Chennai's Desalination plant

If everything goes as per schedule, next Pongal the scene will be different for a water-starved Chennai. Hundreds of skilled labourers are meticulously working on the country’s largest seawater desalination plant being set up at a cost of Rs 510 crore on 60 acres of land at Kattupalli village near Minjur, about 35 km north of Chennai.As 75% of the work has been completed, the 100 million litres per day (mld) plant is expected to be operational from January 15, 2009 onwards. All required material has been procured and only marine works like installation of pipelines in the sea, control and instrumentation and electrical works were remaining, sources said.The plant will supply 100 mld of potable water to Chennai everyday. The city’s water requirement is expected to increase by more than double to 2,700 mld in 2031 due to rapid industrialisation and urbanisation. The Chennai metropolitan area’s present water requirement is 1,200 mld against the supply of 985 mld.The projected shortfall is 15 mld by 2011 and 1,085 mld by 2031.The Chennai Metropolitan Water Supply and Sewerage Board (CMWSSB) is currently dependent on ground water and surface water resources to meet the city's demand. The desalination plant would mostly cater to the water requirement of industries including the North Chennai Thermal Power Plant, Ennore Port Trust and the proposed special economic zone to come up in north Chennai. During drought periods, the water would be supplied to the public, CMWSSB officials said.M/s Chennai Water Desalination Limited (CWDL), a special purpose vehicle launched by Hyderabad-based M/s IVRCL Infrastructure and Projects Limited and M/s Befesa Construccion Y Technologia Ambiental, Spain, is executing the project on DBOOT (design, build, own, operate and transfer) basis. As per the bulk water purchase agreement entered into with the CWDL, the CMWSSB would purchase desalinated water at a cost of Rs 48.66 a kilolitre and supply to industries at a rate of Rs 60 per kl, CMWSSB officials added. The agreement will be valid for 25 years.The Tamil Nadu Electricity Board has installed an exclusive 110/22 KV sub-station on the premises to provide uninterrupted power supply to the plant.CWDL Director D Venkatasubramaniam said plants with a capacity of up to 300 mld were quite common in Europe and the Middle East. Reverse osmosis (RO) technology, a trusted and proven method is widely used for desalination plants, though slight variations are made in the method, depending on the salinity of water at respective locations, he added.Explaining the technical aspects of the plant, he said an intake of 237 mld would be drawn from the sea to generate 100 mld of desalinated water (see graphic: From saline to fresh). The sea water would go through a series of preliminary treatment process before it passed through delicate RO membranes.Flavour is added to the final product to give it taste. The ‘product water’ (or desalinated water) would be collected in a 20 million litre underground water tank from where CMWSSB would transfer the water, Venkatasubramaniam said. He said Gujarat and Andhra Pradesh governments had also shown interest in setting up plants in their states. While Gujarat had already floated tenders for setting up a 150 mld plant, Andhra Pradesh was preparing a project report for a 100 mld plant, he added.