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Treating waste-water

The Membrane Bio-Reactor system installed at Cubbon Park can be a role model for similar systems all over the country

A recent report released by the Central Pollution Control Board points out the rather abysmal state of waste-water collection and treatment in urban India. Out of the estimated 62,000 million litres of wastewater being generated daily in the 819 large towns and cities of India only about 18,883 million litres per day was being treated to some level. No wonder that our lakes and rivers are in a mess.

While the basic methods of treatment such as Oxidation ponds and Activated Sludge Process are the most common methods of treating waste-water, it is time a long, hard look is taken at the technology choices being made and a swift upgradation done to the best waste-water treatment systems. One such system is the Membrane Bio-Reactor or MBR system.

A small MBR system capable of treating 1.50 million litres per day of waste-water has been installed in Cubbon Park, Bengaluru, and has been continuously operational since June 1, 2005. Having completed more than 10 years of operations and still working successfully, the plant has many lessons to offer not only to Bengaluru but other cities in India as well.

Firstly the plant has a very small footprint, meaning the land required for setting it up is occupying only 1.2 acres and the actual footprint of the plant is 0.8 acres. Land required for sewage treatment plants can become very large and in most of urban India it is very difficult to acquire land.

Secondly the plant blends into the landscape and does not smell at all. A major problem with sewage treatment plants is that nobody wants it in their backyard, for the sight and smell can be offensive. The MBR plant at Cubbon Park is visually appealing and there is no odour.

Quality treatment

Thirdly the plant delivers a very high quality of treatment. In fact it meets and exceeds the norms for treated waste-water as set by the Pollution Control Board and with a very small tweak can meet drinking water standards of BIS 10500 as prevalent in India.

Fourthly, as the membrane technology is constantly improving, the life of the membranes is increasing and cost of the membranes decreasing. Fifthly the cost of the treated waste-water including capital cost and running cost results in the treated waste-water costing about Rs. 15 a kilo-litre though in much smaller plants the cost could go up to Rs. 40 a kilo-litre.

Compare this to the water coming from the Cauvery which costs Rs.50 a kilo-litre or the cost of tanker water which can be as high as Rs. 100 a kilo-litre and this treated waste-water becomes economically a viable alternative.

Best technology

For too long waste-water treatment plants have been seen as cost centres and not revenue centres. By choosing the best technology available and taking the treatment quality to the highest possible level, it is possible to generate revenues for the running of the sewage treatment plants at the very least and where opportunity costs for water is high to recover the capital costs too.

Of course it is important to structure the construction and the operation of the plants with companies which have the requisite experience and skills to deliver outcomes desirable to the city.

Decentralised waste-water treatment systems such as the MBR, when spread over the city, can not only treat the sewage flows but also fill our lakes and aquifers with high quality water and pay-back for themselves.

A visit to the MBR based wastewater treatment plant would be the first step in waste-water wisdom.

zenrainman@gmail.com

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Printable version | Feb 26, 2020 12:46:20 AM | https://www.thehindu.com/features/homes-and-gardens/Treating-waste-water/article14026737.ece

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