Despite having one of the world’s largest rivers running the length of its country, Egypt lacks the fresh water needed to supply its growing population. To quench an annual 7 billion cubic meter (247 billion cubic foot) shortfall, the country has looked to desalination, which is energy-intensive and expensive. Now, researchers from Alexandria University have developed a technique for desalinating and cleaning water that uses less than half the energy of current desalination methods, making it potentially cheap enough as a viable fresh water source.
The researchers used a pervaporation method, which pushes pressurized sea water through a membrane that retains salt, before being vaporized by heat in a second purification step. Key to their breakthrough process was the development of a polymer membrane made up of five ingredients commonly available in the region, including cellulose acetate powder, which binds to the salt particles as the water passes through the membrane. The ingredients are cheap and easily produced in a lab, and require minimal power to be effective.
The membrane even works on exceptionally salty water, such as found in the Red Sea, producing potable water with 99.7 percent of the salt removed with one pass through the membrane.
After the water is filtered through, it’s vaporized and then condensed into drinking water. The process also works on water contaminated with sewage or dirt, making it especially beneficial for developing nations. According to Ahmed El-Shafei, associate professor of agriculture and biosystems engineering at Alexandria University, pervaporation eliminates the need for electricity used in traditional desalination processes, which cuts costs significantly.
Pervaporation has been around since the 1990s, and is used in waste water treatment to separate waste water and organic solvents. The saline-removing membrane developed by the researchers can be printed in sheets and cut for individual use, and is currently planned for a pilot desalination plant for large scale testing.
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