United States Office of Water EPA 815-F-98-010
Environmental Protection (4607) December 1998
Agency DRAFT
v>EPAStage 1 Disinfectants and
Disinfection Byproducts Rule
In the past 25 years, the Safe Drinking Water Act (SDWA) has been highly effective in
protecting public health and has also evolved to respond to new and emerging threats to safe
drinking water. 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 through
American cities; 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. In addition, in the past ten years, we
have learned that there are specific microbial pathogens, such as Cryptosporidium, which can
cause chronic illness among those with weakened immune systems, and is highly resistant to
traditional disinfection practices.
• Amendments to the SDWA in 1996 require EPA to develop rules to balance the risks between
microbial pathogens and disinfection byproducts (DBFs). It is important to strengthen protection
against microbial contaminants, especially Cryptosporidium, and at the same time, reduce
potential health risks of DBFs. The Stage 1 Disinfectants and Disinfection Byproducts Rule and
Interim Enhanced Surface Water Treatment Rule, signed in November 1998, are the first of a set
of rules under the 1996 SDWA Amendments. This fact sheet focuses on the Stage 1
Disinfectants and Disinfection Byproducts Rule. A separate fact sheet focuses on the Interim •
Enhanced Surface Water Treatment Rule (EPA 815-F-98-009).
I PUBLIC HEALTH OONGERNSgft
While disinfectants are effective in controlling many microorganisms, they react with natural
organic and inorganic matter in source water and distribution systems to form DBFs. Results
from toxicology studies have shown several DBFs (e.g., bromodichloromethane, bromoform,
chloroform, dichloroacetic acid, and bromate) to be carcinogenic in laboratory animals. Some
DBFs (e.g., chlorite, bromodichloromethane, and certain haloacetic acids) have also been shown
to cause adverse reproductive .or developmental effects in laboratory animals. Several
epidemiology studies have suggested a weak association between certain cancers (e.g., bladder)
or reproductive and developmental effects, and exposure to chlorinated surface water. 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.
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I WHO MUST COMPLY WITH THE RULE7~\
The Stage 1 Disinfectants and Disinfection Byproducts Rule applies to all community
and nontransient noncommunity water systems that treat their water with a chemical
disinfectant for either primary or residual treatment.
WHAT DOES THE RULE REQUIRE? \
The Stage 1 Disinfectant and Disinfection Byproduct Rule updates and supersedes the
1979 regulations for total trihalomethanes. In addition, it will reduce exposure to three
disinfectants and many disinfection byproducts.
The rule establishes maximum residual disinfectant level goals (MRDLGs) and
maximum residual disinfectant levels (MRDLs) for three chemical disinfectants -
chlorine, chloramine and chlorine dioxide (see Table 1). It also establishes maximum
contaminant level goals (MCLGs) and maximum contaminant levels (MCLs^for total
trihalomethanes, haloacetic acids, chlorite and bromate (see Table 1).
Table 1
MRDLGs. MRDLs. MCLGs and MCLs for Stage 1 Disinfectants
and Disinfection Byproducts Rule
DISINFECTANT
RESIDUAL
Chlorine
Chloramine
Chlorine Dioxide
DISINFECTION
BYPRODUCTS- ;
Total trihalomethanes
(TTHM)1
- Chloroform
- Bromodichloromethane
- Dibromochloromethane
- Bromoform
Haloacetic acids (five)
(HAA5)2
- Dichloroacetic acid
- Trichloroacetic acid
* ,. (mg/E)
N/A
0
0
0.06
0
N/A
0
0.3
MRDkOng/L)^
4.0 (as C12)
4.0 (as C12)
0.8 (as C1O2)
MCL(mg/LK
5 - -. " " . '
0.080
0.060
\
COMPLIANCE
.- BASED ON _
Annual Average
Annual Average
Daily Samples
COMPLIANCE
. BASED ON
Annual Average
Annual Average
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Chlorite
Bromate
0.8
0
1.0
0.010
Monthly Average
Annual Average
N/A - Not applicable because there are individual MCLGs for TTHMs or HAAs
1-Total trihalomethanes is the sum of the concentrations of chloroform,
bromodichloromethane, dibromochloromethane, and bromoform.
2-Haloacetic acids (five) is the sum of the concentrations of mono-, di-, and
trichloroacetic acids and mono- and dibromoacetic acids.
Water systems that use surface water or ground water under the direct influence
of surface water and use conventional filtration treatment are required to remove
specified percentages of organic materials, measured as total organic carbon (TOC), that
may react with disinfectants to form DBFs (See Table 2). Removal will be achieved
through a treatment technique (enhanced coagulation or enhanced softening) unless a
• system meets alternative criteria.
