AWWA WQTC71610

The U.S. Environmental Protection Agency's (USEPA's) Long Term 2 Enhanced Surface Water Treatment Rule (LT2) requires all water systems operating under filtration avoidance status to add a second disinfectant to their treatment system or to add filtration. As stated in the LT2 rule, the most economical solution for unfiltered systems to meet the requirements of LT2 is typically ultraviolet (UV) disinfection. Each unfiltered water utility must understand and address all issues that could affect the best method of disinfection before selecting their treatment approach. UV disinfection may not be the best choice in all cases. Systems that have periodic high turbidity events, taste and odor issues, disinfection byproduct (DBP) compliance issues, iron and manganese concerns or the potential for significant changes to their source water supply need to consider other disinfectants to determine the best second disinfectant for their particular water system. Other alternatives may allow these systems to deal with their specific challenges and bring their system into compliance with LT2 at the same time and remain an unfiltered water system. In this context, this study discusses three (Ketchikan Public Utilities, the City of Kodiak, and the City and Borough of Sitka) of Alaska's unfiltered water systems that have water quality challenges that necessitated careful review of the available disinfection alternatives before disinfectant selection was completed. Includes figures.