Current through September 18, 2024
Authority: IC 13-13-5; IC 13-14-8-7; IC 13-14-9; IC
13-18-3-2; IC 13-18-16
Affected: IC 13-18-3-11
Sec. 10.
(a) A PWS
required to develop a disinfection profile under section 9 of this rule shall
follow the requirements of this section, including the following:
(1) A PWS shall monitor at least weekly for a
period of twelve (12) consecutive months to determine the total log
inactivation for Giardia lamblia and viruses as required under subdivision
(4).
(2) If a PWS monitors more
frequently than required under subdivision (1), the monitoring frequency must
be evenly spaced.
(3) A PWS that
operates for fewer than twelve (12) months per year shall monitor weekly during
the period of operation.
(4) Each
PWS shall determine log inactivation for the following:
(A) Giardia lamblia through the entire plant
based on CT99.9 values (where C is the residual
disinfectant concentration and T is the disinfectant contact time) in Tables
1.1 through 1.6, 2.1, and 3.1 of
40 CFR
141.74(b) * as
applicable.
(B) Viruses through the
entire treatment plant based on a protocol approved by the commissioner.
(b)
Disinfectant monitoring requirements to develop a disinfection profile are as
follows:
(1) A PWS with a single point of
disinfectant application prior to the entrance to the distribution system shall
monitor according to this subsection.
(2) A PWS with more than one (1) point of
disinfectant application shall monitor according to this subsection for each
disinfection segment.
(3) A PWS
shall monitor the parameters necessary to determine the total inactivation
ratio using analytical methods in
327
IAC 8-2-8.7.
(4) A PWS using a disinfectant other than UV
shall measure the temperature of the water at:
(A) each residual disinfectant concentration
sampling point during peak hourly flow; or
(B) an alternative location approved by the
commissioner.
(5) A PWS
using chlorine shall measure the pH of the disinfected water at:
(A) each chlorine residual disinfectant
concentration sampling point during peak hourly flow; or
(B) an alternative location approved by the
commissioner.
(6) A PWS
shall determine the disinfectant contact time or times (t) during peak hourly
flow.
(7) A PWS shall measure the
residual disinfectant concentration or concentrations (C) of the water before
or at the first customer and prior to each additional point of disinfectant
application during peak hourly flow.
(c) In lieu of conducting new monitoring
under subsection (b), a PWS may elect to meet the requirements of either of the
following:
(1) A PWS that has at least one
(1) year of existing data that are substantially equivalent to data collected
under the requirements of subsection (b) may use these data to develop
disinfection profiles as specified in this section if the PWS has not:
(A) made a significant change to the
treatment practice; or
(B) changed
sources;
since the data were collected. A PWS may develop a
disinfection profile using up to three (3) years of existing data.
(2) A PWS may use a
disinfection profiledeveloped under section 2 or 2.1 of this rule in lieu of
developing a new profile if the system has not:
(A) made a significant change to the
treatment practice; or
(B) changed
sources;
since the profile was developed. A PWS that did not develop a
virus profile under section 2 or 2.1 of this rule shall develop a virus profile
using the same monitoring data on which the Giardia lamblia profile is
based.
(d) A PWS shall calculate the total
inactivation ratio for Giardia lamblia according to the following:
(1) A PWS using only one (1) point of
disinfectant application may determine the total inactivation ratio for the
disinfection segment based on either of the following methods:
(A) Determine one (1) inactivation ratio
(CTcalc/CT99.9) before or at the first customer during
peak hourly flow.
(B) Determine
successive (CTcalc/CT99.9) values, representing
sequential inactivation ratios, between the point of disinfectant application
and a point before or at the first customer during peak hourly flow. The PWS
shall calculate the total inactivation ratio by determining
CTcalc/CT99.9 for each sequence and use the sum of the
(CTcalc/CT99.9) values to determine
3(CTcalc/CT99.9).
(2) A PWS using more than one (1) point of
disinfectant application before the first customer shall determine the CT
value:
(A) of each disinfection segment
immediately prior to the next point of disinfectant application; or
(B) for the final segment, before or at the
first customer;
during peak hourly flow. The
(CTcalc/CT99.9) value of each segment and
3(CTcalc/CT99.9) must be calculated using the method in
subdivision (1)(B).
(3) A PWS shall determine the total logs of
inactivation by multiplying the value calculated in subdivision (1) or (2) by
three and zero-tenths (3.0).
(4) A
PWS shall calculate the log of inactivation for viruses using a protocol
approved by the commissioner.
(e) A PWS shall use the following procedures
to calculate a disinfection benchmark:
(1)
For each year of profiling data collected and calculated under subsections (a)
through (d), a PWS shall determine the lowest mean monthly level of both
Giardia lamblia and virus inactivation. A PWS shall determine the mean Giardia
lamblia and virus inactivation for each calendar month for each year of
profiling data by dividing the sum of daily or weekly Giardia lamblia and virus
log inactivation by the number of values calculated for that month.
(2) For a PWS with:
(A) one (1) year of profiling data, the
disinfection benchmark is the lowest monthly mean value; or
(B) more than one (1) year of profiling data,
the disinfection benchmark is the lowest monthly mean values of Giardia lamblia
and virus log inactivation in each year of profiling data.
* Tables 1.1 through 1.6, 2.1, and 3.1 of
40 CFR
141.74(b) are incorporated
by reference and are available for review and copying at the Indiana Department
of Environmental Management, Office of Water Quality, 100 North Senate Avenue,
Room N1255, Indianapolis, Indiana 46204.
