03 May 2003
The ocean has long been California's calling card. The majority of the state's residents live within an hour's drive of the Pacific Ocean and the coastline powers a multi-billion dollar tourism economy. Now, the seawater that incessantly pounds the state's shores may become the answer to one of the state's most vexing problems, finding enough fresh water to quench California's growing thirst. Southern California water managers are making a major investment in desalination technology.
Just inside the gate at the Encina Power plant sits a curious collection of freshly painted tanks, pumps and tubes. A private company called Poseidon Resources wants to build a huge desalination plant here and this machinery is a small demonstration facility.
The project is major step toward building a plant capable of producing nearly 190 million liters of fresh water a day. San Diego County Water Authority official Ken Weinberg recently visited the facility. He says desalination could become an important new source of drinking water. "The ocean's here," he says. "It's the world's largest reservoir and it's a reliable source of supply. It's a high quality supply because of the technology. And it's one that's here locally, that would be under our control and would be here [all the time] no matter what the weather is."
For several weeks now, this demonstration project has been turning small amounts of salty ocean water into drinkable water.
The power plant pumps in ocean water to cool its equipment. The Poseidon facility taps into that water circulation system and diverts it into the desalination machinery. Water is forced through two separate tanks filled with sand to filter out suspended objects. Then, the salty water is pumped through long round cylinders tightly packed with thin cellulose membranes.
"If you unrolled them and lined them up end to end there would be enough membrane surface to stretch from here to San Fransisco," says Poseidon spokesman Peter MacLaggan. He says by the time the seawater has passed through all those membranes, the salt has been filtered out, and the water is ready to drink. California has been trying unsuccessfully for years to turn ocean water into drinking water. Santa Barbara's brief flirtation with desalination in the mid-1980's ended after a few months because it simply cost too much.
But water-filtration technology has improved dramatically in the last decade. Mr. MagLaggan says today's filters can produce twice as much water with less energy. The filter cartridges also last a lot longer than earlier models, significantly lowering the cost. At the Encina plant, the process of converting seawater into fresh water only takes 20 minutes and the facility is already producing 130,000 liters of fresh water a day. "Water comes out of the center of the pressure vessel as high quality drinking water. It's ready for human consumption. The water coming out of the back is essentially the seawater that has twice the salt concentration it had when it came in because we've physically removed half the water," he says.
In addition to the desalination equipment, Poseidon Resources has set up a 750-liter salt-water aquarium in a nearby trailer. Peter MacLaggan says the fish tank is designed to replicate how salty discharge will affect marine animals on a calm warm day. Inside are several species of local fish, shellfish and coral. "Probably the spiny sea urchin is the one that's most affected by salt tolerances. What we've found here is that they're doing just fine," he says. "We'll continue to operate this as long as the pilot plant's operating."
The San Diego County Water Authority is so enthusiastic about the technology's potential, it's already exploring the possibility of building two more plants. They eventually hope to draw 15 percent of the county's drinking water from the ocean. With funding from the state's largest water agency, there are currently five desalination projects underway throughout southern California.