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October 9, 2006

Desalination workshop explores environmental impacts

By Jennifer McNulty

The environmental impacts of desalination are a top concern among municipalities considering the technology, and the latest information was shared during a two-day workshop hosted recently by environmental studies professor Brent Haddad.

Photo: Desalination plant

This pilot desalination system and water recycling plant near the Los Angeles Airport is one of the nation's largest facilities dedicated to treating impaired surface and groundwater.

About 55 people attended the invitation-only workshop, including representatives of water and regulatory agencies from around the state, interest groups, and researchers from four UC campuses and other universities.

“Our discussions framed the environmental impacts of desalination in the most comprehensive way I’ve seen to date,” said Haddad, director of a statewide project to help communities assess the viability of desalination. With funds from Proposition 50, the project is a collaboration with water agencies, environmentalists, consultants, and nongovernmental organizations. The goal is to give municipalities the tools they need to assess the costs and benefits of desalination relative to other options in their area.

Discussions of the environmental impacts of desalination have focused on the intake and outfow of coastal facilities, but much of the data is borrowed from coastal power plants, which suck up about a billion gallons per day of seawater, said Haddad. By contrast, the largest proposed desalination plant along the California coast would process 2 percent of that capacity, or about 20 million gallons per day, he said.

“It’s a completely different magnitude of impact, and it’s the same for the discharge,” said Haddad, cautioning that the impacts of desalination on fish and other marine animals that are inadvertently captured during the intake process shouldn’t be assessed by comparing desalination operations to power plants.

Many other environmental impacts have been largely overlooked, including impacts on energy, water quality, and coastal development.

Desalination is “energy intensive,” said Haddad, explaining that salt is removed by forcing water through a series of membranes and filters. “The costs are still high, but they need to be compared to alternatives, which include transporting surface water miles and miles,” he said.

Workshop participants also weighed the pros and cons of “beach wells,” a desalination strategy that attempts to minimize negative impacts on marine life by drawing offshore water from beneath the sand, essentially using sand as the first filter in the process. Calling beach wells an “unproven technology,” Haddad noted their limited capacity and said that using numerous beach wells would drive up costs and increase the footprint of the intake system along the coastline.

The workshop also highlighted the relative viability of desalination for inland areas. Removing salt from impaired inland groundwater, whether naturally salty or degraded by agriculture and other uses, is still far easier than processing sea water, explained Haddad. “The technology has only recently matured in reliability and price to make desal a viable option for the coast. Whether it is right for a particular area is a site-specific and context-specific question,” he concluded.

Communities across California, including Santa Cruz, are increasingly weighing the economic and environmental costs and benefits of desalination as they contemplate future water-supply needs. Local representatives who attended the workshop include Toby Goddard of the City of Santa Cruz Water Conservation Office; Ed Kocher, director of the City of Santa Cruz Water Department, and Linette Almond, deputy water director; and Bruce Daniels, chair of the Soquel Creek Water District Board of Directors.

More than 7,500 desalination plants operate worldwide, according to Haddad, who cited costs of about $500-$2,000 per acre foot of water (325,000 gallons), compared with about $250 per acre foot for water in urban Los Angeles.

The next workshop will focus on policy and financial aspects of desalination and will be held in Sacramento in late November. A final workshop, on engineering and energy issues, will take place in southern California in early 2007.       

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