Tamil Nadu   

Untreated sewage, a looming disaster on Tamil Nadu coast

Vani Doraisamy

The situation may get out of control within next five years, says a study The situation may get out of control within next five years, says a study

CHENNAI: If you think industrial discharge is the single major cause of intense pollution along the State coast, you are perhaps not looking at your own backyard.

Untreated domestic sewage, as much as and perhaps even more than treated industrial effluents, is irreversibly sullying the coast, according to a recent study done by the project directorate of the Integrated Coastal and Marine Area Management under the Ministry of Earth Sciences. If this continues any further, the situation may get out of control within the next five years, the study warns.

The survey, which started in December last, will be repeated every three months at 76 locations across the country, including the Hooghly Estuary, Paradip, Gangavaram, Ennore, Puducherry, Cuddalore and Tuticorin on the east coast.

Parameters to be assessed are pH levels, salinity, dissolved oxygen (DO) levels, nitrite, nitrate, ammonia and phosphate concentrations and bacterial contamination.

The first study analysed seawater near the shore and clean seawater and results were matched with Central Pollution Control Board standards. Pathogenic bacterial contamination, mostly from untreated municipal sewage, was found intense all along the Tamil Nadu shoreline, especially within 500-600 metres from the coast.

"Though the fish catch is unlikely to diminish due to this, as fish normally inhabit waters much beyond, humans — especially fisherfolk and beach users — who come into contact with the contaminated water are at risk. The threat from untreated sewage is present all along the east coast, especially in Chennai, Puducherry, Cuddalore, Nagapattinam and Tuticorin in Tamil Nadu and Kakinada and Vijayawada in Andhra Pradesh," B.R. Subramanian, ICMAM project director, told The Hindu .

Dissolved oxygen levels were also found less than normal at these stations.

A tourist hotspot such as the Marina in Chennai, for example, was extremely vulnerable to bacterial contamination from the seawaters in November, December and January, as the currents moved southward, Mr. Subramanian said.

While industries in Ennore, other than power plants, released 28,000 cubic metres of wastewater a day into the sea, the two power plants alone discharged one lakh cubic metres of coolant water through the Ennore creek. Cuddalore released 13 million litres a day of sewage, apart from the 7,500 kilolitres a day of treated wastewater from the industries.

Puducherry discharged 45 million litres of untreated wastewater a day into the sea through its backwaters and creeks. The same was the case with Tuticorin, which released 17.5 million litres a day of sewage into the sea — again untreated. While industries other than aquaculture discharged 10,400 cubic metres of wastewater, the aquaculture industry alone discharged 91,200 cubic metres.

"The situation can be remedied if sewage and industrial wastes are treated to increase dissolved oxygen levels to at least 5 mg per litre and to reduce the nitrate and phosphate levels. Also, more monitoring is needed to check industrial wastewater discharge," Mr. Subramanian said.

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