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India; Water Harvesting in an Industry in Bangalore


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India; Water Harvesting in an Industry in Bangalore

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India; Water Harvesting in an Industry in Bangalore

  1. 1. exit ‹ previous ^top^ next › ? help Water Harvesting in an Industry – Bangalore, India B.S. Ajit Kumar Escorts-Mahle Ltd., Bangalore, India, email: Introduction Bangalore, the capital of Karnataka State in South India, is located at an altitude of 921 MSL on the Southern edge of the Deccan Plateau. It is a rapidly growing city known as the Silicon Valley of Asia. The current population of 6 million is expected to reach 7 million by 2011. Industries, especially software and automobiles, are flocking in. The water supply infrastructure is under severe stress and groundwater levels are dropping alarmingly. Due to pressure on land, lakes and tanks are being filled up and converted to real estate. This phenomenon makes ground water recharge more difficult thus depleting ground water further. Rainwater harvesting With a view to optimise water usage we were looking at alternatives, which are sustainable, reliable and cost effective. Rainwater harvesting appeared as a potential source of supply. A group was set up within the organisation to pursue the issue further and to take responsibility for its implementation. A group located in Bangalore, called the Rainwater Club was contacted. The teams then worked on the project. Rainfall data was obtained from a source close to the site, the University of Agricultural Sciences which is about 2 kilometres from our plant. The nearness to the site was considered important since rainfall varies considerably even at short distances in Bangalore. The daily rainfall data for 29 years indicated an average rainfall of 923 millimetres. The number of rainy days was 58 spread from April to November. A rainy day being defined as one where there is more than 2.50 mm of rain. This indicated that over the plant layout of 20.234 ha, the average rainwater incident was as high as 186.905 million litres. In the current paradigm all this water was considered a waste and was being let out of the campus. The issue then was to see how this waste could be turned into a resource and to identify the harvestable component of the rainfall. Classification of the entire layout was made into roof area, paved area and unpaved area. Subsequently coefficients of collection were estimated as 0.80 for rooftops, 0.60 for paved areas and 0.15 for unpaved areas. Thus for the roof area of 29961.50 m2, paved area of 43095.66 m2 and unpaved area of 129286.98 m2, it was possible to determine that rainwater harvestable would be 63.94 million litres in a year with average rainfall. A quick calculation at the opportunity cost of this water at the prevailing market tariff for industries of Rs 60/- (US$ 1,28) a kiloliter indicated that the cost was Rs 3.836.000 (US$ 81.965). Market rates of water are further expected to rise to about Rs 90 /- (about US$ 1,91) a kiloliter in the near future. A preliminary decision was taken to go ahead with water harvesting because of the cost economics and it was decided that a pilot rooftop rainwater harvesting project be put in place. 9
  2. 2. exit ‹ previous ^top^ next › ? help Pilot project Pilot projects have the advantage of generating valuable data and performance indicators at low levels of investment. For the pilot project two rooftops, a canteen block and an administrative block, with a combined roof area of 1200 m2 was selected. These blocks had a regular reinforced cement concrete roof. By realigning roof slopes, using extra down pipes and placing filters below the pipes, rainwater was channelled to an underground sump. Further, with optimisation techniques based on rainfall pattern, it was determined that storage of 42,000 litres would be required to harvest a substantial portion of the rain. An underground sump was built as the storage. It was estimated that about 1.05 million litres of rainwater would be harvested in a year with average rainfall. This pilot project was quickly designed, implemented and inaugurated in May 2000. Great care was taken to include all employees in the inauguration and also to brief them on the benefits of rainwater harvesting. This met with immediate approval and positive support of the workers. A new construction block coming up was immediately taken up for rainwater harvesting at the design stage itself. By appropriately sloping rooftops it was possible to collect rainwater in a water recycling unit. This rainwater harvesting unit too is now almost in place. A cycle stand roof made of asbestos was linked to a collection sump. In a phased manner more and more rooftops were brought under rainwater harvesting. Up scaling Acute shortage of water and interest for funding support has resulted in a detailed proposal for water harvesting being worked out for the entire layout. Taking advantage of the contours and natural storm drains, it is now proposed to harvest rainwater at 3 lowest locations in the layout in ponds lined with HDPE film, a cheaper form of storage. Rooftops will be connected to small sumps that will overflow to the drains. The drains will have silt and grease traps at regular intervals and will lead to stilling ponds. From stilling and sedimentation ponds water will be stored in the lined ponds interconnected with each other. Treatment of this rainwater will follow conventional treatment process including screening, aeration, clarification, chlorination, coagulation, rapid sand filter and carbon adsorption procedures. The water will be used for other than potable purpose including processing, cooling and in the toilets. A conscious decision has been taken not to recharge the groundwater but to store water in lined ponds. This is with the view that even accidentally deep bore-well water should not be contaminated as it is impossible to treat such contamination. 10
  3. 3. exit ‹ previous ^top^ next › ? help Land treatment To increase the quantity and quality of surface run-off it will be necessary to take slope and surface characteristics of the layout into account. Slopes will be increased and redirected as appropriate and buffalo grass and other hardy species planted to ensure no erosion of soil. Sediment build up in the surface water is also to be lessened. Being an industrial unit producing pistons and piston rings, the use of chemicals and acids is inevitable in certain areas. Apart from minor realignment of slopes and grass turfing to control silt run-off, isolation of these area will be necessary to prevent non-point source of pollution to the runoff water. This isolation and segregation has been incorporated in the design proposal. Runoff water will be captured from these area, stored in specially designed sumps and sent to treatment units before being recycled. Integration with water cycle The key to water use in our establishment lies in demand management. With efficient use of water, grey water recycling and rainwater harvesting we believe that our factory can become water self-sufficient. By treating our entire layout as a zero discharge area with regard to water, environmental benefits would be large. While grey water recycling is mandatory under pollution control legislation, rainwater harvesting is not, but we believe that social and environmental responsibility of industry demands it being proactive and economically prudent. ESCORTS-MAHLE-GOETZE is showing that sustainable management of water by industries in a developing economy is possible. 11