Researchers have recently warned of a potential mega-drought in the western United States - conditions so dry that our drinking water supplies could be facing historic pressures. Experts say keeping the taps flowing could require a patchwork of solutions, including potentially increasing the use of desalination, turning saltwater into drinking water.
"To us, desalination is kind of the wave of the future," says Stanford researcher William Tarpeh, Ph.D.
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Tarpeh and his colleagues have been refining a technology that could eventually make widespread desalination cheaper and safer for the environment. First, it helps to understand that seawater desalination plants have a major challenge, how to get rid of the concentrated brine that's left over from the purification process.
"Your reject stream is about twice as dense as seawater. And that presents a problem with how you actually manage that in a way that it doesn't have adverse effects." says Stanford environmental engineer professor Dick Luthy, Ph.D.
In some parts of the world, injecting the concentrated salt back into the ocean has threatened sea life and the health of shoreline ecosystems. Now, Stanford researchers are hoping to turn the problem into a partial solution by converting the salt-heavy brine into something useful.
"Because the more desalination plants there are, the more of that salt brine there will be," argues Tarpeh.
To do that, they've built on a technology called Electrodialysis, a kind of saltwater splitter. A combination of electricity and specialized cells force chemicals in the brine to separate. That leaves a less concentrated brine, plus the separated chemicals which can be recovered. Researchers say those can then potentially be used in farm fertilizer, food processing, cleaning agents and much more.
"And so it changes the game, because it incentivizes collection of that waste rather than just letting it into the ocean," Tarpeh believes.
He says the team is now working on improvements that could help scale their prototype up for testing in desalination plants, someday converting pollutants into chemicals for farming and industry, and, if predictions of a possible historic drought are accurate, helping California survive in a new, dryer, normal.
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