USING BENCH SCALE TECHNIQUES TO ASSESS TREATMENT OPTIONS FOR AN ADVANCED WATER PURIFICATION FACILITY

As part of the City of Oxnard's (City) Groundwater Recovery Enhancement and Treatment (GREAT) Program bench scale testing was conducted to assess treatment options for the City's advanced water purification facility (AWPF). Currently the City's Water Pollution Control Facility (WPCF) treats average flow of 22.7 million gallons per day (mgd) and discharges the secondary level treated water to the Pacific Ocean via an ocean outfall. Under the GREAT program; the WPCF will be upgraded with an AWPF to an average capacity of 25 mgd finished water for groundwater recharge and irrigation uses. The advanced tertiary treated effluent from the City's AWPF will be used on the southern Oxnard Plain and Pleasant Valley areas where the severe overdraft conditions exist. The AWPF effluent will conform to all requirements of the CA DHS Title 22 recycled water regulations for direct aquifer injection and irrigation uses. The AWPF will include microfiltration/ultrafiltration (MF/UF), reverse osmosis (RO), and ultraviolet (UV) disinfection including advanced oxidation with hydrogen peroxide. Prior to design of the AWPF, a bench-scale treatability study comprised on MF/UF and RO units was conducted on the WPCF secondary effluent. The study was intended to enable appropriate decisions regarding selection of pretreatment requirements prior to MF/UF and to determine TOC and trace contaminant removal by RO. It was observed that pretreatment (i.e., coagulation) using MF/UF provided a minor removal of TOC, however, RO treatment for the MF/UF treated effluent was found to be significant. RO process was found to remove more than 97% of TOC, improve UV transmittance to above 98%, and RO treatment removed more than 95% of sodium and chloride.