National Primary Drinking Water Regulations: Long Term 1 Enhanced
Surface Water Treatment and Filter Backwash Rule
[Federal Register: April 10, 2000 (Volume 65, Number 69)]
[Proposed Rules]
[Page 19045-19094]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr10ap00-30]
[[Page 19045]]
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Part II
Environmental Protection Agency
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40 CFR Parts 141 and 142
National Primary Drinking Water Regulations: Long Term 1 Enhanced
Surface Water Treatment and Filter Backwash Rule; Proposed Rule
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ENVIRONMENTAL PROTECTION AGENCY
40 CFR Parts 141 and 142
[WH-FRL-6570-5]
RIN 2040-AD18
National Primary Drinking Water Regulations: Long Term 1 Enhanced
Surface Water Treatment and Filter Backwash Rule
AGENCY: Environmental Protection Agency (EPA).
ACTION: Proposed rule.
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SUMMARY: In this document, EPA is proposing the Long Term 1 Enhanced
Surface Water Treatment and Filter Backwash Rule (LT1FBR). The purposes
of the LT1FBR are to: Improve control of microbial pathogens in
drinking water, including Cryptosporidium, for public water systems
(PWSs) serving fewer than 10,000 people; prevent increases in microbial
risk while PWSs serving fewer than 10,000 people control for
disinfection byproducts, and; require certain PWSs to institute changes
to the return of recycle flows within the treatment process to reduce
the effects of recycle on compromising microbial control. Today's
proposal addresses two statutory requirements of the 1996 Safe Drinking
Water Act (SDWA) Amendments. First, it addresses the statutory
requirement to establish a Long Term Final Enhanced Surface Water
Treatment Rule (LTESWTR) for PWSs that serve under 10,000 people.
Second, it addresses the statutory requirement to promulgate a
regulation which ``governs'' the recycle of filter backwash within the
treatment process of public utilities.
Today's proposed LT1FBR contains 5 key provisions for surface water
and ground water under the direct influence of surface water (GWUDI)
systems serving fewer than 10,000 people: A treatment technique
requiring a 2-log (99 percent) Cryptosporidium removal requirement;
strengthened combined filter effluent turbidity performance standards
and new individual filter turbidity provisions; disinfection benchmark
provisions to assure continued microbial protection is provided while
facilities take the necessary steps to comply with new disinfection
byproduct standards; inclusion of Cryptosporidium in the definition of
GWUDI and in the watershed control requirements for unfiltered public
water systems; and requirements for covers on new finished water
reservoirs.
Today's proposed LT1FBR contains three key provisions for all
conventional and direct filtration systems which recycle and use
surface water or GWUDI: A provision requiring recycle flows to be
introduced prior to the point of primary coagulant addition; a
requirement for systems meeting criteria to perform a one-time self
assessment of their recycle practice and consult with their primacy
agency to address and correct high risk recycle operations; and a
requirement for direct filtration systems to provide information to the
State on their current recycle practice.
The Agency believes implementing the provisions contained in
today's proposal will improve public health protection in two
fundamental ways. First, the provisions will reduce the level of
Cryptosporidium in filtered finished drinking water supplies through
improvements in filtration and recycle practice resulting in a reduced
likelihood of outbreaks of cryptosporidiosis. Second, the filtration
provisions are expected to increase the level of protection from
exposure to other pathogens (i.e. Giardia or other waterborne bacterial
or viral pathogens). It is also important to note that while today's
proposed rule contains new provisions which in some cases strengthen or
modify requirements of the 1989 Surface Water Treatment Rule, each
public water system must continue to comply with the current rules
while new microbial and disinfectants/disinfection byproducts rules are
being developed. In conjunction with the Maximum Contaminant Level Goal
(MCLG) established in the Interim Enhanced Surface Water Treatment
Rule, the Agency developed a treatment technique in lieu of a Maximum
Contaminant Level (MCL) for Cryptosporidium because it is not
economically and technologically feasible to accurately ascertain the
level of Cryptosporidium using current analytical methods.
DATES: The Agency requests comments on today's proposal. Comments must
be received or post-marked by midnight June 9, 2000. Comments received
after this date may not be considered in decision making on the
proposed rule.
ADDRESSES: Send written comments on today's proposed rule to the LT1FBR
Comment Clerk: Water Docket MC 410, W-99-10, Environmental Protection
Agency 401 M Street, S.W., Washington, DC 20460. Please submit an
original and three copies of comments and enclosures (including
references).
Those who comment and want EPA to acknowledge receipt of their
comments must enclose a self-addressed stamped envelope. No facsimiles
(faxes) will be accepted. Comments may also be submitted electronically
to ow-docket@epamail.epa.gov. For additional information on submitting
electronic comments see Supplementary Information Section.
Public comments on today's proposal, other major supporting
documents, and a copy of the index to the public docket for this
rulemaking are available for review at EPA's Office of Water Docket:
401 M Street, SW., Rm. EB57, Washington, DC 20460 from 9:00 a.m. to
4:00 p.m., Eastern Time, Monday through Friday, excluding legal
holidays. For access to docket materials or to schedule an appointment
please call (202) 260-3027.
FOR FURTHER INFORMATION CONTACT: Technical inquiries on the rule should
be directed to Jeffery Robichaud at 401 M Street, SW., MC4607,
Washington, DC 20460 or (202) 260-2568. For general information contact
the Safe Drinking Water Hotline, Telephone (800) 426-4791. The Safe
Drinking Water Hotline is open Monday through Friday, excluding federal
holidays, from 9:00 a.m. to 5:30 p.m. Eastern Time.
SUPPLEMENTARY INFORMATION: Entities potentially regulated by the LT1FBR
are public water systems (PWSs) that use surface water or ground water
under the direct influence of surface water (GWUDI). The recycle
control provisions are applicable to all PWSs using surface water or
GWUDI, regardless of the population served. All other provisions of the
LT1FBR are only applicable to PWSs serving under 10,000 people.
Regulated categories and entities include:
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Category Examples of regulated entities
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Industry..................... Public Water Systems that use surface
water or ground water under the direct
influence of surface water.
State, Local, Tribal or Public Water Systems that use surface
Federal Governments. water or ground water under the direct
influence of surface water.
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[[Page 19047]]
This table is not intended to be exhaustive, but rather provides a
guide for readers regarding entities likely to be regulated by the
LT1FBR. This table lists the types of entities that EPA is now aware
could potentially be regulated by this rule. Other types of entities
not listed in this table could also be regulated. To determine whether
your facility is regulated by this action, you should carefully examine
the definition of public water system in Sec. 141.3 of the Code of
Federal Regulations and applicability criteria in Secs. 141.76 and
141.501 of today's proposal. If you have questions regarding the
applicability of the LT1FBR to a particular entity, consult the person
listed in the preceding section entitled FOR FURTHER INFORMATION
CONTACT.
Submitting Comments
Send an original and three copies of your comments and enclosures
(including references) to W-99-10 Comment Clerk, Water Docket (MC4101),
USEPA, 401 M Street, SW., Washington, D.C. 20460. Comments must be
received or post-marked by midnight June 9, 2000. Note that the Agency
is not soliciting comment on, nor will it respond to, comments on
previously published regulatory language that is included in this
document to ease the reader's understanding of the proposed language.
To ensure that EPA can read, understand and therefore properly
respond to comments, the Agency would prefer that commenters cite,
where possible, the paragraph(s) or sections in the proposed rule or
supporting documents to which each comment refers. Commenters should
use a separate paragraph for each issue discussed.
Electronic Comments
Comments may also be submitted electronically to ow-
docket@epamail.epa.gov. Electronic comments must be submitted as an
ASCII, WP5.1, WP6.1 or WP8 file avoiding the use of special characters
and form of encryption. Electronic comments must be identified by the
docket number W-99-10. Comments and data will also be accepted on disks
in WP 5.1, 6.1, 8 or ASCII file format. Electronic comments on this
document may be filed online at many Federal Depository Libraries.
The record for this rulemaking has been established under docket
number W-99-10, and includes supporting documentation as well as
printed, paper versions of electronic comments. The record is available
for inspection from 9 a.m. to 4 p.m., Monday through Friday, excluding
legal holidays at the Water Docket, EB 57, USEPA Headquarters, 401 M
Street, SW., Washington, D.C. For access to docket materials, please
call (202) 260-3027 to schedule an appointment.
List of Abbreviations Used in This Document
ASCE American Society of Civil Engineers
ASDWA Association of State Drinking Water Administrators
ASTM American Society for Testing Materials
AWWA American Water Works Association
AWWARF American Water Works Association Research Foundation
deg.C Degrees Centigrade
CCP Composite Correction Program
CDC Centers for Disease Control
CFE Combined Filter Effluent
CFR Code of Federal Regulations
COI Cost of Illness
CPE Comprehensive Performance Evaluation
CT The Residual Concentration of Disinfectant (mg/L) Multiplied by the
Contact Time (in minutes)
CTA Comprehensive Technical Assistance
CWSS Community Water System Survey
DBPs Disinfection Byproducts
DBPR Disinfectants/Disinfection Byproducts Rule
ESWTR Enhanced Surface Water Treatment Rule
FACA Federal Advisory Committee Act
GAC Granular Activated Carbon
GAO Government Accounting Office
GWUDI Ground Water Under the Direct Influence of Surface Water
HAA5 Haloacetic acids (Monochloroacetic, Dichloroacetic,
Trichloroacetic, Monobromoacetic and Dibromoacetic Acids)
HPC Heterotropic Plate Count
hrs Hours
ICR Information Collection Rule
IESWTR Interim Enhanced Surface Water Treatment Rule
IFA Immunofluorescence Assay
Log Inactivation Logarithm of (No/NT)
Log Logarithm (common, base 10)
LTESWTR Long Term Enhanced Surface Water Treatment Rule
LT1FBR Long Term 1 Enhanced Surface Water Treatment and Filter
Backwash Rule
MCL Maximum Contaminant Level
MCLG Maximum Contaminant Level Goal
MGD Million Gallons per Day
M-DBP Microbial and Disinfectants/Disinfection Byproducts
MPA Microscopic Particulate Analysis
NODA Notice of Data Availability
NPDWR National Primary Drinking Water Regulation
NT The Concentration of Surviving Microorganisms at Time T
NTTAA National Technology Transfer and Advancement Act
NTU Nephelometric Turbidity Unit
PE Performance Evaluation
PWS Public Water System
Reg. Neg. Regulatory Negotiation
RIA Regulatory Impact Analysis
RFA Regulatory Flexibility Act
RSD Relative Standard Deviation
SAB Science Advisory Board
SDWA Safe Drinking Water Act
SWTR Surface Water Treatment Rule
TC Total Coliforms
TCR Total Coliform Rule
TTHM Total Trihalomethanes
TWG Technical Work Group
TWS Transient Non-Community Water System
UMRA Unfunded Mandates Reform Act
URCIS Unregulated Contaminant Information System
x log removal Reduction to 1/10\x\ of original concentration
Table of Contents
I. Introduction and Background
A. Statutory Requirements and Legal Authority
B. Existing Regulations and Stakeholder Involvement
1. 1979 Total Trihalomethane Rule
2. Total Coliform Rule
3. Surface Water Treatment Rule
4. Information Collection Rule
5. Interim Enhanced Surface Water Treatment Rule
6. Stage 1 Disinfectants and Disinfection Byproduct Rule
7. Stakeholder Involvement
II. Public Health Risk
A. Introduction
B. Health Effects of Cryptosporidiosis and Sources and Transmission
of Cryptosporidium
C. Waterborne Disease Outbreaks In the United States
D. Source Water Occurrence Studies
E. Filter Backwash and Other Process Streams: Occurrence and Impact
Studies
F. Summary and Conclusions
III. Baseline Information-Systems Potentially Affected By Today's
Proposed Rule
IV. Discussion of Proposed LT1FBR Requirements
A. Enhanced Filtration Requirements
1. Two Log Cryptosporidium Removal Requirement
a. Two Log Removal
i. Overview and Purpose
ii. Data
iii. Proposed Requirements
iv. Request for Comments
2. Turbidity Requirements
a. Combined Filter Effluent
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i. Overview and Purpose
ii. Data
iii. Proposed Requirements
iv. Request for Comments
b. Individual Filter Turbidity
i. Overview and Purpose
ii. Data
iii. Proposed Requirements
iv. Request for Comments
B. Disinfection Benchmarking Requirements
1. Applicability Monitoring
a. Overview and Purpose
b. Data
c. Proposed Requirements
d. Request for Comment
2. Disinfection Profiling
a. Overview and Purpose
b. Data
c. Proposed Requirements
d. Request for Comments
3. Disinfection Benchmarking
a. Overview and Purpose
b. Data
c. Proposed Requirements
d. Request for Comments
C. Additional Requirements
1. Inclusion of Cryptosporidium In Definition of GWUDI
a. Overview and Purpose
b. Data
c. Proposed Requirements
d. Request for Comments
2. Inclusion of Cryptosporidium Watershed Requirements for
Unfiltered Systems
a. Overview and Purpose
b. Data
c. Proposed Requirements
d. Request for Comments
3. Requirements for Covering New Reservoirs
a. Overview and Purpose
b. Data
c. Proposed Requirements
d. Request for Comments
D. Recycle Provisions for Public Water Systems Employing Rapid
Granular Filtration Using Surface Water and GWUDI as a Source
1. Treatment Processes that Commonly Recycle and Recycle Flow
Occurrence Data
a. Treatment Processes that Commonly Recycle
i. Conventional Treatment Plants
ii. Direct Filtration Plants
iii. Softening Plants
iv. Contact Clarification Plants
v. Package Plants
vi. Summary of Recycle Disposal Options
b. Recycle Flow Occurrence Data
i. Untreated Spent Filter Backwash Water
ii. Gravity Settled Spent Filter Backwash Water
iii. Combined Gravity Thickener Supernatant
iv. Gravity Thickener Supernatant from Sedimentation Solids
v. Mechanical Dewatering Device Liquids
2. National Recycle Practices
a. Information Collection Rule
i. Recycle Practice
b. Recycle FAX Survey
i. Recycle practice
ii. Options to recycle
iii. Conclusions
3. Recycle Provisions for PWSs Employing Rapid Granular
Filtration Using Surface Water or Ground Water Under the Direct
Influence of Surface Water Influence of Surface Water
a. Return Select Recycle Streams Prior to the Point of Primary
Coagulant Addition
i. Overview and Purpose
ii. Data
iii. Proposed Requirements
iv. Request for Comments
b. Recycle Requirements for Systems Practicing Direct Recycle
and Meeting Specific Criteria
i. Overview and Purpose
ii. Data
iii. Proposed Requirements
iv. Request for Comments
c. Requirements for Direct Filtration Plants that Recycle Using
Surface Water or GWUDI
i. Overview and Purpose
ii. Data
iii. Proposed Requirements
iv. Request for Comments
d. Request for Additional Comment
V. State Implementation and Compliance Schedules
A. Special State Primacy Requirements
B. State Recordkeeping Requirements
C. State Reporting Requirements
D. Interim Primacy
E. Compliance Deadlines
VI. Economic Analysis
A. Overview
B. Quantifiable and Non-Quantifiable Costs
1. Total Annual Costs
2. Annual Costs of Rule Provisions
3. Non Quantifiable Costs
C. Quantifiable and Non-Quantifiable Health Benefits
1. Quantified Health Benefits
2. Non-Quantified Health and Non-Health Related Benefits
a. Recycle Provisions
b. Issues Associated with Unquantified Benefits
D. Incremental Costs and Benefits
E. Impacts on Households
F. Benefits From the Reduction of Co-Occurring Contaminants
G. Risk Increases From Other Contaminants
H. Other Factors: Uncertainty in Risk, Benefits, and Cost Estimates
I. Benefit Cost Determination
J. Request for Comment
VII. Other Requirements
A. Regulatory Flexibility Act
1. Today's Proposed Rule
2. Use of Alternative Definition
3. Background and Analysis
a. Number of Small Entities Affected
b. Recordkeeping and Reporting
c. Interaction with Other Federal Rules
d. Significant Alternatives
i. Turbidity Provisions
ii. Disinfection Benchmarking Applicability Monitoring
Provisions
iii. Recycling Provisions
e. Other Comments
B. Paperwork Reduction Act
C. Unfunded Mandates Reform Act
1. Summary of UMRA requirements
2. Written Statement for Rules With Federal Mandates of $100
Million or More
a. Authorizing Legislation
b. Cost Benefit Analysis
c. Estimates of Future Compliance Costs and Disproportionate
Budgetary Effects
d. Macro-economic Effects
e. Summary of EPA's Consultation with State, Local, and Tribal
Governments and Their Concerns
f. Regulatory Alternatives Considered
g. Selection of the Least Costly, Most-Cost Effective or Least
Burdensome Alternative That Achieves the Objectives of the Rule
3. Impacts on Small Governments
D. National Technology Transfer and Advancement Act
E. Executive Order 12866: Regulatory Planning and Review
F. Executive Order 12898: Environmental Justice
G. Executive Order 13045: Protection of Children from Environmental
Health Risks and Safety Risks
H. Consultations with the Science Advisory Board, National Drinking
Water Advisory Council, and the Secretary of Health and Human
Services
I. Executive Order 13132: Executive Orders on Federalism
J. Executive Order 13084: Consultation and Coordination With Indian
Tribal Governments
K. Likely Effect of Compliance with the LT1FBR on the Technical,
Financial, and Managerial Capacity of Public Water Systems
L. Plain Language
VIII. Public Comment Procedures
A. Deadlines for Comment
B. Where to Send Comment
C. Guidelines for Commenting
IX. References
I. Introduction and Background
A. Statutory Requirements and Legal Authority
The Safe Drinking Water Act (SDWA or the Act), as amended in 1986,
requires U.S. Environmental Protection Agency (EPA) to publish a
maximum contaminant level goal (MCLG) for each contaminant which, in
the judgement of the EPA Administrator, ``may have any adverse effect
on the health of persons and which is known or anticipated to occur in
public water systems' (Section 1412(b)(3)(A)). MCLGs are to be set at a
level at which ``no known or anticipated adverse effect on the health
of persons occur and which allows an adequate margin of safety''
(Section 1412(b)(4)).
The Act was again amended in August 1996, resulting in the
renumbering and augmentation of certain sections with additional
statutory language. New sections were added establishing new drinking
water requirements. These modifications are outlined below.
The Act requires EPA to publish a National Primary Drinking Water
Regulation (NPDWR) that specifies
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either a maximum contaminant level (MCL) or treatment technique
(Sections 1401(1) and 1412(a)(3)) at the same time it publishes an
MCLG, which is a non-enforceable health goal. EPA is authorized to
promulgate a NPDWR ``that requires the use of a treatment technique in
lieu of establishing an MCL,'' if the Agency finds that ``it is not
economically or technologically feasible to ascertain the level of the
contaminant.'' EPA's general authority to set MCLGs and NPDWRs applies
to contaminants that may ``have an adverse effect on the health of
persons,'' that are ``known to occur or there is a substantial
likelihood that the contaminant will occur in public water systems with
a frequency and at levels of public health concern,'' and for which
``in the sole judgement of the Administrator, regulation of such
contaminant presents a meaningful opportunity for health risk reduction
for persons served by public water systems'' (SDWA Section
1412(b)(1)(A)).
The 1996 amendments, also require EPA, when proposing a NPDWR that
includes an MCL or treatment technique, to publish and seek public
comment on an analysis of health risk reduction and cost impacts. EPA
is required to take into consideration the effects of contaminants upon
sensitive subpopulations (i.e., infants, children, pregnant women, the
elderly, and individuals with a history of serious illness), and other
relevant factors (Section 1412(b)(3)(C)).
The amendments established a number of regulatory deadlines,
including schedules for a Stage 1 Disinfection Byproduct Rule (DBPR),
an Interim Enhanced Surface Water Treatment Rule (IESWTR), a Long Term
Final Enhanced Surface Water Treatment Rule (LTESWTR), and a Stage 2
DBPR (Section 1412(b)(2)(C)). To provide additional time for systems
serving fewer than 10,000 people to comply with the IESWTR provisions
and also ensure these systems implement Stage 1 DBPR and the IESWTR
provisions simultaneously, the Agency split the IESWTR into two rules:
the IESWR and the LT1ESWTR. The Act as amended also requires EPA to
promulgate regulations to ``govern'' the recycle of filter backwash
within the treatment process of public utilities (Section 1412(b)(14)).
