California's Water: 'Desalting Water'
California water agencies are increasingly looking to ocean desalination as an option to help meet the need for a reliable water supply. Thanks to recent advances in technology, turning ocean water into drinking water is not as energy-intensive as it was a decade ago.
This segment of “California’s Water” focuses on ocean desalination and the potential role it may play in the state’s water portfolio. Viewers will tour a desalination plant to understand how removing salt from seawater is increasingly seen as a viable way to “drought-proof” communities and reduce their dependence on imported water. Projects also are under way to desalt brackish groundwater.
Background on the Issue
Ocean desalination has been used throughout the world for centuries. But since the process of removing salt from seawater to produce high quality fresh water is energy intensive, the lion’s share of desalination facilities are found in oil-rich parts of the world such as the Middle East. Saudi Arabia, for example, relies on desalination plants to produce 70% of its water supply.
While there are no large-scale desalination plants in operation today in California, that could change in the next few years if several proposed plans move ahead. More than 20 proposed projects are in various stages of planning in both Northern and Southern California.
If all or even some are eventually built, the state’s ocean desalination capacity will increase dramatically and meet up to 7% of California’s urban water needs.
The 1987-’92 drought ignited a wave of interest in desalination, particularly in Central Coast communities that experienced serious water shortages. Although several pilot projects were launched in the years following the drought, most did not lead to full-scale desalination plants.
Today, there are several projects under consideration that, if built, would rank among the largest in the United States. A number are along the coast between Los Angeles and San Diego, although others are proposed for the Central Coast and Northern California as well.
San Diego County Water Authority is among the agencies seriously looking at desalination to help meet future needs. The authority is studying the potential to build a desalting plant to diversify the county’s water supply mix and increase the region’s self-reliance.
West Basin Municipal Water District, which brought a pilot desalination plant on-line in May 2002, has proposed building a facility in either Redondo Beach or El Segundo that would produce 20 million gallons per day. West Basin already desalts more than 25 million gallons per day of recycled water, brackish water and ocean water.
Other proposed projects including plants by Los Angeles Department of Water and Power, Municipal Water District of Orange County, the City of Long Beach and East Bay Municipal Utility District.
Marina Coast Water District is considering expansion of its small-scale desalination plant. Marin Municipal Water District is exploring desalination as a way to increase local water supply reliability. In addition, Monterey Peninsula Water Management District is studying a desalination facility as part of its comprehensive aquifer recovery and program.
Two Basic Technologies
Most desalination projects use one of two basic technologies. Reverse osmosis (RO) involves forcing seawater or brackish water through membranes or filters that screen out salt and other minerals. The second method is distillation, in which seawater is heated to produce steam. The steam is then condensed, and the end product is water with a low concentration of salt and impurities.
Most of the recent proposals under consideration in California would use reverse osmosis.
Depending on the technology used, seawater desalination can produce water of exceptionally high quality. It can also allow coastal communities to reduce their dependence on imported water supplies and provide a reliable source of water even during droughts.
Advantages and Disadvantages of Desalination
Although the cost and energy requirements may be coming down, desalination is still costly relative to other supply alternatives. There are also potential environmental impacts associated with disposing of the brine produced in the desalination process.
Most experts agree that desalination will be a key tool in meeting California’s future water needs.