Methods for
detecting chloride in water include Standard Methods 411 OB, 4500-CI"D, and EPA
Method 300.OA. The analysis for chloride is relatively inexpensive at approximately $15
per sample (Kirmeyer et al., 2002b).
Indicator of Breaches of Distribution System Integrity
Because chlorides are found in agricultural, industrial, and domestic wastewaters
and home water softeners, which are known to be associated with cross connections,
chloride presence in the distribution system above background levels may indicate that
backflow is occurring through these types of cross connections. Increases in chloride
concentrations could also indicate intrusions of brackish water.
Indicator of Distribution System Contamination
Conventional methods of sewage treatment do not significantly remove chlorides.
Therefore, detection of higher than normal concentrations of chloride in a body of water
may indicate that treated sewage is being discharged into it (Metcalf and Eddy, 1991).
Detection of increased chloride concentrations in the distribution system may also
indicate contamination by treated or untreated sewage.
Chloride is naturally occurring and can leach into source water from chloride-
containing rocks and soils. Chloride can also occur due to salt-water intrusion. Road
salt, fertilizer, and landfills are other potential sources of chloride. Therefore, although
the presence of increased levels of chloride can indicate contamination, the source of
the contamination may not be clear.
Advantages
The analysis for chloride is relatively simple and inexpensive.
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Disadvantages
A disadvantage of using chloride as a fecal indicator is that there are multiple
potential sources of chloride and therefore the source of chloride contamination may not
be clear.
6.2.15 Microbially Available Phosphorous
Background
In general, phosphorus naturally occurs in groundwater or may be added as part
of corrosion control treatment. The range of naturally occurring phosphorus can vary
widely. Phosphorus has been found to be present at levels as high as 300 |jg/L or as
low as 0.1 |jg/L (Geldreich, 1996). Miettinen et al. (1997a) indicate that most total
phosphorus in drinking water sources is associated with particles. In general, the
dissolved total phosphorus portion, which is biodegradable, is present in very small
amounts. Recent evidence suggests that phosphate concentrations regulate microbial
growth in biofilms (Lehtola et al. 1999; Lehtola et al. 2002). Lehtola et al. (1999)
developed a method to quantify the amount of phosphorus in drinking water that can be
used by microorganisms for growth. Microbially available phosphorus (MAP) can be
determined using a bioassay in which the maximum growth of Pseudomonas
fluorescens P17 is related to the concentration of MAP. Lehtola et al. (1999) found that
the mathematical factor relating maximum growth to MAP is 373,200 ± 9,400 CFU per
microgram of P04-P.
Indicator of Breaches of Distribution System Integrity
In certain environments where phosphorus is the limiting agent, Lehtola et al.
(1999) found that even a very low concentration of phosphorus (below 1 |a,g/L) can
promote extensive microbial growth. In later work, Lehtola et al. (2002) found that when
chlorine was not removed, there was a correlation between MAP and heterotrophic
bacteria growth potential at MAP concentrations less than 2 |a,g/L. Sang et al. (2003)
investigated the influence of P043"-P on bacterial growth in effluent from pilot-scale
drinking water treatment. The results demonstrated that phosphorus became the limiting
nutrient when AOC was 200 |a,g C/L and phosphorus was below 4 |a,g C/L. Increasing
phosphorus above this level resulted in corresponding increases in bacterial growth.
Thus, in phosphorus-limited environments, the presence of even low levels of
phosphorus indicates the potential for microbial growth and increased biofilms.
Advantages
The method for determining MAP was only recently developed and is not yet
widely used. Therefore, insufficient information is available to determine the advantages
of using MAP as an indicator for biofilms.
Disadvantages
Although an association has been shown between MAP and microbial growth,
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the critical concentrations and effects are not sufficiently documented to determine a
cutoff level to which MAP should be limited.
Another disadvantage of the MAP test is that the test typically requires 4 to 8
days to obtain results. Therefore, changes in MAP are not immediately discernable and
the response to such changes is significantly delayed.
6.2.16 Turbidity
Background
Turbidity is a measure of filter efficacy. Current regulations (40 CFR §141.173)
require conventional and direct filtration plants treating surface water or ground water
under the direct influence of surface water to maintain the turbidity of finished water
below 0.3 NTU (in 95 percent of 4-hour monthly readings). Turbidity above this limit
suggests filter deficiencies or other treatment problems that may admit pathogens to the
distribution system.
The method for analyzing turbidity is well established (EPA Method 180.1 or
Standard Method 2130). Turbidity can be measured using on-line turbidimeters,
portable turbidimeters, or bench top turbidimeters that meet EPA-approved methods.
Indicator of Breaches of Distribution System Integrity
Turbidity can be used as an indicator for identifying contamination entry,
hydraulic problems or finished water reservoir rehabilitation frequencies in the
