Work is in full swing to construct the city’s fourth desalination plant at Perur along East Coast Road (ECR), just a few kilometres away from the existing plant at Nemmeli.
Even as the third desalination plant, with a capacity to treat 150 million litres of seawater a day (mld) at Nemmeli, is all set to be inaugurated in a few weeks, civil work has been started to build the facility at Perur, which may be the largest desalination plant in Southeast Asia.
The seawater reverse osmosis (RO) desalination plant will have two 200-mld units, having the capacity to treat 400 mld in total. This will ensure that the plant produces 200 mld of treated water at any given point of time, said officials of the Chennai Metropolitan Water Supply and Sewerage Board or Metrowater.
Excavation work to build various units, such as intake sump and treated water storage system, has started. Moreover, work to build a compound wall and provide separate access roads to two burial grounds on the site is also in progress.
The new plant will have various components such as lamellar clarifier units, dissolved air flotation to remove lighter materials, such as algae and oil, and gravity dual media filters (GDMF) to separate total suspended solids in the seawater. The pre-treatment process, particularly GDMF units, added in the Perur plant will be more efficient in removing the finer particle impurities from raw water. The pre-filtration units have been fine tuned for this purpose.
With the plant expected to be an energy guzzler, there are plans to install energy recovery devices and booster pumps to save on power.
The ₹4,276-crore plant will also incorporate the recommendations of the National Institute of Ocean Technology (NIOT) regarding environmental concerns, including an erosion management plan. Diffusers have been incorporated in the brine (reject water) outfall system for marine life protection as recommended by NIOT. They will slow the release of brine and disperse the high salt concentration over a wider space so as to avoid impacting the local ecosystem negatively, officials said.
Ultrafiltration and RO membranes will bring down the total dissolved solids level from 35,000-40,000 parts per million (ppm) to the drinking water standard of below 500 ppm. Units will be added for post-mineralisation of treated water before supply.
While the 150-mld plant at Nemmeli will produce treated water at a cost of ₹28 per kilolitre, the production cost of the 400-mld one at Perur will work out to around ₹27.65 per kilolitre.
The work is being executed as a joint venture of VA Tech WABAG and Metito Overseas Limited, and is funded by the Japan International Cooperation Agency. The treated water will be supplied through a 59-km pipeline to a new pumping facility at Porur, from where it will be distributed to other areas. Nearly 22.62 lakh people, including those in the Greater Chennai and the Tambaram Corporations, will benefit from this plant. The project is likely to be completed by December 2026.
