‘Use sun to kill germs in water’

Published: March 3, 2011
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6 hours in the sun is enough for water kept in a clear PET bottle to be safe for drinking.

6 hours in the sun is enough for water kept in a clear PET bottle to be safe for drinking.

ISLAMABAD: Solar water disinfection, a method of water purification using PET bottles placed in sunlight, is a viable solution to the problem of clean drinking in Pakistan.

The method, also known as SODIS, is a low cost alternative to other methods of water purification (the only investment required is the purchase of PET bottles), according to speakers at “Importance of Household Water Treatment”, a seminar organised by Sustainable Development and Policy Institute in Islamabad on Tuesday.

Zafar Hameed, representing FALTECH, said the sun’s rays consist of numerous particles including alpha, beta, cosmic, and other types of useful radiation.

He said SODIS was the “cheapest and most natural way of purifying water”. In SODIS, water is placed in clear PET bottles and kept in the sun for four to six hours. The duration is sufficient to kill most of the disease-causing microbes, according to Hameed.

Humayun Shami of Pakistan Economic Forum said that given the energy constraints of Pakistan and the cost of installing and operating water treatment plants, SODIS was the most the viable solution to the problem of potable water. “SODIS is a cost-effective and sustainable method that can be installed anywhere there is a need for cheap, safe drinking water,” he said, adding that even if the rays do not disinfect the water completely, they can reduce the number of micro-organisms.

Dr Amir Malik from COMSATS said that water in most areas of Pakistan has high turbidity (there are particles and sediments suspended in the water). SODIS is ineffective in such cases. He suggested that Horizontal Roughing Filter/Slow Sand Filter be first employed to remove the turbidity in water.

Published in The Express Tribune, March 3rd, 2011.

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Reader Comments (3)

  • Murtaza
    Mar 3, 2011 - 11:51AM

    Article would have been much help if writer indicated where one can buy PET bottles in Pakistan. Whether there are approved plastics bottles in Pakistan. How about break down of PET bottles under intense heat(40c+ nomral in Summer) and leaching harmful chemicals into water. Lastly why glass bottles are not recommended? Are’nt they safer then PET when you ‘re using them under consistent high temp?

    Thanks for your response.Recommend

  • Mar 3, 2011 - 12:33PM

    In the 1st place, what does PET stand’s for? Recommend

  • Mar 5, 2011 - 12:29AM

    PET is the name of the plastic (polyethylene terephthalate). Our research over the past 7 years has shown that there is about an 8 month to one year life for the bottles when handled with reasonable care (filled and consumed every 2 or 3 days). No effects from plastic leaching on this short time frame. Glass bottles can be used but suffer from several issues including much heavier than plastic, tend to shatter when dropped, less plentiful than plastic and do not normaly have screw on tops.Recommend

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