It’s tempting to see desalination as an eventual cure-all for parched places like California — something that is expensive to implement and run because of energy costs, but worth prioritizing someday. Someday, that is, when there is no other way to get enough freshwater. Many countries have turned to it. Unfortunately, cost is not the only reason to put off desalination projects. Their byproducts, or waste, are bad for the environment and difficult to deal with safely. And in California, critics of seawater desalination would add that far more should be done through conservation before turning to drastic measures.
I recently wrote about solar-powered desalination as an alternative to traditional methods that might help California with its record-breaking drought, focusing on WaterFX and its solar distillation of agricultural run-off water for re-use. On Tuesday, The Guardian‘s Oliver Balch picked up on the story in some depth, referring to renewable desalination projects all over the world, but focusing on WaterFX. That prompted a thoughtful article by environmental journalist Chris Clarke for Southern California’s KCET.org. He asked an obvious and very important question: What about all the salt and other stuff we take out of the water?
At the end of any kind of desalination process, you get leftover piles of salt and buckets of super-salty brine. (Use any measurement metaphor you like, appropriate to scale: piles and buckets; hills and lakes; mountains and oceans.) You get a little freshwater and a lot of leftover crap, some potentially useful and some not, and there’s only so much you can do with it. With WaterFX’s solar distillation, you get brine laced with chemicals and solids from the soil, from fertilizers, motor oil and other sources. The company says it can sell the byproducts, but there’s room for skepticism (and leaky landfills standing by). With seawater, desalination projects tend to filter brine back into the ocean, where it dissolves over time. But brine waste, heavier than seawater, can smother sea life on the ocean floor. And, looking ahead, if huge coastal desalination projects continue to spring up all over the world, how much additional salinity can sea life tolerate? Even in the oceans, a little too much salt can kill.
One thing is relatively clear: Powering desalination with renewable energy should bring down long-term energy costs while providing freshwater. But questions and problems remain. In addition to pollution worries, the timing of when to make the big investment can be tricky. As Clarke points out, a large desalination plant opened in Santa Barbara, Calif., in 1992 because of a drought. But the drought ended, and the plant just sat there because it was too expensive to run in the absence of a crippling water shortage. After its test runs, it never produced a drop of potable water. Now, the largest desalination plant in the western hemisphere is slated for 2016 completion in Carlsbad, near San Diego, at a cost of $1 billion.
UPDATE: Desalination could help California — but only if it’s done right – Los Angeles Times
UPDATE: California drought prompts first-ever “zero water allocation” – Los Angeles Times
Carlsbad desalination plant construction on track to meet 2016 goal – KPBS San Diego