CHENNAI: Conservationists who had taken up restoration of the Sembakkam lake have turned to a natural treatment system for wastewater entering the lake, as unabated sewage continues to flow in from neighbouring areas.
The lake presently has an estimated eight million litres per day (MLD) of sewage flowing into it from Tambaram, Pallavaram, and Chitlapakkam areas, which do not have an underground drainage (UGD) system. In the absence of a sewer network, it becomes impossible to plug this quantum of sewage or divert it to other channels which may cause pollution. Additionally, the lake is also used for garbage disposal by people around the lake.
“In an attempt to provide a holistic restoration solution, we have come up with a nature-based treatment system,” said M Nisha Priya of Nature Conservancy Centre, which has taken up the restoration along with Care Earth Trust aided by experts from IIT-Madras and FINISH consortia. The approach adopts a hybrid methodology that uses a combination of mechanised and constructed wetland treatment systems. The treatment is based on phytoremediation technology where the plants, their root-zone and the soil populated with microbes degrade the pollutants and clean up the wastewater.
“It uses nature-based solutions, locally available raw materials, requires no skilled labour and no chemical addition. The capital and operational costs are about 30 per cent and 70 per cent lower than conventional systems, respectively,” Nisha said.
The project, which was taken up in 2018, suffered setbacks due to the sewage challenge, and overshot its initial estimated cost. A year ago, the conservationists spent `12 lakh on removing water hyacinth alone. As of now, silt removal, strengthening and creation of new embankments and creation of pathways have been completed. The rest of the project is to be done in around four months.
While filtration process may have helped expedite restoration, residents believe a UGD system is the only solution. “Work on the Tambaram UGD scheme began in 2009 and even now, works have not been completed. This is the only way to keep sewage from flowing into waterbodies,” said P Viswanathan, a resident.