N.H. Code Admin. R. Env-Ws 380.11

Current through Register No. 25, June 20, 2024

Section Env-Ws 380.11 - Disinfection Requirements for Systems Providing Filtration

Each owner of a public water system that provides filtration treatment shall provide disinfection treatment as follows:

(a) The disinfection treatment shall be sufficient to ensure that the total treatment processes of that system achieve at least 99.9 percent inactivation or removal of giardia lamblia cysts , or both, and at least 99.99 percent inactivation and removal of viruses;

(b) 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;

(c) The residual disinfectant concentration 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, shall be 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 (c)(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 heterotrophic bacteria plate count 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 residual disinfectant concentration is measured but not detected and where the HPC is >500/ml; and

e. e = number of instances where the residual disinfectant concentration is not measured and HPC is >500/ml; and

(5) The value of "V" in 3 above shall not exceed 5 percent in one month for any 2 consecutive months.

N.H. Code Admin. R. Env-Ws 380.11

#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 )