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Thursday, October 12, 2006

Drinking water from the sea

A plan to put desalination plants at sea, as set out here:
An oceangoing seawater conversion vessel doesn't need intake and outfall lines on the seabed, Gordon said. It draws its water a short distance through a telescoping snorkel that can be set to the optimum depth to avoid damage to sea life and get the best-quality water.

Brine -- water with a concentrated salt content that is left after freshwater is processed -- doesn't get pumped out of an outfall onto the near-shore seabed, he said. The proposed ships would be able to mix the brine with raw seawater and discharge the diluted brine in the deep ocean, where it would be further diffused.

There would be no need to pair the desalination plant with a power plant, as most projects do, Gordon said. The ships would generate their own power with jet turbine engines of the type used on jumbo jets, fueled by clean-burning biodiesel oil or marine gas oil, neither of which produce sulphur emissions.

Such engines, he said, have demonstrated their reliability on aircraft, ships and land-based electric power generating plants.

With their own power source, Gordon said, the ships would be immune to power failures, could operate at cheaper rates than land-based plants because of fuel costs, and operate over the horizon to avoid visual impact from the shore.

They aren't vulnerable to earthquakes or tsunamis, and can sail away if a heavy storm looms.

The freshwater would be brought ashore in "food-grade" tankers similar to those used for bulk transport of orange juice concentrate or wine, Gordon said, or by modular tug barge tankers.

The ships would be U.S.-flagged, he said, automatically under the protection of the Navy and Coast Guard, and would be far less vulnerable to terrorist attack or sabotage than a land-based plant.

"This would be supplemental water," Griffin said, not a primary water supply.
Not a bad idea. And it just might work - if the cost of water from other sources is high enough to justify the investment.

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