United States Office of Water EPA 81 5-F-98-0014
Environmental Protection (4607) December 1998
Agency DRAFT
Drinking Water Priority Rule ma king:
Microbial and Disinfection Byproduct Rules
Disinfection of drinking water is one of the major public health advances in the 20th century.
One hundred years ago, typhoid and cholera epidemics were common throughout American
cities and disinfection was a major factor in reducing these epidemics. However, the
disinfectants themselves can react with naturally-occurring materials in the water to form
unintended byproducts which may pose health risks.
Over the past ten years, we have also learned that there are specific microbial pathogens, such as
Cryptosporidium, that are highly resistant to traditional disinfection practices. In 1993,
Cryptosporidium caused 400,000 people in Milwaukee to experience intestinal illness. More
than 4,000 were hospitalized, and at least SO deaths have been attributed to the disease. There
have also been cryptosporidiosis outbreaks in Nevada, Oregon, and Georgia over the past several
years.
A major challenge for water suppliers is how to balance the risks from microbial pathogens and
disinfection byproducts. It is important to provide protection from these microbial pathogens
while simultaneously ensuring decreasing health risks to the population from disinfection
byproducts (DBFs). The Safe Drinking Water Act (SDWA) Amendments, signed by President
Clinton in August 1996, required EPA to develop rules to achieve these goals. The new Stage 1
Disinfectant and Disinfection Byproduct Rule and Interim Enhanced Surface Water Treatment
Rule are the first of a set of rules under the Amendments.
These new rules are a product of six years of collaboration between the water industry,
environmental and public health groups, and local, State and federal government. This fact sheet
contains general information about the two new rules and others that are a part of the
Microbial-Disinfectants and Disinfection Byproducts (M-DBP) Rules. Separate fact sheets focus
on the Interim Enhanced Surface Water Treatment Rule (EPA 81S-F-98-009) and the Stage 1
Disinfectants and Disinfection Byproducts Rule (EPA 815-F-98-010).
Schedule of M-DBP Rules
November 1998 - Final Rule
August 2000 - Final Rule
November 2000 - Final Rule
May 2002 - Final Rule
Interim Enhanced Surface Water Treatment Rule
& Stage 1 Disinfection Byproduct Rule
Filter Backwash Recycling Rule
Long Term 1 Enhanced Surface Water Treatment Rule
& Ground Water Rule
Stage 2 Disinfection Byproduct Rule & Long Term 2
Enhanced Surface Water Treatment Rule
-------
Public Health Concerns
Most Americans drink tap water that meets all existing health standards all the time. These
new rules will further strengthen existing drinking water standards and thus increase
protection for many water systems where new risks from microbial contaminants and DBFs
have emerged.
EPA's Science Advisory Board concluded in 1990 that exposure to microbial contaminants
such as bacteria, viruses, and protozoa (e.g., Giardia lamblia and Cryptosporidiwri) was likely
the greatest remaining health risk management challenge for drinking water suppliers. Acute
health effects from exposure to microbial pathogens is documented and associated illness can
range from mild to moderate cases lasting only a few days to more severe infections that can
last several weeks and may result in death for those with weakened immune systems.
In addition, while.disinfectants are effective in controlling many microorganisms, they react
with natural organic and inorganic matter in source water and distribution systems to form
potentially DBFs. Many of these DBFs have been shown to cause cancer and reproductive
and developmental effects in laboratory animals. More than 200 million people consume
water that has been disinfected. Because of the large population exposed, health risks
associated with DBFs, even if small, need to be taken seriously.
Existing Regulations
• Microbial Contaminants: The Surface Water Treatment Rule, promulgated in 1989,
applies to all public water systems using surface water sources or ground water sources
under the direct influence of surface water. It establishes maximum contaminant level
goals (MCLGs) for viruses, bacteria and Giardia lamblia. It also includes treatment
technique requirements for filtered and unfiltered systems that are specifically designed
to protect against the adverse health effects of exposure to these microbial pathogens.
