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Development of Groundwater Rule Implementation Strategies at the Honolulu Board of Water Supply
Author: Gary P. Silverman, Erwin Kawata, Raymond N. Matasci
Date:
Presented at AWWA Annual Conference and Exposition, June 11-15, Denver, CO, 2000

The Honolulu Board of Water Supply provides drinking water to 800,000 people on the island of Oahu. Their water supply is from over 200 groundwater sources, which are disinfected at a low level to balance microbiological and aesthetic water quality. EPA will promulgate a Ground Water Rule (GWR) by the end of 2002, which may require certain sources to be disinfected to achieve 4-log virus removal depending on the findings of sanitary surveys and source water monitoring. A study was conducted to develop implementation strategies for complying with the GWR. Representative sources were evaluated to determine which could meet the disinfection provisions of the GWR with existing chlorination systems without exceeding a 0.1 mg/l residual at the first customer, a limit established to protect aesthetic quality. For those that cannot, options were developed and conceptual designs prepared to illustrate how facilities might be retrofit at these locations to achieve GWR compliance. Options included adding contact time and switching to an alternate disinfectant.