Bringing water to dry regions: The search for reliable sources of drinking water

  • Living
  • Sunday, 08 Feb 2015

Dairy cows receive a shower to stay cool and produce more milk on the Samar kibbutz in the southern Arava region of Israel. Untreated saline water is used because it is more readily available in the desert. Photo: TNS

Scientists are crafting radical new approaches that may one day rejuvenate the world’s water-starved regions.

The Arava desert, a salty wasteland dotted with tufts of scrub, gets only about an inch of rain each year. And yet cows at dairy farms collectively produce nearly 36 million litres of milk annually. Orange bell peppers flourish in a long swath of greenhouses that skirts the Jordanian border. Kibbutzim (collective communities) with vineyards somehow manage to churn out Shiraz and Sauvignon Blanc, unfazed by the desert sun.

The clusters of farms and wineries in the Arava are a testament to Israel’s acumen in water technology. One of the most parched places on Earth has found a way to beat water woes once so severe that Israel’s national mood rose and fell with the changing level of the Sea of Galilee, one of their most critical water sources.

Thanks to better irrigation technology, date trees can be grown in the desert in the central Arava region of Israel. Photo: TNS

That expertise helps explain why the University of Chicago sought out Israel’s Ben-Gurion University to help tackle one of the world’s most worrisome problems – water scarcity. In laboratories in Chicago and the Israeli desert, scientists are crafting radical new approaches that may one day rejuvenate the world’s water-starved regions.

One project uses a common ink jet printer to apply layers of chemicals to a water filter to repel bacteria and keep the filter clog-free. Another turns radioactive isotopes into tracking devices to trace water movement through aquifers, a development that could lead to the discovery of vast new strata of groundwater. Still another effort strives to create filtering membranes that operate on a molecular level, using electrically charged, cilia-like hairs to repel filter-fouling microbes. The goal is to complete research by the latter part of 2015.

By 2030, nearly half of the world’s population will be living in regions saddled with severe water stress, the United Nations projects. Three quarters of the world is covered by water, but less than 3% is fresh water. Areas with annual water supplies below 1,000 cu m per person are regarded as water-scarce.

Lesson from Israel

Israel is the ideal place to turn to for water research expertise. Since its independence in 1948, Israel has had to find ways to build its society and economy in one of the most water-starved places on the planet. Its game plan for surmounting water scarcity had several pillars. It built a water supply line known as the National Water Carrier that transported water from the Sea of Galilee to the rest of the country, including the barren wastelands of the Negev and Arava deserts. It ingrained water conservation deep in the population’s mindset – for years, Israelis rationed their water use, and even as young children, they were taught to conserve.

“From the age of three, we learned to shut off the faucet while brushing our teeth,” said Udi Tirosh, business development director at IDE Technologies, an Israeli corporation that builds and operates desalination plants in Israel and around the world.

The most significant initiative was Israel’s embracing of desalination technology. It now has five desalination plants producing 500 million cu m of water each year, about half of the country’s drinking water needs. In desalination, water is drawn out of the sea and then pumped through a series of filters to separate the brine and yield fresh water.

Date trees flourish in the desert of Arava, thanks to drip irrigation. Photo: TNS

“Desalination gives you the power to control your supply,” Tirosh said. “Up until a few decades ago, you were waiting for rain or digging a well. Now that you can desalinate, it’s game-changing. You can produce efficient water from the sea, which is important because rivers, lakes and aquifers can dry out.”

There are now more than 17,000 desalination plants in 150 countries, and expanded use of the technology could drastically ratchet up water supplies for water-starved nations. But desalination isn’t problem-free. The bane of desalination plants is bio-fouling, the build-up of microbes on filter surfaces. It makes an already costly approach to creating drinking water even costlier.

To solve the problem of bio-fouling, the researchers at Ben-Gurion and University of Chicago are creating new strand-like molecules less than one-10,000th of the diameter of a human hair, and attaching those strands to the surface of a desalination filter. The strands are electrically charged both positively and negatively, and that combination repels bacteria.

“It’s important to have widespread use of desalination, so it’s important to bring the cost down,” said Matthew Tirell, a professor at University of Chicago. “The potential of this research is to have very long-lasting membranes where the cost of the membranes comes down by a factor of two.”

Ben-Gurion’s role is to find a way to ramp up the scale of production of the strand-covered filters. At its Sede Boker campus in the heart of the Negev desert, biological chemist Christopher Arnusch is relying on an everyday office mainstay – the ink jet printer – to help improve water filtration. He has found a way to use the printers to apply anti-bacterial coatings to filters, a breakthrough that allows scientists to economically affix the right mix of chemicals to sheets of filters a metre wide.

“When you get this slimy, bacterial material on membranes, it makes them ineffective and reduces their shelf life,” Arnusch said. “And it costs more energy to run the systems.”

Searching for water

Another Ben-Gurion scientist, Eilon Adar, is looking for new sources of water. His team is using naturally occurring radioactive isotopes to track the movement of groundwater through aquifers as deep as 1.6km below the surface, relying on a special laser device to detect the number of krypton isotopes in a water sample. Krypton isotopes are used because they begin to decay once they move from surface water to underground strata. The number of isotopes found tells scientists how long the water has been underground. With that information, they can plot the oldest to youngest samples on a map and determine the water’s flow through the aquifer, and ultimately the aquifer’s size and characteristics.

Adar says the research has an intriguing practical application – finding water in the bedrock beneath the world’s deserts. “You cannot sustain a growing population with diminishing amounts of water. So we move into arid and semi-arid basins. And we all know that, under deserts around the world, there are huge groundwater reservoirs.”

Dairy cows receive a shower to stay cool and produce more milk on the Samar kibbutz in the southern Arava region of Israel. Untreated saline water is used because it is more readily available in the desert. Photo: TNS

Adar’s research can also help in Israel, where desert enterprises – from dairy farms to wineries to fish hatcheries – distill their struggles into a single, common plight: lack of water. Israel’s evolution as a wellspring for water technology know-how explains why farms in the Arava thrive. Israel is the birthplace of drip irrigation technology, which conserves by delivering a trickle of water directly to plant roots. Israeli researchers also have fine-tuned how much pure water needs to be added to brackish water drawn from Arava aquifers in order for a given plant species to thrive.

Today, farmers in the Arava grow almost everything found in the nation’s grocery store produce sections: mangoes, pomegranates, grapes, watermelons, tomatoes, potatoes, corn, bell peppers and eggplants. At a kibbutz farm in Samar, the challenge is to keep from overheating dairy cows, livestock that normally would not survive in a desert climate. The solution – showers, seven times a day during summer months, and three or four times a day during the rest of the year.

The wineries of the Arava and Negev face their own daunting obstacles: water and soil that’s too saline, a desert sun that bakes vines with temperatures above 46°C during harvest time. And yet, at Kibbutz Neot Semadar, a winery in the southern end of the Arava desert, an oasis blooms. Gardens of lavender line pools filled with large goldfish. Orchards yield apricots, almonds, apples and plums. And despite the climate, the Shirazes, Merlots and Chardonnays hold up well, locals say.

“Over time, Israel’s farmers have become extremely efficient at using water,” says Jack Gilron, a scientist at Ben-Gurion’s Zuckerberg Institute for Water Research. “For them, water’s scarcity became the spur for how to do water more efficiently.” – Chicago Tribune/Tribune News Service

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