The Total Coliform Rule, revised in 1989, applies to all PWSs and establishes a
maximum contaminant level (MCL) for total coliforms.
• Disinfection Byproducts: In 1979, EPA set an interim MCL for total trihalomethanes
of 0.10 mg/1 as an annual average. This applies to any community water system serving at
least 10,000 people that adds a disinfectant to the drinking water during any part of the
treatment process.
Information Collection Rule
To support the M-DBP rulemaking process, the Information Collection Rule (61 FR 243 54,
May 14, 1996) establishes monitoring and data reporting requirements for large public water
systems serving at least 100,000 people. This rule is intended to provide EPA with
information on the occurrence in drinking water of microbial pathogens and DBFs. In
addition, EPA is collecting engineering data on how PWSs currently control such
-------
contaminants as pan of the Information Collection Rule.
Interim Enhanced Surface Water Treatment Rule
& Stage 1 Disinfectants and Disinfection Byproducts Rule
EPA finalized the Interim Enhanced Surface Water Treatment Rule and Stage 1 Disinfectants
and Disinfection Byproducts Rule in November 1998, as required by the 1996 Amendments
to the Safe Drinking Water Act, Section 1412(b)(2)(C). The final rules resulted from formal
regulatory negotiations with a wide range of stakeholders that took place in 1992-93 and
1997.
Interim Enhanced Surface Water Treatment Rule
The Interim Enhanced Surface Water Treatment Rule applies to systems using surface
water, or ground water under the direct influence of surface water, that serve 10,000
or more persons. The rule also includes provisions for States to conduct sanitary
surveys for surface water systems-regardless of system size. The rule builds upon
the treatment technique requirements of the Surface Water Treatment Rule with the
following key additions and modifications:
• Maximum contaminant level goal (MCLG) of zero for Cryptosporidium
• 2-log Cryptosporidium removal requirements for systems that filter
• Strengthened combined filter effluent turbidity performance standards
• Individual filter turbidity monitoring provisions
• Disinfection profiling and benchmarking provisions
• Systems using ground water under the direct influence of surface water now
subject to the new rules dealing with Crypdosporidium
• Inclusion of Cryptosporidium in the watershed control requirements for
unfiltered public water systems
• Requirements for covers on new finished water reservoirs
• Sanitary surveys, conducted by States, for all surface water systems regardless
of size
The Interim Enhanced Surface Water Treatment Rule, with tightened turbidity
performance criteria and required individual filter monitoring, is designed to
optimize treatment reliability and to enhance physical removal efficiencies to
minimize the Cryptosporidium levels in finished water. In addition, the rule
includes disinfection benchmark provisions to assure continued levels of
microbial protection while facilities take the necessary steps to comply with
new DBP standards.
Stage 1 Disinfectants and Disinfection Byproducts Rule
The final Stage 1 Disinfectants and Disinfection Byproducts Rule applies to
community water systems and non-transient non-community systems, including those
serving fewer than 10,000 people, that add a disinfectant to the drinking water during
-------
any part of the treatment process.
The final Stage 1 Disinfectants and Disinfection Byproducts Rule includes the
following key provisions:
• Maximum residual disinfectant level goals (MRDLGs) for chlorine (4 mg/L),
chloramines (4 mg/L), and chlorine dioxide (0.8 mg/L);
• Maximum contaminant level goals (MCLGs) for four trihalomethanes
(chloroform (0 mg/L), bromodichloromethane (0 mg/L), dibro.mochloromethane
(0.06 mg/L), and bromoform (0 mg/L)), two haloacetic acids (dichloroacetic acid
(0 mg/L) and trichloroacetic acid (0.3 mg/L)), bromate (0 mg/L), and chlorite (0.8
mg/L);
• MRDLs for three disinfectants (chlorine (4.0 mg/L), chloramines (4.0 mg/L),
and chlorine dioxide (0.8 mg/L));
• MCLs for total trihalomethanes - a sum of the four listed above (0.080 mg/L),
haloacetic acids (HAAS) (0.060 mg/L)- a sum of the two listed above plus
monochloroacetic acid and mono- and dibromoacetic acids), and two inorganic
disinfection byproducts (chlorite (1.0 mg/L) and bromate (0.010 mg/L)); and
• A treatment technique for removal of DBF precursor material.