Under 1412(b)(4)(E)(ii), EPA must develop a Small System Technology
List for the LT1FBR. The filtration technologies listed in the Small
System Compliance Technology List for the Surface Water Treatment Rule
and Total Coliform Rule (EPA-815-R-98-001, September 1998) are also the
technologies which would achieve compliance with the provisions of the
LT1FBR. EPA will develop a separate list for the LT1FBR as new
technologies become available.
Although the Act permits small system variances for compliance with
a requirement of a national primary drinking water regulation which
specifies a maximum contaminant level or treatment technique, Section
1415(e)(6)(B) of SDWA, excludes variances for any national primary
drinking water regulation for a microbial contaminant or an indicator
or treatment technique for a microbial contaminant. LT1FBR requires
treatment techniques to control Cryptosporidium (a microbial
contaminant), and as such systems governed by the LT1FBR are ineligible
for variances.
Finally, as part of the 1996 SDWA Amendments, recordkeeping
requirements were modified to apply to every person who is subject to a
requirement of this title or who is a grantee (Section 1445(a)(1)(A)).
Such persons are required to establish and maintain such records, make
such reports, conduct such monitoring, and provide such information as
the Administrator may reasonably require by regulation.
B. Existing Regulations and Stakeholder Involvement
1. 1979 Total Trihalomethane Rule
In November 1979 (44 FR 68624) (EPA, 1979) EPA set an interim MCL
for total trihalomethanes (TTHM--the sum of chloroform, bromoform,
bromodichloromethane, dibromochloromethane) of 0.10 mg/l as an annual
average. Compliance is defined on the basis of a running annual average
of quarterly averages for four samples taken in the distribution
system. The value for each sample is the sum of the measured
concentrations of chloroform, bromodichloromethane,
dibromochloromethane and bromoform.
The interim TTHM standard applies to community water systems using
surface water and/or ground water serving at least 10,000 people that
add a disinfectant to the drinking water during any part of the
treatment process. At their discretion, States may extend coverage to
smaller PWSs; however, most States have not exercised this option. The
Stage 1 DBPR (as discussed later) contains updated TTHM requirements.
2. Total Coliform Rule
The Total Coliform Rule (TCR) (54 FR 27544, June 29, 1989) (EPA,
1989a) applies to all public water systems. The TCR sets compliance
with the Maximum Contaminant Level (MCL) for total coliforms (TC) as
follows. For systems that collect 40 or more samples per month, no more
than 5 percent of the samples may be TC-positive; for those that
collect fewer than 40 samples, no more than one sample may be TC-
positive. If a system has a TC-positive sample, it must test that
sample for the presence of fecal coliforms or E. coli. The system must
also collect a set of repeat samples, and analyze for TC (and fecal
coliform or E. coli within 24 hours of the first TC-positive sample).
In addition, any fecal coliform-positive repeat sample, E-coli.-
positive repeat sample, or any total-coliform-positive repeat sample
following a fecal coliform-positive or E-coli-positive routine sample
constitutes an acute violation of the MCL for total coliforms. If a
system exceeds the MCL, it must notify the public using mandatory
language developed by the EPA. The required monitoring frequency for a
system depends on the number of people served and ranges from 480
samples per month for the largest systems to once annually for the
smallest systems. All systems must have a written plan identifying
where samples are to be collected.
The TCR also requires an on-site inspection (referred to as a
sanitary survey) every 5 years for each system that collects fewer than
five samples per month. This requirement is extended to every 10 years
for non-community systems using only protected and disinfected ground
water.
3. Surface Water Treatment Rule
Under the Surface Water Treatment Rule (SWTR) (54 FR 27486, June
29, 1989) (EPA, 1989b), EPA set maximum contaminant level goals of zero
for Giardia lamblia, viruses, and Legionella and promulgated regulatory
requirements for all PWSs using surface water sources or ground water
sources under the direct influence of surface water. The SWTR includes
treatment technique requirements for filtered and unfiltered systems
that are intended to protect against the adverse health effects of
exposure to Giardia lamblia, viruses, and Legionella, as well as many
other pathogenic organisms. Briefly, those requirements include (1)
Requirements for maintenance of a disinfectant residual in the
distribution system; (2) removal and/or inactivation of 3 log (99.9
percent) for Giardia and 4 log (99.99 percent) for viruses; (3)
combined filter effluent turbidity performance standard of 5
nephelometric turbidity units (NTU) as a maximum and 0.5 NTU
[[Page 19050]]
at the 95th percentile monthly, based on 4-hour monitoring for
treatment plants using conventional treatment or direct filtration
(with separate standards for other filtration technologies); and (4)
watershed protection and other requirements for unfiltered systems.
Systems seeking to avoid filtration were required to meet avoidance
criteria and obtain avoidance determination by December 30, 1991,
otherwise filtration must have been provided by June 29, 1993. For
systems properly avoiding filtration, later failures to meet avoidance
criteria triggered a requirement that filtration be provided within 18
months.
4. Information Collection Rule
The Information Collection Rule (ICR), which was promulgated on May
14, 1996 (61 FR 24354) (EPA, 1996) applied to large public water
systems serving populations of 100,000 or more. A more limited set of
ICR requirements pertain to ground water systems serving between 50,000
and 100,000 people. About 300 PWSs operating 500 treatment plants were
involved with the extensive ICR data collection. Under the ICR, these
PWSs monitored for water quality factors affecting disinfection
byproduct (DBP) formation and DBPs within the treatment plant and in
the distribution system on a monthly basis for 18 months. In addition,
PWSs were required to provide treatment train schematics, operating
data and source water occurrence data for bacteria, viruses, and
protozoa. Finally, a subset of PWSs performed treatment studies, using
either granular activated carbon (GAC) or membrane processes, to
evaluate DBP precursor removal and control of DBPs. Monitoring for
treatment study applicability began in September 1996. The remaining
occurrence monitoring began in July 1997 and concluded in December
1998.
The purpose of the ICR was to collect occurrence and treatment
information to help evaluate the need for possible changes to the
current microbial requirements and existing microbial treatment
practices, and to help evaluate the need for future regulation of
disinfectants and disinfection byproducts (DBPs). The ICR will provide
EPA with additional information on the national occurrence in drinking
water of (1) chemical byproducts that form when disinfectants used for
microbial control react with naturally occurring compounds already
present in source water; and (2) disease-causing microorganisms,
including Cryptosporidium, Giardia, and viruses. Analysis of ICR data
is not expected to be completed in the time frame necessary for
inclusion in the LT1FBR, however if the data is available and has been
quality controlled and peer reviewed during the necessary time frame,
EPA will consider the datat as it refines its analysis for the final
rule.
The ICR also required PWSs to provide engineering data on how they
currently control for such contaminants. The ICR monthly sampling data
will also provide information on the quality of the recycle waters via
monthly monitoring (for 18 months) of pH, alkalinity, turbidity,
temperature, calcium and total hardness, TOC, UV254,
bromide, ammonia, and disinfectant residual (if disinfectant is used).
This data will provide some indication of the treatability of the
water, the extent to which contaminant concentration effects may occur,
and the potential for contribution to DBP formation. However, sampling
to determine the occurrence of pathogens in recycle waters was not
performed.
5. Interim Enhanced Surface Water Treatment Rule
Public water systems serving 10,000 or more people that use surface
water or ground water under the direct influence of surface water
(GWUDI) are required to comply with the IESWTR (63 FR 69477, December
16, 1998) (EPA, 1998a) by December of 2001. The purposes of the IESWTR
are to improve control of microbial pathogens, specifically the
protozoan Cryptosporidium, and address risk trade-offs between
pathogens and disinfection byproducts. Key provisions established by
the rule include: a Maximum Contaminant Level Goal (MCLG) of zero for
Cryptosporidium; 2-log (99 percent) Cryptosporidium removal
requirements for systems that filter; strengthened combined filter
effluent turbidity performance standards of 1.0 NTU as a maximum and
0.3 NTU at the 95th percentile monthly, based on 4-hour monitoring for
treatment plants using conventional treatment or direct filtration;
requirements for individual filter turbidity monitoring; disinfection
benchmark provisions to assess the level of microbial protection
provided as facilities take the necessary steps to comply with new
disinfection byproduct standards; inclusion of Cryptosporidium in the
definition of GWUDI and in the watershed control requirements for
unfiltered public water systems; requirements for covers on new
finished water reservoirs; and sanitary surveys for all surface water
systems regardless of size.
6. Stage 1 Disinfectants and Disinfection Byproduct Rule
The Stage 1 DBPR applies to all PWSs that are community water
systems (CWSs) or nontransient noncommunity water systems (NTNCWs) that
treat their water with a chemical disinfectant for either primary or
residual treatment. In addition, certain requirements for chlorine
dioxide apply to transient noncommunity water systems (TNCWSs). The
Stage 1 DBPR (EPA, 1998c) was published at the same time as the IESWTR
(63 FR 69477, December 16, 1998) (EPA, 1998a). Surface water and GWUDI
systems serving at least 10,000 persons are required to comply with the
Stage 1 Disinfectants and Disinfection Byproducts Rule by December
2001. Ground water systems and surface water and GWUDI systems serving
fewer than 10,000 must comply with the Stage 1 Disinfectants and
Disinfection Byproducts Rule by December 2003.
The Stage 1 DBPR finalizes maximum residual disinfectant level
goals (MRDLGs) for chlorine, chloramines, and chlorine dioxide; MCLGs
for four trihalomethanes (chloroform, bromodichloromethane,
dibromochloromethane, and bromoform), two haloacetic acids
(dichloroacetic acid and trichloroacetic acid), bromate, and chlorite;
and NPDWRs for three disinfectants (chlorine, chloramines, and chlorine
dioxide), two groups of organic disinfection byproducts TTHMs and HAA5
and two inorganic disinfection byproducts, chlorite and bromate. The
NPDWRs consist of maximum residual disinfectant levels (MRDLs) or
maximum contaminant levels (MCLs) or treatment techniques for these
disinfectants and their byproducts. The NPDWRs also include monitoring,
reporting, and public notification requirements for these compounds.
The Stage 1 DBPR includes the best available technologies (BATs) upon
which the MRDLs and MCLs are based. EPA believes the implementation of
the Stage 1 DBPR will reduce the levels of disinfectants and
disinfection byproducts in drinking water supplies. The Agency believes
the rule will provide public health protection for an additional 20
million households that were not previously covered by drinking water
rules for disinfection byproducts.
7. Stakeholder Involvement
EPA conducted two stakeholder meetings to solicit feedback and
information from the regulated community and other concerned
stakeholders on issues relating to
[[Page 19051]]
today's proposed rule. The first meeting was held July 22 and 23, 1998
in Lakewood, Colorado. EPA presented potential regulatory components
for the LT1FBR. Breakout sessions with stakeholders were held to
generate feedback on the regulatory provisions being considered and to
solicit feedback on next steps for rule development and stakeholder
involvement. Additionally, information was presented summarizing
ongoing research and data gathering activities regarding the recycle of
filter backwash. The presentations generated useful discussion and
provided substantial feedback to EPA regarding technical issues,
stakeholder concerns, and possible regulatory options (EPA 1999k). The
second stakeholder meeting was held in Dallas, Texas on March 3 and 4,
1999. EPA presented new analyses, summaries of current research, and
revised regulatory options and data collected since the July
stakeholder meeting. Regional perspectives on turbidity and
disinfection benchmarking components were also discussed with
presentations from EPA Region VI and the Texas Natural Resources
Conservation Commission. Four break-out sessions were extremely useful
and generated a wide range of information, issues, and technical input
from a diverse group of stakeholders (EPA 1999j).
The Agency utilized the feedback received during these two
stakeholder meetings in developing today's proposed rule. EPA also
mailed a draft version of the preamble for today's proposed rule to the
attendees of these meetings. Several of the options which are presented
today represent modifications suggested by stakeholders.
II. Public Health Risk
The purpose of this section is to discuss the health risk
associated with pathogens, particularly Cryptosporidium, in surface
waters and GWUDI. More detailed information about such pathogens and
other contaminants of concern may be found in an EPA criteria document
for Giardia (EPA 1998d), three EPA criteria documents for viruses (EPA,
1985; 1999a; 1999b), the Cryptosporidium and Giardia Occurrence
Assessment for the Interim Enhanced Surface Water Treatment Rule (EPA,
1998b) and the LT1FBR Occurrence and Assessment Document (EPA 1999c).
EPA requests comment on today's proposed rule, the information
supporting the proposal, and the potential impact of proposed
regulatory provisions on public health risk.
A. Introduction
In 1990, EPA's Science Advisory Board (SAB), an independent panel
of experts established by Congress, cited drinking water contamination
as one of the most important environmental risks and indicated that
disease-causing microbial contaminants (i.e., bacteria, protozoa and
viruses) are probably the greatest remaining health risk management
challenge for drinking water suppliers (EPA/SAB, 1990). Information on
the number of waterborne disease outbreaks from the U.S. Centers for
Disease Control and Prevention (CDC) underscores this concern. CDC
indicates that, between 1980 and 1996, 401 waterborne disease outbreaks
were reported, with over 750,000 associated cases of disease. During
this period, a number of agents were implicated as the cause, including
protozoa, viruses and bacteria.
Waterborne disease caused by Cryptosporidium is of particular
concern, as it is difficult to inactivate Cryptosporidium oocysts with
standard disinfection practices (unlike pathogens such as viruses and
bacteria), and there is currently no therapeutic treatment for
cryptosporidiosis (unlike giardiasis). Because Cryptosporidium is not
generally inactivated in systems using standard disinfection practices,
the control of Cryptosporidium is dependent on physical removal
processes (e.g., filtration).
The filter effluent turbidity limits specified under the SWTR were
created to remove large parasite cysts such as Giardia and did not
specifically control for smaller Cryptosporidium oocysts. In addition,
filter backwash water recycling practices such as adding recycled water
to the treatment train after primary coagulant addition may overwhelm
the plant and harm efforts to control Giardia lamblia, Cryptosporidium,
and emerging pathogens. Despite filtration and disinfection,
Cryptosporidium oocysts have been found in filtered drinking water
(LeChevallier, et al., 1991a; EPA, 1999c), and many of the individuals
affected by waterborne disease outbreaks caused by Cryptosporidium were
served by filtered surface water supplies (Solo-Gabriele and
Neumeister, 1996). Surface water systems that filter and disinfect may
still be vulnerable to Cryptosporidium, depending on the source water
quality and treatment effectiveness. EPA believes that today's
proposal, however, will ensure that drinking water treatment is
operating efficiently to control Cryptosporidium (see Sections IV.A and
IV.D) and other microbiological contaminants of concern (e.g.,
Giardia).
In order to assess the public health risk associated with
consumption of surface water or GWUDI from PWSs, EPA has evaluated
information and conducted analysis in four important areas discussed in
the following paragraphs. These areas are: (1) The health effects of
cryptosporidiosis; (2) cryptosporidiosis waterborne disease outbreak
data; (3) Cryptosporidium occurrence data from raw surface water, raw
GWUDI, finished water, and recycle stream studies; and (4) an
assessment of the current baseline surface water treatment required by
existing regulations.
B. Health Effects of Cryptosporidiosis and Sources and Transmission of
Cryptosporidium
Waterborne diseases are usually acute (i.e., sudden onset and
typically lasting a short time in healthy people), and most waterborne
pathogens cause gastrointestinal illness, with diarrhea, abdominal
discomfort, nausea, vomiting, and/or other symptoms. Some waterborne
pathogens cause or are associated with more serious disorders such as
hepatitis, gastric cancer, peptic ulcers, myocarditis, swollen lymph
glands, meningitis, encephalitis, and many other diseases.
Cryptosporidiosis is a protozoal infection that usually causes 7-14
days of diarrhea with possibly a low-grade fever, nausea, and abdominal
cramps in healthy individuals (Juranek, 1995). Unlike giardiasis for
which effective antibiotic therapy is available, an antibiotic
treatment for cryptosporidiosis does not exist (Framm and Soave, 1997).
There are several species of Cryptosporidium which have been
identified, including C. baileyi and C. meleagridis (bird host); C.
muris (mouse host); C. nasorum (fish host), C. parvum (mammalian host),
and C. serpentis (snake host). Cryptosporidium parvum was first
recognized as a human pathogen in 1976 (Juranek, 1995). Recently, both
the human and cattle types of C. parvum have been found in healthy
individuals, and these types, C. felis, and a dog type have been found
in immunocompromised individuals (Pieniazek et al., 1999). Transmission
of cryptosporidiosis often occurs through the ingestion of infective
Cryptosporidium oocysts from feces-contaminated food or water, but may
also result from direct or indirect contact with infected persons or
mammals (Casemore, 1990; Cordell and Addiss, 1994). Dupont, et. al.,
1995, found through a human feeding study that a low dose of C. parvum
is
[[Page 19052]]
sufficient to cause infection in healthy adults (Dupont et. al., 1995).
Animal agriculture as a nonpoint source of C. parvum has been
implicated as the source of contamination for the 1993 outbreak in
Milwaukee, Wisconsin, the largest outbreak of waterborne disease in the
history of the United States (Walker et al., 1998). Other sources of C.
parvum include discharges from municipal wastewater treatment
facilities and drainage from slaughterhouses. In addition, rainfall
appears to increase the concentration of Cryptosporidium in surface
water, documented in a study by Atherholt, et al. (1998).
There is evidence that an immune response to Cryptosporidium
exists, but the degree and duration of this immunity is not well
characterized (Fayer and Ungar, 1986). Recent work conducted by
Chappell, et al. (1999) indicates that individuals with evidence of
prior exposure to Cryptosporidium parvum have demonstrated immunity to
low doses of oocysts (approximately 500 oocysts). The investigators
found the 50 percent infectious dose for previously exposed individuals
(possessing a pre-existing blood serum antibody) to be 1,880 oocysts
compared to 132 oocysts for individuals without prior exposure, and
individuals with prior exposure who became infected shed fewer oocysts.
Because of this type of immune response, symptomatic infection in
communities exposed to chronic low levels of oocysts will primarily be
observed in newcomers (e.g., visitors, young children) (Frost et al.,
1997; Okhuysen et al., 1998).
Sensitive populations are more likely to become infected and ill,
and gastrointestinal illness among this population may be chronic.
These sensitive populations include children, especially the very
young; the elderly; pregnant women; and the immunocompromised (Gerba et
al., 1996; Fayer and Ungar, 1986; EPA 1998e). This sensitive segment
represents almost 20 percent of the population in the U.S. (Gerba et
al., 1996). EPA is particularly concerned about the exposure of
severely immunocompromised persons to Cryptosporidium in drinking
water, because the severity and duration of illness is often greater in
immunocompromised persons than in healthy individuals, and it may be
fatal among this population. For instance, a follow-up study of the
1993 Milwaukee, Wisconsin, waterborne disease outbreak reported that at
least 50 Cryptosporidium-associated deaths occurred among the severely
immunocompromised (Hoxie et al., 1997).
Cases of illness from cryptosporidiosis were rarely reported until
1982, when the disease became prevalent due to the AIDS epidemic
(Current, 1983). As laboratory diagnostic techniques improved during
subsequent years, outbreaks among immunocompetent persons were
recognized as well. Over the last several years there have been a
number of documented waterborne cryptosporidiosis outbreaks in the
U.S., United Kingdom, Canada and other countries (Rose, 1997, Craun et
al., 1998).
C. Waterborne Disease Outbreaks in the United States
The occurrence of outbreaks of waterborne gastrointestinal
infections, including cryptosporidiosis, may be much greater than
suggested by reported surveillance data (Craun and Calderon 1996). The
CDC-EPA, and the Council of State and Territorial Epidemiologists have
maintained a collaborative surveillance program for collection and
periodic reporting of data on waterborne disease outbreaks since 1971.
The CDC database and biennial CDC-EPA surveillance summaries include
data reported voluntarily by the States on the incidence and prevalence
of waterborne illnesses. However, the following information
demonstrates why the reported surveillance data may under-report actual
outbreaks.
The U.S. National Research Council strongly suggests that the
number of identified and reported outbreaks in the CDC database (both
for surface and ground waters) represents a small percentage of actual
waterborne disease outbreaks National Research Council, 1997; Bennett
et al., 1987). In practice, most waterborne outbreaks in community
water systems are not recognized until a sizable proportion of the
population is ill (Perz et al.)
Healthy adults with cryptosporidiosis may not suffer severe
symptoms from the disease; therefore, infected individuals may not seek
medical assistance, and their cases are subsequently not reported. Even
if infected individuals consult a physician, Cryptosporidium may not be
identified by routine diagnostic tests for gastroenteritis and,
therefore, tends to be under-reported in the general population
(Juranek 1995). Such obstacles to outbreak reporting indicate that the
incidence of disease and outbreaks of cryptosporidiosis may be much
higher than officially reported by the CDC.