Table 2
Required Removal of Total Organic Carbon by Enhanced Coagulation and
Enhanced Softening for Subpart H Systems Using Conventional Treatmentl
Source Water TOC
(mg/L)
>2.0-4.0
>4.0-8.0
>8.0
Source Water Alkalinity (mg/L as CaCO3)
0-60
35.0%
45.0%
50.0%
>60-120
25.0%
35.0%
40.0%
>1202
15.0%
25.0%
30.0%
1 Systems meeting at least one of the alternative compliance criteria in the rule are not
required to meet the removals in this table.
2Systems practicing softening must meet the TOC removal requirements in the last
column to the right
WHAT ARE^THBCOMPLLANCE DEADLINES?
Large surface water systems are required to comply with the Stage 1 Disinfectants and
Disinfection Byproducts Rule and Interim Enhanced Surface Water Treatment Rule by
December 2001. Ground water systems and small surface water systems must comply
with the Stage 1 Disinfectants and Disinfection Byproducts Rule by December 2003.
WHAT ARE THE COSTS AND BENEFITS OF
THE RULE?
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EPA estimates that implementation of the Stage 1 Disinfectants and Disinfection
Byproducts Rule will result in:
As many as 140 million eople will have increased protection from DBFs.
24 percent national average reduction in TTHM levels.
Reduction in exposure to the major DBFs from use of ozone (bromate) and
chlorine
dioxide (chlorite).
The total annual cost of the rule is about $700 million. EPA believes that the benefits
exceed the costs of the Stage 1 Disinfectants and Disinfection Byproducts Rule. An
estimated 116 million households are affected by the Stage 1 Disinfectants and
Disinfection Byproducts Rule. EPA estimates that 95 percent of the households will
incur additional costs of less than $1 per month on their water bills. An additional four
percent will pay between $1 and $10 per month more, and one percent are expected to
incur increased water bills of $10 to $40 per month, if they choose to install treatment.
However, many of these systems may chose less costly non-treatment options, such as
consolidation. The majority of households incurring the highest costs are small systems
serving less than 10,000 people that have never been regulated for DBFs.
WHAT TECHNICAL INFORMATION WILL BE
AVAILABLE ON THE RULE?
A series of guidance manuals will support the Stage 1 Disinfectants and Disinfection
Byproducts Rule. The manuals will aid EPA, State agencies and affected public water
systems in implementing the two interrelated rules, and will help to ensure that
implementation among these groups is consistent. EPA anticipates that the manuals will
be available for review in early 1999.
Guidance Manual for Enhanced Coagulation and Enhanced Precipitative Softening
Objective: To assist utilities in implementing, monitoring, and complying with the
treatment technique requirements in the final Stage 1 Disinfectants and Disinfection
Byproducts Rule and to provide guidance to State staff responsible for implementing the
treatment requirements.
Contents: The manual provides detailed information on the total organic carbon (TOC)
removal requirement; explains how to set an alternative TOC removal percentage under
the Step 2 procedure; details monitoring, reporting, and compliance requirements; and
discusses strategies that can be employed to mitigate the potential secondary effects on
plant performance due to implementation of the treatment technique.
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Alternative Disinfectants and Oxidants Guidance Manual
Objective: To provide technical data and engineering information on disinfectants and
oxidants that are not as commonly used as chlorine, so that systems can evaluate their
options for developing disinfection schemes to control water quality problems such as
zebra mussels and Asiatic clams, and oxidation to control water quality problems
associated with iron and manganese.
Contents: The manual discusses six disinfectants and oxidants: ozone, chlorine dioxide,
potassium permanganate, chloramines, ozone/hydrogen peroxide combinations, and
ultraviolet light. A decision tree is provided to assist in evaluating which disinfectant(s)
is most appropriate given certain site-specific conditions (e.g., water, quality conditions,
existing treatment and operator skill). The manual also contains a summary of existing
alternative disinfectants use in the United States and cost estimates for the use of
alternative disinfectants.
M/DBP Simultaneous Compliance Manual
Objective: To assist public water systems on complying simultaneously with various
drinking water regulations (e.g., Stage 1 Disinfectants and Disinfection Byproducts Rule,
Interim Enhanced Surface Water Treatment Rule, Lead and Copper Rule and the Total
Coliform Rule). The manual discusses operational problems systems may encounter
when implementating these rules.
Contents: The manual provides detailed information on the requirements in the Stage 1
Disinfectants and Disinfection Byproducts Rule and the Interim Enhanced Surface Water
Treatment Rule.
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.
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