Washington Administrative Code
Title 173 - Ecology, Department of (See also Titles 197, 317, 372, and 508)
Chapter 173-219 - RECLAIMED WATER
Section 173-219-340 - Disinfection process standards
Current through Register Vol. 24-06, March 15, 2024
(1) Disinfection process: Class A reclaimed water. The engineering report must demonstrate, to the satisfaction of the lead agency that the proposed disinfection method consistently provides the required level of adequate and reliable disinfection to help preserve the quality of water delivered to the use site. All Class A reclaimed water generation disinfection processes must, in combination with treatment processes following biological oxidation, result in a minimum of 4-log virus removal or inactivation. The disinfection process may use any or all of the following:
The lead agency may require additional protections including defined concentration (C), time (T), or chlorine concentration multiplied by (CT) values as needed to protect public health. The lead agency may require a tracer study to determine contact times.
(2) Validation of virus removal. For Class A reclaimed water, virus inactivation performance of the combined treatment processes following biological oxidation must be documented. Performance of the chosen disinfection method must be documented by using one of the following:
Third-party validation studies that have been performed in off-site qualified test facilities and in accordance with the NWRI/AWWARF guidelines are allowed if approved by the lead agency.
(3) Disinfection process: Class B reclaimed water. The engineering report must demonstrate, to the satisfaction of the lead agency that the proposed disinfection method consistently provides the required level of adequate and reliable disinfection to help preserve the quality of water delivered to the use site. All Class B reclaimed water generation disinfection processes must result in a minimum total chlorine residual of at least 1 mg/L, after a T10 contact time of at least thirty minutes based on peak design day flow or a substantially equivalent alternative process approved by the lead agency.