The biggest desalination plant in North America just opened in Tampa, Florida, and is expected to provide 10% of the city’s 2.4 million inhabitants with fresh water. A plant twice the size has now been contracted for Southern California.
Which is good, because we’ve been guzzling our aquifers like petroleum. We’re using our aquifers at a rate that far exceeds their ability to replenish themselves –which leads to land instability and broken links between river/aquifer recharge cycles. Never mind questionable water security for us.
So why has there been a drought of desalination plants in North America until now? For the same reason Arizona isn’t covered in solar panels yet.
Let’s be real here – burning coal to boil fresh water away from seawater (thermal desalination) or using high pressure to squish salt out of seawater through selective membranes (reverse osmosis) are both more expensive and energy-intensive than digging a hole.
The Spanish company Acciona Agua, responsible for the two North American plants, has been working on increasing the efficiency of the reverse osmosis process. The plant currently running in Tampa will sell water for 1,100 dollars an acre-foot (enough for a family of four for one year), but the planned plant in California, because of rapid improvements in the technology, will sell water for only 950 dollars an acre-foot. Water currently goes for 700 dollars an acre-foot in Carlsbad.
And desalination technology continues to evolve, with Abu Dhabi recently touting plans for a solar-powered thermal desalination plant. Now that's something we can really get behind.
Although reducing the drain on our aquifers would be a wise thing to do, the environmental impacts of injecting the salt back into the ocean (which is generally what happens with desalination plants) need more research before this particular process can be thought of as “green.” In any case, the simplest, cheapest, and greenest option will always be to create a society that uses less water. Hopefully we'll move forward on that front as well.
written by Tim, January 31, 2008
written by Emily Marshall, January 31, 2008
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