Nebraska Administrative Code
Topic - HEALTH AND HUMAN SERVICES SYSTEM
Title 179 - PUBLIC WATER SYSTEMS
Chapter 19 - LONG TERM 1 (LT 1) ENHANCED SURFACE WATER TREATMENT (for Systems Serving Fewer Than 10,000 People)
Section 179-19-007 - DISINFECTION PROFILE

Universal Citation: 179 NE Admin Rules and Regs ch 19 ยง 007

Current through September 17, 2024

007.01 What It Is, Who Must Develop One

A disinfection profile is a graphical representation of a system's level of Giardia iambiia or virus inactivation measured during the course of a year. Community and non-transient non-community water systems that use surface water or ground water under the direct influence of surface water and serve fewer than 10,000 persons must develop a disinfection profile unless the Director determines the system's profile is unnecessary. The Director may approve the use of a more representative data set for disinfection profiling than the data set required under 179 NAC 19-007.03 to 19-007.07.

007.02 Criteria used by the Director to determine that a profile is unnecessary

The Director may only determine that a system's profile is unnecessary if a system's TTHM and HAA5 levels are below 0.064 mg/L and 0.048 mg/L, respectively. To determine these levels, TTHM and HAA5 samples must be collected after January 1, 1998, during the month with the warmest water temperature, and at the point of maximum residence time in the distribution system. The Department may approve a more representative TTHM and HAA5 data set to determine these levels.

007.03 Development of a disinfection profile, when to begin

A disinfection profile consists of three steps:

1. First, collect data for several parameters from the plant as discussed in 179 NAC 19-007.04 over the course of 12 months. Systems serving between 500 and 9,999 persons must begin collecting the data no later than July 1, 2003. Systems serving fewer than 500 persons must begin to collect data no later than January 1, 2004.

2. Second, use this data to calculate weekly log inactivation as discussed in 179 NAC 19-007.05 and 19-007.06; and

3. Third, use these weekly log inactivations to develop a disinfection profile as specified in 179 NAC 19-007.07.

007.04 Data Required to Calculate a Disinfection Profile

Systems must monitor the following parameters to determine the total log inactivation using the analytical methods in 179 NAC 13-007.01, once per week on the same calendar day, over 12 consecutive months.

1. The temperature of the disinfected water at each residual disinfectant concentration sampling point during peak hourly flow;

2. For systems that use chlorine, the pH of the disinfected water at each residual disinfectant concentration sampling point during peak hourly flow;

3. The disinfectant contact time(s) ["T"] during peak hourly flow; and

4. The residual disinfectant concentration(s) ["C"] of the water before or at the first customer and prior to each additional point of disinfection during peak hourly flow.

007.05 How To Use the Previous Information to Calculate an Inactivation Ratio

Use the tables in 179 NAC 13-007.02C 5 to determine the appropriate CT99.9 value. Calculate the total inactivation ratio as follows, and multiply the value by 3.0 to determine log inactivation of Giardia lamblia:

If Your System

Your System Must Determine

a. Uses only one point of disinfectant application

1. One inactivation ratio (CTcalc/CT99.9) before or at the first customer during peak hourly flow or

2. 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, your system must calculate the total inactivation ratio by determining (CTcalc/CT99.9) for each sequence and then adding the (CTcalc/CT99.9) values together to determine ([SIGHMA]CTcalc/CT99.9)

b. Uses more than one point of disinfectant application before the first customer

The (CTcalc/CT99.9) 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 using the procedure specified in a.2. above.

007.06 Systems That Use Chloramines, Ozone, or Chlorine Dioxide for Primary Disinfection

These systems must also calculate the logs of inactivation for viruses and develop an additional disinfection profile for viruses using methods approved by the Director.

007.07 After Inactivation Ratio Has Been Developed

Each log inactivation serves as a data point in a system's disinfection profile. Once a system has obtained 52 measurements (one for every week of the year), the system and the Director will have the opportunity to evaluate how microbial inactivation varied over the course of the year by looking at all 52 measurements (the disinfection profile). Systems must retain the disinfection profile data in graphic form, such as a spreadsheet, which must be available for review by the Director as part of a sanitary survey. Systems must use this data to calculate a benchmark if they are considering changes to disinfection practices.

Disclaimer: These regulations may not be the most recent version. Nebraska may have more current or accurate information. We make no warranties or guarantees about the accuracy, completeness, or adequacy of the information contained on this site or the information linked to on the state site. Please check official sources.
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