Nebraska Administrative Code
Topic - HEALTH AND HUMAN SERVICES SYSTEM
Title 179 - PUBLIC WATER SYSTEMS
Chapter 17 - INTERIM ENHANCED SURFACE WATER TREATMENT (SYSTEMS SERVING 10,000 OR MORE PEOPLE)
Section 179-17-004 - DISINFECTION PROFILING AND BENCHMARKING
Universal Citation: 179 NE Admin Rules and Regs ch 17 ยง 004
Current through September 17, 2024
004.01 Determination of Systems Required to Profile
A public water system subject to the requirements of 179 NAC 17 must determine its total trihalomethane (TTHM) annual average using the procedure in 179 NAC 17-004.01A and its five haloacetic acids (HAA5) annual average using the procedure in 179 NAC 17-004.01B. The annual average is the arithmetic average of the quarterly averages of four consecutive quarters of monitoring.
17-004.01A The TTHM annual average must be
the annual average during the same period as is used for the HAA5 annual
average.
17-004.01A1 Those systems that
collected data under the provisions of the Information Collection Rule must use
the results of the samples collected during the last four quarters of required
monitoring. The Department will approve any data, location, handling, and
analytical requirements submitted from previous testing.
17-004.01B The HAA5 annual average must be
the annual average during the same period as is used for the TTHM annual
average.
17-004.01B1 Those systems that
collected data under the provisions of the Information Collection Rule must use
the results of the samples collected during the last four quarters of required
monitoring. The Department will approve any data, location, handling, and
analytical requirements submitted from previous testing.
17-004.01C The system may request that the
Department approve a more representative annual data set than the data set
determined under 179 NAC
17-004.01A or
17-004.01B for
the purpose of determining applicability of the requirements of this
section.
17-004.01D The Department
may require that a system use a more representative annual data set than the
data set determined under 179 NAC
17-004.01A or
17-004.01B for
the purpose of determining applicability of the requirements of 179 NAC
17-004.02.
17-004.01E Any system
having either a TTHM annual average > 0.064 mg/L or an HAA5 annual average
> 0.048 mg/L during the period identified in 179 NAC
17-004.01A and
17-004.01B must
comply with 179 NAC 17-004.02.
004.02 Disinfection Profiling
17-004.02A Any system that meets the criteria
in 179 NAC
17-004.01E must
develop a disinfection profile of its disinfection practice for a period of up
to three years.
17-004.02B The
system must monitor daily for a period of 12 consecutive calendar months to
determine the total logs of inactivation for each day of operation, based on
the CT 99.9 values in Tables 13.1 - 13.6, 13.7, and 13.8 of 179 NAC 13-007.02
as appropriate, through the entire treatment plant. As a minimum, the system
with a single point of disinfectant application prior to entrance to the
distribution system must conduct the monitoring in 179 NAC 17-004.02B items 1
to 4. A system with more than one point of disinfectant application must
conduct the monitoring in 179 NAC 17-004.02B Items 1. to 4. for each
disinfection segment. The system must monitor the parameters necessary to
determine the total inactivation ratio, using analytical methods in 179 NAC
13-007.01 as follows:
1. The temperature of
the disinfected water must be measured once per day at each residual
disinfectant concentration sampling point during peak hourly flow.
2. If the system uses chlorine, the pH of the
disinfected water must be measured once per day at each chlorine residual
disinfectant concentration sampling point during peak hourly flow.
3. The disinfectant contact times ("T") must
be determined for each day during peak hourly flow.
4. The residual disinfectant concentration(s)
("C") of the water before or at the first customer and prior to each additional
point of disinfection must be measured each day during peak hourly
flow.
17-004.02C In lieu
of the monitoring conducted under the provisions of 179 NAC 17-004.02B to
develop the disinfection profile, the system may elect to meet the requirements
of 179 NAC
17-004.02C 1. In
addition to the monitoring conducted under the provisions of 179 NAC
17-004.02B to
develop the disinfection profile, the system may elect to meet the requirements
of 179 NAC
17-004.02C2.