distribution system. Sudden increases in turbidity can indicate main breaks, backflow,
fire fighting or hydrant opening, flushing, scheduled maintenance or repairs, valve
failures, and treatment failures in the distribution system (Kirmeyer et al., 2002b).
Particles in treated drinking water may also be introduced during new construction.
Microorganisms can adhere to particles that protect them from disinfection, provide a
source of nutrients, and facilitate their movement within the distribution system (Gauthier
et al. 1999a; Morin et al. 1999). Furthermore, an increase in turbidity in the
distribution system will exert a greater chlorine demand which could lead to inadequate
disinfection of the distributed water (Kirmeyer et al., 2002b). Thus turbidity can be an
indicator that conditions permit potential microbiological growth in the distribution
system.
Increased turbidity near a finished water reservoir may be an indication of a
water quality problem associated with the reservoir. Increased turbidity may be due to
contamination in the storage tank, water age or mixing issues or tank material
degradation (Kirmeyer et al., 2002b).
Advantages
The method for analyzing turbidity is well established (such as EPA Method
180.1 or Standard Method 2130). Turbidity testing is inexpensive if the system already
owns a turbidimeter and analytical results can be obtained quickly. Water system
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operators can perform testing on-site. Systems required to continuously monitor for
turbidity at the treatment facility will have a baseline when comparing the turbidity
entering the distribution system to the turbidity within the distribution system.
Disadvantages
Turbidity is not an indicator for specific microbiological or chemical contaminants.
6.3 Other Indicators
6.3.1 Temperature
Background
Temperature is a very important parameter for many physical and chemical water
treatment applications (AwwaRF, 2002). Changes in temperature are also important to
predicting distribution system integrity breaches including mains breaks, corrosion,
nitrification and changes in hydraulic conditions (NRC, 2006). Temperature difference
between storage tanks and entry to the distribution system can suggest stratification in
storage tanks and hence degradation of water quality that could lead to microbial
regrowth in the distributions system (Mahmood et. al. , 2005). Many systems conduct
online temperature monitoring both at entry points and within the distribution system
Indicator of Breaches of Distribution System Integrity
An increase in water temperature will also increase the rate of decay for chlorine
(Zhou et al., 2003). A sudden change in water temperature could indicate a problem with
distribution system integrity as water of a different temperature enters the system from a
storage tank, backflow or intrusion.
Warmer temperatures are associated with increased growth rates of bacteria
(Besner et al., 2002). Increases in summer occurrences of total coliform-positive
samples have been reported (Colbourne et al., 1991; Olstadt et al., 1998). Coliform-
positive samples occur more frequently when the distribution system water temperature
is above 15° C (Volk and Joret, 1994; Volk and LeChevallier, 2000; Besner et al., 2001).
Warmer temperature is associated with an increase in corrosion potential
(Besner et al., 2002). Water temperature can be used as an indicator to determine the
corrosivity of water in the distribution system. For example nitrification, which can lead to
corrosive water conditions, most commonly occurs at temperatures greater than 15°C
(Kirmeyer et al., 2002b). Conversely, calcium carbonate has a higher tendency to
precipitate and form a protective layer at higher temperatures, minimizing the effects of
corrosion (AWWA, 2000).
Temperature can indicate potential leaching of vinyl chloride from PVC pipe.
Fluornoy et al. (1999) conducted a survey of water systems using PVC pipe in their
distribution systems. The study identified high temperatures (i.e., > 50 °F) as promoting
vinyl chloride leaching.
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Advantages
Analyzing for temperature is simple and inexpensive since many water-quality
field instruments have a means of measuring temperature that would not require
separate instrumentation. Water system operators can measure water temperature on-
site and the results are immediate.
Disadvantages
A change in temperature is not an indicator for specific types of contaminants.
6.3.2 Pressure
Background
Pathways by which contaminants can enter the distribution system during a
pressure reduction event include cross connections, leaks, water main break and repair
sites, and short-term pressure transients (Kirmeyer et al., 2001; EPA, 2002; Karim et al.,
2003; WHO, 2004).
Pressure monitoring in all parts of the distribution system can identify changes in
pressure that may leave a system vulnerable to contaminant entry into the distribution
system (LeChevallier et al., 2002). Pathogens or chemicals in close proximity to pipes
experiencing low or negative pressures are potential contamination sources even though
they are external to the distribution system. Record keeping about events that contribute
to pressure changes may aid systems in recognizing such events before they occur.
Gullick et al. (2004) used high-speed electronic monitoring devices to determine
the frequency and location of low and negative pressures in representative distribution
systems under normal operating conditions and during specific operational events.
Hydraulic modeling and transient surge modeling can be used to evaluate
