.1*0 ST-,
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON, D.C. 20460
March 13, 1990 EPA-SAB-DWC-90-007
OF
ADMINISTRATION
Mr. William Reilly
Administrator
USEPA
Washington, D.C. 20460
Dear Mr. Reilly;
Attached you will find the report of the SAB's Drinking Water
Committee (DWC) RECOMMENDATIONS FOR RESEARCH IN THE AREA OF
DISINFECTANTS AND DISINFECTION BY-PRODUCTS. This report is the
res'ult of a public meeting of the DWC on October 11-13, 1989,
subsequently discussions of drafts within the Committee, initial
examination of the report by the Executive Committee (EC) at their
public meeting January 8-9, 1990, and final EC review by mail.
The Agency is investigating the risks associated with
different approaches to disinfecting drinking water in the U. S.
Although treatment with chlorine has been used extensively for this
purpose for many years, concerns have been raised about possible
health risks associated with some of the by-products of this
disinfection process. Consequently, alternative forms (e.g.r
ozonation and ehloramination) are being explored and in some cases
employed for disinfection purposes. At the same time, any change
in the treatment applied to drinking water must also maintain a
sufficient level of microbial disinfection to protect public
health.
The issue is a complex one. clearly, there is need for good
scientific and engineering information before final decisions are
made. Hence, the SAB was asked to provide a critical review of
early activities of the Office of Drinking Water (QDW) in this
area .
Specifically, the charge to the DWC was to
a. Review the Office of Drinking Water's (OW) "strawman
regulation", a tentative course of action to address the
issues.
b. Identify significant data gaps that should be filled in order
reach informed decisions on the various approaches under
consideration.
c. Recommend research activities which should be undertaken to
fill thos"e data gaps,
d. Present the recommendations in some priority order.
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in conducting its review the DWG has examined the research
needs in the four general areas ot health effects, microbiology,
chemical characterization, and treatment technologies* After
reading Agency documents on the subjects and receiving briefings
from knowledgeable Agency staff, the Committee identified specific
research needs in each of the area, highlighting those topics of
highest priority.
In the area of health effects, the OWC gives highest priority
to careful consideration of the possible adverse health effects
associated with chlorination. For microbiology, the Committee
assigns high priority to conducting a survey of pathogens in the
drinking water systems and to conducting a workshop on the state
of the current scientific information on microbes in the drinking
water supply. In the area of chemical characterization, the
Committee strongly encourages the Agency to re-exaiaine its
monitoring strategies and to develop expertise in new analytical
methods. Finally, in the area of treatment technologies, the
Committee gives highest priority to both the investigation of
chemical methods to reduce the presence of particular
disinfectants/byproducts in treated waters and to methods for
removing materials with can serve as precursors for microbial
infection and for hazardous byproducts of disinfection treatment.
The attached report contains the rationale for these
recommendations, together with several other suggestions for
moderate priority research.
The Committee appreciated the opportunity to work with your
well-informed, conscientious EPA staff and to provide technical
advice in this important area. We look forward to your formal
response to this report.
Sincerely,
Raymond
"chair, issgu^ive Committee
Dr. WiiTiamf[Me~~~
Chair, Drinking Water Committee
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IPA-SAB-CWC-§0-007
18PQ1T OP TBB DRINKISS WATER COMMITTEE
SCIEHCE ADVISORY BOARD
RECOMMENDATIONS FOR RESEARCH IN THE AREA OF
PISIHFECTAHTS AHD DISIMFECTIOH BYPRODUCTS
MARCH, 1990
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U S. Environmental Protection Agency
Science Advisory Board
Drinking Water Committee - October 11-12, 1989
Or. William H, Glaze, [CHAIR], Department of Environmental Science and
Engineering, CB# 7400, Rosenau Hall, University of North Carolina,
Chapel Hill , NC 27599-7400
Dr. Verne Ray, [VICE-CHAIR]. Medical Research Laboratory. Pfitzer Inc.,
Groton, CT 06340
M-£J1B!R! --_
Dr. Julian 8, Andelman, Graduate School of Public Health. 130 Oesoto
Street, Parran Hall - Room A-711, University of Pittsburgh, Pittsburgh,
PA 15261
Or, Gary Carlson. Department of Pharmacology & Toxicology, School of
Pharmacy & Pharmacal Sciences, Purdue University, West Lafayette, IN 47907
Mr. Keith Cams, Director of Water Quality. East Bay Municipal Utility
District, 2131 Adeline Street, P,0, Box 240S5, Oakland, CA 94623
Or. Rose Dagirmanjian, Department of Pharmacology and Toxicology,
University of Louisville* Louisville, Kentucky 40292
Dr. Charles Gerba, Department of Microbiology, Building #90,
University of Arizona, Tucson, AZ 85721
Dr. J. Donald Johnson, The School of Public Health, Department of
Environmental Sciences, The University of North Carolina, Chapel Hill,
NC 27599-7400
Dr. E. Marshall Johnson, Chairman, Department of Anatomy, Jefferson
Medical College, 1020 Locust Street, Philadelphia, PA 19107
Dr. David Ktufman, Department of Pathology, University of North Carolina,
Brinkhous-iyimt, Room 515, Chapel Hill, NC 27514
Dr. Nancy K1m» Director, Division of Environmental Health Assessment
