Compromising with a necessary evil: this is literally true for chlorination -- the most widely used technology for disinfecting drinking water. A recent study by Spain-based Municipal Institute of Medical Research once again establishes that long-term exposure to the by-products of the process can make consumers prone to cancers of the gastro-intestinal tract and the urinary tract
compromising with a necessary evil: this is literally true for chlorination -- the most widely used technology for disinfecting drinking water. A recent study by Spain-based Municipal Institute of Medical Research once again establishes that long-term exposure to the by-products of the process can make consumers prone to cancers of the gastro-intestinal tract and the urinary tract.
The harmful by-products, such as chloroform and trihalomethanes, are produced when chlorine reacts with organic chemicals of decomposed plants and animal matter, which are often found in untreated water.
Waterworks departments of India, however, still prefer chlorine. Switching over to other disinfectants, as is being tried out by several municipalities in Europe and Canada, is not economically viable. "Very few can match the residual protection that chlorine offers," says P N Sharma, a scientist with the Indian Institute of Chemical Technology (iict), Hyderabad. "Our pipes remain empty for a long duration, as water supply is not constant. This encourages the breeding of microorganisms in the pipelines. That's why steps are taken to ensure that chlorine level of 0.1 milligrams per litre (mg/l) of water is maintained when the water reaches the consumers," says R Ramanujam, managing director of Kerala Water Authority. Officials say that in order to maintain the level of 0.1 mg/l, about 1.5 to 2 mg/l of chlorine is added at the treatment stage. This is much higher than the 0.1 mg/l limit recommended by the World Health Organization. Medical experts are never consulted when the chlorine dosage is increased due to unavoidable circumstances such as an outbreak of cholera or diarrhoea. For instance, in November 2002, following a cholera epidemic, authorities of Chennai Metro Water and Sewage Board increased the chlorine levels at its treatment plants to 10-12 mg/l.
Such high levels particularly affect people, living near the vicinity of the treatment plants -- they inhale huge amounts of chlorine, which gets evaporated very fast. Inhalation of chlorine can cause dizziness, coughing, nausea, headache and breathing problems. In the developed countries, this problem is addressed by adding booster doses (small quantities) of chlorine in the pipelines, instead of doing so during treatment stage. "Such an easy solution is not considered in India," says Ramanujam.
Some alternative disinfection technologies that are being considered across the world are ozonisation, silver ionisation and use of ultraviolet rays. These technologies also have disadvantages. For instance, ozonisation not only kills harmful microorganisms, but also removes colour and organic content of water.
Since these technologies are not considered viable for India, experts feel that chlorine should be used carefully so that its ill affects are minimised. Proper monitoring should be the norm of the day. Officials of the Delhi Jal Board (djb) claim that chlorine levels are monitored every hour. But such claims seldom prove to be true.
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