pressure changes and transient pressure waves associated with rapid changes in fluid
velocity (Walski et al., 2001; Wood et al., 2005). Walski et al. (2006) defined the
orifice/soil number as an indicator of head loss caused by orifice losses relative to
porous media losses.
Indicator of Breaches of Distribution System Integrity
Friedman et al. (2004c.) conducted field studies, laboratory studies, and
hydraulic modeling to verify and quantify the occurrence of low and negative pressure
transients in distribution systems and the potential intrusion of contaminants external to
the pipe caused by pressure transients. These pressure events are caused by sudden
changes in water velocity due to loss of power, sudden valve closure or opening, a
transmission line break, fire flow, or an uncontrolled change in on/off pump status. A
pressure surge is created by these conditions, causing very high pressure followed by
low and negative pressure. When the pressure surrounding the water main exceeds the
internal pressure in the pipe, water external to the main may flow in through leakage
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points, submerged air valves, cross connections, faulty seals, or joints.
Indicator of Distribution System Contamination
Pressure measurement is a useful operational monitoring parameter that can be
used as an indicator of possible contamination in piped distribution systems (WHO,
2004). Fecal contamination may occur in large buildings through cross-connections and
backflow and from buried/immersed tanks and pipes, especially if not maintained with
positive internal water pressure (WHO, 2004). The principal hazards that may accrue in
the drinking-water systems of large buildings are ingress of microbial contamination
(which may affect only the building or also the wider supply), proliferation and dispersal
of bacteria growing on water contact surfaces (especially Legionella) and addition of
chemical substances from piping, jointing and plumbing materials (WHO, 2004).
Boyd et al. (2004a; 2004b) assembled a pilot-scale test rig to simulate intrusion
behavior associated with hydraulic transients and quantified intrusion volumes by two
methods, chemical tracer and volumetric methods, and compared results to theoretical
estimates of intrusion.
Indicator of Public Health Outcome
The public health significance of intrusion from a pressure transient depends on
the number and effective size of orifices (leaks), the type and amount of contaminants
external to the distribution system, the frequency, duration, and magnitude of the
pressure transient event, and the population exposed (LeChevallier et al., 2002b).
Continual monitoring for reduced pressure can give immediate warning of a potential
backflow incident (EPA, 2002).
Outbreaks of fluoride poisoning were reportedly caused by backsiphonage at
water treatment plants in Mississippi and Hawaii (Craun and Calderon, 2001). In
Tennessee, high concentrations of Giardia found in samples collected at a correction
facility attributed to low water pressure for 3 days and a likely cross-connection with the
wastewater pump station (Craun and Calderon, 2001). In 1990, an outbreak of illnesses
in Missouri was associated with municipal drinking water and attributed to sewage
overflow in an area where meters were replaced and a water main break occurred
(Craun and Calderon, 2001). The risks may be elevated seasonally as soil moisture
conditions increase the likelihood of a pressure gradient developing from the soil to the
pipe (WHO, 2004).
Sadiq et al. (2006) proposed the application of evidential reasoning to assess risk
of contaminant intrusion in a given pipe. Data generated through routine water quality
monitoring in distribution networks representing intrusion pathways, driving forces, and
contamination sources can be combined with evidential reasoning to establish risk-
contours of contaminant intrusion and help identify sensitive locations in water
distribution networks, thus helping prioritize control strategies.
Advantages
An advantage of using pressure as an indicator of distribution system integrity is
that data from pressure gages throughout the distribution system can be tied into a
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SCADA system to provide water system operators with real-time data from the
distribution system (Kirmeyer et al., 2002b). This allows rapid detection of potential
problems in the distribution system with minimal need for operator labor. Continual
monitoring for reduced pressure may identify the area where a pressure drop may have
originated, and thus help isolate areas affected by backflow (EPA, 2002). Pressure
monitoring devices are routinely used by utility personnel. High-speed devices are also
commercially available (AWWARF, 2002).
Disadvantages
LeChevallier et al. (2002) described negative pressure events that were brief,
lasting for only seconds or minutes. If pressure monitoring is to be used as an indicator
of distribution system integrity, water pressure would need to be measured very
frequently, if not continuously, in order to catch these brief and intermittent negative
pressure events. High-speed pressure data loggers may be more sensitive than
conventional pressure data loggers, and may be more useful for detecting low-pressure
events. However, many would need to be used to monitor the entire distribution system
and they are expensive.
A drop in operating pressure can only indicate that a backflow event may have
already occurred; it cannot stop an event in progress or prevent an incident, unless the
