Date:15/02/2007 URL: http://www.thehindu.com/2007/02/15/stories/2007021522940300.htm

Karnataka - Bangalore

City's groundwater unsafe

Divya Gandhi

Nitrate level in water has increased manifold in central areas in six years

POISONOUS STREAM: Sewage flows through this storm water drain at Ejipura before reaching the Bellandur Lake. — Photo: K. Murali Kumar

BANGALORE: "You must not drink this water or use it for cooking," said M.V. Shashirekha, chief chemist at the Department of Mines and Geology, to a visitor who walked into collect results of a chemical analysis of water from his borewell. "Your bottle of water contained 70 mg of nitrate. There is not much you can do about it, boiling will not help. May be you should invest in a reverse osmosis purifier."

Dr. Shashirekha has an average of 15 such visitors to her office every day — ordinary residents of Bangalore city who are concerned about the quality of groundwater in their areas.

A comprehensive report on the status of ground water quality in Bangalore, by the department in 2003 had concluded that over 50 per cent of the 900-odd water samples collected was non-potable.

Carcinogen

After bacteriological pollution, the most prevalent and dangerous contaminant was nitrate, a proven carcinogen, which touched 666 mg/l (in parts of Bharathinagar) when the (ISI) permissible limit is 45 mg/l. While nitrate contamination can come from agricultural run-off and industrial effluents, the department has traced the largest number of sources to untreated sewage.

A re-evaluation of 300 samples, conducted by the department six months ago revealed that contamination levels have only increased.

The range now goes up to 747 mg/l (in parts of Shampura).

At a location in Begur village, off Hosur Road, while the nitrate quantities were 139 mg/l three years ago, they are now 227. Shivajinagar was well within the permissible limit three years ago, but parts of it now touch 438 mg/l.

Situation grim

When compared with 1998 figures, the margin becomes starker. Eight years ago, four areas in Bangalore were identified as "major bull's eye" areas where nitrate contamination ranged between 300 and 350 mg/l. Now, says Dr. Shashirekha, she can identify 10 such areas in Bangalore where contamination is "critical".

These include parts of Sultanpalya, Hebbal, Srirampura, Doddabanaswadi, Jayanagar, K.R. Puram, Banashankari, Ulsoor, Shampura and Ejipura.

"Many areas in the city have no collection system at all," says S. Vishwanath of the Rainwater Club. Storm water drains have become nothing more than sewers.

Lakes contaminated

Moreover, since the natural storm water gradient slopes towards lakes, "every one of the 80-odd lakes that remain in Bangalore are highly contaminated and this in turn percolates into the groundwater."

It is no coincidence that of the 24 lakes studied by the department, 22 have been declared highly nitrate-contaminated.

The Jaraganahalli Lake has nitrate levels over 10 times that prescribed by Environment (Protection) Act.

BWSSB Chief Engineer (Corporate Planning and Waste Water Management) S.M. Basavaraju says, "Our pipes are laid only for horizontal growth, not vertical growth.

"The current systems cannot cope with the load."

Even as the 50-year-old sewage network struggles with the growing load, it is no surprise that the 14 sewage treatment plants that together have the capacity to treat 718 million litres of sewage a day (six of which were built last year at a cost of Rs 200 crore) receive just about half that capacity.

"We need an upgrade in the entire network in the BMP and CMC areas", says Mr. Basavaraju.

A proposal has been made to Jawaharlal Nehru National Urban Renewal Mission (JNNURM) for remodelling of the system, the outlay of which is Rs. 600 crore to Rs. 700 crore, he says.