SODIS is a very viable way to purify water that is contaminated with bacteria. It is a way of pasturizing water using a double-whammy: ultra-vilet radiation and increased temperature.

"In 1991 EAWAG (The Swiss Federal Institute for Environmental Science and Technology) and SANDEC (EAWAG's Department of Water and Sanitation in Developing Countries) conducted extensive laboratory and field tests to develop and test the Solar Water Disinfection Process (SODIS)."

If conditions are suitable to raise the temperature of the water to 122F (50C), it only takes one hour to pasturize the water. It is recommended that the water be filtered first, even through a bandana.

http://www.sodis.ch/ and be sure to click on THE METHOD.

Sue