THE FRANCES DESALTER - A KEY TO WATER INDEPENDENCE ON THE IRVINE-RANCH

The Irvine Ranch Water District (District) provides potable and recycl ed water to a myriad of customers in Irvine, California. The District is also pursuing the development of two major brackish groundwater des alination projects and other innovative projects to substantially redu ce dependence on constrained imported water supplies. Linear programmi ng analysis of various alternative supplemental supplies has resulted in a high priority for the Frances Desalter which would treat up to 11 ,000 acre-feet per year (af/y) of degraded groundwater consisting of e levated concentrations of TDS, nitrates, and hardness. At full develop ment, the Frances Desalter would be one of the largest groundwater rec overy facilities in the nation. The paper will discuss feedwater chara cteristics, alternatives for treatment process trains and plant sites, a concentrate disposal analysis, project economics, and the implement ation program. Electrodialysis reversal (EDR), reverse osmosis (RO), o r nanofiltration (NF) together with ion exchange (IX) were the treatme nt process options evaluated for treating the well water. RO is the pr esently preferred process. Four alternatives to dispose of the concent rate from the proposed treatment plant were evaluated. They are: 1) di sposal to the regional sewerage system; 2) disposal to a proposed area -wide Irvine Brineline; 3) concentrate reclamation using EDR; and 4) a distillation concentrator. The brineline is the preferred option. Fea sibility studies indicate a unit production cost range of $500-570/af; the District could save almost $10 million compared to projected impo rted water costs over the project lifetime.