SUBTITLE F: PUBLIC WATER SUPPLIES
CHAPTER I: POLLUTION CONTROL BOARD
PART 611 PRIMARY DRINKING WATER STANDARDS
SECTION 611.242 FILTERED PWSS
Section 611.242 Filtered PWSs
Each supplier providing filtration treatment must provide disinfection treatment:
a) The disinfection treatment must sufficiently ensure that the system's total treatment processes achieve at least 99.9 percent (3-log) inactivation or removal of Giardia lamblia cysts and at least 99.99 percent (4-log) inactivation or removal of viruses.
b) The RDC in the water entering the distribution system, measured as Sections 611.531(b) and 611.533(b) specify, cannot be less than 0.2 mg/L for more than four hours.
c) RDC in the Distribution System
1) The RDC in the distribution system, measured as total chlorine, combined chlorine, or chlorine dioxide, as Sections 611.531(b) and 611.533(c) specify, cannot be undetectable in more than 5 percent of the samples the supplier collects each month for any two consecutive months during which the system serves water to the public. Water in the distribution system with HPC less than or equal to 500/ml, measured as Section 611.531(a) specifies, is deemed to have a detectable RDC for complying with this requirement. Thus, the value "V" in this formula cannot exceed 5 percent in one month, for any two consecutive months:
|
where: a |
= |
The number of times when the supplier measured the RDC; |
|
b |
= |
The number of times when the supplier did not measure the RDC but did measure HPC; |
|
c |
= |
The number of times when the supplier measured but did not detect RDC but did not measure HPC; |
|
d |
= |
The number of times when the supplier measured but did not detect the RDC, and HPC is greater than 500/ml; and |
|
e |
= |
The number of times when the supplier did not measure the RDC, and HPC is greater than 500/ml. |
2) Subsection (c)(1) does not apply if the Agency determines, under Section 611.213, that a supplier has no means for having a sample analyzed for HPC by a certified laboratory under the requisite time and temperature conditions Section 611.531(a) specifies and that the supplier provides adequate disinfection in its distribution system.
BOARD NOTE: This Section derives from 40 CFR 141.72(b).
(Source: Amended at 47 Ill. Reg. 16486, effective November 2, 2023)