United States
Environmental Protection
Agency
<
.
Comprehensive Surface Water Treatment Rules
Quick Reference Guide: Systems Using Slow Sand,
Diatomaceous Earth, or Alternative Filtration
Overview of the Rules
Title*
Purpose
General
Description
Surface Water Treatment Rule (SWTR) - 40 CFR 141 .70-141 .75 j
Interim Enhanced Surface Water Treatment Rule (IESWTR) - 40 CFR 141 .170-141.175
Filter Backwash Recycling Rule (FBRR) 40 CFR 141 .76
Long Term 1 Enhanced Surface Water Treatment Rule (LT1 ESWTR) - 40 CFR 1 41 .500-1 41 .571
Long Term 2 Enhanced Surface Water Treatment Rule (LT2ESWTR) - 40 CFR 1 41 .700-1 41 .722
Improve public health protection through the control of microbial contaminants, particularly
viruses, Giardia lamblia, and Cryptosporidium.
The Surface Water Treatment Rules:
> Applies to all public water systems (PWSs) using surface water or ground water under the direct
influence of surface water (GWUDI), otherwise known as "Subpart H systems."
> Requires all Subpart H systems to disinfect.
> Requires Subpart H systems to filter unless specific filter avoidance criteria are met.
> Applies a treatment technique requirement for control of microbials.
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.
Overview of Requirements
The purpose of this table is to show how the requirements for the IESWTR, LT1ESWTR and LT2ESWTR build
on the existing requirements established in the original SWTR.
APPLICABILITY: PWSs that use surface water or
GWUDI (Subpart H systems) that practice slow
sand, diatomaceous earth or alternative filtration.
Population Served
Regulated
Pathogens
Residual
Disinfection
Requirements
Source Water
Monitoring
Requirements and
Bin Classification
Turbidity
Performance
Standards
Disinfection
Profiling and
Benchmarking
Sanitary Surveys
(state requirement)
Finished
Reservoirs/ Water
Storage Facilities
> 10,000
< 10,000
99.99% (4-log) removal/
inactivation of viruses
99.9% (3-log) removal/
inactivation of Giardia lamblia
99% (2-log) removal of
Cryptosporidium
Entrance to distribution system
(> 0.2 mg/L)
Detectable in the distribution
system
Monitoring to calculate
Cryptosporidium and determine
appropriate bin classification for
each plant required to monitor
Combined Filter Effluent - Slow
Sand and Diatomaceous Earth
Combined Filter Effluent -
Alternative
Systems must profile inactivation
levels and generate benchmark,
if required
CWS**: Every 3 years
NCWS**: Every 5 years
All new facilities constructed must
be covered
Uncovered facilities must be
covered or discharge treated
Operated by Qualified Personnel as Specified by
State
Final Rule Dates
SWTR
1989
^
^
^
^
^
^
^
^
~
^
IESWTR
1998
^
For sanitary
survey
provisions only
Regulated
under SWTR
Regulated
under SWTR
^
Regulated
under SWTR
Regulated
under SWTR
Regulated
under SWTR
^
^
^
^
Regulated
under SWTR
LT1 ESWTR
2002
^H
/
Regulated
under SWTR
Regulated
under SWTR
/
Regulated
under SWTR
LT2ESWTR
2006
*/
*
Regulated under
SWTR
Regulated under
SWTR
Additional
treatment may
be required
Regulated under
SWTR
Regulated I Regulated under
under SWTR | SWTR
Regulated
under SWTR
/
*
Regulated
under
IESWTR
/
Regulated
under SWTR
^
Regulated under
SWTR
Regulated under
SWTR, IESWTR
and LT1 ESWTR
^
Regulated under
IESWTR
Regulated under
LT1 ESWTR
^
Regulated
under SWTR
** Community water system (CWS), Noncommunity water system (NCWS)
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Turbidity
Turbidity is measured as Combined Filter Effluent (CFE) for slow sand, diatomaceous earth, and alternative filtration. The CFE
95th percentile value and CFE maximum value for slow sand and diatomaceous earth were not lowered in the IESWTR and
LT1ESWTR since these filtration technologies are assumed to provide 2-log Cryptosporidium removal with the turbidity limits
established by SWTR. Alternative filtration technologies (defined as filtration technologies other than conventional, direct, slow
sand, or diatomaceous earth) must demonstrate to the state that filtration and/or disinfection achieve 3-log Giardia lambia
and 4-log virus removal and/or inactivation. The IESWTR and LT1ESWTR also require alternative filtration technologies to
demonstrate 2-log Cryptosporidium removal. Subpart H systems using the Treatment Performance Toolbox option under the
LT2ESWTR must meet the more stringent CFE turbidity monitoring levels in order to receive additional Cryptosporidium log credit.
