In impoverished countries where people can't afford to build expensive water treatment plants, they sometimes rely upon a free resource -- sunlight. A combination of heat and ultraviolet radiation from the sun will
wipe out most of the microbes that cause diarrhea, an ailment that claims the lives of 4,000 children in Africa every day. One complication: In order for the process to work, the water has to be clear, which is a problem in rural areas where people get their water from rivers, streams and boreholes that yield water filled with suspended clay particles.
But Joshua Pearce, an associate professor of materials science and engineering at Michigan Technological University, and colleague Brittney Dawney from Queens University in Ontario have a solution. In a 2012 article in the Journal of Water, Sanitation and Hygiene for Development, they proposed a solar disinfection regimen that first treats the water with a process called flocculation, in which a small amount of table salt is added to the water to draw out the clay. While the resulting drinking water has higher levels of salt than Americans are used to, it's still got less in it than Gatorade. "I've drunk this water myself," Pearce said in an interview. "If I were somewhere with no clean water and I had kids with diarrhea, and this could save their lives, I'd use it, no question" [sources: Science Daily, Dawney and Pearce].