Section 179-17-004 - DISINFECTION PROFILING AND BENCHMARKING004.01 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; and3. 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; and3. An analysis of how the proposed change will affect the current levels of disinfection.179 Neb. Admin. Code, ch. 17, § 004