New York State Department of Helath, Room 3SO, 2 University Place,
Albany, NY 12203-6438
Mr, Ramon G» Lee, System Director, Water- Quality Research, American Water
Work Service Co. Inc., 1025 Laurel Qak Road, Voorhees, NJ 08043
Dr. Betty Olson, Program in Social Ecology, University of California,
Irvine, CA 92717
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-2-
Dr. Edo 0. Pellizzari, Vfc President, Research Triangle Institute
P.O. Box 12194. Research Triangle Park, NC 27709
Or. Harold Schechter, Chemistry Department, Ohio State University,
140 West 18th Avenue, Columbus, OH 43201
Or, Vern Snoeyink, Department of Civil Engineering Lab, 3230 Newmark Civil
Engineering Lab, University of Illinois, 205 Mathews Avenue, Urbana, IL 61801
Or. Mark Sobsey, Department of Environmental Sciences and Engineering, School
of Public Health, University of North Carolina, Chapel Hill, NC 27599
Dr. James Symons, Department of Civil Engineering, University of Houston,
Houston, TX 77004
Or. Thomas Tephly, Department of Pharmacology, The Bowen Science Building,
University of Iowa, Iowa City, IA 52242
Or, R, Rhodes Trussell, Vice President, James M. Montgomery, Consulting
Engineers, Inc., 250 North Madison Avenue, Pasadena, CA 91109-7009
EXECUTIVE SECRETARY
Or. C. Richard Cothern, Executive Secretary, U.S. Environmental Protection
Agency, Science Advisory Board [A1Q1F], Washington, D.C. 20460
STAFF SECRETARY
Ms. Joanna Foellmer, U.S, Environmental Protection Agency [A1Q1],
Washington, D.C. 20460
STAFF DIRECTOR
Dr. Donald G. Barnes, U.S, Environmental Protection Agency [A101],
Washington, D.C. 20460
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ABSTRACT
The Drinking Water Committee (DWC) of the Science Advisory
Board has examined a range of possible changes in existing
regulations that currently control drinking water disinfection
practices in the United States. The DWC report addresses areas
of scientific and engineering research that will provide
important insights on the alternatives under consideration.
Research recommendations are made in four areas; health effects,
chemical characterization and monitoring, microbiology, and
treatment technologies. The Committee highlights those
recommendations that are of the highest priority.
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TABLE OF CONTENTS
1.0 Executive Summary .....,»....»....,.», i
2.0 Introduction 3
2,1 Background
2.2 DWC Charge and Review Process
3,0 Research Recommendations Related to Health Effects ... 6
3.1 Highest Priority Recommendation: .......... 6
Describe health effects of chlorination disinfection
by-products more definitively
3.2 Moderate Priority Recommendations . , , 7
3.2,1 Relationship to other programs and laboratory
research
3.2.2 Use of mixtures
3*2*3 Possible susceptible groups
3.2.4 Brominated and iodated compounds
3,2,5 Compounds that may not be of significant health
concern
3.2.6 Epidemiology studies
4,0 Research Recommendations Related to
Chemical Characterization and Monitoring . . , , 11
4.1 Highest Priority Recommendations .... 11
4,1.1 Monitoring strategy
Chemical Characterization and Monitoring
4.1.2 In-depth chemical characterization
4.2 Moderate Priority Recommendations , . . 12
4.2.1 Total oxidizing substances
4.2.2 Methods development
4.2.3 Organic and inorganic bromides
4.2.4 Use of isotopically labelled chemicals
5.0 Research Recommendations Related to Microbial Agents . . 15
5.1 Highest Priority Recommendations. . * ,15
5.1.1 Survey of selected microbiological contaminants
5.1.2 Workshop on potable water microbiology
5.2 Moderate Priority Recommendations. ......... 16
5.2.1 Microbial risk assessment
5,2,2 Epidemiology study
5.2.3 Distribution system studies
5,2.4 Parasites and viruses
6.0 Research Recommendations Related to Treatment, ..... 19
6.1 Precursor Removal ,21
6.1.1 Conventional treatment modifications
6.1.2 Granular activated carbon
6.1.3 Membranes
6.2 Alternative Oxidants. ............... 26
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RECOMMENDATIONS FOR RESEARCH IN THE AREA OF
DISINFECTANTS AND DISINFECTION BY-PRODUCTS
A Report of the Drinking Water Committee
of the USEPA Science Advisory Board
1.0 Executive Summary
The Science Advisory Board's Drinking Water Committee (DWc)
met on October 11-12, 1989 to develop recommendations for
research in the areas of disinfectants and disinfection by-
products. The Office of Drinking Water (ODW) had at that time
developed an outline of a possible "strawman regulation" for
controlling the risks posed by these substances. Toe outline
included various approaches the Agency might take in addressing
certain issues,* e.g., ranges of maximum concentration limits
(MCLs) that could be adopted for different substances in drinking
water. ODW.formally asked the Committee for recommendations on
priority research activities which the Agency should conduct in
order to undergird the technical support for such a regulatory
approach.
The Committee developed recommendations in four research
areas and assigned them to one of two categories? i.e., those
that they felt that the Agency must do and those that they
thought the Agency should do. Those in the former category are:
AREA HIGHEST PRIORITY RESEARCH NEEDS
Health Effects Determine more definitively if the health
consequences of chlorination,
particularly those associated with
formation of chloroform, are of
significant concern by carefully
analyzing the existing data
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Microbiology Survey drinking water systems for pathogens
of concern, particularly
cryptosporidium, enteric viruses,
Aeronomas and Legionella.
