DDW-2024-009553

See Table 2.
Regulated under
Stage 1 DBPR1
Regulated under
Stage 1 DBPR
Regulated under
Stage 1 DBPR
Regulated under
Stage 1 DBPR
Comprehensive Disinfectants and
Disinfection Byproducts Rules (Stage 1
and Stage 2): Quick Reference Guide
Overview of the Rules
Titles*►
►
Stage 1 Disinfectants and Disinfection Byproducts Rule (Stage 1 DBPR) 63 FR 69390,
December 16, 1998, Vol. 63, No. 241
Stage 2 Disinfectants and Disinfection Byproducts Rule (Stage 2 DBPR) 71 FR 388, January 4,
2006, Vol. 71, No. 2
Purpose Improve public health protection by reducing exposure to disinfection byproducts. Some disinfectants
and disinfection byproducts (DBPs) have been shown to cause cancer and reproductive effects in lab animals and suggested bladder cancer and reproductive effects in humans.
General
Description
The DBPRs require public water systems (PWSs) to:
►Comply with established maximum contaminant levels (MCLs) and operational evaluation
levels (OELs) for DBPs, and maximum residual disinfection levels (MRDLs) for disinfectant
residuals.
►Conduct an initial evaluation of their distribution system.
In addition, PWSs using conventional filtration are required to remove specific percentages of
organic material that may react to form DBPs through the implementation of a treatment technique.
Utilities
Covered
The DBPRs apply to all sizes of community water systems (CWSs) and nontransient noncommunity
water systems (NTNCWSs) that add a disinfectant other than ultraviolet (UV) light or deliver
disinfected water, and transient noncommunity water systems (TNCWSs) that add chlorine dioxide.
*This document provides a summary of federal drinking water requirements; to ensure full compliance, please
consult the federal regulations at 40 CFR 141 and any approved state requirements.
1. A new analytical method for bromate was approved with the Stage 2 DBPR.
Overview of Requirements
This table shows how the requirements for the Stage 2 DBPR build on the existing requirements established in
the Stage 1 DBPR. For more information on changes in monitoring requirements, see Table 1.
Stage 1
DBPR
Stage 2
DBPR
For More
Info:
Coverage
All CWSs and NTNCWSs that add
disinfectant other than UV light and
TNCWSs that treat with chlorine dioxide.
Consecutive systems that deliver water
treated with a disinfectant other than UV
light.
TTHM &
HAA5 MCL
Compliance
MCL compliance is calculated using the
running annual average (RAA) of all
samples from all monitoring locations
across the system.See Table 3
and Table 4.MCL compliance is calculated using the
locational RAA (LRAA) for each monitoring
location in the distribution system.
Regulated
Contaminants & Disinfectants
Contaminants
Total Trihalomethanes (TTHM)
5 Haloacetic Acids (HAA5)
Bromate
Chlorite
Disinfectants
Chlorine/chloramines
Chlorine dioxide
Operational
Evaluation
If an operational evaluation level (OEL)
is exceeded, systems must evaluate
practices and identify DBP mitigation
actions.
See Table 5.
10,000 must have at least 25 percent of samples at the location of maximum residence time; the remaining samples
must be representative of average residence time.
Table 1. Changes in Monitoring Requirements
Stage 1 DBPR Stage 2 DBPR
TT
H
M
/
HA
A
5

Ro
u
t
i
n
e

Mo
n
i
t
o
r
i
n
g
Number of Samples Based on source water type, population, and number
of treatment plants or wells.Based on source water type and population.
Sample Locations At location of maximum residence time.1 Based on Initial Distribution System Evaluation
(IDSE) requirements.2
Compliance Calculation RAA must not exceed the MCL for TTHM or HAA5.LRAA must not exceed the MCL for TTHM or HAA5.
Re
d
u
c
e
d

M
o
n
i
t
o
r
i
n
g
Eligibility
TTHM/HAA5
All systems need TTHM RAA < 0.040 mg/L and HAA5
< 0.030 mg/L. Subpart H systems also need source
water TOC RAA at location prior to treatment < 4.0
mg/L .3, 4
The Stage 2 DBPR left eligibility unchanged but
specifies that Subpart H systems must take source
water TOC samples every 30 days. Subpart H
systems on reduced monitoring must take source
water TOC samples every 90 days to qualify for
reduced monitoring.
Bromate5
Source water bromide RAA < 0.05 mg/L.