Turbidity: Monitoring and Reporting Requirements
Turbidity Type and Reporting Requirements
(Reports due by the 10th day of the following
month the system serves water to the public.)
Slow Sand & Diatomaceous
Earth
Alternative
> Membranes
> Cartridges
* Other
CFE 95%
CFE Max
CFE 95%
CFE Max
Monitoring/
Recording
Frequency
At least every 4 hours*
At least every 4 hours*
At least every 4 hours*
At least every 4 hours*
SWTR
As of June
29, 1993
<1 NTU
5NTU
Established by
state
Established by
state
IESWTR
> 10,000 people
As of January 1, 2002
Regulated under SWTR
Regulated under SWTR
Established by state
Established by state
LT1ESWTR I
< 10,000 people
As of January 1, 2005
Regulated under SWTR
Regulated under SWTR
Established by state
(not to exceed 1 NTU)
Established by state
(not to exceed 5 NTU)
'Monitoring frequency may be reduced by the state to once per day for systems using slow sand or alternative filtration. Monitoring frequency may be reduced by
the state to once per day for systems serving 500 or fewer people regardless of type of filtration used.
CFE Turbidity: Reporting Requirements
Report to State:
Within 10 days after
the end of the month:
Within 24 hours:
SWTR Measurements
Total number of monthly
measurements
Number and percent
< designated 95th
percentile turbidity limits
Date and value
exceeding 5 NTU
Exceedances of 5 NTU
for CFE
IESWTR Measurements
Total number of monthly measurements
Number and percent S designated 95th
percentile turbidity limits
Date and value exceeding 5 NTU for slow
sand and diatomaceous earth or maximum
level set by state for alternative filtration
Exceedances of 5 NTU for slow sand and
diatomaceous earth or maximum CFE level
set by state for alternative filtration
LT1ESWTR Measurements**
Total number of monthly measurements
Number and percent S designated 95th
percentile turbidity limits
Date and value exceeding 5 NTU for slow sand
and diatomaceous earth or maximum level set by
state for alternative filtration
Exceedances of 5 NTU for slow sand and
diatomaceous earth or maximum CFE level set
by state for alternative filtration
** Systems serving fewer than 10,000 people must begin complying with these requirements beginning January 1, 2005.
Disinfection
Disinfection must be sufficient to ensure that the total treatment process (disinfection plus filtration) of the system achieves at
least:
> 99.9% (3-log) inactivation and/or removal of Giardia lamblia.
> 99.99% (4-log) inactivation and/or removal of viruses.
Subpart H systems using chlorine dioxide, ozone, or ultraviolet (UV) disinfection may achieve additional Cryptosporidium log credit
by using the Microbial Toolbox option under the LT2ESWTR. Systems must also comply with the maximum residual disinfectant
level (MRDL) and maximum contaminant level (MCL) requirements specified in the Stage 1 Disinfectants and Disinfection
Byproducts Rule (Stage 1 DBPR) and Stage 2 Disinfectants and Disinfection Byproducts Rule (Stage 2 DBPR).
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Residual Disinfectant Monitoring and Reporting Requirements
Location
Concentration
Monitoring Frequency
Reporting
(Reports due 10th of the following month)
Entry to distribution
system.
