CLEANING SEWAGE RIGHT AT THE SOURCE
BMC Plans To Ask New Malls, Hotels, Housing Complexes To Have On-Site Treatment Reactors ………Sharad Vyas | TNN
Mumbai: The Brihanmumbai Municipal Corporation (BMC) is planning to make it mandatory for all large constructions—like malls, hotels and residential complexes—to have on-site treatment of sewage water. The builders would be required to install reactors that treat sewage completely.
The sewage would include waste water from sinks, baths and even toilets. It would be up to the individual construction to decide if they want to dispose of, sell or even reuse the treated water. Such water can generally be reused for flushing, washing cars and gardening, but not drinking. The BMC’s aim is to have less untreated water released into the ground.
Presently, less than twothirds of the city is covered by the BMC’s sewerage network, through which sewage is piped to a plant, where it is treated and flushed into the sea. The remaining constructions—especially new ones in the far-off suburbs—have traditional septic tanks that, according to officials, have no proper system to treat waste.
“We dredge the sewage out of these tanks, but only 20% of it ends up getting treated. Most of it gets discharged into drains, polluting the groundwater,’’ said a senior civic official.
An official in the civic sewerage projects department added, “Only about 60% of the city is part of the BMC’s sewerage network and our goal is to extend this to 80% by 2020. This is being done through the Mumbai Sewerage Disposal Project, which is being funded by the Centre under the Jawaharlal Nehru National Urban Renewal Mission.
However, to take care of the remaining 20%—and that number is likely to rise with population growth—we need to think of better alternatives.’’
The BMC’s plan is to require builders to instal anaerobic baffled reactors, otherwise known as baffled septic tanks, at every large construction.
The technology for this modern version of the conventional septic tank would be imported from Germany.
Last week, a meeting was called by A K Jain, principal secretary (water supply and sanitation), to chalk out the modalities of the new plan. He directed the BMC to recommend to the state some changes in the Development Control Rules (DCR) so the plan can go ahead.
Installing the plant would be made a precondition in the Intimation of Disapproval (IOD), a set of conditions that a builder must fulfil before commencing construction.
Civic officials are tightlipped about the plan because they fear the builders’ lobby will oppose it due to the cost of the reactor. The cost of a plant with a capacity to deal with 14,000 litres per day would be Rs 7.5 lakh. Operating costs would amount to Rs 12,000 a year.
Officials, however, pointed out that the plant would take up an area of four to eight square metres and the space above it could 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.
Incidentally, a 2006 UN report on marine environment had said that Mumbai’s sewage treatment capacity stood at just 15%. Except for a few urban areas, sewage treatment fatalities were inadequate.
Double standards?
Double standards?
While the BMC is planning to force builders to install sewage water treatment facilities at all large projects, the state government has relaxed the rules for builders involved in the cluster redevelopment of dilapidated buildings in the island city.
In a recent notification, the government said that 300-square-foot tenements, which are to be given free to families in dilapidated buildings, don’t need flushes in the toilet. The notification added that a septic tank can be installed where municipal services are likely to be available in four to five years.
In the island city, buildings are all connected to the main sewerage lines and sources have questioned why the government is allowing builders to install the primitive septic tank. TNN
DRAINING AWAY THE DIRT
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 allows the dirty water collected in the middle to be sent to the second compartment. The process is repeated in the next few compartments
Waste water flows from the bottom up, with the result that sludge particles settle against the upstream flow
The treated water can be collected in a reservoir and reused for washing cars, gardening or flushing. The water could even be resold, but can’t be drunk