With the Stage 2 DBPR specified entry point to
distribution system bromate RAA < 0.0025 mg/L.
>1Subpart H systems serving
2All systems are required to satisfy their IDSE requirement by July 10, 2010.
3Subpart H systems are water systems that use surface water or ground water under the direct influence of surface water (GWUDI).
< 0.020 mg/L and a HAA5 RAA < 0.015 mg/L for 1 year.
4Ground water systems serving < 10,000 must meet these RAA for 2 years; can also qualify for reduced monitoring if the TTHM RAA is
5A new analytical method for bromate was established with the Stage 2 DBPR.
MRDL3 (mg/L) MRDLG
3 (mg/L) MRDL (mg/L) MRDLG (mg/L)
Table 2. Regulated Contaminants and Disinfectants
Stage 1 DBPR Stage 2 DBPR
Regulated Contaminants MCL (mg/L)MCLG (mg/L)MCL (mg/L)MCLG (mg/L)
TTHM 0.080 Unchanged2
Chloroform -0.07
Bromodichloromethane Zero Unchanged2
2
2
Dibromochloromethane 0.06 Unchanged
Bromoform Zero Unchanged
HAA5 0.060 Unchanged2
Monochloroacetic acid -0.07
Dichloroacetic acid Zero Unchanged2
Trichloroacetic acid 0.3 0.2
Bromoacetic acid --
Dibromoacetic acid --
Bromate (plants that use ozone)1 0.010 Zero Unchanged2
2
Unchanged2
2Chlorite (plants that use chlorine
dioxide)1.0 0.8 Unchanged Unchanged
Regulated Disinfectants
Chlorine 4.0 as Cl2
2
4 Unchanged2
2
2
Unchanged2
2
2
Chloramines 4.0 as Cl 4 Unchanged Unchanged
Chlorine dioxide 0.8 0.8 Unchanged Unchanged
1
2
3
A new analytical method for bromate was established with the Stage 2 DBPR.
Stage 2 DBPR did not revise the MCL or MRDL for this contaminant/disinfectant.
Stage 1 DBPR included MRDLs and MRDLGs for disinfectants, which are similar to MCLs and MCLGs.
Table 4. Compliance with MCLs and MRDLs (Routine Monitoring)
Contaminant/
Disinfectant
Coverage Stage 1 DBPR Stage 2 DBPR
Source
Water Population Monitoring
Frequency
Total Distribution
System Monitoring
Locations
Monitoring
Frequency1
Total Distribution
System Monitoring
Locations
TTHM/HAA5
Subpart H
< 500 Per year2 1 per treatment plant Per year2 2
500 - 3,300
Per quarter
1 per treatment plant
Per quarter
2
4
8
12
16
20
2
4
6
8
3,301 - 9,999
10,000 - 49,000
4 per treatment plant
50,000 - 249,999
250,000 - 999,999
1,000,000 - 4,999,999
> 5,000,000
Ground
water
< 500 Per year2
1 per treatment plant
Per year2
Per quarter
500 - 9,999
10,000 - 99,999
Per quarter100,000 - 499,999
> 500,000
Bromate3 Systems that use ozone as a
disinfectant Monthly 1 at entry point to
distribution system Unchanged4
Chlorite Systems that use chlorine dioxide as a disinfectant
Daily (at
entrance to
distribution
system);
monthly (in
distribution
system)
1 at entry point to
distribution system; 3 in
distribution system
Unchanged4
4
4
4
Chlorine dixoide Systems that use chlorine dioxide
as a disinfectant Daily 1 at entry point to
distribution system Unchanged
Chorine/Chloramines All systems Same location and frequency as Total
Coliform Rule (TCR) sampling Unchanged
DBP precursors
(TOC sample
set)*
Systems that use conventional
filtration Monthly 1 per source water
source Unchanged
1All systems must monitor during the month of highest DBP concentrations. Systems on quarterly monitoring, except Subpart H systems serving
500 - 3,300, must take dual sample sets every 90 days at each monitoring location. Systems on annual monitoring and Subpart H systems serving
500 - 3,300 are required to take individual TTHM and HAA5 samples (instead of a dual sample set) at the locations with the highest TTHM and HAA5
concentrations, respectively. If monitoring annually, only one location with a dual sample set per monitoring period is needed if the highest TTHM and
HAA5 concentrations occur at the same location and in the same month.
