Current through Register Vol. 48, No. 38, September 20, 2024
a) A
supplier required to develop disinfection profiles under Section
611.1008
must follow the requirements of this Section. The supplier must monitor at
least weekly for a period of 12 consecutive months to determine the total log
inactivation for Giardia lamblia and viruses. If the supplier monitors more
frequently than weekly, the monitoring frequency must be evenly spaced. A
supplier that operates for fewer than 12 months per year must monitor weekly
during the period of operation. A supplier must determine log inactivation for
Giardia lamblia through the entire plant, based on the applicable
CT99.9 values in Appendix B. A supplier must determine
log inactivation for viruses through the entire treatment plant based on a
protocol approved by the Agency by a SEP.
b) A supplier with a single point of
disinfectant application prior to the entrance to the distribution system must
conduct the monitoring in subsections (b)(1) through (b)(4). A supplier with
more than one point of disinfectant application must conduct the monitoring in
subsections (b)(1) through (b)(4) for each disinfection segment. A supplier
must monitor the parameters necessary to determine the total inactivation
ratio, using analytical methods in Section
611.531.
1) For a supplier using a disinfectant other
than UV, the temperature of the disinfected water must be measured at each
residual disinfectant concentration sampling point during peak hourly flow or
at an alternative location approved by the Agency by a SEP.
2) For a supplier using chlorine, the pH of
the disinfected water must be measured at each chlorine residual disinfectant
concentration sampling point during peak hourly flow or at an alternative
location approved by the Agency by a SEP.
3) The disinfectant contact times (t) must be
determined during peak hourly flow.
4) The residual disinfectant concentrations
(C) of the water before or at the first customer and prior to each additional
point of disinfectant application must be measured during peak hourly
flow.
c) In lieu of
conducting new monitoring under subsection (b), a supplier may elect to meet
the following requirements:
1) A supplier that
has at least one year of existing data that are substantially equivalent to
data collected under the provisions of subsection (b) may use these data to
develop disinfection profiles as specified in this Section if the supplier has
neither made a significant change to its treatment practice nor changed sources
since the data were collected. The supplier may develop disinfection profiles
using up to three years of existing data.
2) A supplier may use disinfection profiles
developed under Section
611.742
or Section
611.953 in
lieu of developing a new profile if the supplier has neither made a significant
change to its treatment practice nor changed sources since the profile was
developed. A supplier that has not developed a virus profile under Section
611.742
or Section
611.953 must
develop a virus profile using the same monitoring data on which the Giardia
lamblia profile is based.
d) A supplier must calculate the total
inactivation ratio for Giardia lamblia, as specified in subsections (d)(1)
through (d)(3).
1) A supplier using only one
point of disinfectant application may determine the total inactivation ratio
for the disinfection segment based on either of the following methods:
A) It may determine one inactivation ratio
(Ai) before or at the first customer during peak hourly flow; or
B) It may determine successive Ai 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 supplier must calculate the total inactivation ratio by determining
Ai for each sequence and then adding the Ai values together to determine the
total inactivation ratio ([SIGMA] Ai).
2) A supplier using more than one point of
disinfectant application before the first customer must determine the CT value
of each disinfection segment immediately prior to the next point of
disinfectant application, or for the final segment, before or at the first
customer, during peak hourly flow. The Ai value of each segment and [SIGMA] Ai
must be calculated using the method in subsection (d)(1)(B).
3) The supplier must determine the total logs
of inactivation by multiplying the value calculated in subsection (d)(1) or
(d)(2) by 3.0.
4) The supplier must
calculate the log of inactivation for viruses using a protocol approved by the
Agency by regulation or by a SEP.
e) A supplier must use the following
procedures to calculate a disinfection benchmark:
1) For each year of profiling data collected
and calculated under subsections (a) through (d), the supplier must determine
the lowest mean monthly level of both Giardia lamblia and virus inactivation. A
supplier must 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) The disinfection benchmark is the lowest
monthly mean value (for a supplier with one year of profiling data) or the mean
of the lowest monthly mean values (for a supplier with more than one year of
profiling data) of Giardia lamblia and virus log inactivation in each year of
profiling data.
BOARD NOTE: Derived from
40 CFR
141.709 (2016).
