WaterSan Diego to build largest ocean desalination plant in Western Hemisphere

San Diego County, California will soon become home to a $1 billion desalination plant which would supply drinking water to residents currently having to cut their water consumption by as much as 25 percent in response to the state’s current drought. Small ocean desalination plants already operate throughout the state, but the facility being built in San Diego will be the largest ocean desalination plant in the Western Hemisphere, producing roughly fifty million gallons of drinking water a day.

Supporters of desalination say the technology has improved over the past twenty years. Desalinated water can cost twice as much as conventionally treated water, but it is still less than a penny a gallon.

According to the New York Times, there are more than 15,000 desalination plants around the world, though many are small and treat brackish groundwater. Large plants focused on seawater are rare, but a few exist in the Middle East. Israel will soon get half its water from desalination. Israeli engineers have actually become sought-after partners in many desalination projects and are involved in the San Diego facility.

“It was not an easy decision to build this plant,” said Mark Weston, chairman of the San Diego County Water Authority. “But it is turning out to be a spectacular choice. What we thought was on the expensive side ten years ago is now affordable.”

San Diego County currently depends on imported freshwater supplies from the Colorado River and Northern California. Water bills average about $75 a month, and the new plant is estimated to increase monthly bills by $5 to secure a new supply equal to about 7 or 8 percent of San Diego County’s water consumption. The technology being implemented in San Diego is called reverse osmosis, which involves forcing seawater through a membrane with holes small enough that the water molecules can pass through but large salt molecules cannot.

An enormous amount of energy is required to create enough pressure to shove the water through the membranes. The energy use of desalination plants have been cut in half from twenty years ago, but operating the San Diego plant will still require large amounts of electricity, which will increase the carbon dioxide emissions that cause global warming, further straining existing fresh water supplies. Poseidon Water is developing the plant and has promised to counter the environmental damage by paying into a California program that finances projects to offset emissions of greenhouse gases.

Still, some environmental groups and scientists remain skeptical, saying that should California’s drought conditions end, the desalination plant would become useless. They point to a desalination plant built in Santa Barbara about twenty-five years ago that promptly shut down when rains returned to the region. Australia has built six large desalination plants during a drought period and four of them remain idle, leaving customers with several billion dollars’ worth of construction bills.

“Our position is that seawater desalination should be the option of last resort,” said Sean Bothwell, an attorney with the California Coastkeeper Alliance, an environmental coalition that has battled California’s turn toward desalination. “We need to fully use all the sustainable supplies that we have available to us first.”

Other environmental concerns include the intake of saltwater and the disposal of excess salt into the Pacific Ocean, both harmful to sea life. Collecting large amounts of seawater, for example, can kill fish eggs and larvae by the billions. Embracing desalination, environmentalists argue, represents a failure to manage freshwater supplies effectively. They want the San Diego water agency to stress water conservation and the reuse of existing supplies.

Weston, the head of the local water authority, said since 1990, says his agency has cut county water use by 12 percent, even as population has increased by 30 percent. The region helped pioneer water conservation measures including low-flow bathroom fixtures and more efficient washing machines.

Conservation alone is not enough, Weston said. His agency decided years ago, before the current drought began, to move forward on the desalination plant.

Peter MacLaggan, a vice president of Poseidon Water who is overseeing the project, said the desalination plant has been of interest to locals. “Every time California has a drought, we get letters to the editor pointing out that there’s a lot of water in the Pacific Ocean,” he said. “They say, ‘Hey, guys, what are we waiting for?’”