Freshwater from the sun

An experimental desert oasis in Israel is testing a new solar-powered nanofiltration system to desalinate water for African crops.

 Freshwater from the sun


These crops are being grown with solar-energy desalinated water

By Rivka Borochov

Israel is an undisputed leader in providing desalination plants, equipment, novel technology and know-how for removing salt from water. Israeli company IDE Technologies has installed hundreds of desalination plants around the world to help parched regions make sea and brackish water drinkable.

While IDE is making inroads in becoming more environmentally and economically viable — its new plant in China, for instance, runs on some of the waste heat produced by a power plant — there is still much to be done to make desalination technologies accessible for the world’s neediest citizens, especially in inland locations in the Middle East and Africa.

Thanks to funding from Swiss philanthropist Samuel Josefowitz, a very successful new model for desalinating water in poor regions like Africa has been developed in Israel. Josefowitz chose Israel for its expertise in making water solutions that work.

And the result is a new kind of desert oasis powered by the sun. A full system unit uses solar energy, at a fraction of what’s used in other current models, to power the pumps of a desalination unit that can create clean water as well as wastewater for secondary crops (usually grown as a subsidiary food source for home consumption). Israeli researchers from the Ben-Gurion University of the Negev and Central Arava R&D developed the system, which can be custom-engineered for each situation.

Watered with magnesium and calcium?

The new innovation is now up and running at a quarter-acre test site near Hatzeva in the Arava Valley of Israel, south of the Dead Sea. This basin is very dry, and currently agriculture there uses brackish groundwater from aquifers. At the test site, the researchers focused on increasing efficiency so that fewer solar panels would be needed to drive the desalination system, which can run on varying water salinities and thereby nourish different kinds of crops.

The new plant relies on special nanofiltration membranes that churn out high-value irrigation water and allow the individual farmer or plant manager to decide which minerals should stay in the water and which should be removed. Normally, non-specific desalination filters remove all minerals, which must then be replenished depending on the end need.

According to the researchers, the special membrane enables them to save energy in the pumping, while allowing the water to retain the right essential minerals to support irrigated crops.

“Reverse osmosis is based on membranes, and in this case we are using nanofilters, which [perform] ‘loose’ reverse osmosis, and we will use much less energy in the process,” says Rami Messalem, one of the main researchers in the project. He has been in the desalination membrane research business since the 1960s.

 Freshwater from the sun

Ben-Gurion University’s Rami Messalem has been researching desalination membranes since the 1960s.

Already producing water for crops — and an abundance of excess brackish water that can be fed to salt-loving plants like beets or used in aquaculture for ornamental fish — the pilot plant is ready to scale up, says Messalem. He has selected a 2.5-acre site that will serve as a bigger pilot plant as well as a training center for the thousands of people from poor nations who travel to Israel to learn about successful agricultural methods.

Built for the societies that need it most

Until now, desalination plants have been prohibitively expensive for less-developed nations. They take an enormous amount of electricity to run and need to be built near the grid — usually far from where micro- farms (which make up a large proportion of the agriculture of developing nations) are located.

There have been some ambitious projects to run desalination plants using solar photovoltaic panels, mostly to test new clean technologies, but the cost of these panels is still too high for wide-spread use.

The new Israeli solution created by Messalem and Andrea Ghermandi of the Zuckerberg Institute for Water Research at Ben-Gurion University, with Rivka Offenbach and Shabtai Cohen from Central Arava R&D, is an engineered oasis for solar desalination and arid land agriculture.

“The growing global demand for food and competition for resources among economic sectors compel future agricultural systems to be more efficient in the use of natural resources such as land and water,” said Ghermandi.

So far the experimental results have been extremely promising. The desalinated water enables farmers to use 25 percent less water and fertilizer than usual. In other tests, the treated water did not affect the growth rates and densities of the yield. The researchers report that sorghum and millet yields actually increased.

The researchers now seek an additional half-million-dollar investment to drive their new pilot plant. They aim to build custom-made plants based on the specific needs of populations facing food insecurity.

“The breakthrough here was to make the system more economical, and we’ve done this using nanofiltration cleverly. It needs less energy, and we can use solar energy. Our system is compatible with electricity but is based on the premise that it can be used in poor countries, in places where you don’t have an electricity source –– as a standalone system,” Messalem concludes.