Section 611.1020  Requirements for Microbial Toolbox Components:  Inactivation Toolbox Components

a)         Calculation of CT Values

1)         CT is the product of the disinfectant contact time (T, in minutes) and disinfectant concentration (C, in milligrams per liter).  A supplier with treatment credit for chlorine dioxide or ozone under subsection (b) or (c) must calculate CT at least once each day, with both C and T measured during peak hourly flow, as specified in Sections 611.531 and 611.532.

2)         A supplier with several disinfection segments in sequence may calculate CT for each segment, where a disinfection segment is defined as a treatment unit process with a measurable disinfectant residual level and a liquid volume.  Under this approach, the supplier must add the Cryptosporidium CT values in each segment to determine the total CT for the treatment plant.

b)         CT Values for Chlorine Dioxide and Ozone

1)         A supplier receives the Cryptosporidium treatment credit listed in Table H by meeting the corresponding chlorine dioxide CT value for the applicable water temperature, as described in subsection (a).

2)         A supplier receives the Cryptosporidium treatment credit listed in Table I by meeting the corresponding ozone CT values for the applicable water temperature, as described in subsection (a).

c)         Site-Specific Study.  The Agency may, by a SEP, approve alternative chlorine dioxide or ozone CT values to those listed in Tables H and I on a site-specific basis.  The Agency must base this approval on a site-specific study conducted by the supplier according to an Agency-approved protocol.

d)         Ultraviolet Light.  A supplier receives Cryptosporidium, Giardia lamblia, and virus treatment credits for ultraviolet (UV) light reactors by achieving the corresponding UV dose values shown in Table J.  The supplier must validate and monitor UV reactors, as described in subsections (d)(2) and (d)(3), to demonstrate that they are achieving a particular UV dose value for treatment credit.

1)         UV Dose Table.  The treatment credits listed in Table J are for UV light at a wavelength of 254 nm as produced by a low-pressure mercury vapor lamp.  To receive treatment credit for other lamp types, a supplier must demonstrate an equivalent germicidal dose through reactor validation testing, as described in subsection (d)(2).  The UV dose values in this table are applicable only to post-filter applications of UV in a filtered system supplier and to an unfiltered system supplier.

2)         Reactor Validation Testing.  A supplier must use UV reactors that have undergone validation testing to determine the operating conditions under which the reactor delivers the UV dose required in subsection (d)(1) (i.e., validated operating conditions).  These operating conditions must include flow rate; UV intensity, as measured by a UV sensor; and UV lamp status.

A)        When determining validated operating conditions, a supplier must account for the following factors:  UV absorbance of the water; lamp fouling and aging; measurement uncertainty of on-line sensors; UV dose distributions arising from the velocity profiles through the reactor; failure of UV lamps or other critical treatment system components; and inlet and outlet piping or channel configurations of the UV reactor.

B)        Validation testing must include the following:  Full scale testing of a reactor that conforms uniformly to the UV reactors used by the supplier and inactivation of a test microorganism whose dose response characteristics have been quantified with a low pressure mercury vapor lamp.

C)        The Agency may, by a SEP, approve an alternative approach to validation testing.

3)         Reactor Monitoring

A)        A supplier must monitor its UV reactors to determine if the reactors are operating within validated conditions, as determined under subsection (d)(2).  This monitoring must include UV intensity, as measured by a UV sensor; flow rate; lamp status; and other parameters that the Agency has designated by a SEP based on UV reactor operation.  A supplier must verify the calibration of UV sensors and must recalibrate sensors in accordance with a protocol that the Agency has approved by the SEP.

B)        To receive treatment credit for UV light, a supplier must treat at least 95 percent of the water delivered to the public during each month by UV reactors operating within validated conditions for the required UV dose, as described in subsections (d)(1) and (d)(2).  The supplier must demonstrate compliance with this condition by the monitoring required under subsection (d)(3)(A).

BOARD NOTE:  Derived from 40 CFR 141.720.

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