EPA
United States
Environmental Protection
Agency
1. RESIDUAL DISINFECTANT
Surface Water Treatment Rules Monitoring Requirements (SWTR/LT1ESWTR)
Systems Serving <10,000 People Using Slow Sand, Diatomaceous Earth,
or Alternative Filtration
2. COMBINED FILTER EFFLUENT (CFE) TURBIDITY
Location
Entry Point to the
Distribution System
In the Distribution
System
Frequency
• Continuously monitor
the residual disinfectant
concentration at the
entry point(s) to the
distribution system.
• If monitoring equipment
fails, you can take grab
samples every 4 hours
instead, but for no more
than 5 working days.
• Monitor the residual
disinfectant concentra-
tion in the distribution
system at the same time
and place as you take
total coliform samples.
Details
•The concentration
cannot be less than 0.2
mg/Lfor more than 4
hours.
• Record and report to
your primacy agency
the lowest daily value.
• Residual disinfectant
concentration must be
detected in at least 95%
of all samples taken
every month, for any 2
consecutive months.
Can I perform grab sampling instead of continuous
disinfectant residual monitoring?
Systems serving 3,300 or fewer people can take grab samples
instead of providing continuous monitoring. Contact your pri-
macy agency for more information.
Do I have to monitor the disinfectant residual in the
distribution system?
You can measure the heterotrophic bacteria concentration
instead. A heterotrophic bacteria concentration of less than or
equal to 500 cfu/mL, measured as heterotrophic plate count, is
considered a detectable residual disinfectant.
Filtration
Technology
Slow Sand
Filtration
Diatomaceous
Earth Filtration
Alternative
Filtration
Sampling
Frequency
Once every 4 hours
(with primacy agency
approval you can
sample once per day)
Once every 4 hours (if
your system serves 500
or fewer people, with
primacy agency
approval you can
sample less often)
Once every 4 hours
(with primacy agency
approval you can
sample once per day)
CFE Turbidity in 95%
of samples taken every month
Less than or equal to (<)1 NTU
Less than or equal to (<)1 NTU
Maximum CFE Turbidity
5 NTU
5 NTU
You must meet the limits set by
your primacy agency based on
the filter demonstration data that
you submitted
Besides sampling, what else are we required
to do?
There are requirements on what you must report to your
primacy agency by the tenth day of the following month
and requirements on how and when to notify your custom-
ers if you have a violation. In addition to monitoring and
reporting requirements there are disinfection and filtration
requirements. Contact your primacy agency if you have
any questions regarding these requirements.
/ intend to make a change in my treatment
process. Do I need to complete a disinfection profile?
A disinfection profile and benchmark is required if you
make a significant change to your treatment process. Sig-
nificant changes include: changing the point at which you
disinfect, changing the type of disinfectant you use, chang-
ing the disinfectant process, and any other changes that
your primacy agency considers "significant." Consult your
primacy agency before you make any treatment changes.
Where can I find more information on
these requirements?
You can find more information on these requirements
by visiting EPA's website on microbial and disinfection
byproduct rules atwww.epa.gov/safewater/disinfec-
tion, contacting your primacy agency, or by calling
EPA's Safe Drinking Water Hotline at: 1.800.426.4791.
Primacy Agency.
(contact name and phone number)
Off ice of Water (4606M)
EPA 816-F-08-002 www.epa.gov/safewater
January, 2008
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