In a bustling neighbourhood of Andheri (West), a housing society’s effort to recycle black water is a lesson in self-sufficiency. Evershine Cosmic Co-operative Housing Society, comprising 186 flats, has successfully handled sewage from its homes since 2016. The society has not only reduced its environmental impact but has also managed to use the treated water effectively. This eco-conscious approach has helped the housing society meet its diverse water needs.
Not many housing societies in Mumbai operate their own sewage treatment plants (STP) mainly because this involves demanding work and overseeing every step of the process. Besides, with the Brihanmumbai Municipal Corporation (BMC) offering water at relatively low costs, most societies lack the incentive to take up such initiatives. Yet, Evershine Cosmic chose to lead by example.
How it started
“We were young and many of us were progressive thinkers; we decided to take up the sewage treatment ourselves to generate water and contribute our bit to the environment. We were enthusiastic about being responsible citizens,” recalls Madhu Vannier, secretary of the society, about their decision to handle the sewage treatment of their apartment.
Madhu explains that their builder had set up the plant at the construction stage, and when the apartment association took over from him, it was optional for the residents to either continue with it or connect with the BMC’s central sewer lines.
The process of wastewater treatment
Firstly, the sewage from the entire building is directed into a sewage tank, where non-biodegradable waste — such as plastic items, diapers, and condoms — that residents mistakenly discard into toilets is filtered out. Following the initial filtration, the separated waste material is removed and disposed of through the BMC, while the recycled water is collected in a separate tank for non-potable use.
The housing society employs the Moving Bed Biofilm Reactor (MBBR), a wastewater treatment system that utilises floating biofilm carriers to promote bacterial growth, breaking down pollutants. This process enables the extraction of 1.25 lakh litres of water from black water, converting it into clear water.
The society uses this treated water for non-potable purposes, including watering the garden areas, washing various community spaces, toilet flushing, and cleaning its six levels of parking, basements, and common passages, which are washed every fortnight. Residents confirm that the STP does not emit any unpleasant odours.
At Evershine Cosmic, the STP is installed at the far end of the parking lot, with most residents unaware of its presence. While a few neighbouring housing societies have installed this system, they want to discontinue its use and refused to discuss this with Citizen Matters.
The economics of the STP
- Apart from the treated water, the housing society relies on tanker water to meet its daily requirements.
- They procure three additional tankers, each carrying 20,000 litres, spending approximately ₹6,000 per day for 186 occupied flats.
- The monthly expense for tanker water is around ₹2 lakh.
- The initial investment in the STP was ₹6 lakh.
- Annual maintenance costs for the STP amount to ₹8 lakh.
Additional expenses
- The society spends an additional ₹2 lakh on electricity bills to keep the STP pumps running 24/7.
- Regular pipeline replacements also contribute to expenses.
- A standby pump is maintained to prevent excessive strain on the main pump.
“In an apartment, maximum consumption happens in the toilet flush. Had we not recycled the water in the STP, we would have been water deficient by more than 60%, with water costs of an additional ₹2 lakh per month,” Vannier explains.
Regular maintenance is key
The building has completely outsourced the maintenance and upkeep of the STP to a specialised wastewater treatment agency, which oversees every aspect of its operation, down to the smallest details. Whenever an issue arises, the society manager simply contacts the agency, which promptly addresses the problem. In addition to troubleshooting, the agency is responsible for the routine maintenance of the facility, for which they receive an annual fee.
Vimlesh Verma, proprietor of A R Envirotec, the firm that manages the STP, says: “A builder of a medium or large housing society is required to establish a sewage treatment facility, which they oversee during the construction phase. Once the builder hands over the building to the society, the responsibility for managing the STP is transferred to them. Our firm provides servicing and maintenance for such facilities, from their initial setup by the builder to their eventual handover.”
Having an STP is not without its challenges. While extracting treated water is useful, there are some disadvantages. “The chemicals used to extract the water from the sewage are so strong that they tend to have a corrosive effect on the tap fittings, which need frequent changes,” informs Vannier.
Moreover, there are no incentives from the government. Earlier, the BMC had promised electricity and property tax rebates for housing societies that treat their sewage. This was subsequently withdrawn.
Read more: 1.94 crore litres of water saved: How one Chennai apartment mastered sewage treatment
BMC policy on domestic sewage treatment
While the Evershine community decided to run the STP of their own volition, what are the rules governing sewage water in buildings?
In Mumbai, housing societies and townships of over 20,000 sq ft of built-up space must treat their sewage waste, as mandated by civic authorities. A builder has to set up an independent STP for every new building. Such housing societies are expected to treat their grey water before releasing it into the BMC network, to be treated before being disposed of in the sea.
Ashok Mengde, chief engineer of the Mumbai Sewage Disposal Project (MSDP), explains that when builders construct buildings, they are responsible for establishing the necessary infrastructure to connect them to the city’s sewer network. “We simply handle only the development of the city’s major sewage projects, while the proposals of the sewage management are handled at the local ward level,’’ he adds.
No strict regulations
While it is mandatory to have an STP on the premises, most buildings tend to ignore this guideline. Most STP setups exist as mere tokenism. Most apartments connect their building’s septic tank directly to the city’s sewer network. “There is no mechanism in place by the BMC to individually check if buildings are flouting the norms or not,” says Stalin Dayanand, founder of Vanashakti, the voluntary organisation that had petitioned the National Green Tribunal (NGT) against Mumbai’s rivers and beaches getting polluted with sewage waste dumping.
As per the BMC’s core responsibility distribution, connecting a housing society to the city’s sewer network is done through the local ward offices. However, Sandeep Salunkhe, executive engineer of the K-W ward, says that the ward office has not yet received proposals from any society to take up sewage treatment.
Vimlesh adds that while the BMC handles the networks, the Maharashtra Pollution Control Board (MPCB) oversees and penalises housing societies for not handling their own sewage treatment. Despite the implementation gaps, Evershine residents have ensured that no wastewater from their society pollutes the environment.
Key learnings for other apartments
- Recycling wastewater through an STP decreases dependency on tanker supply and makes an apartment water-sufficient.
- Outsourcing upkeep of the STP to a specialised agency will cut overall costs and ensure smooth running.
- While the enforcement of STP guidelines by civic authorities is weak, compliance will help avoid penalties in future.
- While maintenance costs are high, the benefits of water savings and environmental impact are huge.
Impressive initiative by the housing society! It’s inspiring to see communities take charge of their sustainability efforts. Small steps like this make a big difference in the long run.