The Hindu : High TDS levels in Coimbatore groundwater: survey

Online edition of India's National Newspaper
Tuesday, Mar 30, 2004

Tamil Nadu

Tamil Nadu

High TDS levels in Coimbatore groundwater: survey

By V.S. Palaniappan

COIMBATORE, MARCH 29. A recent study on the quality of water in and around Coimbatore city has expressed concern at the presence of high levels of Total Dissolved Solids (TDS) in groundwater.

During 2003-2004, the CPR Environmental Education Centre (CPREEC) conducted the survey in Coimbatore. The crisis in both availability of water and pollution is worsening with each day. On the one hand, the groundwater table was going down rapidly, and on the other, the quality was getting worse, said the survey report. It was released recently at a seminar on ``Water Quality and Resources Management in Coimbatore City.''

Samples were taken from 130 different sources, largely borewells and wells. One sample was taken from water supplied from the Siruvani. It was taken from an overhead tank in the Veerakeralam town panchayat. The samples were tested and analysed at the CPREEC laboratory in Chennai. The samples were collected in well-cleaned plastic bottles and transferred to the laboratory under cold condition. They were tested as per the methods recommended by the Bureau of Indian Standards and the American Public Health Association. The samples were tested for colour, odour, turbidity, pH, electrical conductivity, TDS, alkalinity, chloride, total hardness, calcium, magnesium, sulphate, phosphate, nitrate, fluoride and manganese.

The TDS levels exceeded 500 mg per litre in at least 88 per cent of the groundwater samples and only 12 per cent showed the desirable limit of 500 mg per litre or less as per the drinking water specifications, IS 10500:1991. Twentythree per cent of the samples contained more than 2,000 mg per litre of TDS, the maximum permissible limit. Based on the TDS content, the water was classified as potable, less brackish, moderately brackish, highly brackish and brine.

High levels of TDS would affect water taste and lead to gastrointestinal irritation. Samples collected from 50 sources contained more than 100 mg per litre of nitrate, the maximum permissible limit in drinking water. Excessive nitrate content was hazardous to infants. For, the nitrates would turn into nitrites in the intestinal track and cause the blue baby syndrome, the report cautioned. Higher levels of lead content beyond 0.05 would lead to hypertension, anaemia and constipation, while sulphate beyond 200 mg per litre would lead to dysentery and pH content beyond 6.5-8.5 units per litre would affect the mucous membrane.

The survey report said proper resource management and rainwater harvesting could ease the situation considerably. When water contained more salt, more freshwater was being added to dilute the taste; likewise by enabling more percolation or infiltration of rainwater, salinity and the TDS levels could be reduced. Overexploitation of groundwater should be stopped on a war-footing, the report said.

Recommending available technology for removing the TDS and nitrate levels, the report suggested that reverse osmosis, electro dialysis, distillation, ion exchange and solar still could be taken up. Of these, only the solar still belonged to the low-cost technology category but it would produce very little water and only on sunny days. Hence, rainwater harvesting was the need of the hour to tide over the problem over a period of time, concluded the report.

The C.P. Ramasamy Aiyar Foundation, in association with the Ministry of Environment and Forests, Government of India, established the CPREEC, a centre of excellence.

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