Water Treatment Technology
Feasibility Support Document
For Chemical Contaminants
In Support of EPA Six-Year Review of
National Primary Drinking Water
Regulations
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Office of Water
Office of Ground Water and Drinking Water (4607M)
EPA815-D-02-001
www.epa.gov/safewater
February 2002
Printed on Recycled Paper
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Water Treatment Technology Feasibility Support Document
for Chemical Contaminants
In Support of EPA Six-Year Review of
National Primary Drinking Water Regulations
February 2002
United States Environmental Protection Agency
Office of Water
Office of Ground Water and Drinking Water
Standards and Risk Management Division
Targeting and Analysis Branch
1200 Pennsylvania Avenue, NW (4607M)
Washington, DC 20460
This report is issued in support of the preliminary revise/not revise decisions for the EPA Six-
Year Review Notice of Intent. It is intended for public comment and does not represent final
agency policy. EPA expects to issue a final version of this report with the publication of the final
EPA notice in 2002, reflecting corrections due to public comment on the preliminary notice and
the supporting documents.
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711 ; i
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TABLE OF CONTENTS
I. Introduction
II. Treatment review for contaminants (MCL-Type) identified as possible candidates
for revision based on EPA health effects technical review
III. Treatment review for chemical contaminants controlled by treatment technique
(TT) requirements
age
3
6
14
IV. Treatment review for chemical contaminants for which current MCL is limited by
analytical feasibility and EPA analytical feasibility analyses suggest a potentially
lower practical quantitative level (PQL) 16
V. Contaminant for which BAT is not clear or incorrectly specified 22
VI. References 23
Page 2 of 24
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I. INTRODUCTION
This water treatment technology feasibility support document summarizes available treatment
information in support of the U.S. Environmental Protection Agency (EPA) review of national
primary drinking water regulations (NPDWRs). A review of NPDWRs is required at least once
every six years under Section 1412(b)(9) of the federal Safe Drinking Water Act, as amended in
1996. The subject Six-Year Review of NPDWRs addresses 68 regulated chemical contaminants,
i.e., most of the chemical contaminants regulated prior to 1996. A formal EPA decision to revise
or not revise NPDWRs is expected in the latter part of 2002.
EPA sets noil-enforceable maximum contaminant level goals (MCLGs), based on health effects
information and related risk analyses. EPA enforceable standards include maximum contaminant
levels (MCLs) and treatment techniques (TT) which are dependent upon EPA-documented
treatment feasibility assessments and other considerations.
EPA developed a systematic approach, or protocol, for the review of these NPDWRs.1 Several
technical analyses have been accomplished by EPA to complete the first round of review of all
pre-1996 chemical NPDWRs. The analyses address human health effects, analytical methods,
treatment technologies, chemical occurrence, and other aspects related to the regulations. These
analyses have been individually conducted in phases, as appropriate, and are documented
separately.
Results of the above-cited analyses were used by EPA to make a preliminary determination as to
which NPDWRS may be subject to revision, i.e., the analyses identified possible or potential
candidates for revision based upon the review of new scientific data. In order to complete the
subject six-year review in a timely manner, the Agency initiated this preliminary review of water
treatment technology, to determine the feasibility of any potential revisions to the NPDWRs.
Ultimately EPA conducted a greater number of such feasibility assessments than required once
the Agency had sufficient data on all aspects of the Six-Year Review to make a decision on
revising, or not revising, standards.
The review of treatment feasibility was completed on individual NPDWRs if either of the
following conditions applied, as per the above-cited protocol:
a health effects technical review suggests a potential change to the MCLG
(these were five in number at the inception of this review);
a health effects assessment is not in process (or scheduled) for the contaminant and one of the
following conditions applies: (1) the analytical feasibility assessment suggests a potential
revision to the regulated level (75 in number at the inception); (2) the NPDWR is a TT-type
rule (four in number at the inception).
In addition, EPA reviewed treatment feasibility information for NPDWRs for which BAT or TT
requirements are not clear or incorrectly specified (one NPDWR was identified).
Table 1 below lists the chemical NPDWRs which are the subject of this report:
1 EPA. Protocol for Review of Existing National Primary Drinking Water Regulations.
Draft report, published at time of Six-Year Review Notice of Intent, March 2002.
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Table I. Chemical NPDWRs Included in This Treatment Feasibility Support Document
5 Contaminants Initially Identified Under the Six-Year Health Effects Review
1
2
3
Beryllium
Chromium
Fluoride
4
5
Oxamyl
Picloram
15 Contaminants for Which Analytical Feasibility Assessments Suggested a Potential Change
1
2
3
4
5
6
7
Benzene
Carbon tetrachloride
Chlordane
1 ,2-Dibromo-3-chloropropane (DBCP)
1 ,2-Dichloroethane
Dichloromethane
1 ,2-Dichloropropane
9
10
11
12
13
14
15
Heptachlor epoxide
Hexachlorobenzene
Tetrachloroethylene ("perc")
Thallium
Toxaphene
1,1 ,2-Trichloroethane
Trichloroethylene
4 Contaminants Regulated by TT Requirements
1
2
3
Acrylamide
Copper
Epichlorohydrin
4
Lead
Contaminant for Which BAT is 'Not Clear or Incorrectly Specified
Cyanide
This document primarily discusses best availably technologies (BATs) specified by EPA to meet
MCLs, and technologies to meet TT-type rules.: Supplemental information is provided on small
systems compliance technologies and other related treatment information. In addition, EPA has
also included, as appropriate, available EPA data on treatment technologies in place at public
water supplies (community type), i.e., baseline treatment characteristics; discussion of the
feasibility of adding treatment or modifications to existing in-place treatments; discussion of
treatment wastes as appropriate; and, preliminary characterization of research areas that may be
pursued prior to revising a NPDWR, as applicable. EPA is relying on available scientific and
engineering data to support this process. The end result of each contaminant-specific review
which follows is a determination regarding the feasibility of treatment technology, i.e., a
determination of whether treatment would pose ja limitation should EPA pursue a revision to a
specified standard.
References cited in this report are listed in the final section of this report. These sources have
been reviewed previously. Some of these are relatively new sources while others were used in
support of the subject NPDWRs which were promulgated in the period of 1985-1992.
The treatment review contains some recent information related to the EPA-estimated occurrence
of the subject contaminants, i.e., levels above current MCL and other threshold values. These
EPA occurrence estimates are available and are in draft status and subject to change; these data
provide indication of contaminant levels in drm)dng water and may be relevant in the assessment
of feasibility of treatment or of making treatment modifications, if applicable. Since no
potential, i.e., 'revised,' maximum contaminant levels (MGLs) for the subject contaminants have
been considered by EPA, this support document does not contain nor assume any particular
revised MCL values.. The purpose of this reporj; is to review available information on treatment
feasibility in anticipation of any potential EPA revise/not revise decisions related to the
NPDWRs. !
