Wisconsin Administrative Code
Department of Natural Resources
NR 800 - Environmental Protection - Water Supply
Chapter NR 810 - Requirements for the operation and maintenance of public water systems
Subchapter II - Surface Water Treatment and Groundwater Under the Direct Influence of Surface Water Treatment Operations
Section NR 810.32 - Disinfection profiling and benchmarking
Universal Citation: WI Admin Code ยง NR 810.32
Current through August 26, 2024
(1) REQUIREMENTS WHEN MAKING A SIGNIFICANT CHANGE IN DISINFECTION PRACTICE.
(a) Following the completion of initial
source water monitoring under s.
NR 809.331, the water supplier for a public water system
that plans to make a significant change to its disinfection practice, as
defined in par. (b), shall develop disinfection profiles and calculate
disinfection benchmarks for Giardia lamblia and viruses as described in sub.
(2). Prior to changing the disinfection practice, the water supplier shall
notify the department and shall include in this notice all of the following
information:
1. A completed disinfection
profile and disinfection benchmark for Giardia lamblia and viruses as described
in sub. (2).
2. A description of
the proposed change in disinfection practice.
3. An analysis of how the proposed change
will affect the current level of disinfection.
(b) Significant changes to disinfection
practice are defined as any of the following:
1. Changes to the point of
disinfection.
2. Changes to the
disinfectants used in the treatment plant.
3. Changes to the disinfection
process.
4. Any other modification
identified by the department as a significant change to disinfection practice.
Additional barriers with no change to existing disinfection practices may be
exempt from these requirements.
(2) DEVELOPING THE DISINFECTION PROFILE AND BENCHMARK. Water suppliers for public water systems required to develop disinfection profiles under sub. (1) shall follow the requirements of this subsection:
(a) Water suppliers shall monitor
at least weekly for a period of 12 consecutive months to determine the total
logs of inactivation for Giardia lamblia and viruses. If water suppliers
monitor more frequently, the monitoring frequency shall be evenly spaced.
Systems that operate for fewer than 12 months per year shall be monitored
weekly during the period of operation. Water suppliers shall determine log
inactivation for Giardia lamblia through the entire plant, based on the CT99.9
(3 log) values in ss.
NR 810.47 to 810.62. Water suppliers shall
determine log inactivation for viruses through the entire treatment plant based
on a protocol approved by the department.
(b) Water suppliers for systems with a single
point of disinfectant application prior to entrance to the distribution system
shall conduct the monitoring in subds. 1. to 4. Water suppliers for systems
with more than one point of disinfectant application shall conduct the
monitoring in subds. 1. to 4. for each disinfection segment. Water suppliers
shall monitor the parameters necessary to determine the total inactivation
ratio, using analytical methods in s.
NR 809.563(2), Table R.
1. For systems using a disinfectant other
than UV, the temperature of the disinfected water shall be measured at each
residual disinfectant concentration sampling point during peak hourly
flow.
2. For systems using
chlorine, the pH of the disinfected water shall be measured at each chlorine
residual disinfectant concentration sampling point during peak hourly
flow.
3. The disinfectant contact
times ("T") shall 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 disinfection shall be measured during peak hourly flow.
(c) In lieu of conducting new
monitoring under par. (b), public water systems may elect to meet the following
requirements:
1. Water suppliers for systems
that have at least one year of existing data that are substantially equivalent
to data collected under par. (b) may use these data to develop disinfection
profiles as specified in this section if the water system has neither made a
significant change to its treatment practice nor changed sources since the data
were collected. Water suppliers may develop disinfection profiles using up to 3
years of existing data.
2. Water
suppliers may use disinfection profile or profiles developed previously in lieu
of developing a new profile if the water system has not made a significant
change, as determined under sub. (1) (b), to its treatment practice or has not
changed sources since the profile was developed. Water suppliers for systems
that have not developed a virus profile shall develop a virus profile using the
same monitoring data on which the Giardia lamblia profile is based.
(d) The water supplier shall
calculate the total inactivation ratio for Giardia lamblia as follows:
1. For water systems using only one point of
disinfectant application, the water supplier may determine the total
inactivation ratio for the disinfection segment based on either of the
following methods:
a. Determine one
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. Under this alternative, the water
supplier shall calculate the total inactivation ratio by determining
(CTcalc/CT99.9) for each sequence and then adding the (CTcalc/CT99.9) values
together to determine (S (CTcalc/CT 99.9)).
2. For systems using more than one point of
disinfectant application before the first customer the water supplier shall
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 (CTcalc/CT99.9) value of each
segment and (S (CTcalc/CT99.9)) shall be calculated using the method in subd.
1.
3. The water supplier shall
determine the total logs of inactivation by multiplying the value calculated in
subd. 1. or 2. by 3.0.
(e) Water suppliers shall determine the total
logs of inactivation for viruses using a protocol approved by the
department.
(f) For water systems
required to calculate a disinfection benchmark water suppliers shall use the
following procedure:
1. For each year of
profiling data collected and calculated under this subsection, the water
supplier shall determine the lowest mean monthly level of both Giardia lamblia
and virus inactivation. The water supplier 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. The disinfection benchmark is the lowest
monthly mean value, for water systems with one year of profiling data, or the
mean of lowest monthly mean values, for water systems with more than one year
of profiling data, of the monthly logs of Giardia lamblia and virus log
inactivation in each year of profiling data.
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