Wednesday, June 19, 2013

Dew harvesting—an innovative technique of extracting water

Dew is the new magic source of ultra-fresh water, which is a scarce commodity these days. Technologies are being developed in several countries to draw water from dew. A former IIM professor Girija Sharan has also developed an elaborate yet simple system that can be put on roof top in any house in coastal areas. He showed one can collect pristine fresh 30 litres of water each day from 300 sqm roof, enough for drinking purposes for a family of seven.
By  Dr PK Mukherjee
Water day-by-day is becoming a scarce commodity. The problem is getting compounded with gradual shrinkage of the water table. Nonetheless, we have knowingly or unknowingly developed the habit of wasting water rather than caring for its conservation. Seldom do we realise that in our country there are millions of people for whom even drinking water is scarcely available. We also forget the woes of womenfolk in some parched, arid areas of the country where they have to walk several kilometres for procuring drinking water for their families. Sandra Postel, a world expert on water policy and conservation, in her book ‘The Last Oasis: Facing Water Scarcity’ has hinted in unequivocal terms that if the next world war is to be fought, it would be on issues related to water. In such a scenario, any innovative idea to solve the water crisis is a welcome step.
      In Bujama village of Peru, condensers are being used to generate water from humid air. After filtering, the water is stored in tanks and then dispensed through taps. In just a few months the village has been able to produce over 9,000 litres of drinking water.
Elsewhere too people are experimenting with technology to generate water. Innovative techniques are being evolved. Take, for example, innovation being tried in Alaska that involves extraction of water from air without the use of expensive electricity. And, surprisingly, dew is the magic source of this precious commodity. In parts of Alaska, water is being obtained through dew harvesting. For this, dew is extracted using non-toxic plastic condensers installed on frames. These condensers cool rapidly at night leading to the formation of dew on them. The dew thus formed is collected in bottles and after proper treatment is used for drinking purposes. Girija Sharan, a former IIM, Ahmedabad professor, is incidentally the first Indian to harvest dew. He recalls how he got attracted to the fascinating and innovative idea of dew harvesting. He had read about dew harvesting being done in Alaska, Latin America and Gulf states. Once on a casual visit to Kutch in Gujarat he saw dew formation on plants. It surprised him because it was the month of April and dew formation normally occurs in winter. Coastal areas like Kutch any way face acute problem of water scarcity. It occurred to Sharan that by collecting dew, water could be obtained without the use of electricity. Plastic condensers come in handy for dew collection.
     In major parts of India, dew formation occurs during a few winter months only. But, in some coastal areas like Kutch in Gujarat dew formation takes place over an extended period of eight months, spanning October to May. Particularly, during the summer months frequent and heavy dew formation takes place.
A four-year R & D programme by Girija Sharan led to large dew harvesting systems being erected on roofs. Non-toxic plastic condensers installed on frame are left on the roof top over night. Besides, plastic metallic condensers can also be used.
     The plastic or metallic condensers undergo rapid cooling and the dew thus formed is collected in bottles. Using this technique, Sharan could collect 30 litres of water daily from a 300 sqm roof. The water thus obtained from dew can be filtered and after boiling or sterilisation with ultraviolet light can be used for drinking purposes. An individual, incidentally, needs four litres of water daily.
Dew harvesting seems to be an attractive proposal and an innovative way of extracting water from air without the use of power. It can be tried in other coastal areas as well. Actually, coastal areas are ideal places for collecting. The extraction of water through such innovative technology might seem trivial in the first place as the water yields are comparatively low. However, whatever little water is obtained, it is pristine fresh. And every drop counts, after all!
(Note: The article was first published in the Lokayat magazine: June, 2013)