17-004.02C1 A PWS that has three years of
existing operational data may submit those data, a profile generated using
those data, and a request that the Department approve use of those data in lieu
of monitoring. The Department will determine whether these operational data are
substantially equivalent to data collected under the provisions of 179 NAC
17-004.02B. These
data must also be representative of Giardia lamblia
inactivation through the entire treatment plant and not just of certain
treatment segments. Until the Department approves this request, the system is
required to conduct monitoring under the provisions of 179 NAC
17-004.02B.
17-004.02C2 In addition to the disinfection
profile generated under 179 NAC
17-004.02B, a PWS
that has existing operational data may use those data to develop a disinfection
profile for additional years. Such systems may use these additional yearly
disinfection profiles to develop a benchmark under the provisions of 179 NAC
17-004.03. The Department will determine whether these operational data are
substantially equivalent to data collected under the provisions of 179 NAC
17-004.02B. These
data must also be representative of inactivation through the entire treatment
plant and not just of certain treatment segments.
17-004.02D The system must calculate the
total inactivation ratio as follows:
1. If
the system uses only one point of disinfectant application, the system may
determine the total inactivation ratio for the disinfection segment based on
either of the following methods:
a. Determine
one inactivation ratio CTcalc/CT( 99.9) before or at the
first customer during peak hourly flow.
b. Determine successive CTcalc/CT(
99.9) 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 system must
calculate the total inactivation ratio by determining CTcalc/CT(
99.9) for each sequence and then adding the CTcalc/CT(
99.9) values together to determine
([SIGHMA]CTcalc/CT99.9).
2. If the system uses more than one point of
disinfectant application before the first customer, the system 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 (CTcalc/CT99.9)
value of each segment and [[SIGHMA](CTcalc/CT99.9)] must
be calculated using the method in 179 NAC
17-004.02D item
1.
3. The system must determine the
total logs of inactivation by multiplying the value calculated in 179 NAC
17-004.02D item 1
or 2 by 3.0.
17-004.02E
A system that uses either chloramines or ozone for primary disinfection must
also calculate the logs of inactivation for viruses using a method approved by
the Department.
17-004.02F The
system must retain disinfection profile data in graphic form, as a spreadsheet,
or in some other format acceptable to the Department for review as part of
sanitary surveys conducted by the Department.
004.03 Disinfection Benchmarking
17-004.03A Any system required to develop a
disinfection profile under the provisions of 179 NAC
17-004.01 and
17-004.02 and that decides to make
a significant change to its disinfection practice must consult with the
Department prior to making such change. Significant changes to disinfection
practice are:
1. Changes to the point of
disinfection;
2. Changes to the
disinfectant(s) used in the treatment plant; and
3. Changes to the disinfection
process.
17-004.03B Any
system that is modifying its disinfection practice must calculate its
disinfection benchmark using the following procedure:
1. For each year of profiling data collected
and calculated under 179 NAC
17-004.02, the system must
determine the lowest average monthly Giardia lamblia
inactivation in each year of profiling data. The system must determine the
average Giardia lamblia inactivation for each calendar month
for each year of profiling data by dividing the sum of daily Giardia
lamblia of inactivation by the number of values calculated for that
month.
2. The disinfection
benchmark is the lowest monthly average value (for systems with one year of
profiling data) or average of lowest monthly average values (for systems with
more than one year of profiling data) of the monthly logs of Giardia
lamblia inactivation in each year of profiling data.
17-004.03C A system that uses
either chloramines or ozone for primary disinfection must also calculate the
disinfection benchmark for viruses using a method approved by the
Department.
17-004.03D The system
must submit the following information to the Department as part of its
consultation process:
1. A description of the
proposed change;
2. The
disinfection profile for Giardia lamblia (and, if necessary,
viruses) under 179 NAC
17-004.02 and benchmark as
required by 179 NAC
17-004.03B;
and
3. An analysis of how the
proposed change will affect the current levels of disinfection.
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