root cause is corrected (EPA, 2002).
Predictive tools using evidential reasoning (Sadiq et al., 2006) are early in
development and not readily available.
6.3.3 Sanitary Survey Results
Background
Sanitary surveys are currently used to help identify deficiencies within the
distribution system. As stated in the December 1995 EPA/State Joint Guidance on
Sanitary Surveys (ASDWA/USEPA, 1995), the primary purpose of a sanitary survey is
"to evaluate and document the capabilities of the water system's sources, distribution
network, operation and maintenance, and overall management to continually provide
safe drinking water and to identify any deficiencies that may adversely impact a public
water system's ability to provide a safe, reliable water supply."
The TCR (40 CFR 141.21(d)) requires that systems taking fewer than 5 samples
per month have a sanitary survey performed by the State every 5 years (10 years for
some systems using protected and disinfected ground water sources). The frequency of
sanitary surveys of systems using surface water or GWUDI as a source was modified by
the IESWTR (40 CFR 142.16) to be no less than every 3 years for all sizes of community
systems, and no less than every 5 years for non-community systems.
The IESWTR also requires that States have the authority to assure that public
water systems using surface water or GWUDI sources respond in writing to significant
deficiencies outlined in sanitary survey reports no later than 45 days after the system
receives the report. In their response, water systems must indicate how and on what
schedule they will address significant deficiencies noted in the survey. The Ground
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Water Rule (GWR) requires that states have similar authority for sanitary surveys of
groundwater systems.
The IESWTR and the GWR (USEPA, 2000) both identify the distribution system
as one of the eight essential elements that must be addressed during the sanitary
survey.
•	Source (Protection, Physical Components and Condition)
•	T reatment
•	Distribution System (emphasis added)
•	Finished Water Storage
•	Pumps/Pump Facilities and Controls
•	Monitoring/Reporting/Data Verification
•	Water System Management/Operations
•	Operator Compliance with State Requirements
In its Guidance Manual for Conducting Sanitary Surveys of Public Water
Systems; Surface Water and Ground Water Under the Direct Influence (GWUDI) of
Surface Water (USEPA, 1999b), EPA provides more specific objectives for addressing
a system's distribution system during the sanitary survey. The three principal objectives
of the distribution system element of the sanitary survey are the following:
•	To determine the potential for degradation of the water quality in the
distribution system
•	To determine the reliability, quality, and vulnerability of the distribution system
•	To ensure that the sampling and monitoring plan(s) for the system conform
with requirements and adequately assess the quality of water in the
distribution system
Sanitary surveys have preventive value in identifying actual or potential
deficiencies within systems. As with issues of system integrity, deficiencies noted in a
sanitary survey may be an indicator of present or possible future contamination in the
distribution system. A survey on best management practices found that, while there was
no relationship between conducting sanitary surveys and occurrence of total coliform
positives, systems that corrected problems identified during sanitary surveys had fewer
total coliform detections (USEPA, 1997).
Indicator of Breaches of Distribution System Integrity
The second objective listed immediately above essentially describes an
assessment of the distribution system integrity. Sanitary surveys offer the opportunity to
inspect above-ground facilities and to identify (to the extent practicable) line and valve
locations, pipe sizes and materials, hydrant locations, locations of dead end mains,
pressure zone boundaries, and locations of storage tanks and booster pump stations.
After assessing the physical condition of the system, the inspector may then be
able to predict whether the system infrastructure could impact water quality and quantity.
During the sanitary survey, inspectors typically also ask questions such as the following
related to operation and maintenance of buried infrastructure (USEPA, 1999b):
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•	Are distribution system maintenance and repair records kept?
•	How frequent are main breaks and where do they occur?
•	Is a leak detection program in place?
•	Are the source and service connection flows metered?
•	Is a regular, systematic flushing program in place?
•	Are distribution system installations, repairs and maintenance routinely
disinfected?
•	Is a cross-connection control program in place?
The answers to these questions, in conjunction with a knowledge of the system
construction, may indicate integrity and potential contaminant pathway issues and
whether there is potential for a problem in the distribution system.
As with issues of system integrity, deficiencies noted in a sanitary survey may be
an indicator of present or possible future fecal contamination in the distribution system.
For example, noted deficiencies, such as loose vents and overflows or an unsealed
hatch could lead to fecal contamination of a water system if birds gained access to
treated drinking water through the unprotected openings (Clark et al., 1994).
Indicator of Distribution System Contamination
During the sanitary survey, inspectors are also encouraged (USEPA, 1999b) to
