Industrial effluents threaten drinking water sources in Cauvery, Palar

Industrial effluents from tanneries and dyeing units discharged into the Palar and Cauvery river basins do not just affect the farming community, but pose a grave threat to drinking water sources in the state’s western and northern districts.
According to a classified document of the municipal administration and water supply department, the industrial and municipal sewage directly discharged into the river systems is polluting the drinking water headworks located in the riverbeds, especially in Palar and Cauvery. The document, which also suggested that a high level panel be formed to look into the issue, was prepared a year ago by a department under deputy chief minister MK Stalin, but no action has been taken on it since, sources say.
River Palar provides water to most of the towns in Vellore, Tiruvannamalai and Kancheepuram districts. It is from Palar that 300 million litres per day is pumped out for the 203 combined water supply schemes. According to the document, the effluents, discharged directly into the Palar from places like Vaniyambadi, Ambur, Ranipet and Vellore (the state’s leather belt), travel a long distance along the riverbed and pollute the drinking water headworks en route.
According to sources, the TWAD has about 40 drinking water headworks to serve the population of Vellore and Tiruvannamalai districts. Almost all of them are at risk of being polluted by effluent discharges, particularly from the tannery clusters upstream. “The pollution affects water headworks in a 100-km stretch along the river
bed,” admitted a senior official seeking anonymity. “We have been taking samples for effective monitoring. It is really getting dangerous, particularly due to totally dissolved solids (TDS).
Occasionally, we shift to alternative sites for pumping out drinking water,” said an engineer. According to WHO standards, the TDS levels have to be below 500 parts per million (ppm). The Tamil Nadu government has already “diluted” the standard to below 2,000 ppm, as the level fit for drinking. According to sources, the levels of TDS polluting the headworks range from 5,000 ppm to 20,000 ppm.
The TWAD Board has a lab in Vellore to test the quality of water, and therefore has an opportunity to seek alternative sources of water when a particular headwork gets polluted. But there are many town panchayats and panchayats which have their own drinking water schemes and which could be drawing the polluted water directly from the borewells and supplying it without realising the presence of hazardous chemicals, TWAD sources say.
The board submitted a report to the Tamil Nadu Pollution Control Board (TNPCB) four months ago, urging it to act fast. It is the same in the case of the 31 combined water supply schemes in the Cauvery and Bhavani river basins, which are polluted mainly by over a thousand dyeing units and a thousand bleaching units discharging effluents with a high concentration of TDS directly into the river systems.
The headworks for these 31 schemes supply 168 million litres of water per day, benefiting a population of 13.75 lakh in the districts of Coimbatore, Erode, Salem, Namakkal, Karur and Tiruchi.