As part of its efforts to reduce stress on freshwater sources, Chennai Metrowater has completed about 60% of the work to construct two tertiary treatment plants in the city. Besides recycling waste water, the pilot projects would make a significant contribution towards groundwater recharge.
The tertiary treatment plants using ultrafiltration (TTUF) are coming up at Perungudi and Nesapakkam with a capacity to treat 10 million litres a day (mld). Treated wastewater would be discharged into Porur and Perungudi lakes.
Officials of the Metrowater said the pilot projects would help recharge the groundwater table in localities in a radius of minimum five km and also promote indirect use of recycled water.
Water drawn again from the lakes would undergo another round of treatment before being blended with the existing drinking water supply system.
The water agency is also in the process of creating infrastructure to convey treated water to the lakes through pipelines, running to a total length of 24 km. The treated water would be discharged into chambers near the waterbodies and then into the lakes.
“This will help in dissipating the velocity of the flow and reduce turbidity during release of water into the lakes,” said an official. These tertiary plants developed based on the designs provided by the IIT Madras would help establish a sustainable alternative source of water supply for the city. Chennai, now mostly depends on freshwater lakes for its drinking needs.
The team from IIT Madras and Metrowater would study the groundwater table and quality near the lakes to assess the impact of the project.
These facilities have three major processes of disinfection - pre-chlorination, ozonation and ultraviolet filtration, for disinfection. However, the work is proving to be a challenge, owing to the ongoing pandemic and lockdown restrictions.
“We face constraints in conveying equipment and materials for the plants from different parts of the country and also imported materials like ultrafiltration membranes,” the official added. Moreover, various other processes, including testing and validating the pilot projects, are involved before commissioning the plants. The Rs.18-crore project is set to be completed by January next year.
Once these pilot projects are in place, the capacity of tertiary treatment of sewage would be scaled up. The water agency has already submitted a detailed project report for the reuse of 260 mld of reclaimed water to the World Bank for funding.
