Waste water recycling gains ground ………Sharad Vyas
Mumbai: The state government in 2008 made it mandatory for large constructionslike malls,hotels and even residential complexesto have on-site treatment of sewage water.Two years hence,officials from the BMCs environment and building construction departments confirm that the scheme has been increasingly accommodated at a steady rate in newer projects,especially in the wake of an unprecedented water crisis.
According to them,in the last one year,the number of proposals which made provisions for sewage treatment plants (STPs) and other alternatives to treat waste water have jumped by 20%.
The end of last year and early this year have seen a steady rise in STP proposals.Our staff has been busy scrutinising these plans and giving them a final approval, said deputy chief engineer (environment),Prafulla Sabnis.Officials from the development plan (DP) department had in 2008,immediately after states announcement,formulated guidelines for waste treatment plants.Though it was initially opposed by builders,this year we have received a large number of proposals that have opted for STPs, said chief engineer,development plan,V L Joshi.
The new rules for waste treatment made it necessary for every new construction with more than 60 units or 240 residents to have a plant.Any project with an area of over 2,000 sq m was also brought under the ambit of the rules.The corporation had warned that projects found violating the guidelines would not be provided work completion certificates.
While many have opted for a traditional STP,some projects went for the latest anaerobic baffled reactors,otherwise known as baffled septic tanksa technology imported from Germany.Most of these reactors have a capacity to deal with 14,000 litre of toilet waste per day and cost Rs 7.5 lakh.Operating costs amount to Rs 12,000 a year.These plants take up an area of four to eight sq m and the space above can be used for parking.The life of a reactor would be around 20 years and one plant would be enough for a population of 200, said an official.
Mumbais households are generating grey water from bathing,washing dishes and laundry.According to an estimate,nearly 10 litre of water is wasted each time a person flushes.Grey water forms 50% of waste water from residential premises and if the sources are efficiently treated,the water shortage can be reduced in the city.This recycled water can be used for non-potable purposes,such as gardening and washing cars, said additional municipal commissioner Anil Diggikar.
Grey Matter
* An Anaerobic Baffled Reactor has a settling tank that has the same dimensions as the first compartment of a conventional septic tank
* Here,scum rises to the top and sludge collects at the bottom
* A baffle exit (opening) allows the rest of the dirty water collected in the middle to be sent to the second compartment
* The process is repeated in a series of other compartments
* The treated water can be collected in a reservoir and reused for washing cars,gardening or flushing.The water can even be resold,but is not potable