dEPA
    United States
    Environmental Protection
    Agency
Comprehensive Surface Water Treatment Rules
Quick Reference Guide: Unfiltered Systems
                          Overview  of  the  Rules
                           Title
                           Purpose
                           General
                           Description
           Surface Water Treatment Rule (SWTR) - 40 CFR 141.70-141.75
           Interim Enhanced Surface Water Treatment Rule (IESWTR) - 40 CFR 141.170-141.175
           Long Term 1 Enhanced Surface Water Treatment Rule (LT1ESWTR) - 40 CFR
           141.500-141.571
           Improve public health protection through the control of microbial contaminants, particularly
           viruses, Giardia, 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 aH Subpart H systems to disinfect.
           > Requires Subpart H systems to filter unless specific filter avoidance criteria are met.
           > Requires unfiltered systems to perform source water monitoring and meet site specific
             conditions for control of microbials.
Overview of Requirements
The purpose of this table is show how the requirements for the IESWTR and LT1 ESWTR build
on the existing requirements established in the original SWTR.
APPLICABILITY: PWSs that use surface water or
ground water under the direct influence of surface
water (Subpart H) that do not provide filtration.
Population Served
Regulated
Pathogens
Residual
Disinfectant
Requirements
Unfiltered System
Requirements
Disinfection
Profiling &
Benchmarking
Sanitary Surveys
(state requirement)
> 10,000
< 10,000
99.99% (4-log) inactivation of
viruses
99.9% (3-log) inactivation of
Giardia lamblia
99% (2-log) removal of
Cryptosporidium (through
watershed control)
Entrance to distribution system
(> 0.2 mg/L)
Detectable in the distribution
system
Avoidance Criteria
Final Rule Dates
SWTR
1989
y
y
y
y
	
y
/
/
Systems must profile inactivation
levels and generate benchmark, if
required
CWS: Every 3 years
NCWS: Every 5 years
Covered Finished Reservoirs/Water Storage Facilities
(new construction only)
Operated by Qualified Personnel as Specified by State


/
IESWTR LT1 ESWTR
1998 2002
I
N/A (except for
sanitary survey
provisions)
Regulated under
SWTR
Regulated under
SWTR
y
Regulated under
SWTR
Regulated under
SWTR
y
/
y
/
Regulated under
SWTR
/
Regulated under
SWTR
Regulated under
SWTR
y
Regulated under
SWTR
Regulated under
SWTR
y
y
Regulated under
IESWTR
y
Regulated under
SWTR
                        I  (CWS) Community Water System    (NCWS) Non-community Water System

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Filtration Avoidance  Criteria
Since December 30,1991, systems must meet source water quality and site specific conditions to remain unfiltered. If any
of the following criteria to avoid filtration are not met, systems must install filtration treatment within 18 months of the
failure. The following table outlines the avoidance criteria established by the SWTR and later enhanced by the IESWTR and
LT1 ESWTR.
 Filtration  Avoidance  Criteria
                                              Requirement
                                                                              Frequency
 SOURCE
 WATER
 QUALITY
 CONDITIONS
Microbial
Quality
Monitor fecal coliform or total coliform density in
representative samples of source water immediately prior
to the first point of disinfectant application:

x  Fecal coliform density concentrations must be
  < 20/100 ml; OR
x  Total coliform density concentrations must be
   < 100/100 ml.

