The long process of laying a pipeline to draw water from the sea to be treated at the upcoming desalination plant at Nemmeli, about 35 km south of Chennai, was completed on Monday. With a significant portion of the project finished, the plant is expected to be commissioned by September.
The work is significant as a 1,050 metre-long pipeline was sunk at a depth of nearly 14 metres on the sea side. It took three days for the mammoth operation to be completed.
Rough sea conditions had delayed the work for almost a year and pushed the deadline further to September. Around 85 per cent of the work to construct the plant with a capacity to treat 100 million litres a day (mld) has been completed so far.
Sources in VA Tech Wabag, which has been entrusted with the construction of the plant, said the giant 1,600 mm diameter pipeline was towed into the sea, aligned using a digital global positioning system and sunk into the sea bed. A variety of marine and onshore equipment were used for the operation.
Nearly 265 mld of sea water will be drawn through this pipeline.
A similar process will be adopted for laying a 750 metre and 1,200 mm dia pipeline to discharge waste water from the plant. The work will begin by the end of this month.
Unlike the 100 mld desalination plant in Minjur, which supplies drinking water to the northern parts of the city, the one in Nemmeli will be owned by Chennai Metrowater.
Sources in Metrowater said that disc filters and ultra filtration membranes, which would remove sediment and finer sand particles from the raw water, are being imported from Israel. The sea water would then be conveyed to the reverse osmosis membranes that would remove salinity. The consignment will reach the city in May.
Similarly, additional reverse osmosis membranes are being imported from Japan. The Rs. 533.38 crore project will supply water to the southern parts of the city, including those recently merged under the Chennai Corporation.
The production cost of treated water at the Nemmeli plant will work out to Rs. 30 per kilolitre. Metrowater is purchasing water from the Minjur plant for Rs.48.66 per kl according to the bulk water purchase agreement with Chennai Water Desalination Limited, a special purpose vehicle promoted by IVRCL.
The tariff at Minjur is high as the company that has set up the plant also has to add in capital and operations costs. The plant at Nemmeli is being constructed with a grant obtained from the Central government, sources said.
Metrowater is also simultaneously carrying out work to lay a 66 km-long pipeline from the plant. Treated water will be transmitted to underground sumps being constructed in localities such as Akkarai, Kelambakkam and Velachery. About 80 per cent of the work has been completed so far.
At present, Metrowater supplies about 830 million litres a day to the city through pipelines and tankers.
