25 Pa. Code § 109.710 - Disinfectant residual in the distribution system
(a) Until April 28, 2019, a disinfectant
residual acceptable to the Department shall be maintained throughout the
distribution system of the community water system sufficient to assure
compliance with the microbiological MCLs and the treatment technique
requirements specified in §
109.202 (relating to State MCLs,
MRDLs and treatment technique requirements). The Department will determine the
acceptable residual of the disinfectant considering factors such as type and
form of disinfectant, temperature and pH of the water, and other
characteristics of the water system.
(b) Until April 28, 2019, a public water
system that uses surface water or GUDI sources or obtains finished water from
another permitted public water system using surface water or GUDI sources shall
comply with the following requirements:
(1) As
a minimum, a detectable residual disinfectant concentration of 0.02 mg/L
measured as total chlorine, combined chlorine or chlorine dioxide shall be
maintained throughout the distribution system as demonstrated by monitoring
conducted under §
109.301(1) and (2) or
(8)(v) (relating to general monitoring
requirements).
(2) Sampling points
with nondetectable disinfectant residuals which have heterotrophic plate count
(HPC) measurements of less than 500/ml are deemed to be in compliance with
paragraph (1).
(3) When the
requirements of paragraph (1) or (2) cannot be achieved, the supplier shall
initiate an investigation under the Department's direction to determine the
cause, potential health risks and appropriate remedial
measures.
(c) Beginning
April 29, 2019, a community water system using a chemical disinfectant or that
delivers water that has been treated with a chemical disinfectant shall
maintain a minimum residual disinfectant concentration throughout the
distribution system sufficient to assure compliance with the microbiological
MCLs and the treatment technique requirements specified in §
109.202. The minimum residual
disinfectant concentration is 0.2 mg/L or another level approved by the
Department for systems using an alternate oxidizing disinfection treatment. The
residual disinfectant concentration shall be measured as follows:
(1) Free chlorine for systems using
chlorine.
(2) Total chlorine for
systems using chloramines.
(3) Both
free chlorine and total chlorine for sampling locations in a mixing zone as
identified in the monitoring plan.
(4) Both free chlorine and total chlorine
when a system using chloramines is conducting a free chlorine burn.
(d) Beginning April 29, 2019, a
nontransient noncommunity water system that has installed chemical disinfection
or a transient noncommunity water system that has installed chemical
disinfection in accordance with §
109.202(c)(1) or
§
109.1302(b)
(relating to treatment technique requirements) shall maintain a minimum
residual disinfectant concentration throughout the distribution system
sufficient to assure compliance with the microbiological MCLs and the treatment
technique requirements specified in §
109.202. The minimum residual
disinfectant concentration is 0.2 mg/L or another level approved by the
Department for systems using an alternate oxidizing disinfection treatment. The
residual disinfectant concentration shall be measured as follows:
(1) Free chlorine for systems using
chlorine.
(2) Total chlorine for
systems using chloramines.
(3) Both
free chlorine and total chlorine for sampling locations in a mixing zone as
identified in the monitoring plan.
(4) Both free chlorine and total chlorine
when a system using chloramines is conducting a free chlorine burn.
(e) Beginning April 29, 2019,
compliance with the disinfectant residual treatment technique will be based on
the number of samples collected each month as specified in the system
distribution sample siting plan submitted to the Department under §
109.701(a)(8)
(relating to reporting and recordkeeping). Compliance will be determined as
follows:
(1) For a public water system that
collects less than 40 samples per month and uses only groundwater or purchased
groundwater sources, if no more than 1 sample collected per month is less than
the minimum level specified in subsection (c) or (d) for 2 consecutive months,
the system is in compliance with the treatment technique.
(2) For a public water system that collects
40 or more samples per month or that uses surface water, GUDI, purchased
surface water or purchased GUDI sources, if no more than 5% of the samples
collected per month are less than the minimum level specified in subsection (c)
or (d) for 2 consecutive months, the system is in compliance with the treatment
technique.
(3) For systems
reporting both free and total chlorine residual measurements in accordance with
subsections (c) and (d), compliance shall be based on the higher residual
measurement.
(4) A public water
system that experiences a treatment technique violation shall notify the
Department within 1 hour of discovery of the violation in accordance with
§
109.701(a)(3) and
issue a Tier 2 public notice in accordance with §
109.409 (relating to Tier 2 public
notice-categories, timing and delivery of notice).
(5) In addition to the requirements in
paragraphs (1)-(4), a public water system that fails to meet the minimum level
specified in subsection (c) or (d) at any sample location for 2 consecutive
months or more shall conduct an investigation to determine the cause and
appropriate corrective actions and shall submit a written report to the
Department within 60 days.
(6) The
Department may approve in writing an alternate compliance schedule if the water
supplier submits a written request with supporting documentation by April 29,
2019.
(f) Public water
systems may increase residual chlorine or chloramine, but not chlorine dioxide,
disinfectant levels in the distribution system to a level that exceeds the MRDL
for that disinfectant and for a time necessary to protect public health or to
address specific microbiological contamination problems caused by circumstances
such as, but not limited to, distribution line breaks, storm runoff events,
source water contamination events or cross-connection
events.
Notes
The provisions of this § 109.710 amended under section 4 of the Pennsylvania Safe Drinking Water Act (35 P.S. § 721.4); and section 1920-A of The Administrative Code of 1929 (71 P.S. § 510-20).
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