collect a total coliform surveillance sample. Thus, the combination of a positive total
coliform test and noted deficiency which could lead to fecal contamination may provide
an indication of the potential for fecal contamination.
Indicator of Public Health Outcome
Similar to that mentioned above, noting an unprotected opening during a survey
may serve as an indicator that there is a high potential for a waterborne disease
outbreak to have occurred prior to the survey and up to the point when the deficiency is
fixed.
Advantages
As discussed above, sanitary surveys are already a required element of a state
primacy program. State primacy agencies are therefore familiar with sanitary survey
requirements and have existing programs in place.
Disadvantages
Since most of the distribution system components are located underground, they
cannot be directly inspected on a routine basis. Therefore, the review tools used to
evaluate the integrity of the distribution system during sanitary surveys include the
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system's design standards, installation procedures, and operation and maintenance
practices. A comparison of system information to current federal, state, and industry
standards and practices may then be made to assess the buried infrastructure
components.
The exteriors of ground-level finished water storage tanks can typically be
inspected during the sanitary survey, but the condition of tank interiors may be difficult to
assess since tanks are normally filled with water and in use during the survey. Elevated
tanks pose more significant challenges because of safety issues involved with tank
access. Therefore, potential problems such as accumulated sediments, biological
growth on the interior tank walls, or corrosion and peeling paint may not be clearly
identified during the sanitary survey. As with the rest of the distribution system,
inspectors may have to rely on information about the system's operational practices to
assess the likely condition of the interior of the storage tank. These limitations
somewhat complicate the use of sanitary surveys as an indicator for distribution system
integrity.
While some states may require more frequent surveys, many adhere to the
federal schedule. Water quality samples taken and deficiencies noted during a survey
therefore provide a snapshot of conditions at points in time that may be separated by 3
to 5 year intervals, or perhaps even longer.
6.3.4 Water Loss
Background
All water systems have some degree of water loss. Water loss can be
determined by comparing records of the amount of water pumped or flowing from the
source(s) to the amount recorded on metered connections. However, accounting
problems and meter inaccuracies may produce some error in water loss calculations.
Water loss may also be estimated in unmetered systems by observing the drop in water
level in a gravity storage tank during periods of normally low-water usage by consumers
(e.g., late at night). Water loss occurs through leaks, main breaks, fire hydrant use, and
unauthorized connections. A leaking main indicates a physical opening within the pipe
that can create a pathway for contaminant entry.
The presence of leaking sewer lines in the vicinity of leaking water main breaks
or repairs provides an opportunity for introduction of pathogens into drinking water
systems. A waterborne disease outbreak in Cabool, Missouri, resulted from a main
break with subsequent sewage contamination (Geldreich, 1992).
Indicator of Breaches of Distribution System Integrity
Systems with high leakage rates may also be more susceptible to main breaks,
as well as intrusions when low pressures occur.
Indicator of Distribution System Contamination
Distribution system locations with shared characteristics of high leakage rates
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and being susceptible to low or negative pressures have the greatest potential for
intrusion. Based on the findings of Friedman et al. (2004), systems can track low or
negative pressures at those locations and infer that these low pressure readings may be
effective indicators of increased likelihood of contamination.
Advantages
An advantage of monitoring water loss as an indicator of distribution system
integrity is that many water systems already have meters at all service connections; so
much of the needed equipment is already in place. Monitoring of losses may also lead
to revenue savings where the causes of the losses are corrected.
Disadvantages
A disadvantage of using water loss monitoring as an indicator of distribution
system integrity is that detection of water loss may not indicate where leaks are
occurring. In order to narrow down where leaks are occurring, it may be necessary to
monitor water loss in smaller zones within the distribution system, rather than solely at
metered connections (AWWA, 2000). Leak detection equipment is also available.
7 Summary of Indicators by Distribution System
Problem
This section summarizes each of the types of distribution system problems and the
indicators that may be applicable toward identification of that problem.
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Exhibit 3 Microbial Indicators
Indicator
Type of Distribution System Problem
Breaches of
Distribution System
Integrity
Contamination
Public Health
Outcome
External
Pathways
Internal
Pathways
Fecal
Toxic or
Carcinogenic
Waterborne
or Endemic
Disease
Total Conforms
E. coli
Thermotolerant (Fecal)
Conforms
Heterotrophic Bacteria
Total Bacterial Counts and
Total Viable Bacterial
Counts
X
X
*

