Current through Bulletin 2024-24, December 15, 2024
(1) Continuous Disinfection.
(a) Continuous disinfection is required of
all ground water sources that do not otherwise continuously meet
microbiological standards. Intermittent or batch disinfection, such as adding
hypochlorite tablets or concentrated hypochlorite solution to a tank, is not
acceptable for ongoing operation if continuous disinfection is
required.
(b) Disinfection is not
an acceptable remedy to physical deficiencies or sources susceptible to surface
water influence. Disinfection shall not be used to mask ongoing contamination
and shall not be used as a substitute for correcting deficiencies.
(c) Where continuous disinfection is
required, the design shall provide a means to isolate or service the
disinfection equipment without allowing untreated water to enter the
distribution system. If the untreated water is to be discharged, it shall not
cause environmental or property damage.
(2) ANSI/NSF Standard 60 Certification.
All chemicals added to drinking water, including chlorine
(i.e., gas, hypochlorite solution, hypochlorite tablets, granules, and powder),
chloramines, and chemicals used to generate hypochlorite solutions and chlorine
dioxide, shall be certified as complying with ANSI/NSF Standard 60, Drinking
Water Treatment Chemicals.
(3) Required Disinfection.
(a) Surface water, or groundwater under the
direct influence of surface water, shall be filtered by conventional surface
water treatment or alternative surface water treatment methods and disinfected
to meet the requirements of
R309-200-7.
(b) Where microbiological treatment is
required for a ground water source that is not under the influence of surface
water, disinfection without filtration may be considered adequate.
(4) Point of Application and CT.
A combination of disinfectant residual and contact time is
defined as disinfection CT in
R309-110-4. The
following requirements apply to disinfectant point of application and
CT:
(a) Consideration shall be given
to the contact time of the disinfectant in water with relation to pH, ammonia,
taste-producing substances, temperature, biological quality, and other
pertinent factors.
(b) Where
possible, the design shall minimize the formation of disinfection by
products.
(c) Treatment of ground
water sources shall provide sufficient CT to achieve a minimum of 4-log virus
inactivation and/or removal.
(d)
Point of application of disinfectants shall be at a location that will achieve
the required disinfection CT prior to the first service connection.
(5) Site Selection.
Disinfection installations shall be sited to permit
convenient access during the operation period. These installations shall be
sited with due consideration of possible danger to nearby population and of
possible jeopardy from seismic fault zones.