Residual disinfectant concentration cannot
be < 0.2 mg/L for more than 4 hours.
Continuous, but states may allow
systems serving < 3,300 persons
to take grab samples from 1 to
4 times per day, depending on
system size.
Lowest daily value for each day, the date and
duration when residual disinfectant was < 0.2
mg/L, and when state was notified of events
where residual disinfectant was < 0.2 mg/L.
Distribution system-
same location as
total coliform sample
location(s).
Residual disinfectant concentration cannot
be undetectable in greater than 5% of
samples in a month, for any 2 consecutive
months. Heterotrophic plate count (HPC)
£ 500/mL is deemed to have detectable
residual disinfectant.
Same time as total coliform
samples.
Number of residual disinfectant or HPC
measurements taken in the month resulting in
no more than 5% of the measurements as
being undetectable in any 2 consecutive
months.
LT2ESWTR Source Water Monitoring and Bin Classification
Bin concentration is calculated by averaging individual sample results from 1 or more years of monitoring (specific procedures
vary by frequency and duration of monitoring).
A combined distribution system (CDS) is an interconnected distribution system consisting of the distribution systems of the
wholesale system and of the consecutive systems that receive finished water from that wholesale system. Under the LT2ESWTR,
wholesale systems in a CDS must comply with the LT2ESWTR based on the population of the largest system in their CDS.
EPA has established four schedule categories based on system size to simplify the discussion of the LT2ESWTR monitoring
requirements. Schedule 1 applies to systems that serve 100,000 or more people or in a CDS that largest system serves 100,000
people. Schedule 2 applies to systems that serve 50,000 to 99,999 people or in a CDS that largest system serves 50,000 to
99,999 people. Schedule 3 applies to systems that serve 10,000 and 49,999 people or in a CDS that largest system serves
10,000 and 49,999 people. Schedule 4 applies to systems that serve less than 10,000 people.
Source water monitoring requirements are as follows:
> Large systems (> 10,000 people served) must sample for Cryptosporidium, E.coli and turbidity at least monthly for 2 years.
> Small systems (< 10,000 people served) must initially sample for E.coli at least once every 2 weeks for 1 year. Cryptosporidium
monitoring is only required if E. coli levels are above certain levels based on the water source type.
> All systems must begin a second round of monitoring 6 years after initial bin classification.
Bin Classification and Additional Treatment Requirements
Bin
Bin 1
Bin 2
Bin 3
Bin 4
Cryptosporidium Bin Concentration
less than .075 oocysts/ L**
.075 oocysts/L or higher, but less than 1 .0 oocysts/L
1 .0 oocysts or higher, but less than 3.0 oocysts/L
3.0 oocysts or higher
Additional Treatment Requirements*
Slow Sand or
Diatomaceous Earth
Filtration
No additional treatment
1 -log treatment***
2-log treatment***
2.5 log treatment***
Alternative Filtration Technologies
No additional treatment
As determined by state: Total must be at least 4-log***
As determined by state: Total must be at least 5-log***
As determined by state: Total must be at least 5. 5-log***
Requirements in addition to those met in full compliance with SWTR, IESWTR, and LT1 ESWTR
** Or Subpart H systems not required to monitor for Cryptosporidium
""Removal and/or inactivation
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Microbial Toolbox: Inactivation Options, Credits and Criteria
The Microbial Toolbox provides a list of the tools that systems can use, and receive treatment credits for, in order to meet
additional treatment requirements of LT2ESWTR. The toolbox provides systems with the flexibility to use any combination of
applicable treatment options as long as the systems are in compliance with design, operational, and performance criteria which
are not detailed in this document. The toolbox options and credits available for systems that use slow sand, diatomaceous earth or
alternative filtration are divided into five categories:
> Source protection and management: watershed control program (0.5-log), alternative source/intake management (no
prescribed credit)
> Prefiltration: presedimentation basin with coagulation (0.5-log), two-stage lime softening (0.5-log), bank filtration (0.5- or 1-log)
> Treatment performance: demonstration of performance (log credit variable)
> Additional filtration: bag and cartridge filters individual (up to 2-log), bag and cartridge filters in series (up to 2.5-log), membrane
filtration (log credit variable), second stage filtration (0.5-log), slow sand filters (2.5- to 3-log)
> Inactivation: chlorine dioxide (log credit variable), ozone (log credit variable), UV (log credit variable)
Disinfection Profiling and Benchmarking Requirements
A disinfection profile is the graphical representation of a system's microbial inactivation over 12 consecutive months.