X1
X

X

X2
X
X
X



X



X
X



Pseudomonas and
Aeromonas
X
X



Enterococci and Fecal
Streptococci
X

X

X
Somatic Coliphage


X


Male-Specific Coliphage
X

X

X
Clostridium perfringens
X

X


Bacteroides phage


X


Notes:
total conforms may be a broad screen for the potential for fecal contamination since some fecal
bacterial pathogens may be present when total conforms are present.
1	= potentially indicative of bacterial pathogens, but not viruses and protozoa (Nwachuku et al.
2002)
2	= not all are pathogenic
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Exhibit 4 Chemical Indicators

Indicator of Type of Distribution System Problem
Pathways that breach
distribution system
integrity.
Contamination
Public Health
Outcome
External
Pathways
Internal
Pathways
Fecal
Toxic or
Carcinogenic
Waterborne or
Endemic
Disease
Residual Disinfectant
PH
Alkalinity
Calcium
Conductivity
Fecal Sterols
X
X


X
X
X



X
X




X



X
X





X


Caffeine and
Pharmaceuticals


X


AOC and BDOC

X



ATP

X



Endotoxin
X
X



Iron
X
X



Ammonia/Nitrate/
Nitrite/Nitrogen

X
X


Aluminum

X



Chloride
X

X


Microbially Available
Phosphorus

X



Distribution System Indicators of Drinking Water Quality
65

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Exhibit 5 Other Indicators
Indicator
Indicator of Type of Distribution System Problem
Pathways that breach
distribution system
integrity.
Contamination
Public
Health
Outcome
External
Pathways
Internal
Pathways
Fecal
Toxic or
Carcinogenic
Waterborne
or Endemic
Disease
Sanitary Survey
Turbidity
Water Loss
Temperature
Pressure
X

X

X
X




X
X
X
X

X
X



X

X
X
X
Distribution System Indicators of Drinking Water Quality
66

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9 Appendices
9.1 Summary Table of Advantages and Disadvantages for Each Indicator
Indicator
Distribution System
Applicability
Advantages
Disadvantages1
Microbial
Total Conforms
External Pathways, Internal
Pathways
Waterborne or Endemic
Disease (weak)
•	Densities are much greater than the
density of fecal indicators
•	Useful in assessing treatment
effectiveness and breaches in the
distribution system.
•	Detection methods are simple and
inexpensive, and laboratories are
familiar with these methods.
•	Can be used as rough screen for fecal
contamination.
•	Determination of whether TCs are of
fecal or environmental origin is difficult.
•	More sensitive to disinfection than some
pathogens.
•	High levels of heterotrophic bacteria
can interfere with total coliform analysis.
•	Do not provide good indication of
specific contamination pathways.
•	Do not provide good indication of
vulnerability to waterborne outbreaks
unless possibly in conjunction with
another indicator or with monitoring
beyond TCR requirements.
1 All indicators have a common disadvantage in that they must be monitored frequently in many locations to be able to identify distribution system contamination
events
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Indicator
Distribution System
Applicability
Advantages
Disadvantages1
E. coli
External Pathways, Fecal
Contamination, Waterborne
or Endemic Disease
•	Analytical methods are simple, reliable,
inexpensive, and produce results within
24 to 48 hours.
•	E. coli is closely associated with recent
fecal contamination.
•	Presence indicates a major deficiency
in the distribution system due to
extreme sensitivity to disinfection.
•	Typically lower in density than total
conforms in water.
•	E. coli may die out more quickly than
some waterborne pathogens due to
succumbing to environmental factors or
to inactivation by disinfectants.
•	Sensitive to Pseudomonas spp., which
may affect ability to detect E. coli.
Thermotolerant (Fecal)
Conforms
External Pathways, Internal
Pathways, Fecal
Contamination
Waterborne or Endemic
Disease (weak)
•	Analytical methods are simple, reliable,
inexpensive, and produce results within
24 to 48 hours.
•	Easier to detect than E. coli due to
typically being present in higher
densities.
•	More specific indicator of fecal
contamination than total conforms.
•	Many thermotolerant conforms are
associated with recent fecal
contamination.
•	Analytical methods for thermotolerant
conforms can detect some
environmental strains, capturing a
larger group than the target organisms.
•	May be difficult to determine source of
contamination.
•	See disadvantages for E. coli.
Total Heterotrophic
Bacteria
External Pathways (weak),
Internal Pathways (weak)
•	Analytical methods are simple, reliable,
inexpensive, and produce results within
48 hours.
•	Effective indicator of biological growth.
•	High HPC measurements can indicate a
range of issues and cannot identify if
the problem is of fecal origin.
•	Standard HPC method is insensitive to
many waterborne bacteria.
•	Measurements can be unreliable due to
difference in methods, sample location,
and season.
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Indicator
Distribution System
Applicability
Advantages
Disadvantages1
Total Bacterial Counts
External Pathways, Internal
Pathways
•	Total counts provide basic information
on numbers of bacteria in water.
•	Viable counts may warn of significant
problems.
•	The analytical methods for viable
counts are relatively simple,
inexpensive, and well-established.
Total bacterial counts capture bacteria
that will not grow on artificial media.
•	Total counts can not distinguish viable
and nonviable cells.
•	Total counts are tedious and time-
consuming.
Pseudomonas and
Aeromonas
External Pathways, Internal
Pathways
• May indicate inadequate chlorine
residual or the presence of biofilm
growth.
•	Pseudomonas and Aeromonas capture
a smaller variety of biofilm bacteria
compared to other potential indicators.
•	The presence of pseudomonads may
interfere with the recovery of other
organisms on certain growth media
•	Pseudomonas and Aeromonas do not
provide an index of fecal contamination.
Enterococci and Fecal
Streptococci
External Pathways, Fecal
Contamination, Waterborne
or Endemic Disease
•	Standardized analytical methods are
available, relatively easy to use, and
provide rapid results.
•	Are generally absent from pure,
unpolluted waters (except in tropical
climates).
•	EPA recommends using enterococci in
conjunction with E. coli as a good
indicator of fecal contamination.
• Not as good a fecal indicator when
pathogenic protozoa are present which
are more resistant to environmental
stress and disinfection than enterococci
and fecal streptococci.
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Indicator
Distribution System
Applicability
Advantages
Disadvantages1
Somatic Coliphage
Fecal Contamination
(weak)
• Standardized methods are available.
•	No direct correlation in numbers of
phages and viruses in human feces.
•	Somatic coliphages can be found in
conditions without presence of fecal
contamination or a health risk.
•	Enteric viruses have been detected in
water environments in the absence of
coliphages.
•	Analytical method is more complicated
and expensive than those for traditional
bacterial indicators.
Male-Specific
Coliphage
External Pathway, Fecal
Contamination
•	Somewhat resistant to disinfection.
•	Standardized methods are available for
use in drinking water.
•	Narrow host range in comparison to
somatic coliphage.
•	Correlate better with presence of
pathogens in human feces than somatic
coliphage.
•	Difficulty in producing reproducible
results.
•	There is no direct correlation in
numbers of phages and viruses in
human feces.
•	Methods are not accessible due to
complexity and time.
•	May not be specific to E. coli.
•	Numbers may be sensitive to
temperature conditions.
Clostridium perfringens
External Pathways, Fecal
Contamination
•	Definitive fecal indicator.
•	Standardized methods are available for
rapid and reliable recovery of the
organism from water.
•	Correlates statistically with
concentrations of enteric viruses and
presence of Giardia cysts in drinking
water.
•	Due to persistence of spores for long
periods, may result in false positives.
•	The analytical method is more complex
than the coliform methods.
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Indicator
Distribution System
Applicability
Advantages
Disadvantages1
Bacteroides fragilis
phages
Fecal contamination
•	Does not grow in the environment.
•	May indicate very recent human fecal
contamination.
•	Complex analytical methods are
required.
•	Bacteroides is an obligate anaerobe
that quickly dies in the environment.
•	Absence of this phage does not provide
evidence of the absence of fecal
contamination.