The terms MRDLG and MRDL, which are not included in the SDWA, were created
during the negotiations to distinguish disinfectants (because of their beneficial use)
from contaminants. The final rule includes monitoring, reporting, and public
notification requirements for these compounds. This final rule also describes the best
available technology (BAT) upon which the MRDLs and MCLs are based.
Future M-DBP Rules: Long Term 1 and 2 Enhanced Surface Water Treatment
Rules, Stage 2 Disinfection Byproduct Rule, Ground Water Rule, and Filter
Backwash Recycling
Long Term 1 Enhanced Surface Water Treatment Rule
While the Stage 1 Disinfectants and Disinfection Byproducts Rule rule will apply to
systems of all sizes, the Interim Enhanced Surface Water Treatment Rule only
applies to systems serving. 10,000 or more people. A Long Term 1 Enhanced
Surface Water Treatment Rule, due in the fall of 2000, will strengthen
microbial controls for small systems i.e., those systems serving fewer than
10,000 people. The rule will also prevent significant increase in microbial risk
where small systems take steps to implement the Stage 1 Disinfectants and
Disinfection Byproducts Rule.
EPA believes that the rule will generally track the approaches in the Interim
Enhanced Surface Water Treatment Rule for improved turbidity control, including
individual filter monitoring and reporting. The rule will also address
disinfection profiling and benchmarking. The Agency is considering what
-------
modifications of some large system requirements may be appropriate for small
systems.
Long Term 2 Enhanced Surface Water Treatment Rule
and Stage 2 Disinfection Byproduct Rule
The SOW A, as amended in 1996, requires EPA to finalize a Stage 2 Disinfectants and
Disinfection Byproducts Rule by May 2002. Although the 1996 Amendments do not
require EPA to finalize a Long Term 2 Enhanced Surface Water Treatment Rule along
with the Stage 2 Disinfectants and Disinfection Byproducts Rule, EPA believes it is
important to finalize these rules together to ensure a proper balance between microbial
and DBP risks.
EPA will begin discussions with stakeholders in December 1998 on the direction for
these rules. EPA anticipates proposed rules in early 2001. The intent of the rules is to
provide additional public health protection, if needed, from DBPs and microbial
pathogens.
Ground Water Rule
EPA is developing a ground water rule which specifies the appropriate use of
disinfection and, just as importantly, addresses other components of ground water
systems to ensure public health protection. There are more than 158,000 public ground
water systems. Almost 89 million people are served by community ground water
systems, and 20 million people are served by non-community ground water systems.
Ninety-nine percent (157,000) of ground water systems serve fewer than 10,000
people. However, systems serving more than 10,000 people serve 55% (more than 60
million) of all people who get their drinking water from public ground water systems.
The Ground Water Rule will be promulgated November 2000.
Filter Backwash Recycling
The 1996 SDWA Amendments require that EPA set a standard on recycling filter
backwash within the treatment process of public water systems by August 2000. The
regulation will apply to all public water systems, regardless of size. EPA is currently
gathering data, reviewing literature, and consulting with industry representatives,
members of the environmental community, and consulting engineers to identify
engineering and cost issues that are salient to regulatory development.
Opportunities for Public Involvement
EPA encourages public input into regulation development. Public meetings and
opportunities for public comment on M-DBP rules are announced in the Federal
Register. EPA's Office of Ground Water and Drinking Water also provides this
information for the M-DBP rule and other programs in its online Calendar of Events.
For more information, contact EPA's Safe Drinking Water Hotline, 1 (800) 426-4791,
or see the Office of Ground Water and Drinking Water web page at
http://www.epa.gov/safewater/standards.html.
------- |