Recycled Water for Bangalore

In the next three years, Bangaloreans in North and West areas will be supplied ultra-filtered, treated sewage water through their taps, just like normal potable water.The BWSSB’s ambitious project to recycle and reuse sewage water for domestic purposes is picking up pace with the first phase ready for implementation. The Vrishabhavathi Integrated Water Management Scheme — first of the four major BWSSB’s projects approved under the JNNURM — will extract 135 MLD of tertiary treated water from the V-Valley treatment plant and make it suitable for drinking. Dasarahalli and RR Nagar will be covered under the scheme, said BWSSB sources.The two main surface water resources — TG Halli and Hesaraghatta — were last seen full in the 1990s. Given the unpredictable monsoon and lack of additional perennial fresh water sources, the only hope now lies in recycle and reuse.Water from the V-Valley plant will be subjected to ultrafiltration or reverse osmosis and then passed through pressure sand filters and activated carbon filters. This helps remove all bacteria and viruses. The treated water will be let into the Arkavathi river course where it blends with fresh water. After travelling nearly 5 km, the combined flow reaches the reservoir, is drawn into the water treatment plant at TG Halli and then distributed to the city.Ultra filtration uses membrane filtration where the level of dissolved salts is retained and can be blended with normal treated water to balance the salts. It costs nearly Rs 20 per kilo litre of output at the plant site. Reverse osmosis removes all impurities and recovery of usable water is 95%. The level of purity equals potable water as all dissolved salts are removed. It costs around Rs 35 per kilo of output at plant site. The V-Valley project could set a new trend in waste water treatment and reuse for drinking purposes with BWSSB being the first water board to venture into this. Developed countries use ultrafiltration to conserve water.The project, expected to begin in a couple of months, is scheduled for completion by March 2011.