Section 611.1018  Requirements for Microbial Toolbox Components:  Treatment Performance Toolbox Components

a)         Combined Filter Performance.  A supplier that uses conventional filtration treatment or direct filtration treatment receives an additional 0.5-log Cryptosporidium treatment credit during any month it meets the criteria in this subsection (a).  Its combined filter effluent (CFE) turbidity must be less than or equal to 0.15 NTU in at least 95 percent of the measurements.  Turbidity must be measured as described in Sections 611.531 and 611.533.

b)         Individual Filter Performance.  A supplier that uses conventional filtration treatment or direct filtration treatment receives 0.5-log Cryptosporidium treatment credit, which can be in addition to the 0.5-log credit under subsection (a), during any month it meets the criteria in this subsection (b).  Compliance with these criteria must be based on individual filter turbidity monitoring as described in Section 611.744 or 611.956(a), as applicable.

1)         The filtered water turbidity for each individual filter must be less than or equal to 0.15 NTU in at least 95 percent of the measurements recorded each month.

2)         No individual filter may have a measured turbidity greater than 0.3 NTU in two consecutive measurements taken 15 minutes apart.

3)         Any supplier that has received treatment credit for individual filter performance and fails to meet the requirements of subsection (b)(1) or (b)(2) during any month does not receive a treatment technique violation under Section 611.1011(c) if the Agency determines the following:

A)        The failure was due to unusual and short-term circumstances that could not reasonably be prevented through optimizing treatment plant design, operation, and maintenance; and

B)        The supplier has experienced no more than two such failures in any calendar year.

c)         Demonstration of Performance.  The Agency may, by a SEP, approve Cryptosporidium treatment credit for drinking water treatment processes based on a demonstration of performance study that meets the criteria in this subsection (c).  This treatment credit may be greater than or less than the prescribed treatment credits in Section 611.1011 or Sections 611.1017 through 611.1020 and may be awarded to treatment processes that do not meet the criteria for the prescribed credits.

1)         The supplier cannot receive the prescribed treatment credit for any toolbox option in Sections 611.1017 through 611.1020 if that toolbox option is included in a demonstration of performance study for which treatment credit is awarded under this subsection (b).

2)         The demonstration of performance study must follow an Agency-approved protocol and must demonstrate the level of Cryptosporidium reduction the treatment process will achieve under the full range of expected operating conditions for the supplier.

3)         Approval by the Agency must be in writing and may include monitoring and treatment performance criteria that the supplier must demonstrate and report on an ongoing basis to remain eligible for the treatment credit.  The Agency may, by a SEP, designate such criteria where necessary to verify that the conditions under which the demonstration of performance credit was approved are maintained during routine operation.

BOARD NOTE:  Derived from 40 CFR 141.718.

(Source:  Amended at 44 Ill. Reg. 6996, effective April 17, 2020)