Conduct a workshop to review the recent
experience in the area of
microbiological contaminants drawing
from experience and expertise both
within and outside the US
Chemical Re-examine monitoring strategies for
Characterization characterizing water supplies.
and Monitoring Develop expertise in new analytical methods
such as high performance liquid
chromatography/mass spectroscopy and
critical fluid chroatatography
Treatment Investigate chemical and physical
Technologies approaches to reducing chlorine dioxide
and chlorite ion levels in treated water
through the use of SO2
Investigate the effectiveness of precursor
removal in reducing drinking water
contamination by conducting a survey of
plants that use coagulation as a method
of color removal.
Evaluate precursor removal by membranes or
granular activated carbon and evaluate
removal by membranes of precursor
materials that lead to the formation of
by-products.
Several other recommendations for needed research were given
moderate priority.
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2.0 Introduction
2.1 Background
During the past 100 years great progress has been made in
improving the public health in this country through the
systematic treatment of its drinking water supplies. The
treatment method of choice during much of this period has been
chlorination. Within the past ten years, however, concerns have
been raised about the possible health risks posed by byproducts
formed during the chlorine disinfection process; e.g.,
trihalomethanes (THMs), such as chloroform*
Consequently, the Agency has been investigating approaches
to reducing the health risks in drinking water. For example, one
approach under consideration would be use alternative forms of
disinfection to reduce or eliminate the use of chlorine; e.g.,
use of ozone, chloride dioxide, or ctiloramine. Another approach
would focus on minimizing formation of hazardous disinfection by-
products (DBF) by increasing the efficiency of removal of
precursors, whose presence can result in increased raicrobial
levels and also provide substrates for formation of hazardous
DBF. Any change in current practice must be done in such a
manner that effective disinfection of the drinking water is not
compromised.
The Agency is still exploring the various options. The ODW
personnel have drafted a "strawman regulation11 which focuses some
of their early thinking on the matter. For example, it is likely
that the final regulation will involve a lower maximum
contaminant level («ct.) for trihalomethanes (THMs); e.g., in the
25-50 ug/L range ('the current standard is 100 ug/L). This will
be coupled with the appropriate monitoring and technology to
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insure that these MCLs can and will be met. Consequently,
drinking water suppliers could face the prospect of a reduced
usage of chlorine. To adequately disinfect drinking water there
would be an increased reliance on alternative oxidants. Probable
scenarios used for disinfection will then be:
a. ozone/conventional treatment/chlorine
b. ozone/conventional treatment/chloramines
c. chlorine dioxide/conventional treatment/sulphur
dioxide/chlorine or chloramine
d. chlorine dioxide/conventional treatment/granular
activated carbon (GAC)/chlorine or chloraaine
e. chlorine dioxide/conventional treatment/chlorine or
chloramine;
possibly,
f. oEOne/GAC/chlorine or chloramine,*
and in a few cases,
g. chlorine dioxide/GAC/chlorine or chloramine.
The values chosen for the MCLs that will be set for both
chlorine and the alternative disinfectants in relationship to
what is needed for effective disinfection and/or treatment will
dictate which of the above scenarios are viable. Therefore, at
this time there is uncertainty concerning which technology is
likely and what all the ramifications are.
2.2 DWC charge and Review Process
The charge to the DWC was to
a. Review the "strawman regulation"
b. Identify significant data gaps that should be filled in
order reach informed decisions on the various
approaches under consideration
c* Recommend research activities which should be undertaken to
fill those data gaps.
d. Present the recommendations in some priority order.
To carry out this charge, the DWC met October 11-12, 1989 in
Washington, D.C. where they were briefed by ODW on the strawman
regulation. The Committee considered four general areas of
research as they relate to disinfectants and disinfection by-
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products: health effects, chemical characterization and
monitoring, microbiology, and treatment including precursor
removal.
This final report contains the DWC's recommendations in each
of the four research areas, presenting them in two priority
categories; highest priority and moderate priority. The artier of
projects within each of these two categories are not in any
particular priority order.
A DWe-approved draft of this report was briefly considered
by the Executive Committee (EC) of the SAB at its meeting on
January 8-9, 1990. The EC formally endorsed the final report
through a subsequent mail review.
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3,0 Research Recommendations Related to Health Effects
The list of known and possible disinfectants and
disinfection by-products is so long that complete and documented
research concerning all the possible health effects for all
contaminants is not feasible. Thus the question is how to
allocate scarce research dollars because no way exists to develop
adequately and completely all the health effects information.
3-1 Highest Priority Recommendation:
Describe health effects of chlorination disinfection by-
products more definitively
Much of the regulation being considered is related to
studies on chloroform. The basic application of the animal tumor
data (including conflicting data on corn oil versus water as a
vehicle) and the relevance of mouse liver tumors suggests that
what is needed is a greater understanding of the relationship of
chese data to human health. The Committee recommends that
research needs to continue to investigate the basic mechanisms
involved in causing the health effects to the liver.
In past reviews concerning disinfectants and disinfection
by-products, the Drinking Water Committee has recommended
research in several areas for disinfectants other than chlorine.
