City of Oxnard's Advanced Water Purification Facility – An Example of Innovative Treatment Application and Design in Maximizing One Southern California Community's Long Term Water Resources

The City of Oxnard, a coastal community in southern California, is implementing a strategic water resources program known as the Groundwater Recovery Enhancement and Treatment (GREAT) program. The capstone of the GREAT program is an advanced water purification facility (AWPF) that will utilize a major portion of the secondary effluent from the City's existing water pollution control facility (WPCF) to produce a high quality treated water. The treated water will be used for multiple beneficial uses including irrigation of edible food crops, landscape irrigation, injection into the groundwater basin to form a barrier to seawater intrusion, as well other possible industrial uses to be identified in the future.The AWPF, currently under design by CH2M HILL, will employ a multiple barrier treatment train consisting of microfiltration/ultrafiltration (MF/UF), reverse osmosis (RO), and ultraviolet (UV)-light-based advanced oxidation (AOX) processes to purify the secondary effluent as required to conform to CA Department of Public Health (DPH) “Title 22” Recycled Water criteria for groundwater recharge.The AWPF, which will have initial and build-out capacities of 6.25 and 25 mgd, respectively, had to be designed to fit on a 4.3-acre site, with more than one acre dedicated to a combination visitor's center and administration building and other uses not associated with the primary treatment processes. Further, the depth below grade and height of the AWPF's structures (buildings, chemical storage structures) were constrained because of the high groundwater table at the site and the high cost of excavation and dewatering, as well as local codes. To accommodate these various restrictions, an innovative design approach has been developed. This paper summarizes the design constraints and innovative solutions for the design of the AWPF.