The CDC database is based upon responses to a voluntary and
confidential survey that is completed by State and local public health
officials. CDC defines a waterborne disease outbreak as occurring when
at least two persons experience a similar illness after ingesting water
(Kramer et al., 1996). Cryptosporidiosis water system outbreak data
from the CDC database appear in Table II.1 and Table II.2.
Table II.1 illustrates the reported number of waterborne disease
outbreaks in U.S. community, noncommunity, and individual drinking
water systems between 1971 and 1996. According to the CDC-EPA database,
a total of 652 outbreaks and 572,829 cases of illnesses were reported
between 1971 and 1996 (see Table II-1). The total number of outbreaks
reported includes outbreaks resulting from protozoan contamination,
virus contamination, bacterial contamination, chemical contamination,
and unknown factors.
Table II.1.--Comparison of Outbreaks and Outbreak-Related Illnesses From Ground Water and Surface Water for the
Period 1971-1996 \1\
----------------------------------------------------------------------------------------------------------------
Cases of \2\ Outbreaks in
Water source Total outbreaks illnesses Outbreaks in CWSs NCWSs
--------------------------------------------\2\-----------------------------------------------------------------
Ground............................ 371 (57%)......... 90,815 (16%)...... 113 258
Surface........................... 223 (34%)......... 471,375 (82%)..... 148 43
Other............................. 58 (9%)........... 10,639 (2%)....... 30 19
[[Page 19053]]
All Systems \3\................... 652 (100%)........ 572,829 (100%).... 291 320
----------------------------------------------------------------------------------------------------------------
\1\ Craun and Calderon, 1994, CDC, 1998.
\2\ Includes outbreaks in CWSs + NCWSs + Private wells.
Epidemiological investigations of outbreaks in populations served
by filtered systems have shown that treatment deficiencies have
resulted in the plants' failure to remove contamination from the water.
Sometimes operational deficiencies have been discovered only during
post-outbreak investigations. Rose (1997) identified the following
types of environmental and operating conditions commonly present in
filtered surface water systems at the time cryptosporidiosis outbreaks
have occurred:
Improperly-installed, -operated, -maintained, or -
interpreted monitoring
Equipment (e.g., turbidimeters);
Inoperable flocculators, chemical injectors, or filters;
Inadequate personnel response to failures of primary
monitoring equipment;
Filter backwash recycle;
High concentrations of oocysts in source water with no
mitigative barrier;
Flushing of oocysts (by heavy rain or snow melt) from land
surfaces upstream of the plant intakes; and
Altered or suboptimal filtration during periods of high
turbidity, with turbidity spikes detected in finished water.
From 1984 to 1994, there have been 19 reported outbreaks of
cryptosporidiosis in the U.S. (Craun et al., 1998). As mentioned
previously, C. parvum was not identified as a human pathogen until
1976. Furthermore, cryptosporidiosis outbreaks were not reported in the
U.S. prior to 1984. Ten of these cryptosporidiosis outbreaks have been
documented in CWSs, NCWSs, and a private water system (Moore et al.,
1993; Kramer et al., 1996; Levy et al., 1998; ; Craun et al., 1998).
The remaining nine outbreaks were associated with recreational
activities (Craun et al., 1998). The cryptosporidiosis outbreaks in
U.S. drinking water systems are presented in Table II.2.
Table II.2.--Cryptosporidiosis Outbreaks in U.S. Drinking Water Systems
--------------------------------------------------------------------------------------------------------------------------------------------------------
Location and CWS, Cases of illness
Year NCWS, or private (estimated) Source water Treatment Suspected cause
--------------------------------------------------------------------------------------------------------------------------------------------------------
1984............................... Braun Station, TX, CWS 117 (2,000)........... Well................. Chlorination......... Sewage-contaminated
well.
1987............................... Carrollton, GA, CWS... (13,000).............. River................ Conventional Treatment
filtration/ deficiencies.
chlorination;
inadequate
backwashing of some
filters.
1991............................... Berks County, PA, NCWS (551)................. Well................. Chlorination......... Ground water under
the influence of
surface water.
1992............................... Medford (Jackson (3,000; combined total Spring/River......... Chlorination/package Source not
County), OR, CWS. for Jackson County filtration plant. identified.
and Talent, below).
1992............................... Talent, OR, CWS....... see Medford, OR....... Spring/River......... Chlorination/package Treatment
filtration plant. deficiencies.
1993............................... Milwaukee, WI, CWS.... (403,000)............. Lake................. Conventional High source water
filtration. contamination and
treatment
deficiencies.
1993............................... Yakima, WA, private... 7..................... Well................. N/A.................. Ground water under
the influence of
surface water.
1993............................... Cook County, MN, NCWS. 27.................... Lake................. Filtered, chlorinated Possible sewage
backflow from toilet/
septic tank.
1994............................... Clark County, NV, CWS. 103; many confirmed River/Lake........... Prechlorination, Source not
for cryptosporidiosis filtration and post- identified.
were HIV positive. filtration
chlorination.
1994............................... Walla Walla, WA, CWS.. 134................... Well................. None reported........ Sewage contamination.
--------------------------------------------------------------------------------------------------------------------------------------------------------
Craun, et al., 1998.
[[Page 19054]]
Six of the ten cryptosporidiosis outbreaks reported in Table II.2
originated from surface water or possibly GWUDI supplied by public
drinking water systems serving fewer than 10,000 persons. The first
outbreak (117 known cases, 2,000 estimated cases of illness), in Braun
Station, Texas in 1984, was caused by sewage leaking into a ground
water well suspected to be under the influence of surface water. A
second outbreak in Pennsylvania in 1991 (551 estimated cases of
illness), occurred at a well also under the influence of surface water.
The third and fourth (multi-episodic) outbreaks took place in Jackson
County, Oregon in 1992 (3,000 estimated cases of illness) and were
linked to treatment deficiencies in the Talent, OR surface water
system. A fifth outbreak (27 cases of illness) in Minnesota, in 1993,
occurred at a resort supplied by lake water. Finally, a sixth outbreak
(134 cases of illness) in Washington in 1994, occurred due to sewage-
contaminated wells at a CWS.
Three of the ten outbreaks (Carollton, GA (1987); Talent, OR
(1992); Milwaukee, WI (1993)) were caused by water supplied by water
treatment plants where the recycle of filter backwash was implicated as
a possible cause of the outbreak. In total, the nine outbreaks which
have taken place in PWSs have caused an estimated 419,939 cases of
illness. These outbreaks illustrate that when treatment in place is not
operating optimally or when source water is highly contaminated,
Cryptosporidium may enter the finished drinking water and infect
drinking water consumers, ultimately resulting in waterborne disease
outbreaks.
D. Source Water Occurrence Studies
Cryptosporidium is common in the environment (Rose, 1988;
LeChevallier et al., 1991b). Runoff from unprotected watersheds allows
the transport of these microorganisms from sources of oocysts (e.g.,
untreated wastewater, agricultural runoff) to water bodies used as
intake sites for drinking water treatment plants. If treatment operates
inefficiently, oocysts may enter the finished water at levels of public
health concern. A particular public health challenge is that simply
increasing existing disinfection levels above those most commonly
practiced for standard disinfectants (i.e., chlorine or chloramines) in
the U.S. today does not appear to be an effective strategy for
controlling Cryptosporidium.
Cryptosporidium oocysts have been detected in wastewater, pristine
surface water, surface water receiving agricultural runoff or
contaminated by sewage, ground water under the direct influence of
surface water (GWUDI), water for recreational use, and drinking water
(Rose 1997, Soave 1995). Over 25 environmental surveys have reported
Cryptosporidium source water occurrence data from surface water or
GWUDI (presented in Tables II.3 and II.4), which typically involved the
collection of a few water samples from a number of sampling locations
having different characteristics (e.g., polluted vs. pristine; lakes or
reservoirs vs. rivers). Results are presented as oocysts per 100
liters, unless otherwise marked.
Each of the studies cited in Tables II.3 and II.4 presents
Cryptosporidium source water occurrence information, including (where
possible): (1) The number of samples collected; (2) the number of
samples positive; and (3) both the means and ranges for the
concentrations of Cryptosporidium detected (where available). However,
the immunofluorescence assay (IFA) method and other Cryptosporidium
detection methods are inaccurate and lack adequate precision. Current
methods do not indicate the species of Cryptosporidium identified or
whether the oocysts detected are viable or infectious (Frey et al.,
1997). The methods for detecting Cryptosporidium were modeled from
Giardia methods, therefore recovery of Cryptosporidium is deficient
primarily because Cryptosporidium oocysts are more difficult to capture
due to their size (Cryptosporidium oocysts are 4-
6m; Giardia cysts are 8-
12m). In addition, it is a challenge to
recover Cryptosporidium oocysts from the filters when they are
concentrated, due to the adhesive character of the organisms. Other
potential limitations to the protozoan detection methods include: (1)
Filters used to concentrate the water samples are easily clogged by
debris from the water sample; (2) interference occurs between debris or
particulates that fluoresce due to cross reactivity of antibodies,
which results in false positive identifications; (3) it is difficult to
view the structure of oocysts on the membrane filter or slide,
resulting in false negative determinations; and (4) most methods
require an advanced level of skill to be performed accurately.
Despite these limitations, the occurrence information generated
from these studies demonstrates that Cryptosporidium occurs in source
waters. The source waters for which EPA has compiled information
include rivers, reservoirs, lakes, streams, raw water intakes, springs,
wells under the influence of surface water and infiltration galleries.
The most comprehensive study in scope and national representation
(LeChevallier and Norton, 1995) will be described in further detail
following Tables II.3 and II.4.
Table II.3.--Summary of Surface Water Survey and Monitoring Data for Cryptosporidium Oocysts
--------------------------------------------------------------------------------------------------------------------------------------------------------
Samples
Number of positive for Range of oocyst conc.
Sample source samples (n) Cryptosporidium (oocysts/100L) Mean (oocysts/100L) Reference
(percent)a
--------------------------------------------------------------------------------------------------------------------------------------------------------
Rivers............................... 25 100 200-11,200.................. 2510........................ Ongerth and Stibbs
1987.
River................................ 6 100 200-580,000................. 192,000(a).................. Madore et al. 1987.
Reservoirs/rivers (polluted)......... 6 100 19-300...................... 99(a)....................... Rose 1988.
Reservoir (pristine)................. 6 83 1-13........................ 2(a)........................ Rose 1988.
Impacted river....................... 11 100 200-11,200b................. 2,500(g).................... Rose et al. 1988ab.
Lake................................. 20 71 0-2200...................... 58(g)....................... Rose et al. 1988bb.
Stream............................... 19 74 0-24,000.................... 109(g)...................... Rose et al. 1988bb
Raw water............................ 85 87 7-48,400.................... 270(g) detectable........... LeChevallier et al.
1991c.
River (pristine)..................... 59 32 NR.......................... 29(g)....................... Rose et al. 1991.
River (polluted)..................... 38 74 0.1-4,400b.................. 66(g)....................... Rose et al. 1991.
Lake/reservoir (pristine)............ 34 53 NR.......................... 9.3(g)...................... Rose et al. 1991.
Lake/reservoir (polluted)............ 24 58 0.1-380b.................... 103(g)...................... Rose et al. 1991.
[[Page 19055]]
River (all samples).................. 36 97 15-45 (pristine) 1000-6,350 20 (pristine) 1,830 Hansen and Ongerth
(agricultural). (agricultural). 1991.
Protected drinking water supply 6 81 15-42....................... 24(g)....................... Hansen and Ongerth
(subset of all). 1991.
Pristine river, forestry area (subset 6 100 46-697...................... 162(g)...................... Hansen and Ongerth
of all). 1991.
River below rural community in 6 100 54-360...................... 107(g)...................... Hansen and Ongerth
forested area (subset of all). 1991.
River below dairy farming 6 100 330-6,350................... 1,072(g).................... Hansen and Ongerth
agricultural activities (subset of 1991.
all).
Reservoirs........................... 56 45 NR.......................... NR.......................... Consonery et al. 1992.
Streams.............................. 33 48 NR.......................... NR.......................... Consonery et al. 1992.
Rivers............................... 37 51 NR.......................... NR.......................... Consonery et al. 1992.
Site 1--River source (high turbidity) 10 100 82-7,190.................... 480......................... LeChevallier and Norton
1992.
Site 2--River source (moderate 10 70 42-510...................... 250......................... LeChevallier and Norton
turbidity). 1992.
Site 3--Reservoir source (low 10 70 77-870...................... 250......................... LeChevallier and Norton
turbidity). 1992.
Lakes................................ 179 6 0-2,240..................... 3.3 (median)................ Archer et al. 1995.
Streams.............................. 210 6 0-2,000..................... 7 (median).................. Archer et al. 1995.
Finished water....................... 262 13 0.29-57..................... 33 (detectable)............. LeChevallier and Norton
1995.
River/lake........................... 262 52 6.5-6,510................... 240 (detectable)............ LeChevallier and Norton
1995.
River/lake........................... 147 20 30-980...................... 200......................... LeChevallier et al.
1995.
River 1.............................. 15 73 0-2,230..................... 188 (a) all samples 43 (g) States et al. 1995.
detected.
River 2.............................. 15 80 0-1,470..................... 147 (a) all samples 61 (g) States et al. 1995.
detected.
Dairy farm stream.................... 13 77 0-1,110..................... 126 (a) all samples 55 (g) States et al. 1995.
detected.
Reservoir inlets..................... 60 5 0.7-24...................... 1.9(g) 1.6 (median)......... LeChevallier et al.
1997b.
Reservoir outlets.................... 60 12 1.2-107..................... 6.1(g) 60 (median).......... LeChevallier et al.
1997b.
River (polluted)..................... 72 40 20-280...................... 24(g)....................... LeChevallier et al.
1997a.
Source water......................... NR 24 1-5,390c.................... 740(a)c 71(g)c.............. Swertfeger et al. 1997.
First flush (storm event)............ 20 35 0-41,700.................... NR.......................... Stewart et al. 1997.
Grab (non-storm event)............... 21 19 0-650....................... NR.......................... Stewart et al. 1997.
River 1.............................. 24 63 0-1,470..................... 58(g)....................... States et al. 1997.
Stream by dairy farm................. 22 82 0-2,300..................... 42(g)....................... States et al. 1997.
River 2 (at plant intake)............ 24 63 0-2,200..................... 31(g)....................... States et al. 1997.
Reservoirs (unfiltered system)....... NR 37-52d 15-43 (maxima)d............. 0.8-1.4d.................... Okun et al. 1997.
Raw water intakes.................... 148 25 0.04-18..................... 0.3......................... Consonery et al. 1997.
Raw water intakes (rural)............ NR NR 40-400...................... NR.......................... Swiger et al. 1999.
Raw Water............................ 100 plants 77 0.5-117..................... 3(g)........................ McTigue, et al. 1998.
DE River, Winter..................... 18 NR NR.......................... 70 per 500L(g).............. Atherholt, et al. 1998.
DE River, Spring..................... 18 NR NR.......................... 100 per 500L(g)............. Atherholt, et al. 1998.
DE River, Summer..................... 18 NR NR.......................... 30 per 500L(g).............. Atherholt, et al. 1998.
DE River, Fall....................... 18 NR NR.......................... 20 per 500L(g).............. Atherholt, et al. 1998.
--------------------------------------------------------------------------------------------------------------------------------------------------------
a Rounded to nearest percent.
b As cited in Lisle and Rose 1995.
c Based on presumptive oocyst count
d Combined monitoring results for multiple sites in large urban water supply.
e As cited in States et al. 1997.
(a) = arithmetic average.
(g) = geometric average.
NR = not reported, NA = not applicable.
[[Page 19056]]
Table II.4.--Summary of U.S. GWUDI Monitoring Data for Cryptosporidium Oocysts
--------------------------------------------------------------------------------------------------------------------------------------------------------
Samples positive for
Sample source Number of samples (n) Cryptosporidium Range of positive Mean (oocysts/ 100L) a Reference
oocysts (percent) values (oocysts/100L)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Well.............................. 17 (6 wells).......... (1 sample)............ .085L NA Archer et al. 1995.
Ground water sources (all 199 sites\b\.......... 11\b\................. 0.002-0.45d NR Hancock et al. 1998.
categories).
Vertical wells (subcategory of 149 sites\b\.......... 5\b\.................. NR NR Hancock et al. 1998.
above ground water sources).
Springs (subcategory of above 35 sites\b\........... 20\b\................. NR NR Hancock et al. 1998.
ground water sources).
Infiltration galleries 4 sites\b\............ 50\b\................. NR NR Hancock et al. 1998.
(subcategory of above ground
water sources).
Horizontal wells (subcategory of 11 sites\b\........... 45\b\................ NR NR Hancock et al. 1998.
above ground water sources).
Ground water...................... 17.................... 41.2.................. NR NR Rosen et al., 1996.
Ground water...................... 18.................... 5.6................... .13 .13 Rose et al. 1991.
Springs........................... 7 (4 springs)......... 57\b\................ 0.25-10 4 Rose et al. 1991.
Wells............................. 5 sites............... 100................... 0.26-3 0.9 SAIC, 1997 c
Vertical well Lemont Well #4 6..................... 66.7.................. NR NR Lee, 1993.
(Center Co., PA, Aug. 1992).
--------------------------------------------------------------------------------------------------------------------------------------------------------
\a\ Geometric mean reported unless otherwise indicated.
\b\ Data are presented as the percentage of positive sites.
\c\ Data included are confirmed positive samples not reported in Hancock, 1998.
NA = not applicable.
NR = not reported.
The LeChevallier and Norton (1995) study collected the most samples
and repeat samples from the largest number of surface water plants
nationally. LeChevallier and Norton conducted the study to determine
the level of Cryptosporidium in surface water supplies and plant
effluent water. In total, surface water sources for 72 treatment plants
in 15 States and 2 Canadian provinces were sampled. Sixty-seven surface
water locations were examined. The generated data set covered a two-
year monitoring period (March, 1991 to January, 1993) which was
combined with a previous set of data (October, 1988 to June, 1990)
collected from most of the same set of systems to create a database
containing five samples (IFA) per site or more for 94 percent of the 67
systems sampled. Cryptosporidium oocysts were detected in 135 (51.5
percent) of the 262 raw water samples collected between March 1991 and
January 1993, while 87 percent of the 85 samples were positive during
the survey period from October, 1988 to June, 1990. The geometric mean
of detectable Cryptosporidium was 240 oocysts/100L, with a range from
6.5 to 6510 oocysts/100L. When the 1991-1993 results (n=262) were
combined with the previous results (n=85), Cryptosporidium was detected
in 60.2 percent of the samples. The authors hypothesize the origin of
the decrease in detections in the second round of sampling to be most
probably linked to fluctuating or declining source water concentrations
of Cryptosporidium oocysts from the first reporting period to the
second.
LeChevallier and Norton (1995) also detected Cryptosporidium
oocysts in 35 of 262 plant effluent samples (13.4 percent) analyzed
between 1991 and 1993. When detected, the oocyst levels averaged 3.3
oocysts/100 L (range = 0.29 to 57 oocysts/100 L). A summary of
occurrence data for all samples in filtered effluents for the years
1988 to 1993 showed that 32 of the water treatment plants (45 percent)
were consistently negative for Cryptosporidium; 24 plants (34 percent)
were positive once; and 15 plants (21 percent) were positive for
Cryptosporidium two or more times between 1988 to 1993. Forty-four of
the plants (62 percent) were positive for Giardia, Cryptosporidium, or
both at one time or another (LeChevallier and Norton 1995).
The oocyst recoveries and densities reported by LeChevallier and
Norton (1995) are comparable to the results of another survey of
treated, untreated, protected (pristine) and feces-contaminated
(polluted) water supplies (Rose et al. 1991). Six of thirty-six samples
(17 percent) taken from potable drinking water were positive for
Cryptosporidium, and concentrations in these waters ranged from .5 to
1.7 oocysts/100L. In addition, a total of 188 surface water samples
were analyzed from rivers, lakes, or springs in 17 States. The majority
of surface water samples were obtained from Arizona, California, and
Utah (126 samples in all), with others from eastern States (28
samples), northwestern States (14 samples), southern States (13
samples), midwestern States (6 samples), and Hawaii (1 sample).
Arithmetic average oocyst concentrations ranged from less than 1 to
4,400 oocysts/100 L, depending on the type of water analyzed.
Cryptosporidium oocysts were found in 55 percent of the surface water
samples at an average concentration of 43 oocysts/100 L.
The LeChevallier and Norton (1995) study collected the most samples
and repeat samples from the most surface water plants on a national
level. Therefore, the data from this study were analyzed by EPA (EPA,
1998n) to generate a distribution of source water occurrence, presented
in Table II.5.