The committee recommends that the health consequences of ingested
chloroform be realistically evaluated, substantiating the need
for decreasing the MCL for THMs. It is recommended that this be
resolved tip soon so that there is a clear basis for seeking
alternative disinfectants to chlorine.
if there is information lacking on the health effects
associated with the disinfection by-products of chlorination, the
Committee recommends that funding go first to establishing a
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scientific basis for the health effects of chlorination
byproducts (e.g., chloroform) and then turn attention and funding
to the determination of the health effects of alternative
disinfectants methods and their resulting disinfection by-
products. The rationale here is that if something is to be
changed, it should first be shown that the existing methods lead
to unacceptable health effects,
3.2 Moderate Priority Recommendations
3,2.1 Relationship to other programs and laboratory research
Collection and analysis of toxicological testing and health
data on DBF is a slow process. It appears that EPA is dependent
upon other agencies, such as the National Toxicology Program
(NTP) for completion of some toxicological testing and has begun
to make better and more effective use of the capabilities of that
group. The Committee recommends that efforts be continued to
enhance the value of this relationship by impressing upon NTP the
priorities in testing disinfectants and DBP. This information
should be pursued with all vigor. Furthermore, the integration
of work being performed at HESL/EPA in Research Triangle Park,
NC, especially in the area of neurotoxicology, is very important
and should be continued.
3.2.2 Use of mixtures
Because of the resource constraints involved in developing
this regulation, it is recommended that the research priorities
in the disinfection area be based on toxicity determinations of
chemical mixtures resulting from the alternate disinfection
processes. Considering the constraints of time, money and
personnel, short-term methodologies appear to be the primary
means for gaining some insight into the appropriateness of any
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rule-making procedure relating to alternative disinfection
approaches.
One possible approach, to analyzing mixtures is to perform a
stepwise concentration and analysis of water samples that have
been treated by the alternate disinfectants. A flow diagram of
one such treatment (for oaonation) follows. At each step three
analyses should be conducted; analytical chemistry, cytotoxicity
in mammalian cells, and genotoxicity in the Ames Salmonella
model. This approach would produce toxicological information for
the effects of the disinfection method at lower cost than
determining separately the effects of each of the individual by-
products .
Analytical chemistry
Cytotoxicity
Genotoxicity
Concentrate
Raw or
Processed
Water
Concentrate
SOX
Concentrate
100X
ETC.
Analytical chemistry
Cytotoxicity
Genotoxicity
Analytical chemistry
Cytotoxicity
Genotoxicity
In the procedure described above one could first concentrate
the sample, following this with disinfection treatment.
Alternatively, one could disinfect first and then concentrate the
sample. The latter approach would maximize the possible chemical
interactions. By testing multiple levels of concentrates,
artificial results produced by interactions of concentrated
compounds could be detected. The Ames Salmonella assay should be
performed using 4-5 strains of Salmonella throughout and not just
one strain because of possible false negatives, Cytotoxicity
could be used as an indicator for additional conventional
toxicity and genotoxicity analysis. Also, the experimental
treatment process steps should reflect actual process sequences;
8
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e.g, ozonation, followed by chloramine or chlorine, etc. Since
the method of concentration could significantly affect the
resulting tests, two methods should be used, e*g. reverse osmosis
and resin treatment, and the resulting total organic carbon
tracked.
3.2.3 Possible susceptible groups
In evaluating the toxicology profile for the disinfectants
and their by-products, either for individual compounds or their
mixtures, special attention needs to be paid to developmental
stages of the target population, including the conceptus and
fetus, that could be easily susceptible to the different health
effect endpoints. The Committee recommends that the EPA
carefully evaluate its data base on the developmental and
reproductive toxicity associated with disinfectants and
disinfection by-products and seek to fill the gaps. It could be
that the reproductive and developmental toxicological effects are
more important than other effects currently being studied.
3.2.4 Brominated and iodated compounds
Brominated compounds are important where bromine is found in
the source water; e.g., situations associated with intrusion from
sea water. This is especially true if ozonation or chlorination
is employed. The Committee recommends that EPA carefully
evaluate the information available on the toxicity of the
brominated disinfection by-products with the understanding that
these may have greater toxicity than the chlorinated analogs*
Health data on inorganic iodated compounds are also needed. The
Committee recommends that care be taken in examining the effects
of iodated compounds as they relate to the thyroid function where
extrapolation from' high to low dose may not be valid.
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3.2.5 Compounds that may not be of significant health concern
The Committee recommends that EPA carefully evaluate how
much effort may go into the examination of the compounds that may
not be of health concern due to low concentrations and/or short
halflives,* e.g., hydrogen peroxide, formaldehyde, and chloral
hydrate which are highly reactive material appearing in low
concentrations. Such compounds should not be ignored, but
careful allocation of time, money and personnel requires putting
contaminants, like these, that are unlikely to have serious
health effects at the levels found in drinking water, in lower
priority categories.
3.2.6 Epidemiology studies
The Committee recommends that EPA continue to pursue the
collection of epidemiology information on both exposure and
health consequences associated with ozonation and chloramination.
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4.0 Research Recommendations Related to
Chemical Characterization and Monitoring
The recommendations described here are based on the preaise
that chemical information concerning a specific disinfection
treatment process is needed for assessing the toxicological
potential in finished drinking water. This information is also
needed for assessing the performance of the treatment processes
against the desired operating specifications during its day-to-
day usage.