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As mentioned above, this treatment technology document identifies areas of water treatment
research which may be required if EPA were to consider revisions to a standard. These are
identified in Sections II and in, in relation to chemical MCL and TT-type rules, respectively.
Section IV, related to MCL-type rules for which analytical assessment indicated the potential for
lowering a standard, does not contain research suggestions, as none have been identified.
Discussion of potential water treatment technology research needs in this phase of the review of
NPDWRs is provided to inform the EPA drinking water program and the public. This
information would be considered within EPA's research planning process, with the longer-term
aim of strengthening regulations such that they may be more effective and implementable.
Research suggestions may also be aimed at defining new technologies that are emerging in the
field, and for qualifying their possible application to specific NPDWRs. Ideally, such
technologies would offer specific advantages, such as lower-cost, and/or ease in operation and
maintenance. They may be specifically targeted for use by certain types of water systems, e.g.,
small water systems. Other research suggestions may be aimed at improving established BATs
or TTs, in light of recently experienced or hypothesized treatment problems. Potential research
areas are indicated at the end of each chemical discussion, as appropriate.
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IL Treatment review for contaminants (MCL-type)
identified as possible candidates for revision based on
EPA health effects technical review
BERYLLIUM
Recent EPA occurrence analyses indicate beryllium occurrence in public water systems based on
a sampling of 16 States [USEPA 2002, draft]. Based on these analyses which included estimated
system mean concentrations, EPA estimates indicate a total 0.079 percent water systems within
these States may exceed the threshold of 0.004 ;mg/L, i.e., the current MCL for beryllium.
Additional occurrence estimates may be found in the above-cited 2002 EPA draft report.
The current BATs for beryllium removal includjs activated alumina, ion exchange, lime
softening, coagulation/filtration and reverse osmosis [USEPA, 1990b, 1990c, 1992].
Compliance technology for small systems includes these same five BATs, plus POU-RO, POU-
IX for small systems [USEPA 1998b]. Removal efficiencies for the above-cited BATs range
from 80% to 99%. Treatment technologies were discussed by EPA in its technical support
documentation on beryllium [USEPA, 1990b]. If a treatment plant were to require upgrading,
additional IX contact units may be added, POU treatment installed, or a modification to
precipitative processes added as appropriate. The preliminary assessment is that treatment
technology would not pose a limitation should EPA pursue a revision to this standard.
Where treatment is currently in place, for this cbntaminant and possibly for others, it is likely to
be operating and valued for other beneficial effects, e.g., for reduction of hardness or other
common impurities. However, EPA does not have data indicating to what extent this may occur
and thus its significance, therefore the Agency is making no assessment as to whether treatment
in place would be maintained or discontinued in the event of the MCL for beryllium being
revised. ; '
CHROMIUM (TOTAL) j
i
Treatment technology: , I
!
Recent EPA occurrence analyses indicate chromium occurrence in public water systems based on
a sampling of 16 States [USEPA 2002, draft}. Based on these analyses which included estimated
system mean concentrations, EPA estimates indicate that 1 water system (credible interval of 0-
3) within these States may exceed the threshold of 0.1 mg/L, i.e., the current MCL for total
chromium; in addition, EPA estimates indicate |a total 7 systems (credible interval of 3-13) within
these States may exceed the threshold of 0.05 mg/L. Additional occurrence estimates may be
found in the above-cited 2002 EPA draft report
'
In publishing the 1989 proposed and 1991 final chromium standard [USEPA, 1989 and USEPA
199la] the Agency discussed best available technologies (BATs) which include:
Page' 6 of 24
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ion exchange (IX): 80 to 96 % efficiency
lime softening (LS) for Chromium III only: 72 to 99% efficiency
coagulation/filtration (CF): 90 to 99% efficiency
reverse osmosis (RO): 82 to 97% efficiency
Due to the ionic properties of the two chromium species in water, Cr HI and Cr VI, there is a
differentiation in BAT specification which may affect treatment selection. Cr III and Cr VI exist
in water in cationic and anionic valence states, respectively. LS treatment is excluded as a BAT
for anionic Cr VI. Regarding the coagulation/filtration option, the choice of coagulant will
impact Cr III and Cr VI removal: ferric sulfate and alum are effective for removal of Cr HI while
ferrous sulfate is effective for removal of Cr VI. Regarding ion exchange, a cation exchange
resin is required for Cr III, while an anionic resin is required for Cr VI. Therefore, prior to use
(or modification) of LS, IX, or CF treatment, a PWS should determine concentrations and
proportions of species of chromium to select proper media or chemical aid.
SDWA 1996 requires EPA to determine small system technologies for compliance purposes, i.e.,
technology designated as suitable for systems serving 25 to 10,000 persons. In 1998 EPA listed
the following compliance technologies for small systems: IX, LS (Cr III only), CF, RO, Point-of-
Use (POU)-RO and POU-IX [USEPA, 1998b].
Due to the high efficiencies of chromium removal by the above technologies, EPA believes that
existing BATs would be adequate in meeting a revised standard (if the standard were lowered).
Thus, the preliminary assessment is that treatment technology would not pose a limitation should
EPA pursue a revision to the chromium standard.
Due to recent interest by the State of California in setting a drinking water standard for Cr VI, the
toxic form of chromium, that State as well as others have initiated treatment studies to determine
the efficacy of treatment technologies in removal of Cr VI. Newer treatments of interest include
an iron-based absorptive filter medium, granular ferric hydroxide (GFH), a technology that has
been piloted for arsenic removal at California water systems, and in the United Kingdom. A
treatment to reduce low levels of Cr VI to Cr III in drinking water by addition of the chemical
stannous chlorine (SnCl2) is currently under investigation at the Glendale, California water
system. EPA will monitor treatment studies to determine acceptability for use in removal of
chromium in drinking water.
