Making drinking water from ocean water

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Earth is a water planet, but only 3% of the liquid stuff is fresh water. All the rest of it is salt or brackish water. Thus the interest in desalination technology in places around the world rich in seawater, but poor in fresh drinking water. (Photo by Saul Gonzalez)

Just look at a picture of Earth from space, and it’s easy to see why our planet is known as a water world, with liquid H20 covering more than 70 percent of the Earth’s surface. But here’s the rub: Only 3 percent of all that cool and beautiful water is fresh water, you know, the kind that you and I can actually drink. All the rest of it, trillions and trillions of gallons, is saltwater. If you tried to drink it regularly (assuming you could keep it down without vomiting), you’d die a pretty slow and painful death.

But for decades the technology has existed to take the salt out of saltwater, turning briny H2O into freshwater. That’s water that can be used for everything from quenching your thirst after a morning jog to irrigating farmland. Not surprisingly maybe, hot and dry countries have long embraced this technology, called desalination. Saudi Arabia, for instance, now gets nearly 70 percent of its drinking water through desalination.

This is the interior of a desalination plant in Israel. Because they're hot and water poor, the countries of the Middle East have particularly embraced this technology. There are thousands of desalination facilities around the world, producing over 35 billion gallons of water a year. The plant proposed for Carlsbad would be the biggest water desalination plant in the Western Hemisphere.
This is the interior of a desalination plant in Israel. Because they’re hot and water poor, the countries of the Middle East have particularly embraced this technology. There are thousands of desalination facilities around the world, producing over 35 billion gallons of water a year. The plant proposed for Carlsbad would be the biggest water desalination plant in the Western Hemisphere.
The $922 million Carlsbad desalination plant would be built between this existing power station and the lagoon. Its supporters say it would produce 50 million gallons of drinking water a day for the people of San Diego County. But critics worry about the possible impact of desalination on the ocean's environment and the price tag that comes with purifiying ocean water. (Photo courtesy of Poseidon Resources)
The $922 million Carlsbad desalination plant would be built between this existing power station and the lagoon. Its supporters say it would produce 50 million gallons of drinking water a day for the people of San Diego County. But critics worry about the possible impact of desalination on the ocean’s environment and the price tag that comes with purifiying ocean water. (Photo courtesy of Poseidon Resources)

California water agencies, though, have largely been reluctant to adopt desalination, despite our state’s penchant for dry weather and droughts. That reluctance was because of desalination’s cost and questions about environmental issues associated with harvesting the open ocean for drinking water.

But that might all be changing now. A company called Poseidon Resources wants to build the largest desalination plant in the Western Hemisphere in the north San Diego community of Carlsbad –  a plant that would produce millions of gallons of drinking water a year for the people of San Diego. And that’s just one plant. Up and down the California coast, there are more than a dozen other proposed desalination facilities on the drawing boards.

But despite the recent interest, many water economists and environmentalists remain leery of desalination. Some groups, such as the Surfrider Foundation, which has fought the proposed construction of the Carlsbad plant in the courts for years, say desalination will damage the ocean’s environment. They particularly worry about marine life being sucked into desalination facilities. Others are concerned about the cost and energy use that come with purifying seawater. They say there are cheaper alternatives to preserve and expand our drinking water supply, namely through new water recycling technologies and old-fashioned conservation.

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