R309-520-6. General

  (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 byproducts.

  (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.