Desalination of Bay Water

The Marin Municipal Water District (MMWD) Seawater Desalination Pilot Program was a successful year-long desalination pilot study of advanced pretreatment and SWRO technologies for desalting water from San Francisco Bay (Bay) from June 2005 to May 2006. Based on the favorable outcome of the pilot program, it was confirmed that seawater desalination can be a local, reliable drought-proof source of drinking water supply for Marin County, California. The MMWD SWRO Program provided preliminary design criteria for a full scale desalination facility, provided data to refine full-scale plant cost opinions, demonstrated the high quality of the desalinated water and facilitated essential environmental studies for a future full scale project. A primary objective of the pilot testing program was to compare the performance of high rejection seawater RO membranes with two different pretreatment alternatives: MF/UF and conventional pretreatment. The pilot program also included analytical testing of over 100 regulated and 500 non-regulated constituents in the Bay water and RO permeate, as well as an evaluation of second pass RO to meet MMWD's stringent finished water boron and sodium requirements. Environmental studies conducted in conjunction with the pilot testing included fish entrainment studies, bioassay studies and California Toxics Rule analysis of the brine discharge and toxicity analysis of the residuals from the pretreatment systems.