Each drop of water counts
Water management as a result of growing scarcity has become imperative for cities. And the BWSSB has taken several steps in this regard.
Sewage treatment and management in big cities attains great importance with the increasing need to recycle and reuse water. Also, in a city like Bangalore, which has only one source of raw water, the scarcity of water has presented itself in a form that recycling water has become all the more imperative. The sewerage system has existed in Bangalore since 1922 and major works have been taken up since 1950. Today, around 215 sq km of the City has been covered with sewerage system through 7,500 km of sewer lines.
The BWSSB (Bangalore Water Supply and Sewerage Board) has taken up a number of initiatives to treat sewage. The five existing treatment plants treat 418 MLD (million litres per day) to secondary levels before letting out the treated water to natural valleys. The board is establishing seven new sewage treatment plants (STPs) in the city, “to connect every inch of Bangalore city by April 30 and make sure that every drop of sewage is treated before releasing the water back into the environment,” says BWSSB Chairman M N Vidyashankar.
The five existing treatment plants are Vrishabhavathi Valley tertiary treatment plant, Koramangala and Chellaghatta plant, Yelahanka tertiary treatment plant, Madiwala and Kempambudhi plants. Of these, the Vrishabhavathi Valley is the biggest with 180 MLD wastewater going into secondary treatment. Of this, 60 MLD wastewater is taken for tertiary treatment. The Vrishabhavathi Valley plant designed and constructed at a cost of Rs 35 crore, is funded by the Indo-French Protocol and HUDCO.
The plant is one of the most advanced and saves potable water required for a population of approximately four lakh. It meets non-potable water needs of non-domestic consumers and industries on Mysore Road.
Designed and constructed at a cost of Rs 34 crore, the 10 MLD capacity Yelahanka plant is unique, as the process of treating fine, suspended solids in the tertiary treatment, has been taken up in a big way in this plant. The plant is fully automated and the end product is chlorinated water which is used extensively for industrial and other non-domestic purposes. The other plants are Madiwala (4 MLD capacity), Kempambudhi (1 MLD capacity) and Koramangala and Chellaghatta plant (K&C Valley).
While the existing sewage treatment plants treat 418 MLD, the newly added seven treatment plants will treat an additional 245 MLD. The seven new sewage treatment plants will come up in K & C Valley (which will be an extension of the existing plant), Raja Canal, Kadubesanahalli, Nagasandra (Tumkur Road), Mylasandra (Mysore Road), K R Puram and Jakkur.
Also, eight intermediate sew-age pumping stations will convey sewage into the treatment plants at a total cost of nearly Rs 300 crore. These 15 works (seven treatment plants and eight intermediate stations) will be commissioned by April this year.
The effluent standards are well within the prescribed norms of the Karnataka State Pollution Control Board, says Mr Vidyashankar. In the primary stage, the wastewater collected is screened for grits and grease. In the secondary stage, it is processed through biological treatments - BOD (bio-chemical oxygen demand) and COD (chemical oxygen demand). Suspended solids are removed.
Treated water is saturated with chlorine with a minimum chlorine contact time of 45 minutes. Sludge is processed through thickeners and dewatering before final disposal. The treatment plant in K&C Valley follows a purely biological process and fish are let into the treated water for a period of 24 hours - a way of checking the treated water.
The existing sewage treatment plants are controlled by computers. With the addition of the seven new plants, all the plants in the city can be managed from a single location. “Water treated in our tertiary treatment plants is as clean as bottled water. We simply cannot afford to waste even a drop of water,” says Mr Vidyashankar.