d = number of instances where no residual disinfectant concentration is detected and where the HPC is > 500/ml.
e = number of instances where the residual disinfectant concentration is not measured and HPC is > 500/ml.
NR 810.31(1)(d)2.2. If the department determines, based on site specific considerations, that a public water system has no means for having a sample transported and analyzed for HPC by a certified laboratory under the requisite time and temperature conditions required in s. NR 809.311 (1), Table F, and that the system is providing adequate disinfection in the distribution system, the requirements of subd. 1. do not apply. NR 810.31(2)(2) Disinfection requirements for public water systems which provide filtration. Each public water system that provides filtration treatment shall provide disinfection treatment as follows: NR 810.31(2)(a)(a) Disinfection treatment shall be sufficient to ensure that the total treatment processes of that system achieve at least 99.9% (3 log) inactivation or removal of Giardia lamblia cysts and at least 99.99% (4 log) inactivation or removal of viruses, as determined by the department. NR 810.31(2)(b)(b) The residual disinfectant concentration in the water entering the distribution system, measured as specified in s. NR 809.563 (2), Table R, may not be less than 0.2 mg/l for more than 4 hours. NR 810.31(2)(c)1.1. The residual disinfectant concentration in the distribution system, measured as total chlorine, combined chlorine or chlorine dioxide, as specified in s. NR 809.563 (2), Table R, may not be undetectable in more than 5% of the samples each month, for any 2 consecutive months that the system serves water to the public. Water in the distribution system with a heterotrophic bacteria concentration less than or equal to 500/ml, measured as heterotrophic plate count (HPC) as specified in s. NR 809.311 (1), Table F, is deemed to have a detectable disinfectant residual for purposes of determining compliance with this requirement. Thus, the value “V” in the following formula may not exceed 5% in one month, for any 2 consecutive months. V = c + d + e/a + b x 100
where:
a = number of instances where the residual disinfectant concentration is measured.
b = number of instances where the residual disinfectant concentration is not measured but heterotrophic bacteria plate count (HPC) is measured.
c = number of instances where the residual disinfectant concentration is measured but not detected and no HPC is measured.
d = number of instances where no residual disinfectant concentration is detected and where the HPC is > 500/ml.
e = number of instances where the residual disinfectant concentration is not measured and HPC is > 500/ml.
NR 810.31(2)(c)2.2. If the department determines, based on site specific considerations, that a public water system has no means for having a sample transported and analyzed for HPC by a certified laboratory under the requisite time and temperature conditions required in s. NR 809.311 (1), Table F, and that the system is providing adequate disinfection in the distribution system, the requirements of subd. 1. do not apply. NR 810.31 HistoryHistory: CR 09-073: cr. Register November 2010 No. 659, eff. 12-1-10. NR 810.32NR 810.32 Disinfection profiling and benchmarking. NR 810.32(1)(1) Requirements when making a significant change in disinfection practice. NR 810.32(1)(a)(a) Following the completion of initial source water monitoring under s. NR 809.331, the water supplier for a public water system that plans to make a significant change to its disinfection practice, as defined in par. (b), shall develop disinfection profiles and calculate disinfection benchmarks for Giardia lamblia and viruses as described in sub. (2). Prior to changing the disinfection practice, the water supplier shall notify the department and shall include in this notice all of the following information: NR 810.32(1)(a)1.1. A completed disinfection profile and disinfection benchmark for Giardia lamblia and viruses as described in sub. (2). NR 810.32(1)(a)3.3. An analysis of how the proposed change will affect the current level of disinfection. NR 810.32(1)(b)(b) Significant changes to disinfection practice are defined as any of the following: NR 810.32(1)(b)4.4. Any other modification identified by the department as a significant change to disinfection practice. Additional barriers with no change to existing disinfection practices may be exempt from these requirements. NR 810.32(2)(2) Developing the disinfection profile and benchmark. Water suppliers for public water systems required to develop disinfection profiles under sub. (1) shall follow the requirements of this subsection: