Solar water disinfection (SODIS) relies on the freely available ultraviolet and infrared rays of the sun, which can disinfect by killing pathogens that contaminate water. The process is as easy as leaving a clear plastic bottle of water out in the sun for six hours.
If clean water is that easy, why are so many people, especially young children, dying from diseases contracted by drinking unclean water? There is a major obstacle to effective use of SODIS: if the water is muddy or murky, pathogens can hide in the shadows of the particulates, avoiding the death-rays of the sun.But Brittney Dawney, a student at Queen's University of Ontario, and Joshua Pearce, associate professor at Michigan Technological University, believe this problem can be solved with an everyday item from the kitchen shelf: table salt.
Salt, a cheap and widely available material, acts as a "flocculant" -- a material which pulls together loose particles in solution until they form an aggregate heavy enough to sink to the bottom, making the murky water clear. Pearce reports:
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.
While slightly salty water baked in plastic bottles might not be the recommended health drink in the developed world, where clean water is not available, this process might be a lifesaver.
The process works best with a type of clay soil called bentonite. With other soils, adding a bit of bentonite with the salt can improve the sedimentation rate. The scientists continue to research the types of soils in Africa to determine where their method might work best. A prepublication version of the paper on Optimizing the Solar Water Disinfection (SODIS) Method by Decreasing Turbidity with NaCl is available on Scribd.