Table II.5.--Baseline Expected National Source Water Cryptosporidium
Distributions
------------------------------------------------------------------------
Source water
Percentile concentration
(oocysts/100L)
------------------------------------------------------------------------
25.................................................... 103
50.................................................... 231
75.................................................... 516
90.................................................... 1064
95.................................................... 1641
Mean.............................................. 470
Standard Deviation................................ 841
------------------------------------------------------------------------
Although limited by the small number of samples per site (one to
sixteen samples; most sites were sampled five times), the mean
concentration at the 69
[[Page 19057]]
sites from the eastern and central U.S. seems to be represented by a
lognormal distribution.
In addition to the source water data, several studies have detected
Cryptosporidium oocysts in finished water. The results of these studies
have been compiled in Table II.6.
Table II.6.--Summary of U.S. Finished Water Monitoring Data for Cryptosporidium Oocysts
--------------------------------------------------------------------------------------------------------------------------------------------------------
Samples
Number of positive for Range of oocyst conc.
Sample source samples (n) Cryptosporidium (oocysts/100L) Mean (oocysts/100L) Reference
(percent)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Filtered water........................ 82 27 0.1-48.................... 1.5...................... LeChevallier et al.
1991a.
Finished water (unfiltered)........... 6 33 0.1-1.7................... 0.2...................... LeChevallier et al.
1992.
Finished water........................ 262 13 0.29-57................... 33 (detectable).......... LeChevallier and Norton
1995.
Finished water (clearwell)............ 14 14 NR........................ NR....................... Consonery et al. 1992.
Finished water (filter effluents)..... 118 26 NR........................ NR....................... Consonery et al. 1992.
Site 1--Filter effluent............... 10 70 1-4....................... NR....................... LeChevallier and Norton
1992.
Site 2--Filter effluent............... 10 10 0.5....................... NA....................... LeChevallier and Norton
1992.
Site 3--Filter effluent............... 10 10 2......................... NA....................... LeChevallier and Norton
1992.
Finished water........................ 1,237 7 NR........................ NR....................... Rosen et al. 1996.
Filtered (non-storm event)............ 87 10 0-420..................... NR....................... Stewart et al. 1997a.
Finished water........................ 24 **8 0-0.6..................... 0.5 (g).................. States et al. 1997.
***13
Finished water........................ 155 2.5 0.02-0.8.................. 0.2...................... Consonery et al. 1997.
Finished water........................ 100 15 0.04-0.08................. 0.08 (g)................. McTigue, et al. 1998.
--------------------------------------------------------------------------------------------------------------------------------------------------------
*Plants
**Confirmed
***Presumed
These studies show that despite some treatment in place,
Cryptosporidium may still pass through the treatment plant and into
finished water.
In general, oocysts are detected more frequently and in higher
concentrations in rivers and streams than in lakes and reservoirs
(LeChevallier et al., 1991b; Rose et al., 1988a,b). Madore et al.
(1987) found high concentrations of oocysts in a river affected by
agricultural runoff (5800 oocysts/L). Such concentrations are
especially significant if the contaminant removal process (e.g.,
sedimentation, filtration) of the treatment plant is not operating
effectively. Oocysts may pass through to the finished water, as
LeChevallier and Norton (1995) and several other researchers also
found, and infect drinking water consumers.
E. Filter Backwash and Other Process Streams: Occurrence and Impact
Studies
Pathogenic microorganisms are removed during the sedimentation and/
or filtration processes in a water treatment plant. Recycle streams
generated during treatment, such as spent filter backwash water,
sedimentation basin sludge, or thickener supernatant are often returned
to the treatment train. These recycle streams, therefore, may contain
high concentrations of pathogens, including chlorine-resistant
Cryptosporidium oocysts. Recycle can degrade the treatment process,
especially when entering the treatment train after the rapid mix stage,
by causing a chemical imbalance, hydraulic surge and potentially
overwhelming the plant's filtration capacity with a large concentration
of pathogens. High oocyst concentrations found in recycle waters can
increase the risk of pathogens passing through the treatment plant into
finished water.
AWWA has compiled issue papers on each of the following recycle
streams: Spent filter backwash water, sedimentation basin solids,
combined thickener supernatant, ion-exchange regenerate, membrane
concentrate, lagoon decant, mechanical dewatering device concentrate,
monofill leachate, sludge drying bed leachate, and small-volume streams
(e.g., floor, roof, lab drains) (Environmental Engineering &
Technology, 1999). In addition, EPA compiled existing occurrence data
on Cryptosporidium in recycle streams. Through these efforts,
Cryptosporidium occurrence data has been found for three types of
recycle streams: Spent filter backwash water, sedimentation basin
solids, and thickener supernatant.
Nine studies have reported the occurrence of Cryptosporidium for
these process streams. Each study's scope and results are presented in
Table II.7, and brief narratives on each major study follow the table.
Note that the results of the studies, if not presented in the published
report as oocysts/100L, have been converted into oocysts/100L.
Table II.7.--Cryptosporidium Occurrence in Filter Backwash and Other Recycle Streams
--------------------------------------------------------------------------------------------------------------------------------------------------------
Number of treatment
Name/location of study Number of samples (n) Type of sample Cyst/oocyst concentration plants sampled Reference
--------------------------------------------------------------------------------------------------------------------------------------------------------
Drinking water treatment 2.................... backflush waters from sample 1: 26,000 oocysts/ 2................... Rose et al. 1986.
facilities. rapid sand filters. gal (calc. as 686,900
oocysts/100L).
sample 2: 92,000 oocysts/
gal (calc as 2,430,600
oocysts/100L)
[[Page 19058]]
Thames, U.K.,..................... not reported......... backwash water from Over 1,000,000 oocysts/ 1................... Colbourne 1989.
rapid sand filter. 100L in backwash water on
2/19/89.
100,000 oocysts/100L in
supernatant from
settlement tanks during
the next few days
Potable water supplies in 17 not reported......... filter backwash from 217 oocysts/ 100 L not reported........ Rose et al. 1991.
States. rapid sand filters (geometric mean).
(10 to 40 L sample
vol.).
Name/location not reported........ not reported......... raw water............ 7 to 108 oocysts/100L..... not reported........ LeChevallier et al.
initial backwash detected at levels 57 to not reported........ 1991c.
water. 61 times higher than in
the raw water.
Bangor Water Treatment Plant (PA). Round 1: 1 (8-hour raw water............ 902 oocysts/100L. 141 oocysts/100L. 1 Cornwell and Lee
composite). filter backwash...... 1993.
supernatant recycle 6
oocysts/100L.
Round 2: 1 (8-hour composite)..... raw water............ 140 oocysts/100L..... 850 oocysts/100L. 750 oocysts/100L. 1 Cornwell and Lee
filter backwash...... 1993.
supernatant recycle..
Moshannon Valley Water Treatment Round 1: 1 (8-hour raw water............ 16,613 oocysts/100L. 82 oocysts/100L. 2,642 oocysts/100L.
Plant. composite). spent backwash....... 1 Cornwell and Lee
supernatant recycle.. 1993.
sludge 13 oocysts/
100L.
Round 2: 1 (8-hour raw water............ 20 oocysts/100L........... 420 oocysts/100L. 1 Cornwell and Lee
composite). supernatant recycle.. 1993.
Plant ``C''....................... 11 samples using 39 samples using backwash water from rapid continuous flow: cartridge filters:
continuous flow cartridge filters. sand filters; samples range 1 to 69 ranges 0.8 to 252/
centrifugation;. collected from oocysts/100 L; 8 of 100 L; 33 of 39
sedimentation basins 11 samples positive. samples positive 1
during sedimentation Karanis et al.
phase of backwash water 1996.
at depths of 1, 2, 3, and
3.3 m.
Pittsburgh Drinking Water 24 (two years of filter backwash...... 328 oocysts/ 100 L non-detect-13,158 States et al. 1997.
Treatment Plant. monthly samples). (geometric mean); (38 oocysts/100L. 1
percent occurrence rate).
``Plant Number 3''................ not reported......... raw water............ 140 oocysts/100L.......... 850 oocysts/100L. not reported
spent backwash....... Cornwell 1997.
``Plant C'' (see Karanis, et al., 12................... raw water............ avg. 23.2 oocysts/100L avg. 22.1 oocysts/ 1 Karanis et al
1996). 50................... backwash water from (max. 109 oocysts/100L) 100L (max. 257 1998.
rapid sand filters. in 8 of 12 samples. oocysts/100L) in 41
of 50 samples
``Plant A''....................... 1.................... rapid sand filter 150 oocysts/100L..........
(sample taken 10
min. after start of
backwashing).
--------------------------------------------------------------------------------------------------------------------------------------------------------
The occurrence data available and reported are primarily for raw
and recycle stream water. If filter backwash enters the treatment train
as a slug load and disrupts the treatment process, it is possible its
effects would not be readily seen in the finished water until several
minutes or hours after returning the filter to service. In addition,
the poor recovery efficiencies of the IFA Cryptosporidium detection
method complicate measurements in dilute finished effluent waters.
As shown in Table II.7, the concentrations of oocysts in backwash
water and other recycle streams are greater than the concentrations
generally found in raw water. For example, four studies (Cornwell and
Lee, 1993; States et al., 1997; Rose et al., 1986; and Colbourne, 1989)
have reported Cryptosporidium oocyst concentrations in filter backwash
water exceeding 10,000 oocysts/100L. Such concentrations illustrate
that the treatment plant has been removing oocysts from the influent
water during the sedimentation and/or filtration processes. As
expected, the oocysts have concentrated on the filters and/or in the
sedimentation basin sludge. Therefore, the recycling of such process
streams (e.g., filter backwash, thickener supernatant, sedimentation
basin
[[Page 19059]]
sludge) re-introduces high concentrations of oocysts to the drinking
water treatment train.
Recycle can potentially return a significant number of oocysts to
the treatment plant in a short amount of time, particularly if the
recycle is returned to the treatment process without prior treatment,
equalization, or some other type of hydraulic detention. In addition,
Di Giovanni, et al. (1999) presented data indicating that viable
oocysts have been detected in filter backwash samples using a cell
culture/polymerase chain reaction (PCR) method. Cell culture is a test
of the viability/infectivity of the oocysts, while PCR identified the
cells infected by C. parvum. Although recovery by IFA was poor (6 to 8
percent for backwash samples), 9 filter backwash recycle samples were
found to contain viable and infectious oocysts, and the infectious
agent was determined to be more than 98 percent similar in structure to
C. parvum. Should filter backwash recycle disrupt normal treatment
operations or should treatment not function efficiently due to other
deficiencies, high concentrations of potentially viable, infectious
oocysts may pass through the plant into finished drinking water. The
recycle stream occurrence studies presented in Table II.7 are described
in further detail in the following sections.
Thames, U.K. Water Utilities Experience with Cryptosporidium, Colbourne
(1989)
In response to a cryptosporidiosis outbreak reported in February of
1989, Thames Water undertook an investigation of pathogen
concentrations within the Farmoor conventional treatment plant's
treatment train, finished and raw waters. The investigation occurred
over a two month period, from February to April 1989 and included
sampling of settled filter backwash, the supernatant from spent filter
backwash, raw water, and water sampled at the end of various Thames
distribution points.
On February 19, 1989 at the start of the outbreak investigation, a
concentration of approximately 1,000,000 oocysts/100L was detected in
the filter backwash water. During the first few days of the following
investigation, the supernatant of the settled backwash water contained
approximately 100,000 oocysts/100L. At the peak of the outbreak, thirty
percent of Thames' distribution system samples were positive for
oocysts, and ranged in concentration from 0.2 to 7700 oocysts/100L. Raw
reservoir water contained oocyst concentrations ranging from .2 to 1400
oocysts/100L. After washing the filters twice in 24 hours, no oocysts
were found in the settled backwash waters. Thames, U.K. Water Utilities
determined that a storm causing intense precipitation and runoff
resulted in elevated levels of oocysts in the source water which led to
the high concentrations of oocysts entering the plant and subsequently
deposited on the filters and recycled as filter backwash.
Survey of Potable Water Supplies for Cryptosporidium and Giardia, Rose,
et al., 1991
In this survey, Rose, et al., collected 257 samples from 17 States
from 1985 to 1988. The samples were collected on cartridge filters and
analyzed using variations of the IFA method. The reported percent
recovery for the method was 29 to 58 percent. Filter backwash samples
were a subset of the 257, 10 to 40 L samples were collected from rapid
sand filters.
Rose, et al. reported the geometric mean of the backwash samples at
217 Cryptosporidium oocysts/100L. This was the highest reported average
Cryptosporidium concentration of any of the water types tested, which
included polluted and pristine surface and ground water sources,
drinking water sources in addition to filter backwash recycle water.
Giardia and Cryptosporidium in Water Supplies, LeChevallier, et al.
(1991c)
LeChevallier et al. conducted a study to determine ``whether
compliance with the SWTR would ensure control of Giardia in potable
water supplies.'' Raw water and plant effluent samples were collected
from 66 surface water treatment plants in 14 States and one Canadian
province, although only selected sites were tested for Cryptosporidium
oocysts in filter backwash and settled backwash water.
In the analysis of pathogen concentrations in the raw water and
filter backwash water of the water treatment process, LeChevallier et
al. (1991c) found very high oocyst levels in backwash water of
utilities that had low raw water parasite concentrations. The pathogens
were detected using a combined IFA method that the authors developed.
Cryptosporidium levels in the initial backwash water were 57 to 61
times higher than in the raw water supplies. Raw water samples were
found to contain from 7 to 108 oocysts/100L. LeChevallier et al.
(1991c) also noted that when Cryptosporidium were detected in plant
effluent samples (12 of 13 times), the organisms were also observed in
the backwash samples. The study concluded that the consistency of these
results shows that accumulation of parasites in the treatment filters
(and subsequent release in the filter backwash recycle water) could be
related to subsequent passage through treatment barriers.
Recycle Stream Effects on Water Treatment, Cornwell and Lee (1993,
1994)
The results described in Cornwell and Lee's 1993 American Water
Works Association Research Foundation Report and 1994 Journal of the
American Water Works Association article on the Bangor and Moshannon
Valley, PA water treatment plants are consistent with the results of
States et al. (1997). In total, Cornwell and Lee investigated eight
water treatment plants, examining treatment efficiencies including
several recycle streams and their impacts, and reporting a range of
pathogen and other water quality data. All of the pathogen testing was
conducted using the EPA IFA method refined by LeChevallier, et al.
(1991c).
Cornwell and Lee (1993) conducted two rounds of sampling at both
the Bangor and Moshannon plants, sampling the different recycle and
treatment streams as eight-hour composites. They detected
Cryptosporidium concentrations of over 16,500 Cryptosporidium oocysts/
100L in the backwash water at an adsorption clarifier plant (Moshannon
Valley) and over 850 Cryptosporidium oocysts/100L in backwash water
from a direct filtration plant (Bangor). The parasite levels in the
backwash samples were significantly higher than concentrations found in
the raw source water, which contained Cryptosporidium oocyst
concentrations of 13-20 oocysts/100L at the Moshannon Valley plant and
6-140 oocysts/100L at the Bangor plant.
In addition, Cornwell and Lee determined oocyst concentrations for
two other recycle streams, combined thickener supernatant and
sedimentation basin solids. The supernatant pathogen concentrations
were reported at 141 Cryptosporidium oocysts/100L at the Bangor plant,
and levels were reported at 82 to 420 oocysts/100L for the Moshannon
plant in Rounds 1 and 2 of sampling, respectively. The sedimentation
basin sludge was reported at 2,642 Cryptosporidium oocysts/100L in the
clarifier sludge from the Moshannon Valley plant.
[[Page 19060]]
Giardia and Cryptosporidium in Backwash Water from Rapid Sand Filters
Used for Drinking Water, Karanis et al. (1996) and Distribution and
Removal of Giardia and Cryptosporidium in Water Supplies in Germany
Karanis, et al. (1998)
Karanis et al. (1996 and 1998) conducted a four-year research study
(samples collected from July, 1993-December, 1995) on the efficiency of
Cryptosporidium removal by six different surface water treatment plants
from Germany, all of which treat by conventional filtration. The method
used was an IFA method dubbed the ``EPA method'', developed by
Jakubowski and Ericksen, 1979.
Karanis et al. (1996) detected Cryptosporidium in 82 percent of the
samples of backwash water from rapid sand filters of a water treatment
plant (``Plant C'') supplied by small rivers. Eight out of 12 raw water
samples tested were positive for Cryptosporidium (range of 0.8 to 109
oocysts/100L). Backwash water samples collected by continuous flow
centrifugation were positive for Cryptosporidium in 8 of 11 samples
(range of 1 to 69/100L). Of 39 samples collected using cartridge
filters, 33 were positive for Cryptosporidium (range of 0.8 to 252/
100L). The authors called attention to the high detection rate of
Cryptosporidium in the backwash waters (82 percent) of Plant C and to
the fact that the supernatant following sedimentation was not free from
cysts and oocysts (Karanis et al. 1996).
In the 1998 publication, Karanis et al. compiled the data from the
1996 study with more backwash occurrence data collected from another
treatment plant (``Plant A''). The filter backwash of Plant A was
sampled 10 minutes after the start of backwashing, and the backwash
water was found to contain 150 Cryptosporidium oocysts/100L.
Protozoa in River Water: Sources, Occurrence, and Treatment, States, et
al. (1997)
Over a two year period (July, 1994-June, 1996), States et al.
sampled monthly for Cryptosporidium in the raw, settled, filtered and
filter backwash water at the Pittsburgh Drinking Water Treatment Plant,
in order to gauge the efficiency of pathogen removal at the plant.
States et al. identified several sources contributing oocysts to the
influent water, including sewage plant effluent, combined sewer
overflows, dairy farm streams, and recycling of backwash water. All
pathogen sampling was conducted with the IFA method.
Cryptosporidium occurred in the raw Allegheny river water supplying
the plant with a geometric mean of 31 oocysts/100L in 63 percent of
samples collected, and ranged from non-detect to 2,333 oocysts/100L
(see Table II.3 for source water information). Of the filter backwash
samples, a geometric mean of 328 oocysts/100L was found at an
occurrence rate of 38 percent of samples, with a range from non-detect
to 13,158 oocysts/100L. The fact that the mean concentration of
Cryptosporidium oocysts in backwash water can be substantially higher
than the oocyst concentration in untreated river water suggests that
recycling untreated filter backwash water can be a significant source
of this parasite to water within the treatment process.
F. Summary and Conclusions
Cryptosporidiosis is a disease without a therapeutic cure, and its
causative agent, Cryptosporidium, is resistant to chlorine
disinfection. Cryptosporidium has been known to cause severe illness,
especially in immunocompromised individuals, and can be fatal. Several
waterborne cryptosporidiosis outbreaks have been reported, and it is
likely that others have occurred but have gone unreported.
Cryptosporidium has been detected in a wide range of source waters,
documented in over 30 studies from the literature, and it has been
found at levels of concern in filter backwash water and other recycle
streams.
One of the key regulations EPA has developed and implemented to
counter pathogens in drinking water is the SWTR (54 FR 27486, June 19,
1989). The SWTR requires that surface water systems have sufficient
treatment to reduce the source water concentration of Giardia and
viruses by at least 99.9 percent (3 log) and 99.99 percent (4 log),
respectively. A shortcoming of the SWTR, however, is that the rule does
not specifically control for Cryptosporidium. The first report of a
recognized waterborne outbreak caused by Cryptosporidium was published
during the development of the SWTR (D'Antonio et al. 1985).
In 1998, the Agency finalized the IESWTR that enhances the
microbial pathogen protection provided by the SWTR for systems serving
10,000 or more persons. The IESWTR includes an MCLG of zero for
Cryptosporidium and requires a minimum 2-log (99 percent) removal of
Cryptosporidium, linked to enhanced combined filter effluent and
individual filter turbidity control provisions.
Several provisions of today's proposed rule, the LT1FBR, are
designed to address the concerns covered by the IESWTR, improving
control of Cryptosporidium and other microbial contaminants, for the
portion of the public served by small PWSs (i.e., serving less than
10,000 persons). The LT1FBR also addresses the concern that for all
PWSs that practice recycling, Cryptosporidium (and other emerging
pathogens resistant to standard disinfection practice) are reintroduced
to the treatment process of PWSs by the recycle of spent filter
backwash water, solids treatment residuals, and other process streams.