The Committee recommends that the highest priority be given
to the minimization of halogen-containing products in
disinfection of drinking water. Chloramination is an example of a
disinfection method for which potential health effects of
disinfection by-products have not been studied extensively.
Possible products of chloramination include a large array of
chemical classes such as nitrogen mustards, N-chloro compounds,
chlorouracils, nitrite ions and various nitrogen containing
heterocycles which are highly potent carcinogens. Isolation,
determination of structures, and development of satisfactory
analytical methods for the nitrogen-containing products of
chloramination will be difficult.
4.l Highest Priority Recommendations
4.1.1 Monitoring strategy
It is recommended that the EPA reexamine the proposals for
its monitoring strategy. Specifically, the Agency should
determine if the proposed sampling frequencies and sites
appropriately reflect the toxicological significance of
disinfection by-products, as well as the disinfection potential
for the active chemical species used in disinfection. With such
11
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information, better options can be described for potential
regulations.
4.1.2 In-depth chemical characterization
It is recommended that a comprehensive chemical
characterization be made of the reactants and products formed
from the U.S. EPA's pilot plant in Cincinnati, Ohio which employs
the disinfection technology or technologies most likely to be
used. In order to perform measurements on the highly polar
products predicted from disinfection processes such as ozone
treatment, chloramine or chlorine dioxide, state-of-the-art
analytical technologies (e.g., high performance liquid
chromatography/mass spectroscopy and supercritical fluid
chromatography) should be employed. Techniques based on gas
chromatography are not adequate for comprehensive analysis of
polar chemicals,
4.2 Moderate Priority Recommendations
4.2.1 Total oxidizing substances
The Committee recommends (within the constraints of time and
funds) development of an analytical technique for the
determination of levels of total oxidizing substances (TOS). An
analytical technique for TOS in ozonation processes may have
potential as a surrogate for DBF monitoring. However, further
effort should be spent to determine whether fOS is an appropriate
surrogate for the toxicologically active ozonation DBF.
4.2,2 Methods development
The Committee recommends that analytical methods for
measuring disinfection by-products be developed, perfected,
optimized, and validated. A priority scheme should be developed
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for which chemicals (e.g. monochloramine, dichloramine,
trichloramine, aldehydes, N-organochlorawines, halogenated acetic
acids, MX (a potent mutagenic agent found in chlorine-treated
water), chlorate, chlorite, and H2O2) should be monitored, based
upon the most probable specific disinfection process system(s) to
be employed at the municipalities. The use of ion chromatography
to analyze chlorite, chlorate, and similar ions appears to be
sound, and the Committee would be interested in seeing the
specific protocols for these methods.
The Committee recommends the evaluation of the following
reported methods for routine monitoring, in addition to those
found in the recent report on disinfection residual analytical
methods from the American Water Works Research Foundation
(Gordon, Gilbert, Disinfectant Residual Measurement ....Methods, AWWA
Research Foundation, Denver, CO, Nov., 1987):
MonQchlgramine, dichloramine. free chlorine
a. Aoki, T., Environ. Sci, & Tech., 23, 46-50 (1989)
b. Jensen, J.N. and D.J. Johnson, Anal. Chem., 61 991 (1989)
c. Lukasewycz, M.T. et al., Environ. Sci. & Tech., 23. 196
(1989).
d. Palin, A.T., J. Am. Water Works Assoc., 72 121 (1980)
e. Scully, F.E. et al,, Proc, AWWA Water Quality Conf.,
llth, 197, (1984),* AWWA Research Found*, Denver,CO
f. Scully, F.E, et al, Environ. Sci. & Tech., it* 787 (1984)
I2Q2
a. Jalkian, R.D., AD-A194307, Femtogram level determination
of cobalt and chromium by luminol chemiluminescence
detected by a charge detector, 5pp», NT IS (1988)
b. Van Zoonen, P. et al, Anal. Chia. Acta, 174 151 (1985)
4.2.3 Organic and inorganic bromides
The Committee recommends that methods be developed for
organic (other than THMs) and inorganic compounds containing
bromine because they may become more important toxicologically
13
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than the chlorides (see section 2.2.4).
4,2,4 Use of isotopically labelled chemicals
It is recommended that bioassay studies (see section 3.2.2
above) be performed utilizing isotopically labelled chemicals for
mass balance accountability (e.g. 15C, 37C1, 15N) , It is important
to trace all of the compounds which might have potential health
effects and for which treatment technologies could be needed.
Further, additional chemicals should be selected for study,
including the catalytic impact of metals.
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5,0 Research Recommendations Related to Mtcrobial Agents
The Committee is concerned that EPA strike an appropriate
balance between health risk from chemical disinfectants and their
by-products, on one hand, and microbial illness that would result
if the disinfection efficacy was reduced, on the other. This
concern must be extend beyond the treatment plant to include
integrity within the distribution system. In the view of the
Committee there is inadequate research into the microbiology of
the treatment and distribution drinking water.
5.1 Highest Priority Recommendations
5.1.1 Survey of selected microbiological contaminants
The Committee recommends that a survey be conducted for
selected pathogens in drinking water distribution systems since
the current information is inadequate to judge their relevance.
The main pathogens of concern are cryptosporidium, enteric
viruses, Aeromonas, and Legionella, This survey is essential,
because if this type of information is not gathered, the Agency
will not be able to 1) optimize disinfection to protect water
quality while minimizing disinfection by-products and 2) balance
the risks between microbial diseases and chemical contaminants.
