A recent study commissioned by the Brihanmumbai Municipal Corporation (BMC) has revealed that toxicological indicators at Mumbai’s Deonar dumping ground surpass the Central Pollution Control Board’s permissible limits by up to four times.
This assessment comes at a time when authorities are considering shifting some of the displaced residents from Dharavi—one of the largest slum redevelopment projects underway—to a site within the Deonar landfill area, once it is cleared.
Situated in the eastern suburbs of Mumbai, the Deonar site spans 326 acres and holds the distinction of being India’s oldest and largest dumping ground. The accumulated waste reaches a height of 35 to 40 metres, roughly equating to a 12-storey building, and is estimated to contain about 1.85 crore metric tonnes of legacy waste—that is, long-standing and accumulated garbage.
Multiple investigations have previously flagged concerns about the exposure of nearby communities to toxic substances such as mercury and harmful gases emanating from the landfill.
The BMC-commissioned waste characterisation report, cited by The Indian Express, examined the concentration of key environmental pollutants such as Biochemical Oxygen Demand (BOD), Chemical Oxygen Demand (COD), and Total Dissolved Solids (TDS) in both the waste and the leachate—the contaminated liquid that drains out from the decomposing waste piles at Deonar.
BOD indicates the quantity of oxygen consumed by microorganisms in breaking down organic substances under aerobic conditions. COD, meanwhile, measures the total oxygen required to chemically oxidise organic matter. TDS represents the cumulative measure of both organic and inorganic matter dissolved in water.
All three metrics are vital to understanding the extent of environmental contamination, with elevated readings signifying higher levels of toxicity.
The study recorded an average BOD level of 390 milligrams per litre in the leachate. In comparison, the permissible limit stands at 100 milligrams per litre for land and just 30 milligrams per litre for water, according to The Indian Express.
It further highlighted that the average COD level stood at 1,002 milligrams per litre, whereas the approved threshold is 250 milligrams per litre for water.
Additionally, the TDS levels measured an average of 6,550 milligrams per litre—significantly overshooting the standard limit of 2,100 milligrams per litre.
The report also pointed out that a substantial portion of the waste—between 30% and 50%—comprises “inert waste” like non-biodegradable materials and construction rubble. The Indian Express quoted the study, stating, “This type of waste poses challenges for disposal and management due to its… low degradation rate.”
The assessment was carried out in 2023 by NETEL India Limited in collaboration with NM Consultants and SKW Soil and Surveys, as per the municipal directive. The findings were made public in May, around the same time BMC announced a ₹2,368 crore tender for bioremediation of the site. This process involves using microorganisms or other biological means to clean up contaminated areas, with a targeted completion period of three years.
Kiran Dighavkar, Deputy Municipal Commissioner overseeing Solid Waste Management, informed The Indian Express: “The tender document has mentioned that the methodology of processing the legacy waste, including the leachate, should be ideated by the contractor who will be awarded the contract.”
He further stated, “After the contractor submits the proposal, we [Brihanmumbai Municipal Corporation] will analyse it and, if required, a peer review process will be carried out through a reputed agency. After we approve the methodology, work will start on the ground.”
Dighavkar also mentioned that the final selection of the contractor is expected by June 23.
The redevelopment of Dharavi is being executed through a special purpose vehicle (SPV), in which the Adani Group holds an 80% share, while the Maharashtra government retains the remaining 20%.
This massive overhaul aims not only to rehabilitate slum dwellers but also to redevelop existing structures and improve essential services such as sewage and water infrastructure in the area, which is among the largest slum settlements in the world.
However, until the entire redevelopment is completed—a task projected to span decades—the state has decided to temporarily resettle some of the population in different parts of Mumbai.
Those who have been categorized as “ineligible” for new housing within Dharavi—including residents living on the upper floors of shanties or those who constructed homes post-2000—will be permanently moved to the Deonar dumping ground site, located approximately 12 km away.
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