Project: Groundwater desalination
Jurisdiction: Oxnard, Calif.
Agency: Public Works Department
Vendor: San Francisco-based Kennedy/Jenks Consultants
Date completed: October 2008
Cost: $22 million

For decades, Oxnard, in semi-arid Southern California, has relied on the California Water Project's imported water to supplement local supplies, but those supplies have been stretched to their limits by growth and development. In 2001, the city began working with the Port Hueneme Water Agency, United Water Conservation District, and Calleguas Municipal Water District to create the Groundwater Recovery Enhancement And Treatment (GREAT) Program that combines groundwater desalination and wastewater reuse to stretch local water supplies.

The first part of the GREAT Program, completed in October, is a new desalination facility called The Desalter, which was built to treat brackish groundwater to potable water standards. The Desalter uses reverse osmosis membranes to produce high-quality potable water that is blended with local groundwater for customer delivery. The facility has an initial capacity of 7.5 million gallons per day (mgd) and could expand to 15 mgd. Brine from the desalting processes and industrial discharges is collected and sent to the sanitary sewer, but there are plans to use the brine to restore coastal wetlands.

The two buildings that make up The Desalter were designed to be a "Water Campus," following the U.S. Green Building Council's LEED design principles. Visitors can tour the campus to learn about green building and the plant's treatment processes. A visitor center and gallery contains interactive kiosks and informative displays, as well as a large window for observing the plant's main treatment area.

As the second part of the GREAT Program, the Oxnard Wastewater Treatment Plant, which treats domestic sewage to secondary treatment standards and then discharges it to the ocean, is adding a tertiary treatment facility so effluent can be used for agricultural irrigation or groundwater recharge. The Advanced Water Purification Facility is being designed to include microfiltration/ultrafiltration, reverse osmosis and advanced oxidation treatment, and to produce 6.25 mgd initially with an ultimate capacity of 25 mgd. Agricultural users eventually will trade their annual groundwater allocation for recycled water.

Read the main story, "A new frontier," to learn more about how membranes are playing a critical role in helping communities stretch the water supplies.