This recommendation is clearly a long term one, but it is
important.
5.1.2 Workshop on potable water microbiology
The Committee recommends that EPA conduct a workshop similar
to that held in 1981 to insure that an adequate consensus is
developed concerning the state of scientific knowledge in the
microbiology of potable waters. Participants should be included
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from Europe and Canada where research experience in the potable
water microbiology area is greater than in the U.S*
5.2 Moderate Priority Recommendations
5,2,1 Microbial risk assessment
The state-of-the art for waterborne microbial risk
assessments is currently inadequate to make the needed comparison
between microbial risks and chemical risks from drinking water
exposures. The Committee recommends that standard methodologies
be developed for estimating microbial risks of illness and
mortality from exposure to pathogens in drinking water. This
information should be used to develop acceptable levels of
illness from microorganisms in drinking water so that this risk
can be balanced against the risks of adverse health effects from
chemical contaminants associated with disinfectants and DBFs.
Microbial risk assessment methodologies are needed because
approaches to estimating microbial risks from drinking water have
received little attention, and such efforts are still in their
infancy.
5,2.2 Epidemiology study
The Committee recommends that a community-wide epidemiology
study be conducted to identify and quantify any health risk of
consumer gastrointestinal illness associated with treated and
distributed tap water due to chlorination and to quantify this
risk. This study could well be done in Europe where some data
are available and the necessary treatment trains are in place.
This study is needed since the surface water treatment rule is
based on treatment and not directly on quantified health risks of
gastrointestinal illness caused by specific microbes in drinking
water. Another reason this study is needed is because pilot
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plant studies being done in support of the surface water
treatment rule are limited to only a few studies, in which
microbiological examination of the water is minimal (only one
model virus indicator is being followed). Therefore, there will
be a very limited scientific basis for stating that treatment
plant alterations to remove precursors will not also decrease
microbial disinfection efficiency, even if the current
concentration times time (CT) values are retained. Further,
because the proposed strawman rule is based on treatment and not
monitoring, it is not necessary to isolate and demonstrate the
microbe causing the disease at the tap. Source water should be
monitored for a variety of important pathogens for which
treatment practices are is designated.
5.2.3 Distribution system studies
Drinking water distribution systems must be recognized as
specialized and unique microbial ecosystems. Therefore, it is
necessary to assess the impact of alternative disinfectants and
combinations of disinfectants, such as ozone, that may stimulate
the growth of microorganisms because they have a significant
impact on assimilable organic carbon (AOC) or more generally
biodegradable organic matter (BOM)* The Committee recommends
that the impact of disinfection practices on the microbial flora
of distribution systems and their ecology be carefully studied
and understood. At least four regional studies should be
initiated to examine the total microbial ecology of the
distribution systems to assess the effects of treatment plant
alteration on distribution system integrity. Research is needed
to develop a methodology, suitable for use by water utilities and
individual systems, that can describe microbial growth in the
distribution system as a function of either AOC or BOM. This
information should- be incorporated into a guidance document for
water suppliers. In addition, changes in microbial flora should
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be ascertained. Specifically, the virulence of these organisms
should be tested using the assay systems developed by EPA, Also,
molecular techniques such as polymerase chain reaction (PCR)
should be used to assess the change in frequency of certain
important opportunistic pathogens such as Legionella, Aeromonas,
and Pseudomonas aeruginosa in the distribution systems.
5.2.4 Parasites and viruses
The Committee recommends that research be conducted which
will lead to optimized disinfection for both parasites and
viruses. This should include extended data collection on CTs for
a wider group of organisms and pilot plants. Pilot plant work
should not be limited to one type of pathogen, but should examine
groups or subgroups (i.e. male specific coliphage, ms2 phage) as
potential viral indicators.
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6,0 Research Recommendations Related to Treatment
The important question here is what constitutes "continued"
use of free chlorine. Surveys in the late 1970s showed more than
95% of U.S. utilities using free chlorine. During the past
decade free chlorine use has dropped to 75% of existing water
suppliers. Far fewer would use free chlorine if DBF MCL's
equivalent to a THM level of 25 ug/L are implemented. Given a
THM MCL of 25 ug/L most utilities would design and operate their
systems to achieve a lower average operating THM level in order
to be consistently below the MCL. If the THM MCL were to be set
at 12,5 ug/L, the American Water Works Association Research
Foundation (AWWARF) survey suggests that about 25% of the U.S.
utilities would be able to operate using their current practice.
Perhaps another 5 to 10% would be able to meet the standard if
efficiencies of coagulation-based precursor removal were improved
from 25% to 50%. Even these numbers are probably optimistic for
two reasons; a) the AWWARF survey covered only about 1/3 of the
surface water supplies? and b) the data in the AWWARF survey were
collected under conditions that do not meet the CT values in the
Surface Water Treatment Rule. The implication is that if a DBF
level equivalent to 25 ug THM/L were set, some 65 to 75% of U.S.
utilities would abandon free chlorine and go to combinations such
as ozone/chloramines or chlorine dioxide/sulfur
dioxide/chloramines. If chloramines were not allowed, these
utilities would likely install precursor removal processes such
as GAC or membranes so that free chlorine could be employed and
still meet the MCL for the THMs* The Committee recommends that
EPA prepare estimates of the impact of the 25 ug/L and 50 ug/L
scenarios and release them for public comment.
