The New Era of DESALINATION
With desalination entering the mainstream, California has found another tool to add to its portfolio of water resources.
The most populous state in the country, California requires a significant supply of water. Despite major strides in water conservation, the state’s 12 million households, 25 million acres of farmland, and hundreds of specialized companies continue to place ever-growing demand on a limited resource. Southern California, where water is in shorter supply and more costly, relies on a combination of water from the Colorado River, regional groundwater, reservoirs, and the State Water Project (a water storage and delivery system of aqueducts, power plants, and pumping stations). Unfortunately, the water provided by these sources cannot reliably meet the region’s water demand. With ever-increasing pressure on freshwater supplies, there is a renewed interest in the promise of salt water.
For decades, small plants around California have been desalting brackish groundwater (groundwater with a salt content lower than seawater but still too high for consumption), for use in irrigation and industry. But taking this one step further — processing brackish water to meet the standards of drinking water — is an idea that’s catching on. A prime example is the Chino Basin Desalter Authority, which operates two state-of-the-art desalination facilities that help serve the needs of customers of the Inland Empire Utilities Agency.
The plants produce 25 million gallons of pure drinking water per day, with a third plant planned that would start operation in 2015. The cost of desalting the relatively low-saline water in the local aquifer is about half that of importing water, and the benefits are immediate. Desalination increases the drinking water supply, cleans up groundwater, and improves the health of the Santa Ana River. Numbers of other communities with brackish aquifers are getting set to do the same.
Carlsbad Embraces Desal
Seawater desalination, more technically challenging than processing brackish water, has been slower to develop in California. Processing the saltier water means higher energy costs and there’s the issue of protecting coastal marine habitats. But as needs grow and technology improves, things are changing: A vast facility recently approved in Carlsbad in late 2009 will join six new facilities operating along the coast, with another 16 in design or construction. This plant — to be the largest in the western hemisphere to date — is slated to yield 50 million gallons of drinking water daily, or about ten percent of the county’s drinking water needs for at least the next 30 years.
California can fairly call itself an early pioneer in the development of desalination technology, specifically reverse osmosis (see sidebar on page 9). In 1967, with the help of federal seed money, San Diego’s General Atomics patented a game-changing filtering membrane technology that is credited with helping reverse osmosis catch on. Today, there are about 30 companies in San Diego County alone working on desalination.
Despite the county’s long association with desalination, it took the public-private partnership behind the Carlsbad project nearly 11 years to clear all the planning, permitting and political hurdles. Some technical and environmental challenges were solved through co-location — the Carlsbad plant rises on a saltwater lagoon adjacent to a shore-sited power plant. This allows the desal facility to take advantage of the intake and discharge facilities that handle the seawater needed to cool the power plant’s operation, a steady source of warmed water that also makes the process more energy efficient. It also provides a way to manage briny discharge resulting from desalination: While half of processed seawater becomes ultra-high-quality fresh water, the other half is mixed with the filtered salt to dilute it to habitat-safe levels before it’s returned to the Pacific.
The California Coastal Commission, the final decision-makers in the Carlsbad approval process, was particularly mindful of the potential for environmental damage that a desal plant might pose to more fragile forms of marine life. It required the plant construction partnership to include in its application a “Coastal Habitat Restoration and Enhancement Plan” that involves restoring nearly 37 acres of previously degraded wetlands within the lagoon. The restoration not only creates the natural conditions for the return of more at-risk marine species than are estimated to be threatened by the Carlsbad operations, but it also provides new foraging, nesting, and cover for numbers of birds, reptiles, mammals and other species that were never at risk.
Desalination is being pursued throughout Northern California as well, where 12 agencies are working on projects that start with source waters as diverse as Pacific Ocean water and brackish groundwater. The projects include a 5 to 15 million-gallons-per-day (mgd) desalination facility by Marin Municipal Water District, a 5-mgd brackish water expansion project by Alameda County Water District, a 2.5-mgd seawater desalination project by the City of Santa Cruz and Soquel Creek Water District, and a brackish to seawater desalination plant with a 71-mgd total capacity being investigated by the San Francisco Bay Area’s four largest water agencies. Additional projects by California American Water, Marina Coast Water District, Sand City, and Cambria Community Services District are also in different stages of development.
Desalination is not a silver bullet solution for the state’s water woes. But increasingly, it will be an important asset in the diversified water portfolio of systems that will serve California’s future.