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Welcome back to Current Climate. From legal fights in the Southwest over access to Colorado River water, to below-average snowpack in California’s Sierra Nevada mountains, to Corpus Christi, Texas, facing a looming shortage, stable supplies of fresh water are becoming a greater concern to large portions of the country.

Desalination is an option to boost supply, and already does so at plants in California, Texas and Florida. But it’s a problematic one because of high costs and big energy needs. It can also harm aquatic life if seawater intake systems aren’t carefully designed. But a startup and a water agency in Los Angeles County are testing a new type of desalination that could provide large amounts of fresh water, using 40% less energy than the conventional variety.

Instead of pumping millions of gallons of seawater to shore and shooting it under high pressure through a series of membranes that remove the salt, desalination pods developed by Menlo Park, California-based OceanWell do the process deep in the ocean, anchored 400 meters below the surface, taking advantage of naturally occurring high pressure at that depth to power the salt-removal process. Seawater flows in through a series of screens, layered with reverse osmosis membranes designed to prevent the tiniest forms of sea life from being sucked in, with freshwater pumped out at the base and brine pumped back to the ocean from the top.

“The depth is a function of the pressure required for a [reverse osmosis] membrane to overcome the osmotic pressure. It's about 800 PSI, and that's normally what you have in an onshore plant – big pumps that pressurize........

© Forbes