Insufficient treatment practices have been cited as the cause of
several reported waterborne disease outbreaks (Rose, 1997). Rose (1997)
also found that a reduction in turbidity is indicative of a more
efficient filtration process. Therefore, the turbidity and filter
monitoring requirements of today's proposed LT1FBR will ensure that the
removal process necessary to protect the public from cryptosporidiosis
is operating properly, and the recycle stream provisions will ensure
that the treatment process is not disrupted or operating inefficiently.
The LT1FBR requirements that address the potential for Cryptosporidium
to enter the finished drinking water supply will be described in more
detail in the following sections.
III. Baseline Information-Systems Potentially Affected By Today's
Proposed Rule
EPA utilized the 1997 state-verified version of the Safe Drinking
Water Information System (SDWIS) to develop the total universe of
systems which utilize surface water or groundwater under the direct
influence (GWUDI) as sources. This universe consists of 11,593 systems
serving fewer than 10,000 persons, and 2,096 systems serving 10,000 or
more persons. Given this initial baseline, the Agency developed
estimates of the number of systems which would be affected by
components of today's proposed rule by utilizing three primary sources:
Safe Drinking Water Information Systems; Community Water Supply Survey;
and Water: Stats. A brief overview of each of the data sources is
described in the following paragraphs.
Safe Drinking Water Information System (SDWIS)
SDWIS contains information about PWSs including violations of EPA's
regulations for safe drinking water. Pertinent information in this
database includes system name and ID, population served, geographic
location,
[[Page 19061]]
type of source water, and type of treatment (if provided).
Community Water System Survey (CWSS)
EPA conducted the 1995 CWSS to obtain data to support its
development and evaluation of drinking water regulations. The survey
consisted of a stratified random sample of 3,700 water systems
nationwide (surface water and groundwater). The survey asked 24
operational and 13 financial questions.
Water:/Stats (WaterStats)
WaterStats is an in-depth database of water utility information
compiled by the American Water Works Association. The database consists
of 898 utilities of all sizes and provides a variety of data including
treatment information.
Information regarding estimates of the number of systems which may
potentially be affected by specific components of today's proposed rule
can be found in the discussion of each proposed rule component in
Section IV.
IV. Discussion of Proposed LT1FBR Requirements
A. Enhanced Filtration Requirements
As discussed earlier in this preamble, one of the key objectives of
today's proposed rule is ensuring that an adequate level of public
health protection is maintained in order to minimize the risk
associated with Cryptosporidium. While the current SWTR provides
protection from viruses and Giardia, it does not specifically address
Cryptosporidium, which has been linked to outbreaks resulting in over
420,000 cases of gastrointestinal illness in the 1990s (403,000
associated with the Milwaukee outbreak). Because of Cryptosporidium's
resistance to disinfection practices currently in place at small
systems throughout the country, the Agency believes enhanced filtration
requirements are necessary to improve control of this microbial
pathogen.
In the IESWTR, the Agency utilized an approach consisting of three
major components to address Cryptosporidium at plants serving
populations of 10,000 or more. The first component required systems to
achieve a 2 log removal of Cryptosporidium. The second component
consisted of strengthened turbidity requirements for combined filter
effluent. The third component required individual filter turbidity
monitoring.
In today's proposed rule addressing systems serving fewer than
10,000 persons, the Agency is utilizing the same framework. Where
appropriate, EPA has evaluated additional options in an effort to
alleviate burden on small systems while still maintaining a comparable
level of public health protection.
The following sections describe the overview and purpose of each of
the rule components, relevant data utilized during development, the
requirements of today's proposed rule (including consideration of
additional options where appropriate), and a request for comment
regarding each component.
1. Two Log Cryptosporidium Removal Requirement
a. Two Log Removal
i. Overview and Purpose
The 1998 IESWTR (63 FR 69477, December 16, 1998) establishes an
MCLG of zero for Cryptosporidium in order to adequately protect public
health. In conjunction with the MCLG, the IESWTR also established a
treatment technique requiring 2 log Cryptosporidium removal for all
surface water and GWUDI systems which filter and serve populations of
10,000 or more people, because it was not economically and
technologically feasible to accurately ascertain the level of
Cryptosporidium using current analytical methods. The Agency believes
it is appropriate and necessary to extend this treatment technique of 2
log Cryptosporidium removal requirement to systems serving fewer than
10,000 people.
ii. Data
As detailed later in this section, EPA believes that the data and
principles supporting requirements established for systems serving
populations of 10,000 or more are also applicable to systems serving
populations fewer than 10,000. The following section provides
information and data regarding: (1) the estimated number of small
systems subject to the proposed 2 log Cryptosporidium removal
requirement; and (2) Cryptosporidium removal using various filtration
technologies.
Estimate of the Number of Systems Subject to 2 log Cryptosporidium
Removal Requirement
Using the baseline described in Section III of today's proposed
rule, the Agency applied percentages of surface water and GWUDI systems
which filter (taken from the 1995 CWSS) in order to develop an estimate
of the number of systems which filter and serve fewer than 10,000
persons. This resulted in an estimated 9,133 surface water and GWUDI
systems that filter which may be subject to the proposed removal
requirement. Table IV.1 provides this estimate broken down by system
size and type.
Table IV.1.--Estimate of Systems Subject to 2 Log Cryptosporidium Removal Requirement a
----------------------------------------------------------------------------------------------------------------
Population served
System type -----------------------------------------------------------------------------
100 101-500 501-1K b 1K-3.3K b 3.3K-10K b Total #Sys.
----------------------------------------------------------------------------------------------------------------
Community......................... 888 1453 950 2022 1591 6903
Non Community..................... 1099 374 78 64 35 1649
NTNC.............................. 214 204 82 64 17 581
-----------------------------------------------------------------------------
Total....................... 2201 2031 1110 2150 1643 b 9134b
----------------------------------------------------------------------------------------------------------------
a Numbers may not add due to rounding
b K = thousands
Cryptosporidium Removal Using Conventional and Direct Filtration
During development of the LT1FBR, the Agency reviewed the results
of several studies that demonstrated the ability of conventional and
direct filtration systems to achieve 2 log removal of Cryptosporidium
at well operated plants achieving low turbidity levels. Table IV.2
provides key information from these studies. A brief description of
each study follows the table.
[[Page 19062]]
Table IV.2.--Conventional and Direct Filtration Removal Studies
----------------------------------------------------------------------------------------------------------------
Type of treatment Log removal Experimental design Researcher
----------------------------------------------------------------------------------------------------------------
Conventional..................... Cryptosporidium 4.2-5.2.. Pilot plants............ Patania et al. 1995
Giardia 4.1-5.1.......... Pilot plants............ Patania et al. 1995
Cryptosporidium 1.9-4.0.. Pilot-scale plants...... Nieminski/Ongerth 1995
Giardia 2.2-3.9.......... Pilot-scale plants...... Nieminski/Ongerth 1995
Cryptosporidium 1.9-2.8.. Full-scale plants....... Nieminski/Ongerth 1995
Giardia 2.8-3.7.......... Full-scale plants....... Nieminski/Ongerth 1995
Cryptosporidium 2.3-2.5.. Full-scale plants....... LeChevallier and Norton
1992
Giardia 2.2-2.8.......... Full-scale plants....... ........................
Cryptosporidium 2-3...... Pilot plants............ LeChevallier and Norton
1992
Giardia and Crypto 1.5-2. Full-scale plant Foundation for Water
(operation considered Research, Britain 1994
not optimized).
Cryptosporidium 4.1-5.2.. Pilot Plant (optimal Kelley et al. 1995
treatment).
Cryptosporidum .2-1.7.... Pilot Plant (suboptimal Dugan et al. 1999
treatment). Dugan et al. 1999
Direct filtration................ Cryptosporidium 2.7-3.1.. Pilot plants............ Ongerth/Pecaroro 1995
Giardia 3.1-3.5.......... Pilot plants............ Ongerth/Pecaroro 1995
Cryptosporidium 2.7-5.9.. Pilot plants............ Patania et al. 1995
Giardia 3.4-5.0.......... Pilot plants............ Patania et al. 1995
Cryptosporidium 1.3-3.8.. Pilot plants............ Nieminski/Ongerth 1995
Giardia 2.9-4.0.......... Pilot plants............ Nieminski/Ongerth 1995
Cryptosporidium 2-3...... Pilot plants............ West et al. 1994
Rapid Granular Filtration (alone) Cryptosporidium 2.3-4.9.. Pilot plant............. Swertfeger et al., 1998
Giardia 2.7-5.4.......... ........................ ........................
----------------------------------------------------------------------------------------------------------------
Patania, Nancy L, et al. 1995
This study consisted of four pilot studies which evaluated
treatment variables for their impact on Cryptosporidium and Giardia
removal efficiencies. Raw water turbidities in the study ranged between
0.2 and 13 NTU. When treatment conditions were optimized for turbidity
and particle removal at four different sites, Cryptosporidium removal
ranged from 2.7 to 5.9 log and Giardia removal ranged from 3.4 to 5.1
log during stable filter operation. The median turbidity removal was
1.4 log, whereas the median particle removal was 2 log. Median oocyst
and cyst removal was 4.2 log. A filter effluent turbidity of 0.1 NTU or
less resulted in the most effective cyst removal, up to 1 log greater
than when filter effluent turbidities were greater than 0.1 NTU (within
the 0.1 to 0.3 NTU range). Cryptosporidium removal rates of less than
2.0 log occurred at the end of the filtration cycle.
Nieminski, Eva C. and Ongerth, Jerry E. 1995
This 2-year study evaluated Giardia and Cryptosporidium cyst
removal through direct and conventional filtration. The source water of
the full scale plant had turbidities typically between 2.5 and 11 NTU
with a maximum of 28 NTU. The source water of the pilot plant typically
had turbidities of 4 NTU with a maximum of 23 NTU. For the pilot plant
achieving filtered water turbidities between 0.1-0.2 NTU,
Cryptosporidium removals averaged 3.0 log for conventional treatment
and 3.0 log for direct filtration, while the respective Giardia
removals averaged 3.4 log and 3.3 log. For the full scale plant
achieving similar filtered water turbidities, Cryptosporidium removal
averaged 2.25 log for conventional treatment and 2.8 log for direct
filtration, while the respective Giardia removals averaged 3.3 log for
conventional treatment and 3.9 log for direct filtration. Differences
in performance between direct filtration and conventional treatment by
the full scale plant were attributed to differences in source water
quality during the filter runs.
Ongerth, Jerry E. and Pecaroro, J.P. 1995
A 1 gallon per minute (gpm) pilot scale water filtration plant was
used to measure removal efficiencies of Cryptosporidium and Giardia
using very low turbidity source waters (0.35 to 0.58 NTU). With optimal
coagulation, 3 log removal for both pathogens were obtained. In one
test run, where coagulation was intentionally sub-optimal, the removals
were only 1.5 log for Cryptosporidium and 1.3 log for Giardia. This
demonstrates the importance of proper coagulation for cyst removal even
though the effluent turbidity was less than 0.5 NTU.
LeChevallier, Mark W. and Norton, William D. 1992
The purpose of this study was to evaluate the relationships among
Giardia, Cryptosporidium, turbidity, and particle counts in raw water
and filtered water effluent samples at three different systems. Source
water turbidities ranged from less than 1 to 120 NTU. Removals of
Giardia and Cryptosporidium (2.2 to 2.8 log) were slightly less than
those reported by other researchers, possibly because full scale plants
were studied under less ideal conditions than the pilot plants. The
participating treatment plants operated within varying stages of
treatment optimization. The median removal achieved was 2.5 log for
Cryptosporidium and Giardia.
LeChevallier, Mark W.; Norton, William D.; and Lee, Raymond G. 1991b
This study evaluated removal efficiencies for Giardia and
Cryptosporidium in 66 surface water treatment plants in 14 States and 1
Canadian province. Most of the utilities achieved between 2 and 2.5 log
removals for both Giardia and Cryptosporidium. When no oocysts were
detected in the finished water, occurrence levels were assumed at the
detection limit for calculating removal efficiencies.
Foundation for Water Research 1994
This study evaluated Cryptosporidium removal efficiencies for
several treatment processes (including conventional filtration) using a
pilot plant and bench-scale testing. Raw water turbidity ranged from 1
to 30 NTU. Cryptosporidium oocyst removal was between 2 and 3 log using
conventional filtration. Investigators
[[Page 19063]]
concluded that any measure which reduced filter effluent turbidity
should reduce risk from Cryptosporidium, and also showed the importance
of selecting proper coagulants, dosages, and treatment pH. In addition
to turbidity, increased color and dissolved metal ion coagulant
concentration in the effluent are indicators of reduced efficiency of
coagulation/flocculation and possible reduced oocysts removal
efficiency.
Kelley, M.B. et al. 1995
This study evaluated two U.S. Army installation drinking water
treatment systems for the removal of Giardia and Cryptosporidium.
Protozoa removal was between 1.5 and 2 log. The authors speculated that
this low Cryptosporidium removal efficiency occurred because the
coagulation process was not optimized, although the finished water
turbidity was less than 0.5 NTU.
West, Thomas; et al. 1994
This study evaluated the removal efficiency of Cryptosporidium
through direct filtration using anthracite mono-media at filtration
rates of 6 and 14 gpm/sq.ft. Raw water turbidity ranged from 0.3 to 0.7
NTU. Removal efficiencies for Cryptosporidium at both filtration rates
were 2 log during filter ripening (despite turbidity exceeding 0.2
NTU), and 2 to 3 log for the stable filter run. Log removal declined
significantly during particle breakthrough. When effluent turbidity was
less than 0.1 NTU, removal typically exceeded 2 log. Log removals of
Cryptosporidium generally exceeded that for particle removal.
Swertfeger et al., 1998
The Cincinnati Water Works conducted a 13 month pilot study to
determine the optimum filtration media and depth of the media to
replace media at its surface water treatment plant. The study
investigated cyst and oocyst removal through filtration alone
(excluding chemical addition, mixing, or sedimentation) and examined
sand media, dual media, and deep dual media. Cyst and oocyst removal by
each of the media designs was > 2.5 log by filtration alone.
Dugan et al., 1999
EPA conducted pilot scale experiments to assess the ability of
conventional treatment to control Cryptosporidium oocysts under steady
state conditions. The work was performed with a pilot plant designed to
minimize flow rates and the number of oocysts required for spiking.
With proper coagulation control, the conventional treatment process
achieved at least 2 log removal of Cryptosporidium. In all cases where
2 log removal was not achieved, the plant also did not comply with the
IESWTR filter effluent turbidity requirements.
All of the studies described above indicate that rapid granular
filtration, when operated under appropriate coagulation conditions and
optimized to achieve a filtered water turbidity level of less than 0.3
NTU, should achieve at least 2 log of Cryptosporidium removal. Removal
rates vary widely, up to almost 6 log, depending upon water matrix
conditions, filtered water turbidity effluent levels, and where and
when removal efficiencies are measured within the filtration cycle. The
highest log pathogen removal rates occurred in those pilot plants and
systems which achieved very low finished water turbidities (less than
0.1 NTU). Other key points related to the studies include:
As turbidity performance improves for treatment of a
particular water, there tends to be greater removal of Cryptosporidium.
Pilot plant study data in particular indicate high
likelihood of achieving at least 2 log removal when plant operation is
optimized to achieve low turbidity levels. Moreover, pilot studies
represented in Table IV.2.a tend to be for low-turbidity waters, which
are considered to be the most difficult to treat regarding particulate
removal and associated protozoan removal.
Because high removal rates were demonstrated in pilot
studies using lower-turbidity source waters, it is likely that similar
or higher removal rates can be achieved for higher-turbidity source
waters.
Determining Cryptosporidium removal in full-scale plants
can be difficult due to the fact that data includes many non-detects in
the finished water. In these cases, finished water concentration levels
are assigned at the detection limit and are likely to result in over-
estimation of oocysts in the finished water. This tends to under-
estimate removal levels.
Another factor that contributes to differences among the
data is that some of the full-scale plant data comes from plants that
are not optimized, but meet existing SWTR requirements. In such cases,
oocyst removal may be less than 2 log. In those studies that indicate
that full-scale plants are achieving greater than 2 log removal
(LeChevallier studies in particular), the following characteristics
pertain:
--Substantial numbers of filtered water measurements resulted in oocyst
detections;
--Source water turbidity tended to be relatively high compared to some
of the other studies; and
--A significant percentage of these systems were also achieving low
filtered water turbidities, substantially less than 0.5 NTU.
Removal of Cryptosporidium can vary significantly in the
course of the filtration cycle (i.e., at the start-up and end of filter
operations versus the stable period of operation).
Cryptosporidium Removal Using Slow Sand and Diatomaceous Earth
Filtration
During development of the IESWTR, the Agency also evaluated several
studies which demonstrated that slow sand and diatomaceous earth
filtration were capable of achieving at least 2 log removal of
Cryptosporidium. Table IV.3 provides key information from these
studies. A brief description of each study follows the table.
Table IV.3.--Slow Sand and Diatomaceous Earth Filtration Removal Studies
----------------------------------------------------------------------------------------------------------------
Type of treatment Log removal Experimental design Researcher
----------------------------------------------------------------------------------------------------------------
Slow-sand filtration............. Giardia & Cryptosporidium Pilot plant at 4.5 to Shuler and Ghosh 1991.
> 3. 16.5 deg.C.. imms et. al. 1995.
Cryptosporidium 4.5...... Full-scale plant........
Diatomaceous earth filtration.... Giardia & Cryptosporidium Pilot plant,............ Shuler et. al. 1990.
> 3. Bench scale............. Ongerth & Hutton, 1997.
Cryptosporidium 3.3-6.68.
----------------------------------------------------------------------------------------------------------------
Shuler and Ghosh 1991
This pilot study was conducted to evaluate the ability of slow sand
filters to remove Giardia, Cryptosporidium, coliforms, and turbidity.
The pilot study was conducted at Pennsylvania State University using a
raw water source with a turbidity ranging from 0.2-0.4 NTU. Influent
concentration of
[[Page 19064]]
Cryptosporidium oocysts during the pilot study ranged from 1,300 to
13,000 oocysts/gallon. Oocyst removal was shown to be greater than 4
log.
Timms et al 1995
This pilot study was conducted to evaluate the efficiency of slow
sand filters at removing Cryptosporidium. A pilot plant was constructed
of 1.13 m\2\ in area and 0.5 m in depth with a filtration rate of 0.3m/
h. The filter was run for 4-5 weeks before the experiment to ensure
proper operation. Cryptosporidium oocysts were spiked to a
concentration of 4,000/L. Results of the study indicated a 4.5 log
removal of Cryptosporidium oocysts.
Shuler et al 1990
In this study, diatomaceous earth (DE) filtration was evaluated for
removal of Giardia, Cryptosporidium, turbidity and coliform bacteria.
The study used a 0.1m\2\ pilot scale DE filter with three grades of
diatomaceous earth (A, B, and C). The raw water turbidity varied
between 0.1 and 1 NTU. Filter runs ranged from 2 days to 34 days. A
greater than 3 log removal of Cryptosporidium was demonstrated in the 9
filter runs which made up the study.
Ongerth and Hutton, 1997
Bench scale studies were used to define basic characteristics of DE
filtration as a function of DE grade and filtration rate. Three grades
of DE were used in the tests. Cryptosporidium removal was measured by
applying river water seeded with Cryptosporidium to Walton test
filters. Tests were run for filtration rates of 1 and 2 gpm/sq ft. Each
run was replicated 3 times. Approximately 6 logs reduction in the
concentration of Cryptosporidium oocysts was expected under normal
operating conditions.
Cryptosporidium Removal Using Alternative Filtration Technologies
EPA recognizes that systems serving fewer than 10,000 individuals
employ a variety of filtration technologies other than those previously
discussed. EPA collected information regarding several other popular
treatment techniques in an effort to verify that these treatments were
also technically capable of achieving a 2 log removal of
Cryptosporidium. A brief discussion of these alternative technologies
follows along with studies demonstrating effective Cryptosporidium
removals.
Membrane Filtration
Membrane filtration (Reverse Osmosis, Nanofiltration,
Ultrafiltration, and Microfiltration) relies upon pore size in order to
remove particles from water. Membranes possess a pore size smaller than
that of a Cryptosporidium oocyst, enabling them to achieve effective
log removals. The smaller the pore size, the more effective the rate of
removal. Typical pore sizes for each of the four types of membrane
filtration are shown below:
Microfiltration--1-0.1 microns (m)
Ultrafiltration--0.1-.01 (m)
Nanofiltration--.01-.001 (m)
Reverse Osmosis--.001 (m)
Bag Filtration
Bag filters are non-rigid, disposable, fabric filters where water
flows from inside of the bag to the outside of the bag. One or more
filter bags are contained within a pressure vessel designed to
facilitate rapid change of the filter bags when the filtration capacity
has been used up. Bag filters do not generally employ any chemical
coagulation. The pore sizes in the filter bags designed for protozoa
removal generally are small enough to remove protozoan cysts and
oocysts but large enough that bacteria, viruses and fine colloidal
clays would pass through. Bag filter studies have shown a significant
range of results in the removal of Cryptosporidium oocysts (0.33-3.2
log). (Goodrich, 1995)
Cartridge Filtration
Cartridge filtration also relies on physical screening to remove
particles from water. Typical cartridge filters are pressure filters
with glass, fiber or ceramic membranes, or strings wrapped around a
filter element housed in a pressure vessel (USEPA, 1997a).
