Residents of Chitlapakkam want the sewage entering the Sembakkam lake to be stopped and encroachments removed as part of the comprehensive restoration project. They raised concerns over certain aspects of the ongoing restoration work. Spread over 100 acres, the lake now has a flood regulator to regulate the discharge of excess water and a better storage capacity.
The project is being jointly implemented by The Nature Conservancy India (TNC), the Care Earth Trust and IIT-Madras with the approval of the Water Resources Department (WRD).
According to Srisarvamangala Nagar residents, the nature-based sewage purification system may not be effective unless the sewage flow into the lake from the northern side was stopped. They demanded more transparency on the project implementation.
M. Ravi, secretary, Srisarvamangala Nagar Residents’ Association, said about 200 encroachments in Thiru.Vi.Ka.Nagar need to be cleared. Moreover, the Water Resources Department must survey the lake area and demarcate the boundary. The ongoing project had helped recharge water table and reduce dependence on tankers.
The association had represented to the government seeking underground drainage network. They alleged that landscaping was planned in catchment areas and it might obstruct free flow of water.
Biological diversity
Jayshree Vencatesan, managing trustee, Care Earth Trust, said several meetings had been organised on the progress of the project and the site engineer had been deployed to clarify residents’ doubts. A wholistic approach to lake restoration had been adopted with design from IIT Madras. Location-specific landscaping had been done in the lake’s periphery with native species to enhance biological diversity.
On the nature-based sewage purification system, K.V. Emmanuel, consultant, TNC, said it was chosen to overcome issues, including high maintenance and operational cost and need for sludge treatment, related to conventional treatment systems. Moreover, it occupies less space.
The solution has a pre-treatment, including screens, to remove large objects in sewage and an aerated lagoon. Wastewater would be fed into reed beds that would remove pollutants like organics and nutrients. “There is no need for disinfection in this system, which would reduce BOD level from 200 ppm to 20 ppm. With its continued functioning, groundwater contamination would be minimised,” Mr. Emmanuel said.
Officials said the project was being monitored and the NGOs had been instructed to reduce the area of the purification system. Efforts are being made to clear encroachments in the lake area. Work would be completed in a few months, they added.
