Treatment of Waste Water
November 15, 2012
Overexploitation of fresh water reserves is a global issue. Especially arid regions are already facing great difficulty in supplying enough water to meet the basic needs of the people living there. Moreover, the small amount of water available, is all too often polluted by untreated sewage and industrial discharge. Now climate change is further compounding the problem.
“If the issue of sewage is not treated urgently, it will fast magnify to an unmanageable level,” states the Central Pollution Control Board, in its report Status of Sewage Treatment in India.
Out of the more than 7000 towns and cities in India, only 269 have sewage treatment plants, most of which don’t have the needed capacity to treat all the waste water generated by the community and industrial areas.
Treating waste water brings countless environmental and societal benefits like preventing contamination of lakes and rivers, recycling of valuable nutrients for agriculture and last, but not the least, reduced exploitation of groundwater and other sources of fresh water, by using recycled water for crop irrigation.
Amrita’s Coimbatore campus, located on 400 acres in an arid area, runs five sewage treatment plants round-the-clock. Together, they process 12 lakhs liters a day. The plants use no chemicals in the treatment process. Their bioremediation is aided by Effective Microbes (EM) technology.
The treatment process is carried out in three steps. In the collection tank, EM is added. A removable grid screen traps stones, plastic and other solid waste material. From here, the effluent is pumped to the aeration tank. A mechanical aerator helps dissolve atmospheric oxygen into the effluent water. After a retention time of 24 hours in the aeration tank, during which microbes act on the wastewater, the effluent is taken to a settling tank where suspended solids are removed.
BOD (biochemical oxygen demand) tests are regularly conducted to ascertain the water quality. “While the BOD of untreated sewage is around 200 ppm, the BOD of treated sewage is less than 20ppm,” explains B. Jaganathan, Manager, Facilities, Coimbatore campus. To operate the five plants, he has a team of one supervisor and three workers.
The treated water is pumped into storage tanks. Approximately 11.6 lakh liters of water that is recovered every day, is used for irrigating the extensive campus lawns and the gardens. In this way, water is injected back into the soil. This has helped recharge ground water levels in nearby Ettimadai village also. Wells there now, seldom run dry.
Plans are afoot to use the treated water also for flushing of toilets. A new biogas plant is being constructed, that will supply methane gas equivalent to 1 LPG cylinder a day, to the adjoining college canteen, resulting in potential savings of Rs. 45,000 per month.
But while the wastewater treatment is essential, it is not cheap. The main cost comes from the electricity usage for the water pumps and the aerators that must operate 24 hours a day. By some estimates, the monthly charges for electricity to run the five sewage treatment plants on campus comes to around Rs. 3.5 lakhs.
There is a great need to reduce the expense involved with treatment of wastewater. Only then, will communities, industries, cities and towns begin to customarily treat their wastewater, before returning it back to Mother Nature. Only then will we have taken the first step towards solving the acute problem of water pollution and scarcity that threatens many of us globally.