The Agency evaluated several studies which demonstrate the ability
of various alternative filtration technologies to achieve 2 log removal
of Cryptosporidium ( in several studies 2 log removal of 4-5
(m) microspheres were used as a surrogate for
Cryptosporidium). These studies demonstrate that 2 log removal was
consistently achievable in all but bag filters. Table IV.4 provides key
information from these studies. A brief description of each study
follows:
Table IV.4.--Alternative Filtration Removal Studies
----------------------------------------------------------------------------------------------------------------
Type of treatment Log removal Experimental design Researcher
----------------------------------------------------------------------------------------------------------------
Microfiltration.................. Cryptosporidium 4.2-4.9 Bench Scale............. Jacangelo et al. 1997.
log.
Giardia 4.6-5.2 log...... ........................
Cryptosporidium 6.0--7.0 Pilot Plant............. ........................
log.
Cryptosporidium 4.3--5.0 Pilot Plant............. Drozd & Schartzbrod,
log. 1997.
Cryptosporidium 7.0-7.7 Bench Scale............. Hirata & Hashimoto,
log. 1998.
Microspheres 3.57-3.71 Full Scale.............. Goodrich et al. 1995.
log.
Ultrafiltration.................. Cryptosporidium 4.4--4.9 Bench Scale............. Jacangelo et al. 1997.
log.
Giardia 4.7-5.2 log...... ........................
Cryptosporidium 5.73-5.89 Bench Scale............. Collins et al. 1996.
log.
Giardia 5.75-5.85 log.... ........................
Cryptosporidium 7.1-7.4 Bench Scale............. Hirata & Hashimoto,
log. 1998.
Cryptosporidium 3.5 log.. pilot Plant............. Lykins et al. 1994.
Microspheres 3-4 log.....
Reverse Osmosis.................. Cryptosporidium > 5.7 log Pilot Scale............. Adham et al. 1998
Giardia > 5.7 log........
Hybrid Membrane.................. Microspheres 4.18 log.... Bench Scale............. Goodrich et al. 1995
Bag Filtration................... Microspheres .33-3.2 log. Pilot Plant............. Goodrich et al. 1995
Cartridge filtration............. Microspheres 3.52-3.68 Pilot Plant............. Goodrich et al. 1995
log. Bench Scale............. Land, 1998.
Particles (5-15 um) > 2
log.
----------------------------------------------------------------------------------------------------------------
[[Page 19065]]
Jacangelo et al., 1997
Bench scale and pilot plant tests were conducted with
microfiltration and ultrafiltration filters (using six different
membranes) in order to evaluate microorganism removal. Bench scale
studies were conducted under worst case operating conditions (direct
flow filtration at the maximum recommended transmembrane pressure using
deionized water slightly buffered at pH 7). Log removal ranged from 4.7
to 5.2 log removal. Pilot plant results ranged from 6.0-7.0 log removal
during worst-case operating conditions (i.e., direct filtration
immediately after backwashing at the maximum recommended operating
transmembrane pressure).
Drozd and Schartzbrod, 1997
A pilot plant system was established to evaluate the removal of
Cryptosporidium using crossflow microfiltration (.2 m
porosity). Results demonstrated Cryptosporidium log removals of 4.3 to
greater than 5.5 with a corresponding mean filtrate turbidity of 0.25
NTU.
Collins et. al., 1996
This study consisted of bench scale testing of Cryptosporidium and
Giardia log removals using an ultrafiltration system. Log removal of
Cryptosporidium ranged from 5.73 to 5.89 log, while removal of Giardia
ranged from 5.75 to 5.85 log.
Hirata & Hashimoto, 1998
Pilot scale testing using microfiltration (nominal pore size of .25
m) and ultrafiltration (nominal cut-off molecular weight (MW)
13,000 daltons) was conducted to determine Cryptosporidium oocyst
removal. Results conducted on the ultrafiltration units ranged from 7.1
to 7.5 logs of Cryptosporidium removal. Results of the microfiltration
studies yielded log removals from 7.0 to 7.7 log.
Lykins et al., [1994]
An ultrafiltration system was evaluated for the removal of
Cryptosporidium oocysts at the USEPA Test and Evaluation Facility in
Cincinnati, Ohio. The filter run was just over 48 hours. A 3.5 log
removal of Cryptosporidium oocysts was observed. Additionally, twenty-
four experiments were performed using 4.5 m polystyrene
microspheres as a surrogate for Cryptosporidium because of a similar
particle distribution. Log removal of microspheres ranged from 3 to 4
log.
Adham et al., 1998
This study was conducted to evaluate monitoring methods for
membrane integrity. In addition to other activities, microbial
challenge tests were conducted on reverse osmosis (RO) membranes to
both determine log removals and evaluate system integrity. Log removal
of Cryptosporidium and Giardia was >5.7 log in uncompromised
conditions, and > 4.5 log in compromised conditions.
Goodrich et al., 1995
This study was conducted to evaluate removal efficiencies of three
different bag filtration systems. Average filter pore size of the
filters was 1 m while surface area ranged from 35 to 47 sq ft.
Bags were operated at 25, 50 and 100 percent of their maximum flow rate
while spiked with 4.5 m polystyrene microspheres (beads) as a
surrogate for Cryptosporidium. Bead removal ranged from .33 to 3.2 log
removal.
Goodrich et al 1995.
This study evaluated a cartridge filter with a 2 m rating
and 200 square feet of surface area for removal efficiency of
Cryptosporidium sized particles. The filter was challenge tested with
4.5 m polystyrene microspheres as a surrogate for
Cryptosporidium. Flow was set at 25 gpm with 50 psi at the inlet.
Results from two runs under the same conditions exhibited log removals
of 3.52 and 3.68.
Land, 1998
An alternative technology demonstration test was conducted to
evaluate the ability of a cartridge filter to achieve 2 log removal of
particles in the 5 to 15 m range. The cartridge achieved at
least 2 log removal of the 5 to 25 m particles 95 percent of
the time up to a 20 psi pressure differential. The filter achieved at
least 2 log removal of 5 to 15 m particles up to 30-psi
pressure differential.
While the studies above note that alternative filtration
technologies have demonstrated in the lab the capability to achieve a 2
log removal of Cryptosporidium, the Agency believes that the
proprietary nature of these technologies necessitates a more rigorous
technology-specific determination be made. Given this issue, the Agency
believes that its Environmental Technology Verification (ETV) Program
can be utilized to verify the performance of innovative technologies.
Managed by EPA's Office of Research and Development, ETV was created to
substantially accelerate the entrance of new environmental technologies
into the domestic and international marketplace. ETV consists of 12
pilot programs, one of which focuses on drinking water. The program
contains a protocol for physical removal of microbiological and
particulate contaminants, including test plans for bag and cartridge
filters and membrane filters (NSF, 1999). These protocols can be
utilized to determine whether a specific alternative technology can
effectively achieve a 2 log removal of Cryptosporidium, and under what
parameters that technology must be operated to ensure consistent levels
of removal. Additional information on the ETV program can be found on
the Agency's website at http://www.epa.gov/etv.
iii. Proposed Requirements
Today's proposed rule establishes a requirement for 2 log removal
of Cryptosporidium for surface water and GWUDI systems serving fewer
than 10,000 people that are required to filter under the SWTR.
Compliance with the combined filter effluent turbidity requirements, as
described later, ensures compliance with the 2 log removal requirement.
The requirement for a 2 log removal of Cryptosporidium applies between
a point where the raw water is not subject to recontamination by
surface water runoff and a point downstream before or at the first
customer.
iv. Request for Comments
EPA requests comment on the 2 log removal requirement as discussed.
The Agency is also soliciting public comment and data on the ability of
alternative filtration technologies to achieve 2 log Cryptosporidium
removal.
2. Turbidity Requirements
a. Combined Filter Effluent
i. Overview and Purpose
In order to address concern with Cryptosporidium, EPA has analyzed
log removal performance by well operated plants (as described in the
previous section) as well as filter performance among small systems to
develop an appropriate treatment technique requirement that assures an
increased level of Cryptosporidium removal. In evaluating combined
filter performance requirements, EPA considered the strengthened
turbidity provisions within the IESWTR and evaluated whether these were
appropriate for small systems as well.
ii. Data
In an effort to evaluate combined filter effluent (CFE)
requirements, EPA collected data in several areas to
[[Page 19066]]
supplement existing data, and address situations unique to smaller
systems. This data includes:
An estimate of the number of systems subject to the
proposed strengthened turbidity requirements;
Current turbidity levels at systems throughout the U.S.
serving populations fewer than 10,000;
The ability of package plants to meet strengthened
turbidity standards; and
The correlation between meeting CFE requirements and
achieving 2 log removal of Cryptosporidium.
Estimate of the Number of Systems Subject to Strengthened CFE Turbidity
Standards
Using the estimate of 9,134 systems which filter and serve fewer
than 10,000 persons (as described in Section IV.A.1 of today's
proposal), the Agency used the information contained within the CWSS
database to estimate the number of systems which utilized specific
types of filtration. The data was segregated based on the type of
filtration utilized and the population size of the system. Percentages
were derived for each of the following types of filtration:
Conventional and Direct Filtration;
Slow Sand Filtration;
Diatomaceous Earth Filtration; and
Alternative Filtration Technologies.
The percentages were applied to the estimate discussed in Section
IV.A.1 of today's proposal for each of the respective population
categories. Based on this analysis, the Agency estimates 5,896
conventional and direct filtration systems will be subject to the
strengthened combined filter effluent turbidity standards. EPA
estimates 1,756 systems utilize slow sand or diatomaceous earth
filtration, and must continue to meet turbidity standards set forth in
the SWTR. The remaining 1,482 systems are estimated to use alternative
filtration technologies and will be required to meet turbidity
standards as set forth by the State upon analysis of a 2 log
Cryptosporidium demonstration conducted by the system.
Current Turbidity Levels
EPA has developed a data set which summarizes the historical
turbidity performance of various filtration plants serving populations
fewer than 10,000 (EPA, 1999d). The data set represents those systems
that were in compliance with the turbidity requirements of the SWTR
during all months being analyzed. The data set consists of 167 plants
from 15 States. Table IV.5 provides information regarding the number of
plants from each State. The data set includes plants representing each
of the five population groups utilized in the CWSS (25-100, 101-500,
501-1,000, 1,001-3,300, and 3,301-10,000). The Agency has also received
an additional data set from the State of California (EPA, 2000). This
data has not been included in the assessments described below. The
California data demonstrates similar results to the larger data set
discussed below.
Table IV.5.--Summary of LT1FBR Turbidity Data Set
------------------------------------------------------------------------
Number of
State Plants
------------------------------------------------------------------------
Alabama.................................................... 1
California................................................. 1
Colorado................................................... 16
Illinois................................................... 13
Kansas..................................................... 20
Louisiana.................................................. 6
Minnesota.................................................. 3
Montana.................................................... 2
North Carolina............................................. 16
Ohio....................................................... 4
Pennsylvania............................................... 27
South Carolina............................................. 16
Texas...................................................... 23
Washington................................................. 17
West Virginia.............................................. 2
------------
Total.................................................. 167
------------------------------------------------------------------------
(EPA, 1999d)
This data was evaluated to assess the national impact of modifying
existing turbidity requirements. The current performance of plants was
assessed with respect to the number of months in which selected 95th
percentile and maximum turbidity levels were met. The data show that
approximately 88 percent of systems are also currently meeting the new
requirements of a maximum turbidity limit of 1 NTU (Figure IV.1). With
respect to the 95th percentile turbidity limit, roughly 46 percent of
these systems are currently meeting the new requirement of 0.3 NTU
(Figure IV.2) while approximately 70 percent meet this requirement 9
months out of the year. Estimates for systems needing to make changes
to meet a turbidity performance limit of 0.3 NTU were based on the
ability of systems currently to meet a 0.2 NTU. This assumption was
intended to take into account a utility's concern with possible
turbidity measurement error and to reflect the expectation that a
number of utilities will attempt to achieve finished water turbidity
levels below the regulatory performance level to assure compliance.
As depicted in Figure IV.1 and IV.2, the tighter turbidity
performance standards for combined filter effluent in today's proposed
rule reflect the actual, current performance many systems already
achieve nationally. Revising the turbidity criteria effectively ensures
that these systems continue to perform at their current level while
also improving performance of a substantial number of systems that
currently meet existing SWTR criteria, but operate at turbidity levels
higher than proposed in today's rule.
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Package Plants
During development of today's proposed rule, some stakeholders
expressed concern regarding the ability of ``package plants'' to meet
the proposed requirements. EPA evaluated these systems by gathering
data from around the country. The information affirms the Agency's
belief that package plants can and currently do meet the turbidity
limits in today's proposed rule.
Package plants combine the processes of rapid mixing, flocculation,
sedimentation and filtration (rapid sand, mixed or dual media filters)
into a single package system. Package Filtration Plants are
preconstructed, skid mounted and transported virtually assembled to the
site. The use of tube settlers, plate settlers, or adsorption
clarifiers in some Package Filtration Plants results in a compact size
and more treatment capacity.
Package Filtration Plants are appropriate for treating water of a
fairly consistent quality with low to moderate turbidity. Effective
treatment of source waters containing high levels of or extreme
variability in turbidity levels requires skilled operators and close
operational attention. High turbidity or excessive color in the source
water could require chemical dosages above the manufacturer's
recommendations for the particular plant. Excessive turbidity levels
may require presedimentation or a larger capacity plant. Specific
design criteria of a typical package plant and operating and
maintenance requirements can vary, but an example schematic is depicted
in Figure IV.3.
[[Page 19070]]
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[[Page 19071]]
The Agency believes that historic data show that package plants
have a comparable ability to meet turbidity requirements as
conventional or direct filtration systems.
A 1987 report of pilot testing using a trailer-mounted package
plant system to treat raw water from Clear Lake in Lakeport, California
demonstrates the ability of such systems to achieve low turbidity
requirements. The raw water contained moderate to high turbidity (18 to
103 NTU). Finished water turbidities ranged from 0.07 to 0.11 NTU (EPA,
1987). Two previous studies (USEPA, 1980a,b and Cambell et al., 1995)
also illustrate the ability of package systems throughout the country
to meet historic turbidity performance criteria. These studies are
described briefly:
Package Water Treatment Plant Performance Evaluation (USEPA, 1980a,b)
The Agency conducted a study of package water treatment systems
which encompassed 36 plants in Kentucky, West Virginia, and Tennessee.
Results from that study showed that the plants could provide water that
met the existing turbidity limits established under the National
Interim Primary Drinking Water Standards. Of the 31 plants at which
turbidity measurements were made, 23 (75 percent) were found to be
meeting existing standards. Of the 8 which did not meet requirements,
one did not use chemical coagulants, and 6 operated less than four
hours per day. (USEPA, 1980a, b)
Package Plants for Small Systems: A Field Study (Cambell et al, 1995)
This 1992 project evaluated the application of package plant
technology to small communities across the U.S. The project team
visited 48 facilities across the U.S. Of the 29 surface water and GWUDI
systems, 21 (72 percent) had grab turbidity samples less than 0.5 NTU,
the 95 percent limit which became effective in June of 1993. Twelve
systems (41 percent) had values less than today's proposed 0.3 NTU 95
percent turbidity limit. (Cambell et al., 1995) It should be noted that
today's rule requires compliance with turbidity limits based on 4 hour
measurments.
The Agency recently evaluated Filter Plant Performance Evaluations
(FPPEs) conducted by the State of Pennsylvania, in an effort to
quantify the comparative abilities of package plants and conventional
filtration systems to meet the required turbidity limits. The data set
consisted of 100 FPPEs conducted at systems serving populations fewer
than 10,000 (PADEP, 1999). Thirty-seven FPPEs were conducted at
traditional conventional filtration systems while 37 were conducted at
package plants or ``pre-engineered'' systems. The remaining 26 systems
utilized other filtration technologies.
The FPPEs provided a rating of either acceptable or unacceptable as
determined by the evaluation team. This rating was based on an
assessment of the capability of individual unit processes to
continuously provide an effective barrier to the passage of
microorganisms. Specific performance goals were utilized to evaluate
the performance of the system including the consistent ability to
produce a finished water turbidity of less than 0.1 NTU, which is lower
than the combined filter effluent turbidity requirement in today's
proposed rule. Seventy-three percent of the traditional conventional
filtration systems were rated acceptable and 89 percent of the package
plants were rated acceptable.
The Agency also evaluated historic turbidity data graphs contained
within each FPPE to provide a comparison of the ability of package
plants and conventional systems to meet the 1 NTU max and 0.3 NTU 95
percent requirements that are contained in today's proposed rule.
Sixty-seven percent of the conventional systems would meet today's
proposed requirements while 74 percent of package systems in the data
set would meet today's proposed requirements. The Agency believes that,
when viewed alongside the aforementioned studies (USEPA, 1980a,b and
Cambell et al., 1995), it is apparent that package systems have the
ability to achieve more stringent turbidity limits.
Correlation Between CFE Requirements and 2-log Cryptosporidium Removal
Recent pilot scale experiments performed by the Agency assessed the
ability of conventional treatment to control Cryptosporidium under
steady state conditions. The work was performed with a pilot plant that
was designed to minimize flow rates and as a result the number of
oocyst required for continuous spiking. (Dugan et al. 1999)
Viable oocysts were fed into the plant influent at a concentration
of 106/L for 36 to 60 hours. The removals of oocysts and the
surrogate parameters turbidity, total particle counts and aerobic
endospores were measured through sedimentation and filtration. There
was a positive correlation between the log removals of oocysts and all
surrogate parameters through the coagulation and settling process. With
proper coagulation control, the conventional treatment process achieved
the 2 log total Cryptosporidium removal required by the IESWTR. In all
cases where 2 log total removal was not achieved, the plant also did
not comply with the IESWTR's CFE turbidity requirements. Table IV.6
provides information on Cryptosporidium removals from this study.
Table IV.6.--Log Removal of Oocysts (Dugan et al. 1999)
------------------------------------------------------------------------
Log removal
Run crypto Exceeds CFE requirements
------------------------------------------------------------------------
1................................ 4.5 No.
2................................ 5.2 No.
3................................ 1.6 Yes, average CFE 2.1
NTU.
4................................ 1.7 Yes, only 88% CFE under
0.3 NTU.
5................................ 4.1 No.
6................................ 5.1 No.
7................................ 0.2 Yes, average CFE 0.5
NTU.
8................................ 0.5 Yes, only 83% CFE under
0.3 NTU.
9................................ 5.1 No.
10............................... 4.8 No.
------------------------------------------------------------------------
[[Page 19072]]
iii. Proposed Requirements
Today's proposed rule establishes combined filter effluent
turbidity requirements which apply to all surface water and GWUDI
systems which filter and serve populations fewer than 10,000. For
conventional and direct filtration systems, the turbidity level of
representative samples of a system's combined filter effluent water
must be less than or equal to 0.3 NTU in at least 95 percent of the
measurements taken each month. The turbidity level of representative
samples of a system's filtered water must not exceed 1 NTU at any time.
For membrane filtration, (microfiltration, ultrafiltration,
nanofiltration, and reverse osmosis) the Agency is proposing to require
that the turbidity level of representative samples of a system's
combined filter effluent water must be less than or equal to 0.3 NTU in
at least 95 percent of the measurements taken each month. The turbidity
level of representative samples of a system's filtered water must not
exceed 1 NTU at any time. EPA included turbidity limits for membrane
systems to allow such systems the ability to opt out of a possible
costly demonstration of the ability to remove Cryptosporidium. The
studies displayed previously in Table IV.4, demonstrate the ability of
these technologies to achieve log-removals in excess of 2 log. In lieu
of these turbidity limits, a public water system which utilizes
membrane filtration may demonstrate to the State for purposes of
membrane approval (using pilot plant studies or other means) that
membrane filtration in combination with disinfection treatment
consistently achieves 3 log removal and/or inactivation of Giardia
lamblia cysts, 4 log removal and/or inactivation of viruses, and 2 log
removal of Cryptosporidium oocysts. For each approval, the State will
set turbidity performance requirements that the system must meet at
least 95 percent of the time and that the system may not exceed at any
time at a level that consistently achieves 3 log removal and/or
inactivation of Giardia lamblia cysts, 4 log removal and/or
inactivation of viruses, and 2 log removal of Cryptosporidium oocysts.
