First the word to describe it was ‘sewage.’ Then the name changed to ‘waste-water.’ Now it is felt that it is best described as ‘used water’ or even better, ‘reusable water.’ A look by S.Vishwanath

Bangalore as a city is distinguished by many firsts. It has the largest number of solar water heaters for any city in India for one. It has the costliest water for another, since the water has to come from a river nearly 100 km away and about 300 metres below the city. It also has the single largest number of waste-water treatment plants in India with nearly 700 of them of various scales.

Treatment of used water is of primarily three types: primary, secondary and tertiary. Primary treatment is usually holding the water for it to settle all sludge and then release it. Secondary treatment usually involves mechanical separation of physical and biological matter; and finally tertiary treatment means that the waste-water can be reused.

Bangalore has secondary and tertiary treatment plants and the tertiary treatment plant located in the Vrishbhavati valley is one of India’s largest. Of particular interest is the tertiary treatment plant at Yelahanka, where the treated waste-water is sent to several industries including the International Airport.

Plant details

The 10 million litres per day (MLD) treatment plant at Jakkur is very interesting. Here, using the Up-flow Anaerobic Sludge Digestion process and subsequent aeration, the treated water is let into a wetland. The wetland further cleans up the water and subsequently this flows into a large lake. The Jakkur Lake is always full thanks to the treated waste-water unit. Even the sludge generated at the unit, almost two truckloads of them every day, is taken away and used by farmers as fertilizer for their coconut and arecanut groves.

The city will eventually have to be treating 1100 MLD of used water. If it develops a comprehensive plan then all this recycled water will substitute for fresh water and be of great help in overcoming the water shortage.

At an apartment and layout level recycled water can substitute easily for flushing water requirements as well as that of watering the garden and cleaning the cars.

At a larger level, recycled water flowing through wetlands can become the filler of lakes, keeping the many tanks full and also allowing recharge of groundwater.

Finally after tertiary treatment this recycled water can be used for various industrial purposes where non-potable water of a certain standard is required.

A waste-water master plan, the appropriate location of the treatment plants, the creation of wetlands and water bodies are all what is needed. Bangalore has been the pioneer in many such initiatives and in cleaning up our environment it can be the leader too. In this lies water wisdom.