In a first such experiment to revive a polluted and dying pond in the city, floating wetlands are being used to clean the water body and give aquatic life a chance to flourish again.
On August 14, the National Environmental Engineering Research Institute (NEERI) placed two floating wetlands in the Bujale Talao at Malad as part of their pilot project to clean up the polluted water body.
Floating wetlands are similar to natural wetlands that improve water quality.
Essentially, they are rafts of native plants with their roots suspended in water.
They absorb excess nutrients, trap sediments and block pollutants.
“Instead of using chemical processes to clean up the water, floating wetlands will absorb excess nutrients and naturally produce oxygen which is good for the health of the pond,” said Rakesh Kumar, chief scientist and head, NEERI Mumbai Zonal Centre. “If this experiment is successful, we can replicate it for the Powai lake.”
Apart from creating new land mass for fish and aquatic birds, the floating wetlands can capture carbon and other greenhouse gases and the harvested biomass can be sold as briquettes.
“If this project is successful, we can look at trying this out for other such water bodies to improve their situation,” said Rajiv Jalota, additional municipal commissioner, Brihanmumbai Municipal Corporation (BMC).
Every year, locals use the talao during the Ganesh festival to immerse about 500 colourful idols made of Plaster of Paris, thereby polluting it as the material does not dissolve in water. What remains is the pungent smell of chemicals emanating from the reddish-pink water.
Nestled between residential buildings and a temple, locals are also seen throwing flowers and garbage into the talao.
HT had, in March 2011, written about the state of the pond.
Initially, the institute had 5ft x 5ft PVC pipes and plastic nets to make the rafts. Local plants such as Canna, Scripus and Cyperus in early stages of growth are used.
The roots are suspended in water through plastic nets. shortlisted the Sion talao for the experiment but owing to a dispute in ownership at Sion talao, the NEERI team zeroed in on Bujale talao.
Analysis of water samples from the pond showed low levels of dissolved oxygen (DO) which indicates poor water quality. DO is the amount of oxygen in water that is important for aquatic life to survive.
Six samples showed levels between 0 and 2.9 milligram per litre (mg/lt) while the permissible limit is 5mg/lt.