Mich. Admin. Code R. 325.10722

Current through Vol. 24-19, November 1, 2024

Section R. 325.10722 - Filtration and disinfection; disinfection profiling and benchmarking

Rule 722.

(1) A subpart H supply making a significant change to its disinfection practice, as described in subrule (4)(a)(i) to (iv) of this rule shall consult with the department before making the change. An approved significant change in disinfection practices shall not jeopardize current levels of disinfection.

(2) A subpart H community or nontransient noncommunity supply that develops a disinfection profile under R 325.10720c of weekly log inactivations over 52 weeks shall report to the department under R 325.10720a(5).

(3) All of the following provisions apply to disinfection profiling:

(a) To determine the total log inactivation for Giardia lamblia and viruses, supplies shall monitor at least weekly for a period of 12 consecutive months. If supplies monitor more frequently, the monitoring frequency shall be evenly spaced. Supplies that operate for fewer than 12 months per year shall monitor weekly during the period of operation. Supplies shall monitor all of the following parameters:

(i) If a disinfectant other than UV is used, the temperature of the disinfected water shall be measured at each residual disinfectant concentration sampling point during peak hourly flow or at an alternative location approved by the department.

(ii) If chlorine is used, the pH of the disinfected water shall be measured at each chlorine residual disinfect disinfectant concentration sampling point during peak hourly flow or at an alternative location approved by the department.

(iii) Disinfectant contact time or times ("T") shall be determined during peak hourly flow.

(iv) Residual disinfectant concentration or concentrations ("C") of the water before or at the first customer and before each additional point of disinfectant application shall be measured during peak hourly flow.

(b) A supply shall determine log inactivation for Giardia lamblia through the entire plant, based on CT99.9 values in Tables 1.1 to 1.6, 2.1 and 3.1 of 40 CFR §141.74(b)(3)(v), as applicable, as adopted by reference in R 325.10112. A supply shall calculate the total logs of inactivation for Giardia lamblia as follows:

(i) A supply using only 1 point of disinfectant application shall determine the total inactivation ratio for the disinfection segment based on either of the following methods:

(A) Determine 1 inactivation ratio (CTcalc/CT99.9) before or at the first customer during peak hourly flow.

(B) Determine successive CTcalc/CT99.9 values, representing sequential inactivation ratios, between the point of disinfectant application and a point before or at the first customer during peak hourly flow. The supply shall calculate the total inactivation ratio by determining (CTcalc/CT99.9) for each sequence and then adding the (CTcalc/CT99.9) values together to determine [SIGMA] (CTcalc/CT99.9).

(ii) A supply using more than 1 point of disinfectant application before the first customer shall determine the (CTcalc/CT99.9) value of each disinfection segment immediately before the next point of disinfectant application, or for the final segment, before or at the first customer, during peak hourly flow. The (CTcalc/CT99.9) value of each segment and [SIGMA] (CTcalc/CT99.9) shall be calculated using the method specified in paragraph (i)(B) of this subdivision.

(iii) The supply shall determine the total logs of inactivation by multiplying the value calculated in paragraph (i) or (ii) of this subdivision by 3.0.

(c) A supply that uses chloramines, ozone, or chlorine dioxide for primary disinfection, and a supply subject to R 325.10720d, shall calculate the logs of inactivation for viruses through the entire treatment plant based on CT99.99 values in the tables in Appendix B of the LT1ESWTR Disinfection Profiling and Benchmarking Technical Guidance Manual, as adopted by reference in R 325.10112, as applicable, and develop a disinfection profile for viruses. A supply shall calculate the total log of inactivation for viruses as follows:

(i) A supply using only 1 point of disinfection application shall determine the total inactivation ratio for the disinfection segment based on either of the following methods:

(A) Determine 1 inactivation ratio (CTcalc/CT99.99) before or at the first customer during peak hourly flow.

(B) Determine successive CTcalc/CT99.99 values, representing sequential inactivation ratios, between the point of disinfectant application and a point before or at the first customer during peak hourly flow. The supply shall calculate the total inactivation ratio by determining (CTcalc/CT99.99) for each sequence and then adding the (CTcalc/CT99.99) values together to determine [SIGMA] (CTcalc/CT99.99).

(ii) A supply using more than 1 point of disinfectant application before the first customer shall determine the (CTcalc/CT99.99) value of each disinfection segment immediately before the next point of disinfectant application, or for the final segment, before or at the first customer, during peak hourly flow. The (CTcalc/CT99.99) value of each segment and [SIGMA] (CTcalc/CT99.99) shall be calculated using the method specified in paragraph (i)(B) of this subdivision.

(iii) The supply shall determine the total logs of inactivation by multiplying the value calculated in paragraph (i) or (ii) of this subdivision by 4.0.

(d) The disinfection profile of the 52 measurements of log inactivations shall be represented in a graphic form, such as a spreadsheet and shall be retained and be available for review by the department as part of a sanitary survey. The data shall be used to create the disinfection benchmark under subrule (4) of this rule.

(4) All of the following provisions apply to disinfection benchmarking:

(a) Significant changes to disinfection practice include all of the following:

(i) Changes to the point of disinfection.

(ii) Changes to the disinfectant or disinfectants used in the treatment plant.

(iii) Changes to the disinfection process.

(iv) Any other modification identified by the department as a significant change to disinfection practices.

(b) Prior to changing the disinfection practice, the supply shall notify the department and shall include in this notice the following information:

(i) A description of the proposed change in disinfection practice.

(ii) A completed disinfection profile and disinfection benchmark for Giardia lamblia and viruses as described in R 325.10720d.

(iii) An analysis of how the proposed change will affect the current level of disinfection.

(iv) Any additional information requested by the department to demonstrate the results or benefits, or both, of the change to the disinfection practice.

(c) Supplies shall use the following procedures to calculate a disinfection benchmark:

(i) For each year of profiling data collected and calculated under subrule (3)(a) to (c) of this rule and R 325.10720d(3), supplies shall determine the lowest mean monthly level of both Giardia lamblia and virus inactivation. Supplies shall determine the mean Giardia lamblia and virus inactivation for each calendar month for each year of profiling data by dividing the sum of daily or weekly Giardia lamblia and virus log inactivation by the number of values calculated for that month.

(ii) The disinfection benchmark is the lowest monthly mean value, for supplies with 1 year of profiling data, or the mean of the lowest monthly mean values, for supplies with more than 1 year of profiling data, of Giardia lamblia and virus log inactivation in each year of profiling data.

Mich. Admin. Code R. 325.10722

1979 AC; 2005 AACS; 2009 AACS; 2015 MR 20, Eff. 10/16/2015