New light on water disinfection

With a simple modification, ordinary tubelights can be used to provide clean drinking water.

 
Published: Sunday 31 October 1993

-- AN INDIAN scientist from the University of California, Berkeley, suggests ordinary tubelights can be used to cheaply disinfect water, especially in rural areas.

"It's not as if I have discovered something new," says Ashok Gadgil. "In fact, breweries, bakeries and pharmaceutical laboratories use mercury vapour lamps (such as tubelights) to disinfect water. But its potential for providing safe drinking water in Indian villages and urban areas is enormous and should be exploited," he says.

It's well-known that ultraviolet-C (UV-C) rays, produced in mercury vapour lamps, kill germs and viruses that cause such diseases as cholera and typhoid, by inactivating the life-giving deoxyribonucleic acid (DNA) of these pathogens.

Gadgil has set up a system that filters water using the method he propounds. It consists of a storage tank for untreated water, a sand filter to remove particulate matter, a chamber in which the water is disinfected and a storage tank for potable water. The sand filter is needed to reduce the number of particles, which can scatter UV rays and make them less effective.

The mercury lamp used in the set-up is the same as an ordinary tubelight, but without the phosphor coating on its inner surface that traps the germ-killing UV rays.

Gadgil estimates that for a village with 2,000 people, the per capita cost for using this method works out to a paltry 75 paise per 1,000 litres of potable water. "In fact," says Gadgil, "if installed in urban areas, it could give costly water filters that use the same principle, a run for its money."

Gadgil, who was recently in the Capital, has approached the Indian government, the drinking water mission and the Council of Scientific and Industrial Research, to seriously consider this method of disinfecting water.

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