Systems utilizing slow sand or diatomaceous earth filtration must
continue to meet the combined filter effluent limits established for
these technologies under the SWTR (found in Sec. 141.73 (b) and (c)).
Namely, the turbidity level of representative samples of a system's
filtered water must be less than or equal to 1 NTU in at least 95
percent of the measurements taken each month and the turbidity level of
representative samples of a system's filtered water must at no time
exceed 5 NTU.
For all other alternative filtration technologies (those other than
conventional, direct, slow sand, diatomaceous earth, or membrane),
public water systems must demonstrate to the State for purposes of
approval (using pilot plant studies or other means), that the
alternative filtration technology in combination with disinfection
treatment, consistently achieves 3 log removal and/or inactivation of
Giardia lamblia cysts, 4 log removal and/or inactivation of viruses,
and 2 log removal of Cryptosporidium oocysts. For each approval, the
State will set turbidity performance requirements that the system must
meet at least 95 percent of the time and that the system may not exceed
at any time at a level that consistently achieves 3 log removal and/or
inactivation of Giardia lamblia cysts, 4 log removal and/or
inactivation of viruses, and 2 log removal of Cryptosporidium oocysts.
iv. Request for Comments
EPA solicits comment on the proposal to require systems to meet the
proposed combined filter effluent turbidity requirements. Additionally,
EPA solicits comment on the following:
The ability of package plants and/or other unique
conventional and/or direct systems to meet the combined filter effluent
requirements;
Microbial attachment to particulate material or inert
substances in water systems may have the effect of providing
``shelter'' to microbes by reducing their exposure to disinfectants
(USEPA, 1999e). While inactivation of Cryptosporidium is not a
consideration of this rule, should maximum combined filter effluent
limits for slow sand and diatomaceous earth filtration systems be
lowered to 1 or 2 NTU and/or 95th percentile requirements lowered to
0.3 NTU to minimize the ability of turbidity particles to ``shelter''
Cryptosporidium oocysts?
Systems which practice enhanced coagulation may produce
higher turbidity effluent because of the process. Should such systems
be allowed to apply to the State for alternative exceedance levels
similar to the provisions contained in the rule for systems which
practice lime softening?
Issues specific to small systems regarding the proposed
combined filter effluent requirements;
Establishment of turbidity limits for alternative
filtration technologies;
Allowance of a demonstration to establish site specific
limits in lieu of generic turbidity limits, including components of
such demonstration; and
The number of small membrane systems employed throughout
the country.
The Agency also requests comment on establishment of turbidity
limits for membrane systems. While integrity of membranes provides the
clearest understanding of the effectiveness of membranes, turbidity has
been utilized as an indicator of performance (and corresponding
Cryptosporidium log removal) for all filtration technologies. EPA
solicits comment on modifying the requirements for membrane filters to
meet integrity testing, as approved by the State and with a frequency
approved by the State.
b. Individual Filter Turbidity
i. Overview and Purpose
During development of the IESWTR, it was recognized that
performance of individual filters within a plant were of paramount
importance to producing low-turbidity water. Two important concepts
regarding individual filters were discussed. First, it was recognized
that poor performance (and potential pathogen breakthrough) of one
filter could be masked by optimal performance in other filters, with no
discernable rise in combined filter effluent turbidity. Second, it was
noted that individual filters are susceptible to turbidity spikes (of
short duration) which would not be captured by four-hour combined
filter effluent measurements. To address the shortcomings associated
with individual filters, EPA established individual filter monitoring
requirements in the IESWTR. For the reasons discussed below, the Agency
believes it appropriate and necessary to extend individual filter
monitoring requirements to systems serving populations fewer than
10,000 in the LT1FBR.
ii. Data
EPA believes that the support and underlying principles regarding
the IESWTR individual filter monitoring requirements are also
applicable for the LT1FBR. The Agency has estimated that 5,897
conventional and direct filtration systems will be subject to today's
proposed individual filter turbidity requirements. Information
regarding this estimate is found in Section IV.A.2.a of today's
proposal. The Agency has analyzed information regarding turbidity
spikes and filter masking which are presented next.
[[Page 19073]]
Turbidity Spikes
During a turbidity spike, significant amounts of particulate matter
(including Cryptosporidium oocysts, if present) may pass through the
filter. Various factors affect the duration and amplitude of filter
spikes, including sudden changes to the flow rate through the filter,
treatment of the filter backwash water, filter-to-waste capability, and
site-specific water quality conditions. Recent experiments have suggest
that surging has a significant effect on rapid sand filtration
performance (Glasgow and Wheatley, 1998). An example filter profile
depicting turbidity spikes is shown in Figure IV.4.
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Studies considered by both EPA and the M-DBP Advisory Committee
noted that the greatest potential for a peak in turbidity (and thus,
pathogen breakthrough) is near the beginning of the filter run after
filter backwash or start up of operation (Amirtharajah, 1988; Bucklin,
et al. 1988; Cleasby, 1990; and Hall and Croll, 1996). This phenomenon
is depicted in Figure IV.4. Turbidity spikes also may occur for a
variety of other reasons. These include:
Outages or maintenance activities at processes within the
treatment train;
Coagulant feed pump or equipment failure;
Filters being run at significantly higher loading rates
than approved;
Disruption in filter media;
Excessive or insufficient coagulant dosage; and
Hydraulic surges due to pump changes or other filters
being brought on/off-line.
A recent study was completed which evaluated particle removal by
filtration throughout the country. While the emphasis of this study was
particle counting and removal, fifty-two of the 100 plants surveyed
were also surveyed for turbidity with on-line turbidimeters. While all
of the plants were able to meet 0.5 NTU 95 percent of the time, it was
noted that there was a significant occurrence of spikes during the
filter runs. These were determined to be a major source of raising the
95th percentile value for most of the filter runs. (McTigue et al.
1998)
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Masking of Filter Performance
Combined Filter Effluent monitoring can mask poor performance of
individual filters which may allow passage of particulates (including
Cryptosporidium oocysts). One poorly performing filter, can be
effectively ``masked'' by other well operated filters because water
from each of the filters is combined before an effluent turbidity
measurement is taken. The following example illustrates this
phenomenon.
The fictitious City of ``Smithville'' (depicted in Figure IV.6)
operates a conventional filtration plant with four rapid granular
filters as shown below. Filter number 1 has significant problems
because the depth and placement of the media are contributing to
elevated turbidities. Filters 2, 3, and 4 do not have these problems
and are operating properly.
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Turbidity measurements taken at the clearwell indicate 0.3 NTU.
Filter 4 produces water with a turbidity of 0.08 NTU, Filter 3 a
turbidity of 0.2 NTU, Filter 2 a turbidity of 0.1 NTU, and Filter 1 a
turbidity of 0.9 NTU. Each filter contributes an equal proportion of
water, but each is operating at different turbidity levels which
contributes to the combined filter effluent of 0.32 NTU.
([0.08+0.2+0.1+0.9]4 = 0.32 NTU)
As discussed previously in Section IV.2.a, the Agency believes that
a system must meet 0.3 NTU 95 percent of the time an appropriate
treatment technique requirement that assures an increased level of
Cryptosporidium removal. While the fictitious system described above
would barely meet the required CFE turbidity, it is entirely possible
that they would not be achieving an overall 2 log removal of
Cryptosporidium with one filter achieving considerably less than 2-log
removal. This issue highlights the importance of understanding the
performance of individual filters relative to overall plant
performance.
iii. Proposed Requirements
Today's proposed rule establishes an individual filter turbidity
requirement which applies to all surface water and GWUDI systems using
filtration and which serve populations fewer than 10,000 and utilize
direct or conventional filtration. In developing this requirement, the
Agency evaluated several alternatives (A, B and C) in an attempt to
reduce the burden faced by small systems while still providing: (1) A
comparable level of public health protection as that afforded to
systems serving 10,000 or more people and (2) an early-warning tool
systems can use to detect and correct problems with filters.
Alternative A
The first alternative considered by the Agency was requiring direct
and conventional filtration systems serving populations fewer than
10,000 to meet the same requirements as established for systems serving
10,000 or more people. This alternative would require that all
conventional and direct filtration systems must conduct continuous
monitoring of turbidity (one turbidity measurement every 15 minutes)
for each individual filter. Systems must provide an exceptions report
to the State as part of the existing combined filter effluent reporting
process for any of the following circumstances:
(1) Any individual filter with a turbidity level greater than 1.0
NTU based on two consecutive measurements fifteen minutes apart;
(2) Any individual filter with a turbidity greater than 0.5 NTU at
the end of the first four hours of filter operation based on two
consecutive measurements fifteen minutes apart;
(3) Any individual filter with turbidity levels greater than 1.0
NTU based on two consecutive measurements fifteen minutes apart at any
time in each of three consecutive months (the system must, in addition
to filing an exceptions report, conduct a self-assessment of the
filter); and
(4) Any individual filter with turbidity levels greater than 2.0
NTU based on two consecutive measurements fifteen minutes apart at any
time in each of two consecutive months (the system must file an
exceptions report and must arrange for a comprehensive performance
evaluation (CPE) to be conducted by the State or a third party approved
by the State).
Under the first two circumstances identified, a system must produce
a filter profile if no obvious reason for the abnormal filter
performance can be identified.
Alternative B
The second alternative considered by the Agency represents a slight
modification from the individual filter monitoring requirements of
large systems. The 0.5 NTU exceptions report trigger would be omitted
in an effort to reduce the burden associated with daily data
evaluation. Additionally, the filter profile requirement would be
removed. Requirement language was slightly modified in an effort to
simplify the requirement for small system operators. This alternative
would still require that all conventional and direct filtration systems
conduct continuous monitoring (one turbidity measurement every 15
minutes) for each individual filter, but includes the following three
requirements:
(1) A system must provide an exceptions report to the State as part
of the existing combined effluent reporting process if any individual
filter turbidity measurement exceeds 1.0 NTU (unless the system can
show that the next reading is less than 1.0 NTU);
(2) If a system is required to submit an exceptions report for the
same filter in three consecutive months, the system must conduct a
self-assessment of the filter.
(3) If a system is required to submit an exceptions report for the
same filter in two consecutive months which contains an exceedance of
2.0 NTU by the same filter, the system must arrange for a CPE to be
conducted by the State or a third party approved by the State.
Alternative C
The third alternative considered by the Agency would include new
triggers for reporting and follow-up action in an effort to reduce the
daily burden associated with data review. This alternative would still
require that all conventional and direct filtration systems must
conduct continuous monitoring (one turbidity measurement every 15
minutes) for each individual filter, but would include the following
three requirements:
(1) A system must provide an exceptions report to the State as part
of the existing combined effluent reporting process if filter samples
exceed 0.5 NTU in at least 5 percent of the measurements taken each
month and/or any individual filter measurement exceeds 2.0 NTU (unless
the system can show that the following reading was 2.0 NTU).
(2) If a system is required to submit an exceptions report for the
same filter in three consecutive months the system must conduct a self-
assessment of the filter.
(3) If a system is required to submit an exceptions report for the
same filter in two consecutive months which contains an exceedance of
2.0 NTU by the same filter, the system must arrange for a CPE to be
conducted by the State or a third party approved by the State.
For all three alternatives the requirements regarding self
assessments and CPEs are the same. If a CPE is required, the system
must arrange for the State or a third party approved by the State to
conduct the CPE no later than 30 days following the exceedance. The CPE
must be completed and submitted to the State no later than 90 days
following the exceedance which triggered the CPE. If a self-assessment
is required it must take place within 14 days of the exceedance and the
system must report to the State that the self-assessment was conducted.
The self assessment must consist of at least the following components:
assessment of filter performance;
development of a filter profile;
identification and prioritization of factors limiting
filter performance;
assessment of the applicability of corrections; and
preparation of a filter self assessment report.
In considering each of the above alternatives, the Agency attempted
to reduce the burden faced by small systems. Each of the three
alternatives was judged to provide levels of public health protection
comparable to those in the IESWTR for large systems. Alternative A,
because it contains the
[[Page 19085]]
same requirements as IESWTR, was expected to afford the same level of
public health protection. Alternative B, (which removes the four-hour
0.5 NTU trigger and the filter profile requirement) was expected to
afford comparable health protection because the core components which
provide the overwhelming majority of the public health protection
(monitoring frequency, trigger which requires follow-up action, and the
follow-up actions) are the same as the IESWTR. Alternative C was
expected to provide comparable health protection because follow-up
action is the same as under the IESWTR and a 0.5 NTU 95percent
percentile trigger was expected to identify the same systems which the
triggers established under the IESWTR would identify. All three were
also considered useful diagnostic tools for small systems to evaluate
the performance of filters and correct problems before follow-up action
was necessary. The first alternative was viewed as significantly more
challenging to implement and burdensome for smaller systems due to the
amount of required daily data review. This evaluation was also echoed
by small entity representatives during the Agency's SBREFA process as
well as stakeholders at each of the public meetings held to discuss
issues related to today's proposed rule. While Alternative C reduced
burden associated with daily data review, it would institute a very
different trigger for small systems than established by the IESWTR for
large systems. This was viewed as problematic by several stakeholders
who stressed the importance of maintaining similar requirements in
order to limit transactional costs and additional State burden.
Therefore, the Agency is proposing Alternative B as described above,
which allows operators to expend less time to evaluate their turbidity
data. Alternative B maintains a comparable level of public health
protection as those afforded large systems, reduces much of the burden
associated with daily data collection and review (removing the
requirement to conduct a filter profile allows systems to review data
once a week instead of daily if they so choose), yet still serves as a
self-diagnostic tool for operators and provides the mechanism for State
follow-up when significant performance problems exist.
iv. Request for Comments
The individual filter monitoring provisions represent a challenging
opportunity to provide systems with a useful tool for assessing filters
and correcting problems before State intervention is necessary or
combined filter turbidity is affected and treatment technique
violations occur. The Agency is actively seeking comment on this
provision. Because of the complexity of this provision, specific
requests for comment have been broken down into five distinct areas.
Comments on the Alternatives
EPA requests comment on today's proposed individual filter
requirement and each of the alternatives as well as additional
alternatives for this provision such as establishing a different
frequency for individual filter monitoring (e.g., 60 minute or 30
minute increments). The Agency also seeks comment or information on:
Tools and or guidance which would be useful and necessary
in order to educate operators on how to comply with individual filter
provisions and perform any necessary calculations;
Data correlating individual filter performance relative to
combined filter effluent;
Contributing factors to turbidity spikes associated with
reduced filter performance;
Practices which contribute to poor individual filter
performance and filter spikes; and
Any additional concerns with individual filter
performance.
Modifications to the Alternatives
The Agency also seeks comment on a variety of proposed
modifications to the individual filter monitoring alternatives
discussed which could be incorporated in order to better address the
concerns and realities of small surface water systems. These
modifications include:
Modification of the alternatives to include a provision
which would require systems which do not staff the plant during all
hours of operation, to utilize an alarm/phone system to alert off-site
operators of significantly elevated turbidity levels and poor
individual filter performance;
A modification to allow conventional and direct filtration
systems with either 2-3 or less filters to sample combined filter
effluent continuously (every 15 minutes) in lieu of monitoring
individual filter turbidity. This modification would reduce the data
collection/analysis burden for the smallest systems while not
compromising the level of public health protection;
A modification to lengthen the period of time (120 days or
a period of time established by the State but not to exceed 120 days)
for completion of the CPE and/or a modification to lengthen the
requirement that a CPE must be conducted no later than 60 or 90 days
following the exceedance; and
A modification to require systems to notify the State
within 24 hours of triggering the CPE or IFA. This would inform States
sooner so they can begin to work with systems to address performance of
filters and conduct CPEs and IFAs as necessary.
Establishment of Subcategories
The Agency is also evaluating the need to establish subcategories
in the final rule for individual filter monitoring/reporting. EPA is
currently considering these three categories:
1. Systems serving populations of 3,300 or more persons;
2. Systems with more than 2 filters, but less than 3,300 persons;
and
3. Systems with 2 or fewer filters serving populations fewer than
3,300 persons.
Individual filter monitoring requirements would also be based on
these subcategories. Systems serving 3,300 or greater would be required
to meet the same individual turbidity requirements as the IESWTR
(Alternative A as described above). Systems serving fewer than 3,300
but using more than 2 filters would be required to meet a modified
version of the IESWTR individual filter requirements (Alternative B as
described above). Systems serving fewer than 3,300 and using 2 or fewer
filters would continue to monitor and report only combined filter
effluent turbidity at an increased frequency (once every 15 minutes, 30
minutes, or one hour).
Input and or comment on cut-offs for subcategories and how to apply
subcategories to Alternatives is requested. The Agency would also like
to take comment on additional strategies to tailor individual filter
monitoring for the smallest systems while continuing to maintain an
adequate level of public health protection. Such possible strategies
include:
Since small systems are often understaffed one approach
would require those systems utilizing only two or fewer filters to
utilize, maintain, and continually operate an alarm/phone system during
all hours of operation, which alert off-site operators of significantly
elevated turbidity levels and poor individual filter performance and/or
automatically shuts the system down if turbidity levels exceed a
specified performance level. This modification would be in addition to
the proposed requirements.
Establishing a more general modification which would
require systems which do not staff the plant during all hours of
operation to utilize
[[Page 19086]]
an alarm/phone system to alert off-site operators of significantly
elevated turbidity levels and poor individual filter performance, and/
or to automatically shut the system down if turbidity levels exceed a
specified performance level.
If systems with 2 or fewer filters is allowed to sample
combined filter effluent in lieu of individual filter effluent with a
frequency of a reading every hour and combined filter effluent
turbidity exceeds 0.5 NTU, should the system be required to take grab
samples of individual filter turbidity for all filters every 15 minutes
until the results of those samples are lower than 0.5 NTU?
Reliability
Maintaining reliable performance at systems using filtration
requires that the filters be examined at intervals to determine if
problems are developing. This can mean that a filter must go off-line
for replacement or upgrades of media, underdrains, backwash lines etc.
In order to provide adequate public health protection at small systems,
the lack of duplicate units can be a problem. EPA is considering
requiring any system with only one filter to install an additional
filter. The schedule would be set by the primacy agency, but the filter
would have to be installed no later than 6 years after promulgation.
EPA is requesting comment on this potential requirement.
Data Gathering Recordkeeping and Reporting
The Agency is evaluating data gathering/reporting requirements for
systems. A system collecting data at a frequency of once every 15
minutes, (and operating) 24 hours a day, would record approximately
2800 data points for each filter throughout the course of the month.
Although the smallest systems in operation today routinely operate on
the average of 4 to 12 hours a day (resulting in 480 to 1400 data
points per filter), these systems do not typically use sophisticated
data recording systems such as SCADAs. The lack of modern equipment at
small systems may result in difficulty with retrieving and analyzing
data for reporting purposes. While the Agency intends to issue guidance
targeted at aiding these systems with the data gathering requirements,
EPA is also seeking feedback on a modification to the frequency of data
gathering required under each of the aforementioned options.
Specifically, the Agency would like to request comment on modifying the
frequency for systems serving fewer than 3,300 to continuous monitoring
on a 30 or 60 minute basis. EPA also requests comment on the
availability and practicality of data systems that would allow small
systems, State inspectors, and technical assistance providers to use
individual filter turbidity data to improve performance, perform filter
analysis, conduct individual filter self assessments, etc. The Agency
is interested in specific practical combinations of data recorders,
charts, hand written recordings from turbidimeters, that would
accomplish this.
Failure of Continuous Turbidity Monitoring
Under today's proposed rule, the Agency requires that if there is a
failure in the continuous turbidity monitoring equipment, the system
must conduct grab sampling every four hours in lieu of continuous
monitoring until the turbidimeter is back on-line. A system has five
working days to resume continuous monitoring before a violation is
incurred. EPA would like to solicit comment on modifying this component
to require systems to take grab samples at an increased frequency,
specifically every 30 minutes, 1 hour, or 2 hours.
