environment: disinfecting water through solar means

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http://www.sodis.ch/index.htm

DUBENDORF, SWITZERLAND, May 3, 2007: Solar Water Disinfection, SODIS, improves

the microbiological quality of drinking water by using solar UV-A radiation and

temperature to inactivate pathogens causing diarrhea. This simple, low-tech

application of the sun's rays and the ubiquitous PET (Polyethylene

Terephthalate) plastic bottles can dramatically help people without safe

drinking water. At least one third of the population in developing countries has

no access to safe drinking water.

 

SODIS requires sun radiation and temperature. The container must be exposed to

the sun for 6 hours if the sky is bright or up to 50% cloudy and for up to two

consecutive days if the skies are 100% cloudy. During days of continuous

rainfall, SODIS does not perform satisfactorily. Rainwater harvesting is

recommended during these days. If a water temperature of at least 50 degrees

Celsius (122F) is reached, an exposure time of one hour is sufficient. The most

favorable region for SODIS lies between latitudes 15 degrees and 30 degrees

above and below the equator. These semi-arid regions are characterized by high

solar radiation and limited cloud coverage and rainfall (3,000 hours sunshine

per year). The second most favorable region lies between 15 degrees above and

below the equator itself. The scattered radiation in this slightly cloudier

region is still quite high (2,500 hours sunshine per year).

 

In addition to the sun's radiation and cloud cover, water turbidity is also an

issue. The more suspended particles in the water, the less penetration of solar

radiation. To be successful, SODIS requires relatively clear water. To read the

full and detailed instructions for SODIS water purification, go to source.