The Hindu : Karnataka / Bangalore News : Reaping a bumper harvest

Online edition of India's National Newspaper
Wednesday, Feb 14, 2007
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Karnataka

Karnataka - Bangalore

Reaping a bumper harvest

Raghava M.

BANGALORE: By supplying harvested rainwater and recycling wastewater, the Indian Institute of Science (IISc.) may soon save Rs. 5 crore a year. The premier science institution plans to reduce the dependence on fresh water from the present 98 per cent to 20 per cent. About 8,000 people reside on campus.

Achanta Ramakrishna Rao, Professor in the IISc's Department of Civil Engineering, who prepared the rainwater harvest plan, says there will be a separate pipeline to bathrooms and kitchens and for toilets in the apartment blocks on the campus. Fresh water, along with harvested rainwater and ground water, will be available in every bathroom and kitchen.

The rainwater on the campus will flow into two huge storage tanks of 67,800 cubic metres capacity. The rainwater will be pumped to a common supply point from where pipelines take them to individual homes and departments.

The water flowing out from the kitchens and bathrooms (not toilets) goes to another storage tank with a treatment plant. This water is pumped to another overhead tank to supply water to flush toilets.

Wastewater from bathrooms and kitchens — which is easier to clean and recycle — can also be used for other non-potable use such as washing cars and gardening.

The Rs. 14-crore project is estimated to reduce the annual payment to the BWSSB from Rs. 8 crore to Rs. 1.6 crore. Take away Rs. 1.4 crore towards annual maintenance and the IISc. will still save Rs. 5 crore. The cost of laying the new water supply model can be recovered in three years, Mr. Rao said.

Individual households too can adapt a cost-effective rainwater harvesting (RWH). RWH is cheaper if incorporated at the time of construction. It is important to provide a gentle slope on the roof so that water is easily directed to the pipe to take it to the filter. As rainwater is usually muddy, it has to be filtered before it enters the sump.

The filter is nothing but a plastic drum of required size with two openings — one at the bottom and the other at the top. Rainwater should enter the filter from the opening at the bottom. As the water in the filter rises, it passes through a sponge. The water at the top is cleaner and it can be let into the sump and used for any non-potable purpose — gardening, washing utensils and flushing the toilets.

Those who have borewells may use rainwater to recharge the groundwater. To achieve this, earth is dug and layers of sand and soil are provided so that clean water seeps into the ground. Details are available on the websites www.ksphc.org; www.bwssb.org

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