Myanmar University Students’ Social Club

Solar water Disinfection (SODIS) method is one of the cheapest and most effective way that can be used in rural and for emergency purpose usually post-disaster period. This method can be applied at household level and has been recognized by World Health Organization (WHO).

The method of SODIS is based on the principle that exposure of sunlight diarrhea causing organisms in polluted water. The effects of solar radiation can inactivate pathogenic organisms. Scientists separated the various ultraviolet radiation effects that contain in solar radiation:

• UV-A interferes directly with the metabolism and destroys cell structures of bacteria.
• UV-A (wavelength 320-400nm) reacts with oxygen dissolved in the water and produces highly reactive forms of oxygen (oxygen free radicals and hydrogen peroxides), that are believed to also damage pathogens.
• Infrared radiation heats the water. If the water temperatures raises above 50°C, the disinfection process is three times faster.

The steps of SODIS has been explained with diagrams for easy-understanding:

If the weather is sunny, the minimum treatment duration should be at least 6 hours. When the weather is 100% cloudy, the minimum treatment should be 2 days. But when there is continuous rainfall, rainwater is suggested.