Pioneering desalination to stave off water crisis

The State went for the technology as early as the 1990s

Updated - February 25, 2022 02:40 am IST

Published - February 24, 2022 03:37 pm IST

 Metrowater established the desalination plant at Nemmeli for water supply to south Chennai.

 Metrowater established the desalination plant at Nemmeli for water supply to south Chennai.

Tamil Nadu has been at the forefront of drinking water supply management conceiving technology-aided solutions to stave off a crisis in coastal districts. It pioneered desalination as early as the 1990s. The arid Ramanathapuram district and the expanding Chennai city that grapple with a severe water scarcity were the first to get desalination plants.

The Tamil Nadu Water Supply and Drainage Board (TWAD) had initially set up nearly 15 small-scale reverse osmosis desalination plants in Ramanathapuram, which are over 30 years old. Subsequently, during the government of M. Karunanidhi in 1999, one of the first major seawater desalination plants was commissioned at Narippaiyur in Ramanathapuram with a capacity to treat 3.80 million litres a day (mld). The facility was maintained by BHEL, Ranipet.

While at that point in time desalination technology was a saviour, the State has re-examined its strategy, over the years, drawing from its experience of high operation and maintenance cost of the plants. Recently the plants in Ramanathapuram were closed.

TWAD officials acknowledged the plants helped in removing the total dissolved solids in the water. The agency is now moving towards region-specific water management solutions.

Pointing out the production cost of desalinated water was ₹100 per kilolitre in the old facilities, a senior TWAD official said, “Our focus is now on Combined Water Supply Schemes with the Cauvery river source to supply water on a long-term basis at a cost of ₹8.50 per kilolitre. Residents of Ramanathapuram and Sivagangai districts receive water supply under the scheme. A proposal is under consideration for providing an additional 55 litres per capita per dayof water.”

At the same time, proposals for establishing 60-mld-capacity desalination plants at Kuthiraimozhi, Ramanathapuram and Koonimedu near Marakkanam are under consideration. Feasibility of alternative sources is also being considered.

As for Chennai, it is home to the largest seawater desalination plants in Minjur and Nemmeli with a combined capacity to treat 210 mld. Acclaimed to be South Asia’s first largest SWRO desalination plant, the 100-mld plant at Kattupalli, Minjur, has been supplying water to the 10 lakh residents in the city since July 2010.

Spread over 60 acres, the Minjur plant was established on a design, build, own, operate and transfer basis by Chennai Water Desalination Limited, a special purpose vehicle of IVRCL Infrastructures and Project Ltd, Chennai, and Befesa, Spain. Metrowater is purchasing water at a rate of ₹55 per kilolitre from the Minjur plant under a bulk purchase agreement.

While the treated water from the Minjur plant is being consumed by north Chennai residents, Metrowater established another desalination plant at Nemmeli, along East Coast Road, in 2013 for southern parts of Chennai, which teeters between floods and droughts.

The capacity of the plant, operated and maintained by VA Tech Wabag, was upgraded to 110 mld.

Officials note that when massive droughts hit the city in 2017 and 2019, the two desalination plants helped to manage the crisis considerably. Growing demands for freshwater in the metropolis and industrial needs have prompted the government to go for two more plants at Nemmeli and Perur.

Another milestone will be achieved after the construction of the 150-mld SWRO desalination plant on a 10.6-acre land adjacent to the Nemmeli facility. This will be the first plant in India of that capacity built in a smaller area. The ₹1,259.38-crore project is being funded by AMRUT and KfW and would benefit nine lakh residents of south Chennai and merged areas by April next year.

Officials noted that the challenges found in other facilities like tackling suspended solids, which led to higher chemical consumption and an increase in maintenance cost, would be addressed in the new facility. The production cost in the new plant will work out to ₹28 per kilolitre.

The dredging would be carried out only in the pipeline corridor to minimise destruction of marine ecology. Other environmental concerns, such as discharge of brine and entrapment of marine organisms, would also be addressed, officials said.

Chennai’s coastline will soon have a fourth desalination plant at Perur with the largest capacity of 400 mld among those in the city. In a few years, the plant is expected to supply treated water to nearly 23 lakh residents of southern suburbs, including Tambaram and Pallavaram.

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