Undeniable Need
Summer 2008 hadn't even started when California Gov. Arnold Schwarzenegger declared a statewide drought in early June. By that time, some Northern California cities had already made water rationing mandatory; in Southern California, limits on personal use are still optional.
Research being done at Scripps and elsewhere (see "Welcome to the New Normal," explorations, April 2008) suggests today's seemingly extreme measures stand a good chance of being commonplace in the future. The situation has accelerated the search for new sources of water, including the oceans.
For millennia, people have created drinking water from the sea by distilling the water to separate it from salts. But it's only been a half-century since cost-effective methods for bringing water to large numbers of people have existed. Today the high-pressure filtration method called reverse osmosis has become the leading technique for desalinating large amounts of water. The technique was pioneered in the 1960s by UCLA researcher Sidney Loeb who created specialized membranes through which water, but not salt ions, could pass. He also created the first facility capable of desalinating ocean water in 1967 at the Scripps campus. Proposed Poseidon facilities would produce water with a slight sweetness because it has less salt in it than tap water. The company would have to add minerals to it to keep the desalinated water, which is purer and thus slightly more acidic from corroding city water pipes.
Using either reverse osmosis or distillation, an estimated 13,000 desalination plants operate throughout the world, with the highest concentration found in the countries that ring the Mediterranean and Arabian seas. But few studies have tracked the ecological impact of these plants, which take few precautions to mitigate the environmental damage inflicted as they take in water and return it to the sea.
At the beginning of the process, intake pipes suck in and destroy myriad forms of plankton including phytoplankton and the larvae of invertebrates and fish. The removal of these members of the local ecosystem exacts a certain toll, one for which Jenkins has attempted to formulate mitigation measures for Poseidon.
At the end of the process, desalination plants that create a gallon of freshwater from every two gallons of seawater must find a way to dispose of the remainder. The by-product water has roughly double the salinity of seawater, a concentration well beyond the tolerance of most marine organisms. Many operators of existing desalination plants disregard the danger and simply discharge the hypersaline water back into the ocean. Scientific observations show that some marine organisms have vanished from the areas around underwater outfall pipes where undiluted wastewater is returned to the oceans.
Next page: The price of 50 million gallons a day