Section Env-Ws 380.10 - Disinfection for Systems Not Providing Filtration(a) Each public water system owner that does not provide filtration treatment shall provide disinfection treatment as follows:(1) The disinfection treatment shall be sufficient to ensure at least 99.9 percent inactivation of giardia lamblia cysts and 99.99 percent inactivation of viruses, every day the system serves water to the public, except any one day each month;(2) Each day a system serves water to the public, the owner shall calculate the CT value(s) from the system's treatment parameters, using the procedure specified in Env-Ws 380.14(f) and (g), and determine whether this value(s) is sufficient to achieve the specified inactivation rates for giardia lamblia cysts and viruses;(3) If a system uses a disinfectant other than chlorine, the owner shall demonstrate to the department, through the use of on-site disinfection challenge studies or other information, that CT99.9 values other than those specified in Tables 380-8 and 380-9 or other operational parameters are adequate to demonstrate that the system is achieving minimum inactivation rates required by this paragraph;(4) The disinfection system shall have redundant components, including an auxiliary power supply with automatic start-up and alarm to ensure that disinfectant application is maintained continuously while water is being delivered to the distribution system;(5) The residual disinfectant concentration in the water entering the distribution system shall not be less than 0.2 mg/l for more than 4 hours.(b) The residual disinfectant concentration in the distribution system shall be as follows: (1)The residual disinfectant concentration measured as total chlorine, combined chlorine, or chlorine dioxide shall not be undetectable in more than 5 percent of the samples each month, for any 2 consecutive months that the system serves water to the public;(2) Water in the distribution system with a heterotrophic bacteria concentration less than or equal to 500/ml, measured as HPC, is deemed to have a detectable disinfectant residual for purposes of determining compliance with this requirement;(3) The value "V" in the following formula shall be calculated each month: V = c + d + e/a + b x 100
(4) The terms in the formula in (b)(3) above shall be as follows:a. a = number of instances where the residual disinfectant concentration is measured;b. b = number of instances where the residual disinfectant concentration is not measured but HPC is measured;c. c = number of instances where the residual disinfectant concentration is measured but not detected and no HPC is measured;d. d = number of instances where the residual disinfectant concentration is measured but not detected and where the HPC is >500/ml; ande. e = number of instances where the residual disinfectant concentration is not measured and HPC is >500/ml; and(5)The value of "V" in (b)(3) above shall not exceed 5 percent in one month for any 2 consecutive months.N.H. Admin. Code § Env-Ws 380.10
#5098, eff 3-18-91, EXPIRED 3-18-97
New. #6521, eff 6-4-97 (See Revision Note at chapter heading for Env-Ws 300); ss by #8352, eff 5-14-05 (formerly part of Env-Ws 380.15 )