AWWA ACE94015

Treatment facilities have been designed and constructed for two small communities on Clear Lake, California, which have been proven to be extremely efficient and cost-effective in producing a high quality water supply from a heavily algae-laden water source with an established history of being extremely difficult and expensive to treat. Both treatment plants use pre-ozonation followed by complete treatment package plants using the adsorption clarification/tri-mixed media filtration process. GAC contactors are used to provide final polishing of the finished water prior to distribution to the consumers. The combination process featuring ozone oxidation and granular activated carbon adsorption has proven to be very effective in removing high concentration of extremely obnoxious taste and odors produced by blue-green algae, Anabaena, Microcystis and Aphanizomenon. Construction costs were manageable by the residents of the two communities with financial assistance through State of California, Clean Water Bond Law Act grants and low interest loans. Operating costs, although high by conventional standards, are reasonable considering water produced by the two treatment plants meets all drinking water quality regulations. Most importantly, the utility receives no taste and odor complaints even when the lake turns "pea-green" and exudes the aroma of dead fish. Construction of these two facilities eliminated 65 small systems which, because of inadequate design and operation, were not meeting water quality standards and constituted a continuous threat to public health.