Could startup company bolster Arizona water supply with undersea desalination system?

PHOENIX – A desalination startup company hopes to gain Arizona customers as the state prepares for more cuts to its Colorado River water supply.

Desalination is the process of taking ocean water and removing the salt to make it drinkable. California-based OceanWell is developing a subsea system that is more energy efficient than traditional onshore desalination.

OceanWell is three years into a five-year research and development phase to create an underwater operation called Water Farm I about 4.5 miles off the coast of Malibu in Santa Monica Bay.

It will consist of large purification pods that sit on the ocean floor. The system is designed to use natural ocean pressure to push seawater through the pods’ reverse osmosis membranes for desalination.

OceanWell’s desalination system harnesses natural ocean pressure

“We changed the location where you do the R.O. from the shore out to sea and at depth — down about 400 meters, about 1,300 feet or so,” OceanWell water policy strategist Tim Quinn told KTAR News 92.3 FM last month.

While energy is required to pump the newly created fresh water to shore, it’s about 40% less expensive than buying the energy needed for onshore desalination, Quinn explained.

“You have to purchase energy to create about 800 pounds per square inch of pressure to push the seawater through R.O. membranes and separate out the salt from the fresh water,” Quinn said about the traditional desalination method.

There isn’t much sunlight or marine life at the depth of OceanWell’s water farm. Still, the system was designed with something called Life Safe technology to minimize potential harm to living creatures.

“As it’s pulling water through the membranes, the Life Safe technology, any microscopic living thing that has gotten that far gets brushed out back into the ocean, where it has a very strong chance of survival,” Quinn said.

The OceanWell desalination system produces a brine byproduct that goes straight back into the ocean. Quinn said the saltier byproduct is just a drop in an ocean-sized bucket.

“Our outfall water is only about 10% saltier than the ambient ocean water around it. And we believe that it will dissipate to ambient levels within a few meters of leaving the outfall,” he said.

How could OceanWell’s desalination system boost Arizona’s water supply?

OceanWell is in talks with Central Arizona Project, which delivers Colorado River water to about 80% of Arizona’s population through a canal system that stretches more than 300 miles.

CAP is bracing for another reduction to Arizona’s Colorado River water allocation as seven basin states try to hammer out a new sharing agreement.

OceanWell would have to figure out a way to efficiently get drinkable water to Arizona. One possible solution would be a water credit exchange program, which would be more cost-effective than building a pipeline from the Pacific Ocean to the desert Southwest.

In that scenario, OceanWell might deliver desalinated water to the Metropolitan Water District of Southern California, which in turn would leave some of its Colorado River allotment untapped.

“Metropolitan then would have access to a new supply that strengthens their reliability. And that would allow them to say, ‘I’ve got this. I’ll release some water on the Colorado River that I am otherwise entitled to use.’ And that water will be available for use in Arizona,” Quinn said.

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