Indicator
Distribution System
Applicability
Advantages
Disadvantages
Chemical
Residual Disinfectant
External Pathways, Internal
Pathways, Waterborne or
Endemic Disease
•	EPA-approved analytical methods exist.
•	Analytical methods are cheap and
results are immediate.
•	Reductions in residual disinfectant may
indicate contamination from many
different types of sources.
•	Frequency of monitoring may not be
often enough to capture short-term
events.
•	Historical records are necessary for
comparison.
•	No documented cases could be found
where a reduction alerted operators or
officials to a waterborne disease
outbreak.
•	Does not identify a single contaminant
pathway.
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Indicator
Distribution System
Applicability
Advantages
Disadvantages
PH
External Pathways, Internal
Pathways
• Many systems already monitor for pH,
have equipment and are familiar with
pH measurement.
•	A change in pH does not identify a
single contaminant pathway.
•	pH changes may be minimized by
highly buffered water.
•	Equipment used for measurement must
be routinely maintained and calibrated.
•	Equipment may be expensive to
purchase, depending upon site-specific
monitoring requirements.
Alkalinity
External Pathways, Internal
Pathways
•	Method is well established and
inexpensive.
•	Results are obtained quickly.
•	Testing can be performed on-site.
•	Alkalinity is not an indicator of a specific
problem.
•	Current monitoring is typically limited in
scope and frequency due to current
regulations.
•	Baseline conditions would need to be
established before this could provide
indication of water quality changes.
Calcium
Internal Pathways
•	Method is well established and fairly
inexpensive.
•	Analytical results can be obtained
quickly.
• Calcium is not an indicator of a specific
contaminant. Would need to be used in
conjunction with other indicators or
information.
Conductivity
External Pathways, Internal
Pathways
•	Method is well established and fairly
inexpensive.
•	Measurement can be continuous.
•	If the system has the necessary
instrumentation, results are immediate.
• Conductivity is not an indicator of a
specific contaminant. Would need to be
used in conjunction with other indicators
or information.
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Indicator
Distribution System
Applicability
Advantages
Disadvantages
Fecal Sterols
Fecal Contamination
• Fecal sterols may allow differentiation
between human sewage pollution and
fecal contamination from animals.
•	The analytical method is expensive and
complex.
•	Many drinking water treatment facilities
do not have this equipment.
•	Do not indicate non-fecal
contamination.
•	May be present in source water and it is
questionable how much is removed
during treatment.
Caffeine and
Pharmaceuticals
Fecal Contamination
•	The caffeine concentration in waste
waters is typically much greater than in
drinking water.
•	The presence of pharmaceuticals is a
clear indicator of human-caused
pollution.
•	The analytical method is expensive and
complex.
•	Many drinking water treatment facilities
do not have this equipment.
•	Caffeine can break down in the
environment.
•	Presence of pharmaceuticals is
unpredictable.
•	Because some plants produce caffeine,
it is not associated solely with fecal
contamination.
•	May be present in source water and it is
questionable how much is removed
during treatment.
AOC and BDOC
Internal Pathways
• Several studies have shown that limiting
AOC concentrations can control the
growth of biofilms in the distribution
system.
•	The analytical method can be
expensive and 2 to 3 days up to 4
weeks are required to obtain results.
•	Although limiting AOC concentrations
has been shown to control biofilms,
measuring AOC alone may not be an
accurate predictor of microbial growth.
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Indicator
Distribution System
Applicability
Advantages
Disadvantages
ATP
Internal Pathways
• General indicator for biofilms and
microbial growth.
•	The bioassay method for measuring
ATP is a complex method.
•	There is no EPA-approved method for
ATP.
•	Rapid, easy methods have been
developed for use in the food industry,
but their applicability to treated drinking
water is not known.
•	There is limited application for ATP
testing at temperatures less than 10 °C
or for stressed cells.
•	Interpretation of data may be difficult.
Endotoxin
External Pathways, Internal
Pathways
•	A highly sensitive standard method is
available.
•	Test kits are available for use on-site.
•	There is poor correlation between
endotoxin results and HPCs.
•	Limited specificity as an indicator.
Iron
External Pathways, Internal
Pathways
•	High concentrations of iron clearly
indicate corrosion and increased
concentrations could indicate sloughing.
•	The analytical method is fairly
inexpensive and may detect additional
metals.
• It is difficult to relate measurement of
iron to location of actual problem due to
migration.
Ammonia/Nitrate/
Nitrite/Nitrogen
Internal Pathways, Fecal
Contamination
• The analytical method is relatively easy.
• Monitoring may become expensive if
continuous monitoring is employed.
Aluminum
Internal Pathways
•	Sampling and analysis are relatively
straightforward and inexpensive.
•	Sampling in pipe sections with cement-
mortar lining may easily detect
aluminum leaching.
•	Detection of elevated aluminum does
not identify the corrosive conditions.
Further investigation may be necessary.
•	Alum floe may accumulate in
distribution system.
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Indicator
Distribution System
Applicability
Advantages
Disadvantages
Chloride
External Pathways, Fecal
Contamination
• The analytical method is relatively
simple and inexpensive.
• There are multiple potential sources
and the source of contamination may
not be clear.
Microbiological
Available Phosphorus
Internal Pathways
• Insufficient information.
•	The analytical method takes 4 to 8
days.
•	The critical concentrations and effects
are not sufficiently documented to
determine a level to which MAP should
be limited.
Turbidity
External Pathways
•	The analytical method is well-
established and relatively inexpensive.
•	Many systems already monitor turbidity
entering the distribution system, which
can be used to establish a baseline.
• Turbidity is not an indicator of specific
contaminant.