Additional information:
Of additional interest to EPA is the likelihood that disinfection treatment, including chlorination,
plays a role in transforming, by oxidation, Cr III to Cr VI in water. The EPA Manual of
Treatment Techniques (USEPA, 1977) and the EPA Occurrence and Exposure report for
Chromium (USEPA, 1990) discussed the effect of prechlorination on Cr III removal by
coagulation, and the underlying effect of free residual chlorine on oxidation of Cr HI to Cr VI. In
the 1977 report, tests were cited in which a low chlorine dosage, 2 mg/L, with up to 6 hours,
contact time, lowered Cr III removals by 10 percent using alum and ferric sulfate treatment; and,
that with contact extended to about 20 hours, alum treatment removals dropped to less than 10
Page 7 of 24
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percent of the more effective removals. In the latter (1990) report, EPA cites Ulmer (pre-
publication report) in testing Cincinnati tap water: 4 samples of water, at pH levels 5, 6,7, and 8,
containing added Cr IE at 0.462 mg/L. With an adjusted initial free residual chlorine level of 2
mg/L, after 30 minutes of contact, at the four pH levels cited, the investigator found that 1.5%,
4.0 %, 3.7% and 2.7% of the added Cr III had been oxidized to Cr VI; after 24 hours, 27%, 43%,
30% and 21% of the added CR HI had been oxidized to Cr VI in the same samples at the 4
respective pH levels. Time of contact between ichlorination treatment and water tap varies
greatly among systems. The above-cited chlorination tests represent a wide range of plausible
contact times, including water storage, i.e., from 30 minutes to 24 hours. In addition, the above-
referenced testing at Glendale, California of SnCI2 as a Cr VI mitigation treatment includes
investigation of re-oxidation of Cr III to Cr VI under various chlorination and ammoniation
treatment disinfection scenarios. :
The Health Canada criteria summary on chromium in drinking water also indicates some
uncertainty in regard to whether post-treatment; chlorination and conversion of residual Cr III to
Cr VI may reverse in passage through iron pipes in distribution (Health Canada, 1986).
The above information provides a minimum baseline of information on potential transformations
of Cr HI to Cr VI, and treatment effects; more information may be required regarding these and
other potential treatment effects. ;
!
In regard to small system technologies, EPA would review available information on newer
potential treatments as research and field studies are undertaken and publicized. EPA may also
need additional data on issues related to ion exchange POU treatment, which was discussed in a
January 2001 (arsenic) EPA notice [USEPA, 2001]. It is not known if IX-POU will be a feasible
compliance option, due to operational and waste discharge concerns and related economic issues.
Potential in-place treatment modifications: j
I . ,
EPA has previously published analyses of dataicollected in the 1995 Community Water System
Survey (CWSS), on treatment in place at community water systems [USEPA, 2000aj. The data
indicate that a majority of larger systems and mainly surface water supplied systems are much
more likely to have CF or LS treatment in placs. Some of these systems may need to modify
existing treatment to allow for more efficient removal of chromium to comply with a more
stringent chromium standard. For example, an existing LS plant may need to enhance the
process to operate at a pH of 11 to 11.5 for optimum removal; or an existing CF plant may need
to change to ferric or ferrous coagulant aid to lower chromium levels in drinking water. The
CWSS data also indicate that small systems would more likely face modifying, or adding new,
treatment, centrally or installing POU treatment, to meet a standard.
The option of modifying existing treatment may be possible for a limited number of systems, as
0.7% to 4.6% of small groundwater systems currently have IX treatment in place, and most of
these are likely to be cationic resin types (whereas anionic resins may be required to remove
excess chromium); virtually none of the small surface water supplies have this treatment in place.
Page 8 of 24
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1.5% to 8.1% of small groundwater systems currently have CF or LS treatment in place; and, a
large percentage of small (and nearly all large) surface water supplies have either CF or LS
treatment in place. However, given the occurrence information, it appears that the majority of
treatment upgrades would occur at small groundwater systems, many requiring new treatments,
possibly pressurized, packaged treatment technology or other emerging treatments mentioned
above .
Tables 2a. and 2b. below contain results of the above-cited 1995 CWSS data analyses and are
provided for reference.
TABLE 2 a. Groundwater Systems: Percentage (%) of CWSs with Various Types of Treatment In-Place
Treatment Types
(CWSS 1995 Information)
Ion Exchange Treatment
Coagulation/Filtration
Lime/Soda Ash Softening
25-100
0.7
1.5.
2.1
Service Population Category
101-5000 501-1,000 1,001-3,300 3,300-10,000
1.6
5.4
3.7
3.8
4.2
4.1
1.9 4.6
3.4 8.1
5.2 7.0
(Source: USEPA, 2000a. Geometries and Characteristics of Public Water Systems)
TABLE 2 b. Surface Water Systems: Percentage (%) of CWSs with Various "types of Treatment In-PIace
Treatment Types
(CWSS 1995 Information)
Ion Exchange Treatment
Coagulation/Filtration
Lime/Soda Ash Softening
25-100
0
27.5
3.9
Service Population Category
101-5000 501-1,000 1,001-3,300 3,300-10,000
0
52.6
8.1
000
, 70.2 78.5 95.4
20.5 17.5 10.8
(Source: USEPA, 200Qa. Geometries and Characteristics of Public Water Systems')
Potential chromium treatment research:
Prior to conducting analyses in support of a NPDWR revision, EPA review of literature and/or
new treatment research may be required. This may include documentation of bench, pilot, and/or
full-scale studies on granular ferric hydroxide, other adsorption media, and membrane
technologies. POU -IX studies on chromium removal may be required, including tests on
efficacy of treatment and disposal of related wastes. Studies may include optimization of
centralized IX treatment efficiency and waste treatment and handling/disposal. Effects of
disinfection treatments, as well as addition of reducing agents such as SnCl2, on chromium in
water may require further study should a more stringent chromium MCL be considered. These
needs may be forwarded within EPA for potential research.
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1 li
FLUORIDE
Treatment technology:
Recent EPA occurrence analyses indicate fluoride occurrence in public water systems based on a
sampling of 16 States [USEPA 2002, draft]. Based on these analyses which included estimated
system mean concentrations, EPA estimates indicate that 106 water systems (credible interval of
91-123) within these States may exceed the threshold of 4 mg/L, i.e., the current MCL for
fluoride; in addition, EPA estimates indicate a total 603 (credible interval of 566-640) water
systems within these States may exceed the threshold of 2 mg/L. Additional occurrence
estimates may be found in the above-cited 2002 EPA draft report.
I i ' ' ' I'1
The 1986 final fluoride regulation set "best technologies generally available" (BTGA) as
activated alumina (AA) and reverse osmosis (RO). BTGA was defined prior to the SDWA.
Amendments of 1986, and was based upon measures of technological efficiency and economic
availability (i.e., "reasonably affordable by regional and large metropolitan public water
systems"). The following factors were considered in determination of BTGA: high removal rate;
wide applicability; compatibility with other treatments; and ability to achieve compliance for all
water in the PWS [USEPA, 1986]. These requirements are comparable with current SDWA
requirements for BAT determination. j
i , .
