The Oxnard advanced water purification facility: combining indirect potable reuse with reverse osmosis concentrate beneficial use to ensure a California community's water sustainability and provide coastal wetlands restoration

The City of Oxnard in California is implementing a strategic water resources program known as the Groundwater Recovery Enhancement and Treatment (GREAT) program, which includes an Advanced Water Purification Facility (AWPF) that will use a major portion of the secondary effluent from the City's existing Water Pollution Control Facility to produce high-quality treated water to be used for irrigation of edible food crops, landscape irrigation, injection into the groundwater basin to form a barrier to seawater intrusion, and other industrial uses. The AWPF, currently under design by CH2M HILL, will employ a multiple-barrier treatment train consisting of microfiltration, reverse osmosis, and ultravioletlightbased advanced oxidation processes to purify the secondary effluent to conform to California Department of Public Health Title 22 Recycled Water Criteria for groundwater recharge. The AWPF, which will have initial and build-out capacities of ca. 24,000 and ca 95,000 m(3)/day, respectively, was limited to a 1.8-hectare site, with 0.4 hectares dedicated to a Visitor's Center and administration building. Further, the depth below grade and height of the AWPF's structures were constrained because of the high groundwater table at the site, the high cost of excavation and dewatering, and 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.