The Hindu : Tamil Nadu / Chennai News : Chennai Petroleum refinery shows the way

Online edition of India's National Newspaper
Thursday, Apr 29, 2004

Tamil Nadu

Tamil Nadu - Chennai

Chennai Petroleum refinery shows the way

By K. Lakshmi

CHENNAI, APRIL 28. When most industrial units at Manali struggle to meet their water needs, Chennai Petroleum's refinery, using considerable amount of water to cool crude oil, gets half of its supply by recycling sewage and effluents, in the process reducing pollution.

And not a drop of water is discharged from the sprawling plant.

The Chennai Petroleum Corporation Ltd., (CPCL) buys 25 lakh gallons of sewage from Metrowater, removes biological and chemical impurities through a series of filters and uses the water to run its plant, which converts crude oil into petrol, diesel and other products.

Its success has spawned enquiries from industries across the country as water shortage becomes increasingly common.

The technique uses a sheet of polymer or membrane that reverses osmosis, the process by which something is acquired by absorption.

The CPCL was among the pioneers in treating sewage. In 1991, it built a plant to recycle secondary-treated sewage it bought from Metrowater. At the plant, the sewage is first allowed to settle in huge ponds, then aerated to reduce organic pollutants and pumped through filters to remove chemicals. The water is finally pumped under high pressure through imported membranes in a reverse osmosis unit.

The water by now is clear - 98.8 pure -- but unfit for human consumption.

The CPCL was buying sewage from Metrowater at Rs. 8 a kilolitre, a refinery official said.

It was forced to scale down its operation two years ago because of water crisis.

The corporation has set up a zero-discharge plant, which treats 1.5 lakh litres of water an hour. "Earlier, we used to discharge our industrial waste into the Buckingham canal," the official said. "Now, we do not add to the pollution of the city as we reuse every litre of sewage." There is no stench in the treatment process.

During the treatment, the sludge is fed to earthworms and the vermicompost is used to fertilise the lush vegetation on the campus. The plant produces four tonnes of manure a month, some of which is given free to farmers. Engineers and scientists at the CPCL are trying to reduce the number of steps involved in the current technology. They are building an ultra filtration system that will compress all the processes and save time and space.

It is also testing a membrane developed by the government-run Central Salt and Marine Chemicals Laboratory in Bhavnagar, Gujarat.

Last month, the corporation started a demonstration plant that can treat 1 million litres of sewage a day. The project was aimed at developing commercial-sized membranes to match imported membranes, said S. Pandarinathan, general manager.

Simultaneously, it also plans to set up a desalination plant soon because of chronic shortage of water in Chennai, but details are not immediately known.

The technologies adopted by the CPCL would be of use for other water-intensive industrial units and could be adopted by public water supply units for recovering potable water from brackish water, the official added.

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