EPA does not present a sufficient basis for the expectation
that an additional 50% removal of precursors can be accomplished
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with alum doses of 40 to 90 mg/L and a pH of 6 or less. EPA
should also gather data on other coagulants. The Committee does
not believe coagulation will be shown to be equivalent to GAG
treatment where precursor removal is concerned.
The AWWARF survey indicates that 75% of the utilities meet
the THM level of 50 ug/L today. There are several problems with
this statement besides the weaknesses of the AWWARF database.
First, a large portion of those utilities not meeting the
standard are large systems, and hence more than 25% of the
surveyed population is exposed to levels above 50 ug/L. Second,
EPA should recognize that it is not only those utilities with
THMs above 50 ug/L who must modify treatment. Most utilities
with THM levels within a factor of two from the standard will
undertake changes in order to have a reasonable factor of safety
where the standard is concerned. In addition, many utilities
treating surface water will require more disinfection to meet the
new Surface Water Treatment Rule, aggravating the problem
further. Thus a much larger fraction of the industry and an even
larger fraction of the nation's treatment capacity will be
affected. It is recommended that EPA conduct a more complete
survey of U.S. drinking water industry.
Coagulation enhancement will only allow THM levels of 25-50
ug/L to be achieved in 10 to 15% of the cases. It is not clear
that the adverse health impacts of mineralization (aluminum from
alum arid calcium or sodium from lime and/or caustic) are any more
desirable than DBF precursors.
Treatment involved in the control of disinfection by-
products involves many different possible approaches. Among the
most promising precursor removal technigues are conventional
coagulation treatment for water for general contaminants,
granular activated carbon filters, and membrane filters.
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Research is needed in these areas, as well as in the areas of
alternative oxidants. The needs in these different areas are
discussed below.
The highest priority research efforts in the treatment area
are:
a. Removal of CIO, DBF by S02 or GAG as described in 6.2
b. The above mentioned industrial survey
c. Evaluation of precursor removal by membranes (6,1,3) or
GAG (6.1.2) if the THM MCL is 25 ug/L or support
conventional treatment if the THM MCL is higher
(6.1.1).
All other proposals are of moderate priority.
6.1 Precursor Removal
Although it is unclear at this time what, if any, part of
the regulation will involve precursor removal, this is an
important area and the possible treatment techniques need to be
better developed.
The stated goal of removal of 50% of precursor material will
only be of marginal assistance in meeting a new, and possibly
tougher, regulation. Removals of 90 to 95% are required if many
utilities are to meet DBF levels equivalent to a trihalomethane
(THM) level of 25 to 50 ug/L when free chlorine is used.
Research should be aimed at producing these higher removal rates.
6,1.1 Conventional treatment modifications
Enhanced coagulation is the principal modification to
conventional treatment that can be expected to increase precursor
removal. As most water treatment plants on surface water
supplies already achieve 20 to 30% removal of precursors, an
enhancement to 50% will result in some improvement, A better
information base is required to make sound judgments concerning
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the extent of precursor removal that is achievable through
coagulation techniques. It is important that a sound judgment be
made because, as coagulation facilities are often already in
place, removal of precursors by coagulation will appear to be
convenient and economical. The Committee recommends the
following actions to provide a sound basis for possible
regulation:
a. Survey several existing water treatment plants which are
currently using coagulation as a technique for color
removal for disinfection by-product concentration
levels* Since DBF precursors and color are thought to
derive from aquatic humus, it seems reasonable to
assume that these plants are nearly optimized for
removal of precursors as well as color. A survey of
such plants will give EPA a first hand grasp of removal
rates that are achievable with high-humus waters, with
important design features and with operational
experiences that are encountered in a full scale plant
of this type. There are many highly colored waters,
but water treatment plants removing color by
coagulation are not common, suggesting that design and
operating details may deserve some scrutiny,
b. Conduct studies of precursor removal from a variety of
water qualities using a standardized, bench scale jar
test. These studies will allow EPA to systematically
characterize the variation in performance of
coagulation in removing precursors from different water
qualities. From these studies it could be determined
if 50% is a reasonable expectation for most locales.
c. Use available data on THM levels in and treatment practice
at drinking water utilities in order to estimate the
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impact of broad-scale adoption of enhanced coagulation
on DBF levels,
d. Conduct pilot scale studies of enhanced coagulation at the
Cincinnati pilot plant to determine if it is possible
to achieve DBF levels equivalent to THM levels of 25 to
50 ug/L. EPA should then transport their portable
pilot plant to sites with higher precursor levels and
do similar work at those sites. These pilot activities
will give EP&'s research staff a first hand feel for
the details of the process and its transferability from
one site to the next.
e. Work with several U.S. utilities to conduct full-scale
tests of the performance of coagulation in removing THM
precursors on a variety of water qualities with a
variety of coagulants.
f. Examine the impact of acidification, high levels of
coagulation addition, and final upward pH adjustment on
the mineral quality of the product water.
g. Examine the effectiveness of alternative coagulants such as
ferric salts, poly aluminum chloride, and polymers to
reduce disinfection by-product levels.