Indicator
Distribution System
Applicability
Advantages
Disadvantages
Other
Temperature
External Pathways, Internal
Pathways
•	Method is well established, simple, and
inexpensive.
•	Testing can be performed on-site and
results are immediate.
• Temperature change is not an indicator
of a specific contaminant.
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Pressure
External Pathways, Fecal
Contamination,
• Continual monitoring may identify the
area where a pressure drop originated
and isolate areas affected by a backflow
event.
•	Only provides information on an event
that may have already occurred.
•	Pressure would need to be measured
very frequently in order to catch brief
and intermittent negative pressure
events.
•	Predictive tools are in early
development and not readily useable.
Sanitary Survey
External Pathways, Fecal
Contamination, Water-
borne or Endemic Disease
• States and systems are familiar with
sanitary survey requirements.
•	Buried distribution system components
cannot be directly inspected.
•	Interiors of storage tanks that are in
service cannot be easily accessed.
•	Sanitary survey frequency is 3-5 years.
O&M Practices
External Pathways, Internal
Pathways, Fecal
Contamination, Toxic or
Carcinogenic Compounds
• Many systems already have meters at
all service connections, so equipment
necessary for monitoring for water loss
is already in place.
•	Customer complaints are voluntary.
•	Water loss monitoring may not indicate
specifically where leaks are occurring.
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