In addition, SDWA 1996 requires EPA to determine small system technologies for compliance
purposes, i.e., technology designated as suitablk for systems serving 25 to 10,000 persons. In
1998 EPA listed small system compliance technologies, including both AA and RO treatment for
removal of fluoride in drinking water; EPA also included POU- RO treatment as a small system
compliance technology for fluoride [USEPA, 1998].
Pending completion of the subject review of NpDWRs, the Agency may decide to reset the
fluoride BATs including those that were set in 1986 as 'BTGA.' This may or may not occur
along with a more substantive revision to the standard, and would represent a minor revision.
The pertinent sections of US Code are §141.62; MCLs for Inorganic Contaminants, and §142.61
which specifies variance technologies for fluoride [US CFR, Part 141 and Part 142].
Previously published research and EPA technologies and costs documents [USEPA 1984] on
these technologies indicate that, due to high efficiencies of removal, the above-cited treatment
technologies would not be a limiting factor in setting a lower fluoride MCL. Efficiencies of
removal range from 85% to 95%, depending upon treatment system design. Thus, the
preliminary assessment is that treatment technology would not pose a limitation should EPA
pursue a revision to the fluoride standard.
Both AA and RO treatment remove arsenic and fluoride among other impurities. Using AA
treatment, optimum removals for both contaminants may occur in a similar range of pH 5.5 to
pH 6 [USEPA, 1985; US EPA, 2000b]. However, because arsenic-V and silica are
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preferentially adsorbed by AA media, effectiveness of AA where arsenic and fluoride co-occur
may require some investigation. Another AA treatment shortcoming, discussed further below, is
the operational difficulty of adding pH adjustment for optimizing removal efficiency (i.e.,
adjusting pH prior to and after treatment). For some small systems treatment may be limited to
using 'natural' pH levels (i.e, unadjusted) thus sacrificing some removal efficiency; however,
this application for fluoride removal is not documented).
Technical issues related to AA technology were discussed in the above-cited fluoride final rule.
These included waste generation and disposal. More recent EPA publications have also
examined the operation of AA technology and perceived difficulties posed by chemical handling,
i.e., for pH adjustment and for regeneration ofthe media, by small systems, as well as the
alternatives to regeneration of AA media In the case of arsenic treatment, it was decided that
regeneration of AA media at both small centralized treatment and POU applications would not be
recommended, due in part to the difficulty of disposing of brine wastes (additional rationale is
cited below). EPA instead assumed that spent AA media would be disposed of directly at a
landfill on a 'throw-away' basis and that, based upon arsenic TCLP testing, this waste would not
be deemed 'hazardous' [USEPA, 2000b and USEPA, 2001]. However, except where arsenic and
fluoride were being co-treated, this information should not (alone) be applied to fluoride
treatment wastes because RCRA regulations do not regulate fluoride under the Toxicity
Characteristic hazardous waste identification rule (40 CFR 261.24). That stated, there may be
concerns regarding waste brine, i.e., regenerate solution, that have not yet been anticipated.
Recent activity on the arsenic standard also addressed the issues of treatment optimization (pH
adjustment) at AA POU. For arsenic it was determined that use of AA POU (and POE) would be
limited due to the practical limitation of adjusting pH and then re-adjusting following treatment
for corrosion control. The option of using AA at an unadjusted 'natural pH' range of 7 to 8 was
discussed as the probable application at very small systems due to the operational capabilities
that are required [USEPA, 2000b and USEPA, 2001].
While not currently a 'BTGA' or 'BAT', modified lime softening (30-70% removal) may also be
used where this treatment is in place, to remove excess fluoride [USEPA, 1985, T&C].
The following summarizes additional information that may relate to setting, revising, and/or
application ofthe above two BATs and the POU compliance option for fluoride.
Potential in-place treatment modifications:
Cost of treatment may drive systems above the compliance level to the less expensive option,
i.e., activated alumina, or to newer treatments as they become available. Where de-fluoridation
treatment is already in place, due to prior exceedance ofthe current F MCL, systems may opt to
increase the proportion of water treated, or add more capacity to existing treatment (or add
additional media vessels in series). Where a centralized treatment may be less feasible, some
very small systems may install POU treatment (RO more likely) which may present operational
advantages and additional treatment benefits. The BATs are known to remove fluoride and
arsenic (As V is preferentially adsorbed by AA media); RO treatment would remove additional
Page 11 of 24
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regulated and secondary contaminants such as tptal dissolved solids, hardness, iron, and
manganese, which may co-occur with fluoride iin water.
EPA's 1995 Community Water System Survey data is summarized and has been utilized in
recent EPA technical support materials [EPA 2000a (Geometries ofPWS), and the USEPA
Baseline Handbook, Draft}. These provide some understanding of numbers and types of
treatments in place at community systems; however, they do not specifically include AA
treatment information. Therefore it is not possible to estimate a relationship between systems
now treating with AA and those that may need to treat further to meet a lower standard (however,
in areas with high background levels (especially if above 4 mg/L), treatment of fluoride may
already be in place). The followup 2000 Community Water System Survey results are expected
to include AA treatment information and these will be available in early 2002.
The CWSS summary tables indicate (see Tables 2a. and 2b.) that existing lime/soda ash
softening capacity exists and may provide, especially for surface water systems, a base for
increased fluoride removal via enhanced lime softening treatment.
Potential fluoride treatment research:
Prior to conducting analyses in support of a NPt>WR revision, EPA review of literature and/or
new treatment research may be required. This may include documentation of bench, pilot,
and/or full-scale studies related to AA de-fiuoridation treatment effectiveness at natural vs.
adjusted pH levels, with and without competition from arsenic V. Documentation of bench,
pilot, and/or full-scale engineering studies on other adsorption treatment processes may be
required. Documentation and/or study of waste treatment, handling and disposal, and POU
treatment studies, may also be required should a more stringent fluoride MCL be considered.
These needs may be forwarded within EPA for potential research.
i
OXAMYL !
Recent EPA occurrence analyses indicate oxamyl occurrence in public water systems based on a
sampling of 16 States [USEPA 2002, draft]. Based on these analyses which included estimated
system mean concentrations, EPA estimates indicate zero (in number and percent) water systems
within these States exceed the threshold of .0.2 img/L, i.e., the current MCL for total oxarnyl.
Additional occurrence estimates may be found
in the above-cited 2002 EPA draft report.
The current BAT is granular activated carbon (<3AC), and removal efficiency ranges from 85%
to 95% depending upon design parameters [USEPA, 1990a, 1990c, 1992]. Compliance
technology for small systems includes GAC, powdered activated carbon (PAC), and POU-GAC
[USEPA, 1998b].