2Ground water systems serving < 10,000 and Subpart H systems serving < 500 must increase monitoring to quarterly if an MCL is exceeded.
3A new analytical method for bromate was established with the Stage 2 DBPR.
4Stage 2 DBPR did not revise the monitoring frequency or location requirements for this contaminant/disinfectant.
1
2
*
Table 3. Compliance Determination
Stage 1 DBPR Stage 2 DBPR
TTHM/HAA5 RAA LRAA
Bromate1 RAA Unchanged2
2
2
2
Chlorite Daily/follow-up monitoring Unchanged
Chorine dioxide Daily/follow-up monitoring Unchanged
Chlorine/chloramines RAA Unchanged
DBP precursors
(TOC sample set)*Monthly for TOC and alkalinity Every 30 days for TOC and alkalinity
A new analytical method for bromate was established with the Stage 2 DBPR.
Stage 2 DBPR did not change the compliance requirements for this contaminant/disinfectant.
TOC sample set is comprised of source water alkalinity, source water TOC, and treated TOC.
*TOC sample set is comprised of source water alkalinity, source water TOC, and treated TOC.
http://water.epa.gov/drink August 2010EPA 816-F-10-080Office of Water (4606M)
For additional information
on the DBPRs:
Call the Safe Drinking
Water Hotline at 1-800-
426-4791; visit the EPA
web site at http://water.
epa.gov/drink; or contact
your state drinking water
representative.
Table 5. Operational Evaluation Levels (OELs)
Applies to:All systems subject to Stage 2 DBPR monitoring requirements that conduct compliance
monitoring and collect samples quarterly.
Purpose of
establishing OELs: To reduce peaks in DBP levels and exposure to high DBP levels.
OEL calculations:Calculated for both TTHMs and HAA5s at each monitoring location using Stage 2 ►
DBPR compliance monitoring results.
OEL is determined by the sum of the two previous quarter’s TTHM or HAA5 result ►
►
plus twice the current quarter’s TTHM or HAA5 result at that location, divided by four.
OEL = (Q1 + Q2 + 2Q3) / 4
OELs are exceeded:During any quarter in which the OEL is greater than the TTHM or HAA5 MCL.
If an OEL is
exceeded, a system must:
Conduct an operational evaluation.►
►
►
Submit a written report of the evaluation to the state no later than 90 days after being
notified of the analytical results that caused the exceedance(s).
Keep a copy of the operational evaluation report and make it publically available
upon request.
The operational
evaluation must
include:
An examination of the treatment and distribution systems’ operational practices that ►
may contribute to TTHM and HAA5 formation.
Steps to minimize future exceedances.►
OEL requirements
take effect:When the system begins compliance monitoring for the Stage 2 DBPR.
Table 6. Standard Monitoring Compliance Dates
If You are a System Serving:Schedule1 Begin LRAA TTHM & HAA5
Monitoring By:
At least 100,000 people or part of a
combined distribution system (CDS) serving
at least 100,000 people.
1
2
3
4
April 1, 2012
50,000 to 99,999 people or part of a CDS
serving 50,000 to 99,999 people.October 1, 2012
10,000 to 49,999 people or part of a CDS serving 10,000 to 49,999 people.October 1, 2013
Less than 10,000 people or part of a CDS
serving less than 10,000 people.October 1, 20132
1Your schedule is determined by the largest system in your CDS.
2Systems not conducting Cryptosporidium monitoring under Long Term 2 Enhanced Surface Water Treatment
Rule (LT2ESWTR) must begin LRAA TTHM/HAA5 monitoring by this date. Systems conducting Cryptosporidium
monitoring under LT2ESWTR must begin LRAA TTHM/HAA5 monitoring by October 1, 2014.
Table 7. TOC Removal
Subpart H systems that use conventional filtration treatment are required to remove specific percentages of
organic materials, measured as total organic carbon (TOC), that may react with disinfectants to form DBPs.
Removal must be achieved through a treatment technique (enhanced coagulation or enhanced softening) unless
a system meets alternative criteria. Systems practicing softening must meet TOC removal requirements for
source water alkalinity greater than 120 mg/L CaC03.
Source Water TOC
(mg/L)
Source Water Alkalinity, mg/L as CaCO3
0 - 60 > 60 to 120 > 120
> 2.0 to 4.0 35.0%25.0%15.0%
> 4.0 to 8.0 45.0%35.0%25.0%
> 8.0 50.0%40.0%30.0%