Via Afrigadget, a visual explanation of how to disinfect water with just a PET plastic bottle. The diagram, developed by Unicef, pretty much speaks for itself. Too much gunk in the water? Let it settle and filter through some cloth. At least six hours of sunlight will be enough UV to kill bad buggies. Using solar water disinfection, or “SODIS”, replaces the need to boil water, thus reducing deforestation to supply fire wood.
Obviously, this is not a long term solution. Drinking water out of heated plastic bottles can’t be a good thing. But in a pinch . . .
More info here.