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A study led by Professor Daniel Mäusezahl of the
Institute of Tropical Diseases, University of Basel, and
conducted with scientists from the University of
California and also with the University of Cochabamba in
Bolivia into the disinfection of water using solar
methods has yielded negative results.
The method of solar water disinfection (SODIS), used to
prevent diarrhoea in children under the age of five, was
tested by scientists in 11 communities consisting of 200
households and 349 children separated into two groups.
Method
Solar disinfection entails the exposure of water to
sunlight for six hours in transparent water bottles,
since it is believed that ultraviolet radiation and
increased temperature deactivates the germs causing the
disease. SODIS requires water bottles made out of
plastic to treat the water and uses the synergy of solar
UV-A radiation and temperature to destroy pathogenic
micro-organisms in the liquid. Its application is most
effective in small amounts of contaminated water. The
liquid is then emptied into plastic bottles and exposed
to sunlight for at least six hours. If the water
temperature exceeds 50 degrees Celsius within one hour,
it is enough.
Tests
One of the groups carried out the procedure for one year
while the other group continued with their collection
and use of water as it had always done, without using
the solar method. At the study’s conclusion, the data
revealed that in the first group had seen 3.6 episodes
of diarrhoea and the other 4.3.
According to scientists, despite the promotion of solar
disinfection technology, the investigation did not
establish evidence that solar disinfection reduces cases
of diarrhoea. The report added that before continuing
the promotion of the process, they should have a greater
knowledge of their true effects.
Contaminated water and poor hygiene are major risk
factors for diarrhoea, a condition that kills about 1.8
million people worldwide annually, especially children
under the age of 5 in developing countries.
A Hard Blow to the Promoters of SODIS
These results come as a discouraging blow to the
precursors of the development of SODIS, who received
financial support from the Swiss Agency for Development
and Cooperation. This SODIS system began in 2001 in
seven countries in Asia, Africa and Latin America. In
Bolivia the project is supported and funded by the NGO’s
Helvetas and Eawag, and also by Migros, the largest
co-operative in Switzerland.
In 2001 the Swiss Tropical Institute in the area of
Misque in Bolivia, an assessment of 18 communities found
that those using the SODIS system saw an average
decrease of 35% in occurrences of diarrhoea. A pioneer
for this method is Professor Martin Wegelin, Department
of Water and Sanitation for Developing Countries from
the Swiss Federal Institute of Environmental Science and
Technology.
Swisslatin / adapted by Stephen Inch
(20.08.2009) |