If water treatment systems were to require upgrading, additional GAC contactor(s) may be added
or PAC added, as appropriate. Given available^ information on treatment efficacy and on
Page il 2 of 24
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occurrence levels, the preliminary assessment is that treatment technology would not pose a
limitation should EPA pursue a revision to this standard.
PICLORAM
Recent EPA occurrence analyses indicate picloram occurrence in public water systems based on
a sampling of 16 States [USEPA 2002, draft]. Based on these analyses which included estimated
system mean concentrations, EPA estimates indicate zero (number and percent) water systems
within these States exceed the threshold of 0.5 mg/L, i.e., the current MCL for total picloram.
Additional occurrence estimates may be found in the above-cited 2002 EPA draft report.
The current BAT for picloram removal is GAG treatment. Treatment technologies were
discussed by EPA in its technical support documentation [USEPA 1990a, 1990c, 1992]. Small
systems compliance technologies are GAG, powdered activated carbon (PAG), and POU GAG
[USEPA, 1998b].
If treatment were to require upgrading, additional GAG contact units may be added or POU
treatment installed. Given available information on treatment efficacy and on occurrence levels,
the preliminary assessment is that treatment technology would not pose a limitation should EPA
pursue a revision to this standard.
Where treatment is currently in place, for this contaminant and possibly for others, it is likely to
be operating and valued for other beneficial effects, e.g., for reduction of other organics or other
common impurities. However, EPA does not have data indicating to what extent this may occur
and thus its significance, therefore the Agency is making no assessment as to whether treatment
in place would be maintained or discontinued in the event of the MCL for picloram being
revised.
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III. Treatment review for chemical contaminants
controlled by treatment technique (TT) requirements
ACRYLAMIDE and EPICHLORO
HYD
RIN
EPA regulations for these two contaminants, including technology-related polymer addition
practices, were discussed in Federal Register notices of 1989 and 1991 [USEPA 1989, USEPA
199la]. EPA has no new information that suggests it is appropriate to revise the TT
requirements for acrylamide and epichlorohydrm at this time.
LEAD AND COPPER RULE
The Lead and Copper Rule (LCR) [USEPA 1991b] relates to the mitigation of lead and copper in
public drinking water supplies through treatments, mainly through optimizing corrosion control
treatment and through related monitoring strategies.
The LCR establishes treatment-type measures tjo control levels of lead and copper in public
drinking water, including corrosion control treatment requirements for small, medium and large
water systems. Treatment may be triggered following sampling and analysis of tap water that
suggests an exceedance of the lead or copper action levels, 0.015 mg/L and 1.3 mg/L (90th
percent levels), respectively.
Under the LCR, PWS corrosion control studies are required to evaluate the effectiveness of each
of the following treatments and if appropriate combinations of the following treatment:
alkalinity and pH adjustment !
calcium hardness adjustment ,
addition of a phosphate or silicate based corrosion inhibitor.
!
PWS are also required to measure the following water quality parameters, before and after
evaluating the above treatments: lead, copper, pH, alkalinity, calcium, conductivity,
orthophosphate or silicate (where added), and water temperature. Water systems must identify
constraints that limit or prohibit the use of. a particular corrosion control treatment(s), and
evaluate effect(s) of corrosion control chemicals on other water quality treatment processes. On
the basis of the above, a PWS recommends the treatment option best suited for its system, and
the State review agency considers the PWS information then designates optimal treatment for
that system. I
i
EPA has no information that suggests it is appropriate to revise the current TT requirement for
lead and copper.
Page 14 of 24
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Issues related to implementation of LCR, such as record keeping and reporting requirements, are
addressed in a separate EPA document and do not directly contribute to the subject review of
treatment related to the LCR.
However, EPA suggests that exploratory-type research on treatment aspects of the LCR, i.e., on
effective corrosion control measures, may be appropriate.
Among potential LCR-related research areas are the following:
1. Improving corrosion control treatment and determination of treatment 'optimization' in
cases where high alkalinity and/or high hardness in source water may result in copper
exceedences.
2. Studying possibilities of targeted monitoring for control of copper under certain
conditions. Problems have been cited by various entities: EPA Regions and State
regulators.
3. Determining whether use of a chemical marketed as a corrosion inhibitor, i.e., stannous
chloride, produces positive and measurable effects related to LCR compliance. Possible
research areas include: investigation of effectiveness of LCR monitoring (i.e., how and
what parameter(s) to monitor for optimum performance); and, investigation of potential
secondary effects of this chemical, including effects on disinfectant chlorine residuals in
distribution system [Note: effects related to addition of stannous chloride-as a reducing
agent are also cited in an earlier section on chromium treatment].
4. Determining relationship of disinfection and oxidation treatments, such as for iron and
manganese control, and age of plumbing material on copper levels in water and/or lead
scale in distribution systems.
5. Gathering of information on Pb(IV) solids which may be found in pipe films, to
determine if and how 'optimization' occurs; other treatments may impact Pb(TV) solids
and require clarification. Pb(IV) occurrence levels are not well characterized. Research
would improve predictive ability in this regard.
6. Determining additional treatment effects on LCR corrosion control: these may include
investigation of aluminum and/or phosphate deposition in distribution in relation to
corrosion control treatment(s); investigation of long-term impacts of the use of silicates in
lieu of phosphates in corrosion control treatment (due to contemporary wastewater
concerns); investigation of optimizing iron and manganese control with lead and copper
control; and, investigation of effects on corrosion control by DBP precursor removal aids,
i.e., in switching coagulants from alum to ferric type.
Page 15 of 24
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IV. Treatment review for chemical contaminants for
which current MCL is limited by analytical feasibility and
EPA analytical feasibility analyses suggest a potentially
lower practical quantitatioii level (PQL)
NOTE: For all contaminants discussed in this section the preliminary assessment is that
treatment technology would not pose a limitatijon should EPA pursue a revision to any of the
referenced standards. Chemical occurrence is not referenced since the known occurrence levels
would not pose an obstacle to treatment specification.
Volatile Organic Contaminants: \
i
BENZENE |
The current MCL for this contaminant is 0.005| mg/L. Since the results of the analytical methods
feasibility review suggests that it may be possible to recalculate the PQL for benzene, EPA. has
reviewed treatment feasibility. BAT for benzene includes both PTA and GAG [USEPA 1991a].
EPA listed the following small systems compliance technologies for benzene: PTA, diffused
aeration, multi-stage bubble aerators, tray aeration, shallow tray aeration, and GAC [EPA
1998b]. ' |
* !
