Solar technology used to clean water for crops

FRESNO, Calif.

With the cutoff of state and federal water supplies, growers who can are pumping well water to irrigate their crops, or drilling new wells to get more water. But the deeper they go, the saltier the water gets, and most crops can't take it.

Aaron Mandell thinks he has a solution. It's a big, shiny contraption being built in western Fresno County near Firebaugh.

"This is a concentrated solar still. It's a device that we've developed for capturing solar energy and using it to treat and distill out fresh water. So, it's a water maker," said Mandell.

The still uses big reflectors to magnify and direct the sun's heat to a tube, which gets hot enough to boil water into steam then distill the salts out of it and create clean water. The process is known as desalinization. It can clean water from salty wells, or from used irrigation water.

About 1/4 of the water used to irrigate a farm field on the western side of Fresno County becomes drainage water. It runs off the fields but is loaded with mineral salts and won't grow anything. That's why a desalinization plant is one way to clean the water up so it can grow more food.

"Ultimately you could use this technology to treat any type of water -- it could be sea water, it could be brackish groundwater, it could even be waste water from a municipal plant," said Mandell.

Mandell says a solar still that takes up just one acre of land could produce enough clean water to irrigate 100 acres of vegetable crops.

He estimates the cost of the water at about $450 an acre foot. It's on the high end of what growers pay in a normal year, but is a bargain during the drought. He's in partnership with the Panoche Water District, looking for a long -term solution to the Valley's water problems.

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