Solar-powered desalination could be part of solution to drought

California firm proving design concept

FRESNO COUNTY, Calif - Climate change and a punishing four-year drought are forcing us to look for new sources of fresh water in California. Dozens of start-up companies are developing new technologies to reclaim and recycle contaminated ground water. Perhaps nowhere is that technology needed most than here in the central valley where, given the right technology, millions of acre-feet of subsurface groundwater could be converted into fresh drinking water. And one California company is proving how centuries-old technology can be used today to make water from the sun.

Aaron Mandell is founder and chairman of WaterFX and the mastermind behind this contraption that uses energy from the sun to turn tainted water into fresh water. His invention is essentially a large still, powered by the sun.

"That's right," Mandell said. "It's a distillation process. The oldest technique in the world for separating fresh water from any impaired fluid. But the difference is we're using the power of the sun."

Concave mirrors, called a solar trough, focus the sun's rays on a pipe, filled with oil. The sun's energy heats the oil.

"It comes into this unit which is the heat pump," said Mandell. "This is where we generate steam in the distillation process. The steam is used to evaporate salt water in these distillation units over here. The condensate goes into that large shaft overhead and drops into the product water bucket on the other side."

What is left over is a briny residue, and when dried, looks like yellow powder.

"A bunch of different salts in there, metals. Recovered fertilizer, gypsum for wallboard, all usable materials," said Mandell.

If he can find a market for it.

"Right. That's our job," he said.

Mandell says he would have no problem drinking his product.

"Oh yeah. This is the cleanest water you could drink," he said.

So why this pilot project on this plot of land east of Interstate 5 and west of Firebaugh in Fresno County? This part of the San Joaquin Valley has been plagued for decades by irrigation drainage problems. Minerals like selenium and boron leached from the soil during the irrigation process end up trapped in the subsurface aquifer and that water is unfit for most crops, and of course for humans.

In 1983, an ecological disaster swept across Kesterson National Wildlife Refuge near Merced. Sick birds, deformed embryos - the result of habitat contaminated by selenium-tainted drainage water. The disaster halted the practice of ponding drainage water, leaving farmers with one less option in disposing of their brackish runoff, captured through what's known as tiled drainage. In four years, discharging that water into the San Joaquin river will be prohibited.

Betty Hurley-Lindeman works for the Bureau of Reclamation and the Panoche Water and Drainage District near Firebaugh in Fresno County.

"After 2019 we are not allowed to discharge water out to the San Luis Drain to the San Joaquin River which eventually goes into the delta," said Hurley-Lindeman. "And we started this project in the reuse area about 15 years ago."

The recycling project takes brackish drainage water from 90-thousand acres of farmland and reuses it, irrigating six thousand acres of salt-tolerant crops like wheat grass and alfalfa which is sold as feedstock to local dairies.

"Once it comes to me on this project, my fields are also tiled so I get to use it once, and I'll use it three, four or five times again, and the crops can take it," she said.

But eventually, that water becomes overloaded, and has to be treated.

"There's nothing we can do with the water at this point," she said.

That's where WaterFX comes in with its solar-powered desalination plant, the first in the central valley.

"They are using my drain water that I can't displace and they're providing fresh water. This is huge," said Hurley-Lindeman.

Aaron Mandell says his process can produce fresh water for half the cost of conventional desalination.

His energy source is free. No fossil fuels. No carbon footprint. At $450 an acre-foot, it's still too expensive for most growers. But if this technology catches on, growers would be able to join forces and create their own water treatment utilities and avoid up-front costs of building bigger plants like this.

"So that's our business model," said Mandell. "We want to enter into a water contract with growers and other large water users and not have to have them put up the costs of installing a solar desalination system."

Desalination is really just a fancy term for reclaiming and recycling water. And shallow aquifers in the central valley hold an untapped source of groundwater that could be purified.

"Right below our feet there are hundreds of thousands of acre feet of water that can be converted into fresh water," said Mandell. "So what this is doing is allowing farmers to actually use every drop of water ten times, not just once and if you're doing that you're reducing your water footprint, which leads to sustainable use of water."

Mandell has signed contracts to build a full-sized 30-million dollar desalination plant here, capable of producing five thousand acre-feet of fresh water a year, enough to supply 7,500 homes. It's slated to go online next summer.

His Hydro-Revolution system represents a hat trick in water management: turning a waste product into a valuable water product, providing a solution to the region's drainage problems, and creating a new revenue stream for water districts which could either use the water or sell it to other growers, after capital costs are recovered.

"I don't know if we've satisfied all the naysayers," said Mandell. "That will only come once we have a fully-commercial plant. But what we have done is demonstrated the basic treatability of this salty drainage water and we've demonstrated the cost effectiveness of using solar energy to do this process."

WaterFX, of course, is looking for investors. The company has launched a direct public offering, only for California residents, who can own a piece of the company going forward.  For more information on that, check out their website at

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