AWWA REUSE52115

In response to increasing demands for potable water in southern California, the Orange County Water District and Sanitation District of Fountain Valley, California, have developed a joint Groundwater Replenishment (GWR) System. This project will treat secondary wastewater effluent, currently discharged to the ocean, to produce high quality water for recharge of the Orange County groundwater basin and injection into a sea water intrusion barrier. The three-phase project, beginning in 2003, will ultimately produce 100,000 acre-feet per year by 2020. Phase 1 of the GWR project, with a capacity of about 80 million gallons per day (mgd), has been conceptualized and the preliminary design has begun. Phase 1 adopts the add-on approach. Microfiltration (MF), followed by reverse osmosis (RO), is to be added on to the end of the secondary treatment process to produce high-quality water for reuse. Phases 2 and 3 of the GWR system project, however, present a number of different challenges including a shortage of land, high costs associated with additional secondary wastewater treatment facilities, and the disposal of additional biosolids. A new treatment approach that utilizes membrane processes in combination with anaerobic biological treatment could alleviate such problems. The proposed approach utilizes the MF process to treat primary effluent followed by reverse osmosis (RO), or nanofiltration (NF), to concentrate soluble biological oxygen demand (BOD) and produce a high quality effluent for reuse. The RO concentrate, which is free of suspended material, is then treated in a high-rate anaerobic digestion process that eliminates the need for conventional secondary activated sludge treatment. This paper presents details of the process as well as preliminary pilot plant results from continuous testing of the new treatment approach at Orange County. Includes 7 references, tables, figures.