Is desalination the answer to California's drought? Here's what experts say

ByJuan Carlos Guerrero KGO logo
Thursday, July 29, 2021
Here's how seawater could be answer to California's drought
As the drought worsens, some communities are taking a closer look at seawater desalination as a reliable source of drinking water.

NEWARK, Calif. (KGO) -- As more communities impose water use restrictions because of the drought, the California Coastal Commission is likely to vote on a controversial proposal later this year that could ease water worries for millions of Orange County residents.

After decades of debate, Poseidon Water just needs approval from the commission to begin the construction of a desalination facility in Huntington Beach that would produce 50 million gallons of drinking water per day.

Poseidon Water already runs a desalination facility in Carlsbad which is the largest in the Western Hemisphere. The facility was built in 2015 and provides about 12% of the water used in San Diego County.

While desalination is not a new technology, it is controversial. Many communities have looked at desalination during times of drought but have been dissuaded by its cost and environmental impact.

Desalination is the process of converting seawater into drinking water by removing its salt content.

"The Pacific Ocean is the largest reservoir in the world. It's always full and we have the technology to turn that saltwater into drinking water," said Vice President for Project Development at Poseidon Water Scott Maloni.

Many countries have made big investments in desalination, especially in the Middle East.

Australia built several desalination plants during the "Millennium" drought but then shut many of them down when the drought ended. Several facilities are being restarted this year as drought conditions return.

California currently has 12 seawater desalination facilities in operation. The Huntington Beach proposal has the backing of Governor Gavin Newsom who said he wants to diversify the state's water supply.

But environmentalists have concerns.

"Seawater desalination is one option for California, but it's the most expensive option and it has significant energy and greenhouse gas impacts and it affects our marine environment," said the Director of Research at the Pacific Institute Heather Cooley.

Critics of desalination worry about the amount of energy needed to extract salt from seawater which is done by reverse osmosis.

That's a process that pushes water under high pressure through semi-permeable membranes effectively filtering out salts and minerals.

Historically, water has been cheap in California and that made desalination prohibitive. But that gap has narrowed as the cost of water has risen in the state.

The other concern is the environmental impact. While desalination can produce freshwater, it also generates brine, a highly concentrated salt water mixture that is then pumped back into the ocean.

The higher concentration of salt in the water can be damaging to marine life.

"When the water is discharged, it creates a plume around the discharge which is very salty. Even though marine organisms can handle salts, they do have a range in which they can handle it," said Cooley.

To minimize the impact, California adopted strict environmental regulations around desalination including the use of diffusers on the brine discharge so that it dissipates quicker in the ocean water.

But not all desalination treat seawater. A brackish desalination facility has been operating in Newark since 2003.

Brackish water contains a mixture of fresh water and saltwater. Since it is less salty than ocean water, it requires less energy to treat.

The Alameda County Water District built the Newark desalination facility to treat groundwater near the San Francisco Bay that had been contaminated with bay water.

Whereas before it would just pump out the saltier water, now it treats it and produces about 12 million gallons per day, or about 25% of the overall water supply for the southern Alameda County area.

"The facility has become especially important during drought conditions when we really need to rely on local supplies and local production," said Ed Stevenson, general manager of Alameda County Water District.

Running the facility requires much less energy than a seawater desalination plant would need. Any unused energy is sent back into the system. Stevenson said the overall cost of the facility is the lowest of all the water treatment plants operated by the district.

The brine produced is also handled differently. Since brackish water is already less salty than seawater, the resulting brine is also less salty, below the salt concentration of regular bay water. The concentrated stream is discharged at a location where the salt levels match the receiving water.

"With improvements in technology that are happening today and other advancements in water treatment, I think desalination will have a big part to play in the future of California and the West," said Stevenson.

In Antioch, which has dealt with water rationing in the past, construction is underway on a brackish water desalination facility that would be the first to operate in the Sacramento-San Joaquin Delta.

The Marin Municipal Water District is considering leasing two prepackaged desalination facilities from an Australian company to provide nearly a third of its drinking water needs.

Forecasts warn that Marin could run out of water by next summer if the drought does not improve this year.

"California water has been plentiful and cheap historically and now we're seeing with climate change that is no longer the case," said Maloni. "While seawater desalination was maybe not a viable option 20 years ago, it is today."

Environmentalists want to see more investment in conservation and efficiency.

"There are opportunities around storm water capture and water reuse," said Cooley. "So instead of discharging waste water into the ocean, you're now treating it again and using it to meet your water demand."