Authority: IC 13-13-5-1; IC 13-14-8-7; IC 13-18-3; IC
13-18-16
Affected: IC 13-18
Sec. 8.6.
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:
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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.