6.1.2 Granular activated carbon
The Committee recommends that EPA consider a broad range of
alternatives be studied for the use of granular activated carbon
(GAG) in precursor removal. Possible approaches include
replacement of existing filter media with GAC, use of engineered
filter-absorbers with longer contact times, or use of filter-
adsorbers and post-filter adsorbers with regeneration. Depending
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on their design criteria and how they are operated, these
alternatives represent a wide range of costs and performance.
The Committee recommends the following actions to obtain
additional information to allow better prediction of likely
national experience for GAC:
a. Survey the experience of precursor removal at existing U.S.
GAC filters operating without a chlorine residual in
the GAC influent. Such a survey could provide direct
input on the performance of GAC processes of modest
design. Because ehlorination is so common in the U.S.,
it may be necessary to aslc some utilities to change
their operations temporarily to get the necessary data.
b. Survey precursors in water from European plants using GAC
with and without regular regeneration and with and
without preozonation. Such a survey cannot just be a
gathering of European operating data, but must be a
sampling survey where samples are analyzed by a
standard formation potential test, such as Method 5710
in the 17th Edition of Standard Methods.
c. Survey GAC performance in several U.S. water supplies using
a minicolumn test to be used along with modelling to
predict the spectrum of responses that can be expected
for precursor removal around the country. These tests
should include some of the very high total organic
carbon (TOC) level waters found in the Southeastern
U.S. Such test data would represent a conservative
view of performance because minicolumn tests, being
short-term, operate only via the adsorption mechanism
and the test results will not show the benefit of any
additional removal that occurs in full-scale facilities
due to biological removal.
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d. Conduct research to determine the potential for precursor
removal by biological oxidation in GAC or other porous
support media, so that GAG does not have to be
regenerated. Special attention should be given to
processes that reduce the TOC component of the chlorine
demand of the water.
6.1.3 Membranes
The Committee recommends that EPA examine closely whether
membrane processes should be considered as best available
technology (BAT). Although plants using the new low pressure
membranes, which are most cost effective for precursor removal,
do not exist at large scale facilities, there are more than 100
reverse osmosis plants in the U.S. Not only are these plants
almost identical in design to their low pressure counterparts
(they have larger pumps and a different membrane material, but
have the same physical configurations), they also exhibit
substantial precursor removal rates. The Committee recommends
the following actions;
a. Visit several U.S. reverse osmosis plants and develop a
summary of U.S. experience in the reduction of DBF,
including measurements of performance levels where
total organic carbon removal is involved.
b. Consider carefully whether existing pilot scale data,
combined with the results of the upcoming one year test
at Daytona Beach will be sufficient, when combined with
experience involving full-scale conventional reverse
osmosis, to meet the Safe Drinking Water Act's "full
scale experience" clause.
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c. Meet with membrane manufacturers and invite them to share
information and data. Membrane technology is a rapidly
developing field led by a small number of U.S.
companies. EPA should meet with the leadership of
these companies, give them useful information on the
precursors to be removed (e.g. molecular weight,
structure, surface active groups, etc,)/ tell them
about EPA's regulatory needs, and invite them to
produce membranes "tailored" to precursor removal.
6.2 Alternative Qxidants
Three areas of research effort are important in regard to
alternative oxidants to chlorine. These areas include the use of
chlorine, chloramines and chlorine dioxide. The magnitude of the
proposed MCL for trihalomethanes and others will strongly
influence the direction different public water supplies are
likely to take*
The idea that chlorine dioxide and chlorite ions could be
chemically reduced is attractive. It makes the C1Q2/SQ2/NH2C1
option a lower capital cost alternative to Oj/NHjCl* This
reduction of C1O2 and C102- via S02 has been demonstrated in the
laboratory and via GAG in the laboratory and in the field.
The capacity of GAC for removing chlorine dioxide and
chlorite under a variety of operating conditions is poorly
understood, and using GAC for their removal is likely to be
expensive if it controls GAC replacement frequency. At the same
time a great deal of work must be done with S02 reduction before
the influences of pH, temperature, contact time, etc. are well
understood. The Committee recommends looking to the European
experience for more information on GAC and SO2 treatment. The
Committee recommends the following actions to address these
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issues?
a. Study C1OZ and ClO^- removal via GAC on the plant-scale in
a variety of water qualities. There is a need to know
how effective this process is, the conditions under
which it is effective, and how long a given bed of GAC
can be expected to perform.
b. Conduct laboratory studies to characterize the effect of
pH, temperature, contact time, and other parameters on
the SO2/C1Q2/C1Q2- redox reactions. Once this is done,
full scale studies should be conducted to examine the
process in a variety of water qualities.
e. Investigate the possibility of producing chlorate-free
chlorine dioxide under typical plant operating
conditions. In principle, methods for generating
chlorate-free chlorine dioxide are available.
d. Distribute ion chromatography-based analytical methods for
C1Q2~ to interested parties so that broader experience
can be gained.
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NOTICE
This report has been written as a part of the activities of
the science Advisory Board, a public advisory group providing
extramural scientific information and advice to the Administrator
and other officials of the Environmental Protection Agency. The
Board is structured to provide a balanced, expert assesssraent of
scientific matters related to problems facing the Agency. this
report has not been reviewed for approval by the Agency? hence,
the contents of this report do not neqesssarily represent the
views and policies of the Environmental Protection Agency or of
other Federal agencies. Any mention of trade names or commercial
products does not constitute endorsement or recommendation for
use.
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