Solar water disinfection method promises clean water for everyone


Washington, May 20 (ANI): A scientist has developed a simple and cheap way to make water safe to drink, even if it is muddy. Nearly 80 percent of disease in developing countries is linked to bad water and sanitation. It's easy enough to purify clear water. The solar water disinfection method, or SODIS, calls for leaving a transparent plastic bottle of clear water out in the sun for six hours. That allows heat and ultraviolet radiation to wipe out most pathogens that cause diarrhea, a malady that kills 4,000 children a day in Africa. It's a different story if the water is murky, as it often is where people must fetch water from rivers, streams and boreholes. "In the developing world, many people don't have access to clear water, and it's very hard to get rid of the suspended clay particles," Joshua Pearce from Michigan Technological University, said. "But if you don't, SODIS doesn't work. The microorganisms hide under the clay and avoid the UV," he said. Thus, to purify water, you first have to get the clay to settle out, a process called flocculation. Working with student Brittney Dawney of Queen's University in Ontario, Pearce discovered that one of the most abundant minerals on Earth does this job very well: sodium chloride, or simple table salt. Salt is inexpensive and available almost everywhere. And it doesn't take very much to make muddy water clear again. "The water has a lower sodium concentration than Gatorade. "I've drunk this water myself. If I were somewhere with no clean water and had kids with diarrhea, and this could save their lives, I'd use this, no question," Pearce said. Salt works best when the suspended particles are a type of clay called bentonite. The technique doesn't work as well with other kinds of clay. However, by adding a little bentonite with the salt to water containing these different clays, most of the particles glom together and settle out, creating water clear enough for SODIS treatment. The paper has been accepted for publication in the Journal of Water, Sanitation, and Hygiene for Development. (ANI)