Sample results must satisfy the criteria listed above in at
least 90% of the measurements from previous 6  months.
1  to 5 samples per week depending on
system size and every day the turbidity of
the source water exceeds 1 NTU.
              Turbidity
             Prior to the first point of disinfectant application, turbidity
             levels cannot exceed 5 NTU.
                                                    Performed on representative grab samples
                                                    of source water every four hours (or more
                                                    frequently).
              Systems
              must:
             Calculate total inactivation ratio daily and provide 3-log
             Giardia lamblia and 4-log virus inactivation daily (except
             any one day each month) in 11 of 12 previous months (on
             an ongoing basis).
                                                    Take daily measurements before or at the
                                                    first customer at each residual disinfectant
                                                    concentration sampling point:
                                                    x  Temperature
                                                    x  pH (if chlorine used)
                                                    x  Disinfectant contact time (at peak
                                                       hourly flow)
                                                    x  Residual disinfectant concentration
                                                       measurements (at peak hourly flow)
 SITE
 SPECIFIC
 CONDITIONS
System
must
comply
with:
x  MCL for total coliforms in 11 of 12 previous months (as per Total Coliform Rule).
x  Stage  1 Disinfection Byproducts Rule requirements (as of January 1, 2002, for
   systems serving > 10,000 or January 1, 2004, for systems serving < 10,000).
              Systems
              must have:
               Adequate entry point residual disinfectant concentration (see disinfection requirements).
               Detectable residual disinfectant concentration in the distribution system (see disinfection
               requirements).
               Redundant disinfection components or automatic shut-off whenever residual disinfectant concentration
               < 0.2 mg/L.
               A watershed control program minimizing potential for contamination by Giardia lamblia cysts and
               viruses in source water; ESWTR and LT1 ESWTR update this requirement by adding
               Cryptosporidium control measures.
               An annual on-site inspection by state or approved third party with reported findings.
               Not been identified as a source of a waterborne disease outbreak.
                                                                                                                    J

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Disinfection

Disinfection must be sufficient to ensure that the total treatment process of the system achieves at least:

>      99.9% (3-log) inactivation of Giardia lamblia.
>      99.99% (4-log) inactivation of viruses.

Currently, Cryptosporidium must be controlled through the watershed control program and no inactivation credits are currently
given for disinfection. Systems must also comply with the maximum residual disinfectant level (MRDL) requirements
specified in the Stage 1 Disinfectants/Disinfection Byproducts Rule (Stage 1 DBPR).
 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 or fewer
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.
System Reporting Requirements
Report to State:
Within 10 days after
the end of the month:
By October 10 each
year:
Within 24 hours:
As soon as possible
but no later than the
end of the next
business day:
What to report:
> Source water quality information (microbial quality and turbidity measurements).
> In addition to the disinfection information above, systems must report the daily residual disinfectant
concentration(s) and disinfectant contact time(s) used for calculating the CT value(s).
> Report compliance with all watershed control program requirements.
> Report on the on-site inspection unless conducted by state in which the state must provide the system a
copy of the report.
> Turbidity exceedances of 5 NTU and waterborne disease outbreaks.
> Instance where the residual disinfectant level entering the distribution system was less than 0.2 mg/L.

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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  Under
 IESWTR  & LT1ESWTR
 The purpose of disinfection profiling and benchmarking is to allow systems and states to assess whether a change in disinfection
 practices creates a microbial risk. Systems should develop a disinfection profile that reflects Giardia lamblia inactivation (systems
 using ozone or chloramines must also calculate inactivation of viruses), 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
 AFFECTED SYSTEMS:
Community, non-transient non-community, and
transient systems.
     Community and non-transient non-community
     systems only.
 BEGIN PROFILING BY:
April 1,2000
     > July 1, 2003 for systems serving 500-9,999
       people.
     > January 1, 2004 for systems serving fewer than
       500 people.
 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.
 STATES MAY WAIVE
 DISINFECTION
 PROFILING
 REQUIREMENTS IF:
TTHM annual average <0.064 mg/L and HAA5
annual average <0.048 mg/L:
>  Collected during the same period.
>  Annual average is arithmetic average of the
   quarterly averages of four 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 HAA5
     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.
 DISINFECTION
 BENCHMARK MUST BE
 CALCULATED IF:
Systems required to develop a disinfection profile
and are considering any of the following:
>  Changes to the point of disinfection.
>  Changes to the disinfectant(s) used.
>  Changes to the disinfection process.
>  Any other modification identified by the state.

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.
      Office of Water (4606)
         EPA816-F-04-001
www.epa.gov/safewater
August 2004

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