Posted on January 13, 2022
Officials say about 32% of the work has been completed on the project
Nearly 32% of the work on the third desalination plant at Nemmeli along the East Coast Road with a capacity to treat 150 million litres a day (mld) of seawater has been completed. Work is in progress to simultaneously lay a pipeline to supply treated water to various south Chennai and suburban areas, catering to 9 lakh population. The plant is expected to be ready by April next year.
The ₹1,259.38-crore project is being implemented under the AMRUT scheme and with financial assistance from KfW (German Development Bank) at a 10.6-acre site in the same site of 100 mld desalination plant. It would occupy less space than the existing plant.
Work is on to build various integral components of the plant, including intake sump, dissolved air flotation and ultra filter and reverse osmosis units. Officials said the challenging work to lay pipeline to draw seawater and outfall pipeline in the sea bed may be carried out between March and May. The size of the intake pipeline would be about 2,250 mm in diameter, which may be one of the first to be used for a desalination plant in the country.
The dredging would be confined only to the pipeline corridor to reduce destruction of the marine ecology and the dredged material would be used to refill after laying the pipeline. The intake head has been designed to have low velocity and prevent marine organisms getting trapped in it.
The pipeline to be laid to release brine into the sea had been designed in such a way as to enhance faster dilution of brine with seawater and without affecting the marine organisms, the officials said.
Another challenge found during the operation of the plant was suspended solids in seawater that led to higher chemical consumption and increased maintenance cost.
To ensure smooth functioning of the plant, the design of the new facility would focus on pre-treatment process to extend the life of the reverse osmosis (RO) membranes. The dissolved air flotation unit, a water treatment process to remove suspended solids, would be added. In this process, suspended matter floats to the surface of the water.
The production cost of the treated water in the new plant is estimated to be ₹28 per kilo litre. About 49% of the work to lay the 47.78-km pipeline to supply water to south Chennai and Tambaram Corporation has been completed so far.
On the fourth desalination plant proposed with 400 mld capacity, officials said the tenders had been called for establishing the plant at Perur and the bids would be opened by this month-end.