New Desalination Tech Spur Growth in Water Reuse

New Technologies Are Improving Traditional Desalination and Opening up New Frontiers in Reusing Everything from Agricultural Water to Industrial Effluent

A ferry plows along San Francisco Bay, trailing a tail of churned up salt, sand, and sludge and further fouling the already murky liquid that John Webley intends to turn into drinking water. But Webley, CEO of a Bay Area start-up working on a new, energy-skimping desalination system, isn't perturbed.

"Look at the color of this intake," he says, pointing to a tube feeding brown fluid into a device the size of a home furnace. There, through a process called forward osmosis, a novel solution the company developed pulls water molecules across a membrane, leaving salt and impurities behind.

When low temperature heat is applied, the bioengineered solution separates out like oil, allowing clean water to be siphoned off.

This method uses less than a quarter of the electricity needed for standard desalination, making it easier for the technology to run on renewable power, said Webley. His company,Trevi Systems, recently won an international low-energy desalination competition and is building a pilot solar plant to desalinate seawater in the United Arab Emirates.

With world water demands rising and extreme droughts like the one now gripping California expected to grow more frequent and widespread as the climate warms, drawing fresh water from oceans and other salty sources will be increasingly important.

However, desalination is expensive, energy-intensive, and can damage marine ecosystems. Moreover, while seawater accounts for 60 percent of desalinated water today, Sedlak and others say it's much more practical and sustainable to desalinate less-salty brackish water and use the technology to recycle wastewater. So companies around the world are working on new technologies that cut desalination costs, reduce environmental impacts, and broaden its applications.

In addition to removing salt from seawater, technologies like Trevi's also can economically cleanse brackish groundwater, industrial effluent, and other forms of liquid waste. That includes desalinating sewer water to recharge groundwater aquifers, which it will soon begin doing for a largeurban water district in Southern California.

More than 17,000 desalination plants are now operating in 150 countries worldwide, a capacity that could nearly double by 2020, according to theUnited Nations World Water Development Report 2014. Desalination produces 21 billion gallons of water a day, according to theInternational Desalination Association, providing a crucial water source in arid places such as the Middle East and Australia. Major new desalination facilities are in the works inChina,Chile, and elsewhere.

However, the current standard technology, reverse osmosis — in which high-pressure pumps force water through semi-permeable membranes to exclude salt and impurities — uses large amounts of energy and has an outsized impact on the environment. These effects include damage to aquatic ecosystems, such as sucking in fish eggs with its intake water; using harsh chemicals to clean membranes; and releasing large volumes of highly salty liquid brine back into the water.

Engineers and entrepreneurs across the globe are now trying to devise greener desalination. Some are inventing new alternatives to traditional reverse osmosis. Among them: Israel, whose own dependence on desalinated water has made it a world leader in the process, has come out with several state-of-the-art technologies, including a novel "semi-batch" reverse osmosis process developed by Desalitech that shrinks energy and brine, and a chemical-free "plant in a box," produced byIDE Technologies; and Memsys, of Singapore and Germany, is working on hybrid-thermal membrane technology that is energy-efficient enough to run on solar power.

Source: Environment 360

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Taxonomy

• Sludge Separation
• Water Recycling
• Desalination