N.H. Admin. Code § Env-Ws 380.26

Current through Register No. 50, December 12, 2024

Section Env-Ws 380.26 - Disinfection Benchmarking

(a) The system owner shall use the profiling data from Env-Ws 380.24 through Env-Ws 380.25 to calculate a disinfection benchmark prior to changing disinfection practices.

(b) Disinfection benchmarking shall be conducted as follows:

(1) The owner of a system required to develop a disinfection profile under the provisions of this section shall consult with the department prior to making a significant change to the system's disinfection practice;

(2) Significant changes to disinfection practice shall include:

a. Changes to the point of disinfection;

b. Changes to the disinfectant(s) used in the treatment plant;

c. Changes to the disinfection process; or

d. Any other disinfection modification identified by the department; and

(3) The owner of a system shall submit the following information to the department as part of the consultation process identified in (b)(1) above:

a. A description of the proposed change;

b. The disinfection profile for giardia lamblia, and, if necessary, viruses, and the disinfection benchmark as required by (d) below;

c. An analysis of how the proposed change will affect the current levels of disinfection; and

d. Any additional information requested by the department based on a determination that the information is needed to make a fully informed decision.

(c) The department shall respond to the request in writing and shall approve the change to the disinfectant practice if it finds that such change complies with department rules and statutes.

(d) The owner of a system receiving department approval to modify the system's disinfection practice shall calculate the disinfection benchmark using the procedures specified in (1) and (2) below:

(1) For each year of profiling data collected and calculated under (p) above, the system owner shall:

a. Determine the average giardia lamblia inactivation for systems serving at least 10,000 for each calendar month for each year of profiling data by dividing the sum of daily giardia lamblia logs of inactivation by the number of values calculated for that month;

b. Determine the average giardia lamblia inactivation for systems serving fewer than 10,000 for each calendar month of profiling data by dividing the sum of weekly giardia lamblia logs of inactivation for that month by the number of values calculated for that month;

c. Determine the lowest average monthly giardia lamblia inactivation for systems serving at least 10,000 in each year of profiling data; or

d. Determine the lowest average monthly giardia lamblia inactivation for systems serving fewer than 10,000 in one year of profiling data; and

(2) The disinfection benchmark shall be the lowest monthly average value, for systems with one year of profiling data, or the average of lowest monthly average values, for systems with more than one year of profiling data, of the monthly logs of giardia lamblia inactivation in each year of profiling data.

(e) A system ownerusing chloramines, chlorine dioxide, or ozone for primary disinfection shall:

(1) Calculate the disinfection benchmark for viruses using the method in (d) above; and

(2) Submit the information specified in (b)(3) above, to the department within 10 days of obtaining the information.

N.H. Admin. Code § Env-Ws 380.26

#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 380.28 )