Treatment for VOCs was discussed in the 1985 EPA proposal [USEPA 1985]. Under optimum
conditions, up to 99.9 percent removal of VOGs may be achieved by aeration technology, while
99 percent reduction may be considered reasonable engineering practice. The above-cited EPA
proposal also discussed GAC treatment for VOCs, with a reasonable engineering assumption of
99 percent removal capability. Treatment is not known to be a limiting concern for the current
MCL. ; .
i ,
Based on the above information, the preliminary assessment is that treatment technology would
not pose a limitation should the Agency consider revising the current MCL.
I , ' :
CARBON TETRACHLORIDE
The current MCL for this contaminant is 0.005; mg/L. Since the results of the analytical methods
feasibility review suggests that it may be possible to recalculate the PQL for carbon tetrachloride,
EPA has reviewed treatment feasibility. BAT for carbon tetrachloride includes both PTA and
GAC [USEPA 1985]. EPA listed the following small systems compliance technologies for
carbon tetrachloride: PTA, diffused aeration, multi-stage bubble aerators, tray aeration, shallow
tray aeration, and GAC [USEPA 1998b]. Treatment is not known to be a limiting concern for
the current MCL. ! '
Page ,1 6 of 24
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Treatment for VOCs was discussed in the 1985 EPA proposal [USEPA 1985]. Under optimum
conditions, up to 99.9 percent removal of VOCs may be achieved by aeration technology, while
99 percent reduction may be considered in reasonable engineering practice. The above-cited
Federal Register Notice also discussed GAC treatment for VOCs, with a reasonable engineering
assumption of 99 percent removal capability. Based on the above information, the preliminary
assessment is that treatment technology would not pose a limitation should the Agency consider
revising the current MCL.
l,2-DIBROMO-3-CHLOROPROPANE (DBCP)
Since the results of the analytical methods feasibility review suggests that it may be possible to
recalculate the PQL for DBCP, EPA has reviewed treatment. BATs include aeration and GAC
[USEPA 1989 and USEPA 199la]. Compliance technologies for small systems include GAC,
PAC, and POU-GAC [EPA 1998b]. Treatment is not known to be a limiting concern for the
current MCL.
Since the Henry's coefficient for this contaminant is relatively low (i.e., 7 atm DBCP which is
considered 'less strippable' than other contaminants), GAC may in some cases be the preferred
treatment. Based on the above information, the preliminary assessment is that treatment
technology would not pose a limitation should the Agency consider revising the current MCL.
1,2-DICHLOROETHANE (Ethylene Bichloride)
Since the results of the analytical methods feasibility review suggests that it may be possible to
recalculate the PQL for 1,2-dichloroethane, EPA has reviewed treatment feasibility. BATs for
1,2-dichloroethane includes both PTA and GAC [USEPA 1985]. EPA listed the following small
systems compliance technologies for this contaminant: PTA, diffused aeration, multi-stage
bubble aerators, tray aeration, shallow tray aeration, and GACJUSEPA 1998b]. Treatment is
not known to be a limiting concern for the current MCL.
Treatment for VOCs was discussed in the 1985 EPA proposal [USEPA 1985]. Under optimum
conditions, up to 99.9 percent removal of VOCs may be'achieved by aeration technology, while
99 percent reduction may be considered in reasonable engineering practice. The above-cited
Federal Register Notice also discussed GAC treatment for VOCs, with a reasonable engineering
assumption of 99 percent removal capability. Based on the above information, the preliminary
assessment is that treatment technology is not anticipated to pose a limitation should the Agency
consider revising the current MCL.
DICHLOROMETHANE (Methylene Chloride)
Since the results of the analytical methods feasibility review suggests that it may be possible to
recalculate the PQL for dichloromethane, EPA has reviewed treatment feasibility. As a volatile
organic contaminant (VOC), BAT for dichloromethane is PTA [USEPA 1992]. EPA listed the
following small systems compliance technologies for dichloromethane: PTA, diffused aeration,
Page 17 of 24
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multi-stage bubble aerators, tray aeration, shallow tray aeration, and granular activated carbon
(GAG) [USEPA 1998b]. Treatment is not known to be a limiting concern for the current MCL.
Treatment for VOCs was also discussed in a 1985 EPA proposal [USEPA 1985]. Under optimum
conditions, up to 99.9 percent removal of VOGs may be achieved by aeration technology, while
99 percent reduction may be considered reasonable engineering practice. Based on the above
information, the preliminary assessment is that treatment technology is not anticipated to pose a
limitation should the Agency consider revising! me current MCL.
!
1,2-DICHLOROPROPANE
i
I ' ''
Since the results of the analytical methods feasibility review suggests that it may be possible to
recalculate the PQL for 1,2-dichloropropane, EPA has reviewed treatment feasibility to
determine if it is likely to become an issue if EPA were to revise the MCL. BATs for 1,2-
dichloropropane includes both PTA and GAG [USEPA 1989 and USEPA 1991 a]. EPA listed
the following small systems compliance technologies for this contaminant: PTA, diffused '
aeration, multi-stage bubble aerators, tray aeration, shallow tray aeration, and GACJTJSEPA
1998b]. Treatment is not known to be a limiting concern for the current MCL.
!
Among volatile contaminants, this contaminant exhibits 'average strippability' [USEPA 1989].
Treatment for VOCs was also discussed in the [1985 EPA proposal [USEPA 1985 (pp. 46909-
46916)]. Under optimum conditions, up to 99.J9 percent removal of VOCs may be achieved by
aeration technology, while 99 percent reductioA may be considered in reasonable engineering
practice. The 1985 Federal Register Notice alsp discussed GAC treatment for VOCs, with a
reasonable engineering assumption of 99 percent removal capability. Based on the above
information, the preliminary assessment is that1 treatment technology is not anticipated to pose a
limitation should the Agency consider revising the current MCL.
I ,
TETRACHLOROETHYLENE ("Perc")
Since the results of the analytical methods feasibility review suggests that it may be possible to
recalculate the PQL for tetrachloroethylene, EPA has reviewed treatment feasibility. BAT for
tetrachloroethylene includes packed tower aeration (PTA) and granular activated carbon (GAC)
[USEPA 199la]. EPA listed the following small systems compliance technologies for
tetrachloroethylene: PTA, diffused aeration, multi-stage bubble aerators, tray aeration, shallow
tray aeration, and GAC [USEPA 1998b]. Treatment is not known to be a limiting concern for
the current MCL. ' j '
I
The high level of volatility of tetrachloroethyiejne is reflected in this chemical's Henry's Law
Coefficient of 214.0 atmospheres. Design of air stripping equipment was discussed in the
proposal for this NPDWR. Several factors which effect engineering design include: air-to-water
ratio; packed material height; available area for mass transfer; water and air temperature; and,
physical chemistry of the contaminant [USEPA1 1989 (p. 22118)]. Tetrachloroethylene, while
volatile, is also highly amenable to GAC adsorption treatment. Carbon use rates for this
Page jl 8 of 24
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contaminant are relatively low. Treatment for VOCs was also discussed in the 1985 EPA
proposal [USEPA 1985 (pp. 46909-46916)]. Under optimum conditions, up to 99.9 percent
removal of VOCs may be achieved by aeration technology, while 99 percent reduction may be
considered in reasonable engineering practice. The 1985 Federal Register Notice also discussed
GAC treatment for VOCs, with a reasonable engineering assumption of 99 percent removal
capability.
Based on the above information, the preliminary assessment is that treatment technology is not
anticipated to pose a limitation should the Agency consider revising the current MCL.
TRICHLOROETHYLENE
Since .the results of the analytical methods feasibility review suggests that it may be possible to
recalculate the PQL for trichloroethylene, EPA has reviewed treatment feasibility. BAT for
trichloroethylene includes both PTA and GAC. EPA listed the following small systems
compliance technologies for trichloroethylene: PTA, diffused aeration, multi-stage bubble
aerators, tray aeration, shallow tray aeration, spray and mechanical aeration, and GAC [EPA
1998b]. Treatment is not known to be a limiting concern for the current MCL.
Treatment for VOCs was discussed in the 1985 EPA proposal [USEPA 1985]. Under optimum
conditions, up to 99.9 percent removal of VOCs may be achieved by aeration technology, while
99 percent reduction may be considered reasonable engineering practice. The above-cited
Federal Register Notice also discussed GAC treatment for VOCs, with a reasonable engineering
assumption of 99 percent removal capability. Based on the above information, the preliminary
assessment is that treatment technology is not anticipated to pose a limitation should the Agency
consider revising the current MCL.
Other Organic Contaminants and Thallium:
CHLORDANE
BAT for chlordane is GAC [USEPA 199la]. Treatment is not known to be a limiting concern for
the current MCL. However, since the results of the analytical methods feasibility review
suggests that it may be possible to recalculate the PQL for chlordane, EPA has reviewed
treatment feasibility. Chlordane is a moderately adsorbed pesticide [USEPA 1989 and USEPA
199la], therefore the preliminary assessment is that treatment technology is not anticipated to
pose a limitation should the Agency consider revising the current MCL.
HEPTACHLOR
BAT for heptachlor is GAC [USEPA 1991 a]. EPA listed the following small systems
compliance technologies for heptachlor: GAC, POU-GAC, and PAC [USEPA 1998b]. Since
the results of the analytical methods feasibility review suggests that it may be possible to
Page 19 of 24
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recalculate the PQL for heptachlor, EPA has reviewed treatment feasibility to determine if it is
likely to become an issue if EPA were to revise the MCL. Treatment is not known to be a
limiting concern for the current MCL. I
i
Heptachlor is a moderately adsorbed organic contaminant [USEPA 1989 and USEPA 199la].
Based on the above information, the preliminary assessment is that treatment technology is not
anticipated to pose a limitation should the Agency consider revising the current MCL.
HEPTACHLOR EPOXIDE
BAT for heptachlor epoxide is GAC [USEPA 1199la]. Compliance technologies for small
systems include GAC, PAC, and POU-GAC [USEPA 1998b]. Since the results of the analytical
methods feasibility review suggests that it maybe possible to recalculate the PQL for heptachlor
epoxide, EPA has reviewed treatment feasibility to determine if it is likely to become an issue if
EPA were to revise the MCL. Treatment is not! known to be a limiting concern for the current
MCL. \
i .
Heptachlor epoxide is a strongly adsorbed organic contaminant, generally attributed to a low
carbon usage rate [USEPA 1989 and USEPA 1991a]. Based on the above information, the
preliminary assessment is that treatment technology is not anticipated to pose a limitation should
the Agency consider revising the current MCL:
! .
HEXACHLOROBENZENE
I
BAT for hexachlorobenzene is GAC [USEPA 1992]. Compliance technologies for small
systems include GAC, PAC, and POU-GAC [USEPA 1998b]. Since fee results of the analytical
methods feasibility review suggests that it may be possible to recalculate the PQL for
hexachlorobenzene, EPA has reviewed treatment feasibility to determine if it is likely to become
an issue if EPA were to revise the MCL. Treatment is not known to be a limiting concern for
the current MCL. . - '!
Since hexachlorobenzene is a moderately adsorbed contaminant, based on the above information,
the preliminary assessment is that treatment technology is not anticipated to pose a limitaition
should the Agency consider revising the current MCL.
j
i
THALLIUM ; .
BATs for thallium include activated alumina (AA) and ion exchange (IX) [USEPA 1992]. EPA
also listed small systems compliance technologies for this contaminant as AA, IX, POU-IX
[USEPA 1998b]. Treatment is not known to be a limiting concern for the current MCL.
According to technical information provided previously by EPA for thallium, competing ions in
water may affect treatment run lengths [USEP^. 1998.b]. Given reasonable engineering practice,
high removals of this contaminant are feasible.! Removals may be expected to be greater than
Page!20 of 24
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90% using cation exchange systems, and greater than 95% using AA treatment [USEPA 1990c].
Based on the above information, the preliminary assessment is that treatment technology is not
anticipated to pose a limitation should the Agency consider revising the current MCL.
TOXAPHENE
BAT for toxaphene is GAC [USEPA 199la]. EPA also listed small systems compliance
technologies for this contaminant as GAC, POU-GAC, and PAC [USEPA 1998b]. Treatment is
not known to .be a limiting concern for the current MCL.
According to technical information provided with the final NPDWR for toxaphene, this
compound is among those that are moderate to well-adsorbed, exhibiting a relatively low carbon
usage rate [USEPA 1989 and USEPA 1991a]. Given reasonable engineering practice, high
removals of this contaminant are feasible. Based on the above information, the preliminary
assessment is that treatment technology is not anticipated to pose a limitation should the Agency
consider revising the current MCL.
1,1,2-TRICHLOROETHANE
BATs for 1,1,2-trichloroethane includes both PTA and GAC [USEPA 1992]. EPA listed the
following small systems compliance technologies for this contaminant: PTA, diffused aeration,
multi-stage bubble aerators, tray aeration, shallow tray aeration, and GAC [USEPA 1998b].
Treatment is not known to be a limiting concern for the current MCL.