A disinfection benchmark is the lowest monthly average microbial inactivation value. The disinfection benchmark is used as a
baseline of inactivation when considering changes in the disinfection process.
Disinfection Profiling and Benchmarking Requirements
The purpose of disinfection profiling and benchmarking is to allow systems and states to assess whether a change in disinfection
practices reduces microbial protection. Systems must develop a disinfection profile that reflects Giardia lamblia and viruses inactivation,
calculate a benchmark (lowest monthly inactivation) based on the profile, and consult with the state prior to making a significant change to
disinfection practices.
Requirement
IESWTR
LT1ESWTR
LT2ESWTR
Affected
Systems:
Community water systems (CWS), nontransient
noncommunity water systems (NTNCWS),
and transient noncommunity water systems
(TNCWS)>10,000.
CWS and NTNCWS systems
<10,000 only.
Any CWS, NTNCWS, TNCWS that proposes to
make a significant change in disinfection practice*.
Begin
Profiling By:
April 1, 2000
July 1, 2003, for systems
serving 500-9,999 people.
January 1, 2004, for systems
serving < 500 people.
Upon completion of initial round of source
water monitoring, AND
12 consecutive months prior to making the
proposed change.
Frequency &
Duration:
Daily monitoring for 12 consecutive calendar
months to determine the total logs of Giardia
lamblia inactivation (and viruses, if necessary)
for each day in operation.
Weekly inactivation of Giardia
lamblia (and viruses, if necessary),
on the same calendar day each
week over 12 consecutive months.
At least weekly inactivation of Giardia lamblia and
viruses, for at least 1 year. May use data collected
for profile under IESWTR or LT1ESWTR.
States
May Waive
Disinfection
Profiling
Requirements
If:
TTHM annual average < 0.064 mg/L and HAAS
annual average < 0.048 mg/L:
^ Collected during the same period.
^ Annual average is arithmetic average of the
quarterly averages of 4 consecutive quarters
of monitoring.
^ At least 25% of samples at the maximum
residence time in the distribution system.
> Remaining 75% of samples at representative
locations in the distribution system.
One TTHM sample < 0.064 mg/L
and one HAAS sample < 0.048
mg/L:
> Collected during the month of
warmest water temperature;
AND
> At the maximum residence time
in the distribution system.
Samples must have been collected
after January 1, 1998.
The system has an existing disinfection profile
for both Giardia lamblia and viruses, and
has neither made a significant change to its
treatment practices nor changed sources since
the profile was developed; OR,
The system has at least 1 year of existing data
that can be used to complete a disinfection
profile and has neither made a significant
change to its treatment practices nor changed
sources since the data were collected.
Disinfection
Benchmark
Must be
Calculated If:
Systems required to develop a disinfection
profile and are considering making a
significant changes in disinfection practice*.
Systems must consult the state prior to
making any modifications to disinfection
practices.
Same as IESWTR, and systems
must obtain state approval prior
to making any modifications to
disinfection practices.
Complete a disinfection profile and benchmark for
viruses and Giardia lamblia.
*A significant change in disinfection practice is defined as (1) change in the point of disinfection, (2) change to the type of disinfectant, (3) change to the disinfection
process, or (4) any other modification designated by the state.
Office of Water (4606M)
EPA 816-F-10-076
http://water.epa.gov/drink
August 2010
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