B. Disinfection Benchmarking Requirements
Small systems will be required to comply with the Stage 1
Disinfection Byproduct Rule (Stage 1 DBPR) in the first calendar
quarter of 2004. The Stage 1 DBPR set Maximum Contaminant Levels (MCLs)
for Total Trihalomethanes (chloroform, bromodichloromethane,
chlorodibromomethane, and bromoform), and five Haloacetic Acids (i.e.,
the sum of the concentrations of mono-, di-, and trichloroacetic acids
and mono- and dibromoacetic acids.) The LT1FBR follows the principles
set forth in earlier FACA negotiations, i.e., that existing microbial
protection must not be significantly reduced or undercut as a result of
systems taking the necessary steps to comply with the MCL's for TTHM
and HAA5 set forth in Stage 1 DBPR. The disinfection benchmarking
requirements are designed to ensure that risk from one contaminant is
not increased while risk from another contaminant is decreased.
The Stage 1 DBPR was promulgated because disinfectants such as
chlorine can react with natural organic and inorganic matter in source
water and distribution systems to form disinfection byproducts (DBPs).
Results from toxicology studies have shown several DBPs (e.g.,
bromodichloromethane, bromoform, chloroform, dichloroacetic acid, and
bromate) to potentially cause cancer in laboratory animals. Other DBPs
(e.g., certain haloacetic acids) have been shown to cause adverse
reproductive or developmental effects in laboratory animals. Concern
about these health effects may cause public water utilities to consider
altering their disinfection practices to minimize health risks to
consumers.
A fundamental principle, therefore, of the 1992-1993 regulatory
negotiation reflected in the 1994 proposal for the IESWTR was that new
standards for control of DBPs must not result in significant increases
in microbial risk. This principle was also one of the underlying
premises of the 1997 M-DBP Advisory Committee's deliberations, i.e.,
that existing microbial protection must not be significantly reduced or
undercut as a result of systems taking the necessary steps to comply
with the MCL's for TTHM and HAA5 set forth in Stage 1 DBPR. The
Advisory Committee reached agreement on the use of microbial profiling
and benchmarking as a process by which a PWS and the State, working
together, could assure that there would be no significant reduction in
microbial protection as the result of modifying disinfection practices
in order to comply with Stage 1 DBPR.
The process established under the IESWTR has three components: (1)
Applicability Monitoring; (2) Disinfection Profiling; and (3)
Disinfection Benchmarking. These components have the following three
goals respectively: (1) determine which systems have annual average
TTHM and HAA5 levels close enough to the MCL (e.g., 80 percent of the
MCL) that they may need to consider altering their disinfection
practices to comply with Stage 1 DBPR; (2) those systems that have TTHM
and HAA5 levels of at least 80 percent of the MCLs must develop a
baseline of current microbial inactivation over the period of 1 year;
and (3) determine the benchmark, or the month with the lowest average
level of microbial inactivation, which becomes the critical period for
that year.
The aforementioned components were applied to systems serving
10,000 or more people in the IESWTR and were carried out sequentially.
In response to concerns about early implementation (any requirement
which would require action prior to 2 years after the promulgation date
of the rule), the Agency is considering modifying the IESWTR approach
for small systems, as described in the following section. Additionally,
the specific provisions have been modified to take into account
[[Page 19087]]
specific needs of small systems. EPA's goal in developing these
requirements is to recognize the specific needs of small system and
States, while providing small systems with a useful means of ensuring
that existing microbial protection must not be significantly reduced or
undercut as a result of systems taking the necessary steps to comply
with the MCL's for TTHM and HAA5 set forth in Stage 1 DBPR.
The description of the disinfection benchmarking components of
today's proposed rule will be broken into the three segments: (1)
Applicability Monitoring; (2) Disinfection Profiling; and (3)
Disinfection Benchmarking. Each section will provide an overview and
purpose, data, a description of the proposed requirements, and request
for comment.
1. Applicability Monitoring
a. Overview and Purpose
The purpose of the TTHM and HAA5 applicability monitoring is to
serve as an indicator for systems that are likely to consider making
changes to their disinfection practices in order to comply with the
Stage 1 DBPR. TTHM samples which equal or exceed 0.064 mg/L and/or HAA5
samples equal or exceed 0.048 mg/L (80 percent of their respective
MCLs) represent DBP levels of concern. Systems with TTHM or HAA5 levels
exceeding 80 percent of the respective MCLs may consider changing their
disinfection practice in order to comply with the Stage 1 DBPR.
b. Data
In 1987, EPA established monitoring requirements for 51 unregulated
synthetic organic chemicals. Subsequently, an additional 113
unregulated contaminants were added to the monitoring requirements.
Information on TTHMs has become available from the first round of
monitoring conducted by systems serving fewer than 10,000 people.
Preliminary analysis of the data from the Unregulated Contaminant
Information System (URCIS, Data) suggest that roughly 12 percent of
systems serving fewer than 10,000 would exceed 64 /L or 80
percent of the MCL for TTHM (Table IV.7). This number is presented only
as an indicator, as it represents samples taken at the entrance to
distribution systems. In general, TTHMs and HAA5s tend to increase with
time as water travels through the distribution system. The Stage 1
Disinfection Byproducts Rule estimated 20 percent of systems serving
fewer than 10,000 would exceed 80 percent of the MCLs for either TTHMs
or HAA5s or both. EPA is working to improve the knowledge of TTHM and
HAA5 formation kinetics in the distribution systems for systems serving
fewer than 10,000 people. EPA is currently developing a model to
predict the formation of TTHM and HAA5 in the distribution system based
on operational measurements. This model is not yet available. In order
to develop a better estimate of the percent of small systems that would
be triggered into the profiling requirements (i.e., develop a profile
of microbial inactivation over a period of 1 year) EPA is considering
the following method:
Use URCIS data to show how many systems serving 10,000 or
more people have TTHM levels at or above 0.064 mg/L;
Compare those values to the data received from the
Information Collection Rule for TTHM average values taken at
representative points in the distribution system;
Determine the mathematical factor by which the two values
differ; and
Apply that factor to the URCIS data for systems serving
fewer than 10,000 people to estimate the percent of those systems that
would have TTHM values at or above 0.064mg/L as an average of values
taken at representative points in the distribution system.
Table IV.7.--TTHM Levels at Small Surface Systems
[Data from Unregulated Contaminant Database, 1987-92 \1\]
------------------------------------------------------------------------
Number of
systems w/
ave. TTHM Maximum
Total level of
System size (population served) number of 64 g/L (80 (g/
% of MCL) L)
------------------------------------------------------------------------
500............................. 74 0 (0%) 56
501-1,000....................... 44 6 (13.6%) 222
1,001-3,300..................... 114 12 (10.5%) 172
3,301-10,000.................... 116 25 (21.6%) 279
---------------------------------------
Total....................... 348 43 (12.4%) 279
------------------------------------------------------------------------
\1\ In Unregulated Contaminant Database (1987-1992), there are ten
States (i.e., CA, DE, IN, MD, MI, MO, NC, NY, PR, WV). However, only
eight of them can be identified with the data of both population and
TTHM for systems serving fewer than 10,000 people (See next page).
The Agency requests comment on this approach to estimating TTHM
levels in the distribution system based on TTHM levels at the entry
point to the distribution system. The Agency also requests comment on
the relationship of HAA5 formation relative to TTHM formation in the
distribution system. Specifically, is there data to support the
hypothesis that HAA5s do not peak at the same point in the distribution
system as TTHMs?
The Agency also received two full years of TTHM data for seventy-
four systems in the State of Missouri (Missouri, 1998). This data
consisted of quarterly TTHM data, which was converted into an annual
average. The data (presented in Table IV.8) demonstrates a very
different picture than that displayed by the URCIS data described
above. In 1996, 88 percent of the systems exceeded 64 g/L,
while in 1997, 85 percent exceeded 64 g/L. Figure IV.7
graphically displays this data set.
[[Page 19088]]
Table IV.8.--TTHM Levels at Small Surface Systems in the State of
Missouri
[State of Missouri, 1996, 1997]
------------------------------------------------------------------------
Number of
systems w/
ave. TTHM Maximum
Total Level of
Year number of 64 g/L (80 (g/
percent of L)
MCL)
------------------------------------------------------------------------
1996............................ 74 65 (88%) 276
1997............................ 75 64 (85%) 251
All years....................... 149 129 (87%) 276
------------------------------------------------------------------------
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There are several potential reasons for the differences between the
data shown in Tables IV.7 and IV.8. Data in Table IV.7 contains zero
values which may be indicative of no sample being taken rather than a
sample with a value of zero. Additionally, data shown in IV.8 was
collected within the distribution system, while data in Table IV.7 was
taken at the entry point to the distribution system. The data
collection method used in collecting the data
[[Page 19090]]
shown in Table IV.8 is similar to the methodology required under the
Stage 1 DBPR.
c. Proposed Requirements
EPA considered four alternatives for systems to use TTHM and HAA5
data to determine which systems whether they would be required to
develop a disinfection profile. In today's proposed rule, EPA is
proposing Alternative 4.
Alternative 1
The IESWTR required that systems monitor for TTHMs at four points
in the distribution system each quarter. At least one of those samples
must be taken at a point which represents the maximum residence time of
the water in the system. The remaining three must be taken at
representative locations in the distribution system, taking into
account number of persons served, different sources of water and
different treatment methods employed. The results of all analyses per
quarter are averaged and reported to the State.
EPA considered applying this alternative to systems serving fewer
than 10,000 people and requested input from small system operators and
other interested parties, including the public. Based on the feedback
EPA received, two other alternatives were developed for consideration
(listed as Alternatives 2 and 3).
Alternative 2
EPA considered requiring systems serving fewer than 10,000 people
to monitor for TTHM and HAA5 at the point of maximum residence time
according to the following schedule:
No less than once per quarter per treatment plant operated
for systems serving populations between 500 and 10,000 persons; and no
less than once per year per treatment plant during the month of warmest
water temperature for systems serving populations less than 500. If
systems wish to take additional samples, however, they would be
permitted to do so.
Systems may consult with States and elect not to perform
TTHM and HAA5 monitoring and proceed directly with the development of a
disinfection profile.
This alternative provides an applicability monitoring frequency
identical to the DBP monitoring frequency under the Stage 1 DBPR that
systems will have to comply with in 2004. In addition, it allows
systems the flexibility to skip TTHM and HAA5 monitoring completely,
pending State approval, and begin profiling immediately.
Alternative 3
EPA considered requiring all systems serving fewer than 10,000
people to monitor once per year per system during the month of warmest
water temperature of 2002 and at the point of maximum residence time.
During the SBREFA process and during stakeholder meetings, EPA
received some positive comments regarding Alternative 3 as the least
burdensome approach. Other stakeholders, however, pointed out that
Alternative 3 does not allow systems to measure seasonal variation as
is done in Alternative 2 for systems serving populations between 500
and 10,000. Several stakeholders agreed that despite the costs, the
information obtained from applicability monitoring will be useful. EPA
agrees that it is valuable to systems to monitor and understand the
seasonal variation in TTHM and HAA5 values, however, EPA has determined
that requiring a full year of monitoring may place an excessive burden
on both States and systems. In order to complete a full year of
monitoring and another full year of disinfection data gathering,
systems would have to start TTHM and HAA5 monitoring January of 2002.
Under SDWA, States have two years to develop their own regulations
as part of their primacy requirements, EPA recognized that requiring
Applicability Monitoring during this period would pose a burden on
States. In response to these concerns, the Agency developed a new
alternative, described in the following paragraph.
Alternative 4
Applicability Monitoring is optional and not a requirement under
today's proposed rule. If a system has TTHM and HAA5 data taken during
the month of warmest water temperature (from 1998-2002) and taken at
the point of maximum residence time, they may submit this data to the
State prior to [DATE 2 YEARS AFTER PUBLICATION OF FINAL RULE]. If the
data shows TTHM and HAA5 levels less than 80 percent of the MCLs, the
system does not have to develop a disinfection profile. If the data
shows TTHM and HAA5 levels at or above 80 percent of the MCLs, the
system would be required to develop a disinfection profile in 2003 as
described later in section IV.B.2. If the system does not have, or does
not gather TTHM and HAA5 data during the month of warmest water
temperature and at the point of maximum residence time in the
distribution system as described, then the system would automatically
be required to develop a disinfection profile starting January 1 of
2003. This option still provides systems with the necessary tools for
assessing potential changes to their disinfection practice, (i.e. the
generation of the profile), while not forcing States to pass their
primacy regulations, contact all small systems within their
jurisdiction, and set up TTHM and HAA5 monitoring all within the first
year after promulgation of this rule. Systems will still be able to
ensure public health protection by having the disinfection profile when
monitoring under Stage 1 DBPR takes effect. It should be noted that EPA
estimates the cost for applicability monitoring (as described in
Alternative 4) and disinfection profiling (as described in Alternative
3 in Section IV.B.2.c of this preamble) are roughly equivalent. EPA
anticipates that systems with known low levels of TOC may opt to
conduct the applicability monitoring while the remaining systems will
develop a disinfection profile.
d. Request for Comment
EPA requests comment on the proposed requirement, other
alternatives listed, or other alternatives that have not yet been
raised for consideration. The Agency also requests comment on
approaches for determining the percent of systems that would be
affected by this requirement. Specifically:
With respect to Alternative 4, the Agency requests comment
on approaches for determining the percent of systems that might
demonstrate TTHM and HAA5 levels less than 80 percent of their
respective MCLs and would therefore not develop a disinfection profile.
The Agency requests additional information (similar to the
State of Missouri data discussed previously) on the current levels of
TTHM and HAA5s in the distribution systems of systems serving fewer
than 10,000 people.
The Agency requests comment on developing a TTHM and HAA5
monitoring scheme during the winter months as opposed to the current
monitoring scheme based on the highest TTHM/HAA5 formation potential
during the month of warmest water temperature. If a relationship can be
established, and shown to be consistent through geographical
variations, EPA would consider modifying an alternative so that
applicability monitoring would occur during the 1st quarter of 2003.
The Agency requests comment on modifying Alternative 3, to
require systems to begin monitor for TTHMs and HAA5s during the warmest
water temperature month of 2003. The results of this monitoring would
be used to
[[Page 19091]]
determine whether a system would need to develop a disinfection profile
during 2004. This option is closer in structure and timing to the
IESWTR and has been included for comment. It should be noted, however,
that postponing the disinfection profile until 2004 would prevent
systems from having inactivation data prior to their compliance date
with the Stage 1 DBPR, possibly compromising simultaneous compliance.
2. Disinfection Profiling
a. Overview and Purpose
The disinfection profile is a graphical representation showing how
disinfection varies at a given plant over time. The profile gives the
plant operator an idea of how seasonal changes in water quality and
water demand can have a direct effect on the level of disinfection the
plant is achieving.
The strategy of disinfection profiling and benchmarking stemmed
from data provided to the EPA and M-DBP Advisory Committee by PWSs and
reviewed by stakeholders. The microbial inactivation data (expressed as
logs of Giardia lamblia inactivation) used by the M-DBP Advisory
Committee demonstrated high variability. Inactivation varied by several
log on a day-to-day basis at any particular treatment plant and by as
much as tens of logs over a year due to changes in water temperature,
flow rate (and, consequently, contact time), seasonal changes in
residual disinfectant, pH, and disinfectant demand and, consequently,
disinfectant residual. There were also differences between years at
individual plants. To address these variations, M-DBP stakeholders
developed the procedure of profiling inactivation levels at an
individual plant over a period of at least one year, and then
establishing a benchmark of minimum inactivation as a way to
characterize disinfection practice. This approach makes it possible for
a plant that may need to change its disinfection practice in order to
meet DBP MCLs to determine the impact the change would have on its
current level of disinfection or inactivation and, thereby, to assure
that there is no significant increase in microbial risk. In order to
develop the profile, a system must measure four parameters (EPA is
assuming most small systems use chlorine as their disinfection agent,
and these requirements are based on this assumption):
(1) Disinfectant residual concentration (C, in mg/L) before or at
the first customer and just prior to each additional point of
disinfectant addition;
(2) Contact time (T, in minutes) during peak flow conditions;
(3) Water temperature ( deg.C); and
(4) pH.
Systems convert this operational data to a number representing log
inactivation values for Giardia by using tables provided by EPA.
Systems graph this information over time to develop a profile of their
microbial inactivation. EPA will prepare guidance specifically
developed for small systems to assist in the development of the
disinfection profile. Several spreadsheets and simple programs are
currently available to aid in calculating microbial inactivation and
the Agency intends to make such spreadsheets available in guidance.
b. Data
Figure IV.8a depicts a hypothetical disinfection profile showing
seasonal variation in microbial inactivation.
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[[Page 19093]]
c. Proposed Requirements
EPA considered four alternatives for requiring systems to develop
the disinfection profile.
Alternative 1
The IESWTR requires systems serving 10,000 or more persons to
measure the four parameters described above and develop a profile of
microbial inactivation on a daily basis. EPA considered extending this
requirement to systems serving fewer than 10,000 persons and requested
input from small system operators and other interested stakeholders
including the public. EPA received feedback that this requirement would
place too heavy of a burden on the small system operator for at least
two reasons:
Small system operators are not present at the plant every
day; and
Small systems often have only one operator at a plant who
is responsible for all aspects of maintenance, monitoring and
operation.
Alternative 2
EPA also considered not requiring the disinfection profile at all.
After consideration of the feedback of small system operators and other
interested stakeholders, however, EPA believes that there is a strong
benefit in the plant operator knowing the level of microbial
inactivation, and that the principles developed during the regulation
negotiation and Federal Advisory Committee prior to promulgation of the
IESWTR could be applied to small systems for the purpose of public
health protection. Recognizing the potential burdens the profiling
procedures placed on small systems, EPA considered two additional
alternatives.
Alternative 3
EPA considered requiring all systems serving fewer than 10,000
persons, to develop a disinfection profile based on weekly measurements
for one year during or prior to 2003. A system with TTHM and HAA5
levels less than 80 percent of the MCLs (based on either required or
optional monitoring as described in section IV.B.1) would not be
required to conduct disinfection profiling. EPA believes this
alternative would save the operator time (in comparison to Alternative
1), and still provide information on seasonal variation over the period
of one year.
Alternative 4
Finally, EPA considered a monitoring requirement only during a one
month critical monitoring period to be determined by the State. In
general, colder temperatures reduce disinfection efficiency. For
systems in warmer climates, or climates that do not change very much
during the course of the year, the State would identify other critical
periods or conditions. This alternative reduces the number of times the
operator has to calculate the microbial inactivation.
EPA considered all of the above alternatives, and in today's
proposed rule, EPA is proposing Alternative 3. First, this alternative
does not require systems to begin monitoring before States have two
years to develop their regulations as part of primacy requirements.
Given early implementation concerns, the timing of this alternative
appears to be the most appropriate in balancing early implementation
issues with the need for systems to prepare for implementation of the
Stage 1 DBPR and ensuring adequate and effective microbial protection.
Second, it allows systems and States which have been proactive in
conducting applicability monitoring to reduce costs for those systems
which can demonstrate low TTHM and HAA5 levels. Third, this alternative
allows systems and States the opportunity to understand seasonal
variability in microbial disinfection. Finally, this alternative takes
into account the flexibility needed by the smallest systems while
maintaining comparable levels of public health protection with the
larger systems.
Request for Comments
EPA requests comment on this proposed requirement as well as
Alternatives 1,2, and 4. The Agency also requests comment on a possible
modification to Alternatives 1, 3 and 4. Under this modification,
systems serving populations fewer than 500 would have the opportunity
to apply to the State to perform the weekly inactivation calculation
(although data weekly data collection would still be required). If the
system decided to make a change in disinfection practice, then the
State would assist the system with the development of the disinfection
profile.
The Agency also requests comment on a modification to Alternative 3
which would require systems to develop a disinfection profile in 2004
only if Applicability Monitoring conducted in 2003 indicated TTHM and
HAA5 levels of 80 percent or greater of the MCL. This modification
would be coupled with the applicability monitoring modification
discussed in the previous section.
3. Disinfection Benchmarking
a. Overview and Purpose
The DBPR requires systems to meet lower MCLs for a number of
disinfection byproducts. In order to meet these requirements, many
systems will require changes to their current disinfection practices.
In order to ensure that current microbial inactivation does not fall
below those levels required for adequate Giardia and virus inactivation
as required by the SWTR, a disinfection benchmark is necessary. A
disinfection benchmark represents the lowest average monthly Giardia
inactivation level achieved by a system. Using this benchmark States
and systems can begin to understand the current inactivation achieved
at the system, and estimate how changes to disinfection practices will
affect inactivation.
b. Data
Based on the hypothetical disinfection profile depicted in Figure
IV.8a, the benchmark, or critical period, is the lowest level of
inactivation achieved by the system over the course of the year. Figure
IV.8b shows that this benchmark (denoted by the dotted line) takes
place in December for the hypothetical system.
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