According to technical information provided by EPA within the final NPDWR for 1,1,2-
trichloroethane, this compound is among those moderately adsorbed chemicals, exhibiting an
moderate carbon usage rate. 1,1,2-trichloroethane may be among the less volatile organic
chemicals JTJSEPA 1990c]. Given reasonable engineering practice, treatment for removal of this
contaminant is feasible. Based on the above information, the preliminary assessment is that
treatment technology is not anticipated to pose a limitation should the Agency consider revising
the current MCL.
Page 21 of 24
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I '
V. Contaminant for which BAT is not clear or incorrectly
specified
CYANIDE
i
BATs for cyanide include ion exchange, reverse osmosis, and "chlorine" treatment, according to
the US Code of Federal Regulations [US CFRj. A revision such as a technical amendment to the
NPDWRs for cyanide may be required in regard to the above-stated "chlorine" treatment BAT.
CFR §141.62, which contains BAT information which is also cited in §142.62 (variances and
exemptions), should read "alkaline chlorination" in lieu of "chlorine" as a BAT for cyanide.
Chlorination was discussed in EPA's proposal for the cyanide standard, and in the final rale
announcement [USEPA, 1990c and 1992, respectively]. The effectiveness of oxidation of
cyanide at high pH was discussed in the pertinent technology support document [USEPA,
1990bj. !
In addition, since this standard was promulgated, a "Public Water System Warning" [USEPA,
1994] was distributed by EPA through its regional offices. This warning included information
on the use of chlorination (non-alkaline) and the potential for formation of harmful cyanogen
chloride, due to reaction of chlorine with cyanide in water under those conditions. NOTE: this
Warning also states, "EPA will change the regulations specifying BAT for removing cyanide
from chlorination to alkaline chlorination." |
Alkaline chlorination, through use of excess chlorine at pH values greater than 8.5, oxidizes
cyanide to harmless bicarbonate and nitrogen gas. The higher the pH, the faster this reaction
proceeds. The above-cited PWS warning explains this process in detail and outlines treatment
practice, including contact times, required chlorine concentrations, and compensation for
temperature effects.
Page 22 of 24
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VI. References
[Health Canada, 1986] Federal-Provincial Subcommittee on Drinking Water. Guidelines for
Canadian Drinking Water Quality - Supporting Document (Chromium). Updated September
1986. Accessed on internet October 15, 2001:
http://www.hc-sc.gc.ca/ehp/ehd/catalogue/bch_pubs/dwgsup_doc/dwgsup_doc.htm
[USEPA, 1977] US Environmental Protection Agency. Manual of Treatment Techniques for
Meeting the Interim Primary Drinking Water Regulations. Cincinnati, OH. May 1977.
[USEPA, 1985] US Environmental Protection Agency. National Primary Drinking Water
-Regulations: Proposed Rules. Federal Register, Vol 50, No. 219, November 13, 1985 (pp.
46909-46916].
[USEPA, 1986] US Environmental Protection Agency. National Primary Drinking Water
Regulations; Volatile Synthetic Organic Chemicals; Final Rule and Proposed Rule. Federal
Register, Vol. 51, No. 63, pp. 11398-11401. April 2, 1986.
[USEPA, 1989] US Environmental Protection Agency. National Primary and Secondary
Drinking Water Regulations; Proposed Rule. Federal Register, Vol. 54, No. 97, pp.22105-
22112. May 22,1989.
[USEPA, 1990] US Environmental Protection Agency. Occurrence and Exposure Assessment for
Chromium in Public Drinking Water Supplies. July 24, 1990.
[USEPA, 1990a] US Environmental Protection Agency. Technologies and Costs for the
Removal of Phase V Synthetic Organic Chemicals From Potable Water Supplies. Malcolm
Pirnie, Inc. May 1990.
[USEPA, 1990b] US Environmental Protection Agency. Technologies and Costs for the
Removal of Phase V Inorganic Contaminants From Potable Water Sources. Revised Draft.
Malcolm Pirnie, Inc. January 1990.
[USEPA, 1990c] US Environmental Protection Agency. National Primary and Secondary
Drinking Water Regulations; Synthethic Organic Chemicals and Inorganic Chemicals; Proposed
Rule. Federal Register, Vol. 55, No. 143, pp. 30416-30425. July 25, 1990.
[USEPA, 1991 a] US Environmental Protection Agency. National Primary Drinking Water
Regulations; Final Rule. Federal Register, Vol. 56, No. 20, pp. 3552-3557. January 30, 1991.
[USEPA 1991b] US Environmental Protection Agency. Drinking Water Regulations
Maximum Contaminant Level Goals and National Primary Drinking Water Regulations for Lead
and Copper; Final Rule. Federal Register, Vol. 56, No. 110. June 7, 1991.
Page 23 of 24
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j
[USEPA, 1992] US Environmental Protection Agency. National Primary Drinking Water
Regulations; Synthethic Organic Chemicals and Inorganic Chemicals; Final Rule. Federal
Register, Vol. 57, No. 138, pp.31809-31817. July 17, 1992.
| ' ]
i
[USEPA, 1994] US Environmental Protection Agency. Office of Ground Water and Drinking
Water. Public Water System Warning: EPA PWS Cyanide Warning.
i , , _ :
[USEPA, 1998a] US Environmental Protection Agency. Cost Evaluation of Small System
Compliance Options- Point-of-Use and Point-qf-Entry Treatment Units. Cadmus Group. 1998.
[USEPA, 1998b] US Environmental Protectionj Agency. Small System Compliance Technology
List for the Non-Microbial Contaminants Regulated Before 1996 (EPA 815-R-98-002).
September 1998. !
[USEPA, 1999] US Environmental Protection Agency. Evaluation of Central Treatment 'Options
as Small System Treatment Technologies. JanAary 28, 1999.
[USEPA, 2000a] US Environmental Protection Agency. Geometries and Characteristics of
Public Water Systems. SIAC, Inc. December 2,000. (Cited in US US Environmental Protection
Agency, Drinking Water Baseline Handbook. Second Edition (Draft). March 17, 2000.).
[USEPA, 2000b] US Environmental Protection1 Agency. Technologies and Costs for the
Removal of Arsenic From Drinking Water. EPA 815-R-00-028. December 2000.
!
i
[USEPA, 2001] US Environmental Protection Agency. National Primary Drinking Water
Regulations; Arsenic and Clarifications to Compliance and New Source Contaminants
Monitoring; Final Rule. Federal Register, Vol.i66,No. 14,pp.7034-7038. January 22, 2001.
[EPA, 2002] US Environmental Protection Agfency. Occurrence Estimation Methodology and
Occurrence Findings Report for Six-Year Review of NPDWRs. Produced by Cadmus, Inc. for
OGWDW. Draft February 2002. I
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