Section 327IAC8-2-8.6. Disinfection treatment

  6. Effective June 29, 1993, each PWS that provides filtration treatment must provide disinfection treatment as follows:

(1) The disinfection treatment must be sufficient to ensure that the total treatment processes of that system achieve:

(A) at least ninety-nine and nine-tenths percent (99.9%) (3-log) inactivation or removal of Giardia lamblia cysts; and

(B) at least ninety-nine and ninety-nine hundredths percent (99.99%) (4-log) inactivation or removal of viruses, as determined by the commissioner.

(2) The residual disinfectant concentration in the water entering the distribution system, measured as specified in sections 8.7(5), 8.7(7), 8.7(8), and 8.8(e) of this rule, may not be less than two-tenths (0.2) milligram per liter for more than four (4) hours.

(3) The residual disinfectant concentration in the distribution system, measured as total chlorine, combined chlorine, or chlorine dioxide, as specified in sections 8.7(5), 8.7(7), 8.7(8), and 8.8(c) of this rule, may not be undetectable in more than five percent (5%) of the samples each month for any two (2) consecutive months that the system serves water to the public. Water in the distribution system with a heterotrophic bacteria concentration less than or equal to five hundred (500) per milliliter, measured as heterotrophic plate count (HPC) as specified in section 8.7(3) of this rule, is deemed to have a detectable disinfectant residual for purposes of determining compliance with this requirement. Thus, the value V in the following formula may not exceed five percent (5%) in one (1) month for any two (2) consecutive months:

Where:	a	=	number of instances where the residual disinfectant concentration is measured
	b	=	number of instances where the residual disinfectant concentration is not measured but HPC is measured
	c	=	number of instances where the residual disinfectant concentration is measured but not detected and no HPC is measured
	d	=	number of instances where no residual disinfectant concentration is detected and where the HPC is greater than five hundred (500) per milliliter
	e	=	number of instances where the residual disinfectant concentration is not measured and HPC is greater than five hundred (500) per milliliter

(4) The requirements of subdivision (3) do not apply if the commissioner determines, based on site-specific considerations, that a PWS:

(A) has no means for having a sample transported and analyzed for HPC by a certified laboratory under the requisite time and temperature conditions specified in section 8.7 of this rule; and

(B) is providing adequate disinfection in the distribution system.

(Water Pollution Control Division; 327 IAC 8-2-8.6; filed Dec 28, 1990, 5:10 p.m.: 14 IR 1024; errata filed Jan 9, 1991, 2:30 p.m.: 14 IR 1070; filed Apr 12, 1993, 11:00 a.m.: 16 IR 2161; filed May 7, 2010, 9:30 a.m.: 20100602-IR-327080198FRA)