Section 611.954  Disinfection Benchmark

a)         Applicability.  A Subpart B system supplier that must develop a disinfection profile under Section 611.953 must develop a disinfection benchmark if it decides to significantly change its disinfection practice.  The supplier must receive a SEP from the Agency approving a significant change before implementing the change in its disinfection practice.

b)         Significant Changes to Disinfection Practice.  Certain changes are significant changes to disinfection practice:

1)         Changing the point for applying disinfectant;

2)         Changing the applied disinfectant;

3)         Changing the disinfection process; or

4)         Any other modification the Agency identifies.

c)         Considering a Significant Change.  A supplier considering a significant change to its disinfection practice must calculate a disinfection benchmark, as subsections (d) and (e) describe, and provide the benchmarks to the Agency.  A supplier may only significantly change its disinfection practice after receiving a SEP from the Agency approving the change.  A supplier must submit certain information to the Agency to gain approval of a significant change:

1)         A description of the proposed change;

2)         The disinfection profile for Giardia lamblia (and, if necessary, viruses) and disinfection benchmark;

3)         An analysis of how the proposed change will affect the current levels of disinfection; and

4)         Any additional information the Agency requests.

d)         Calculation of a Disinfection Benchmark.  A supplier significantly changing its disinfection practice must calculate a disinfection benchmark using the specified procedure:

1)         Step 1:  Using the data that the supplier collected to develop the disinfection profile, determine the average Giardia lamblia inactivation for each calendar month by dividing the sum of all Giardia lamblia inactivations for that month by the number of values calculated for that month; and

2)         Step 2:  Determine the lowest monthly average value out of the 12 values.  This value becomes the disinfection benchmark.

e)         If a supplier uses chloramines, ozone, or chlorine dioxide for primary disinfection the supplier must calculate the disinfection benchmark from the data that the supplier collected for viruses to develop the disinfection profile under subsection (d).  The supplier must calculate this viral benchmark in the same manner as calculating the Giardia lamblia disinfection benchmark under subsection (d).

BOARD NOTE:  This Section derives from 40 CFR 141.540 through 141.544.

(Source:  Amended at 47 Ill. Reg. 16486, effective November 2, 2023)