The Tamil Nadu Public Works Department (PWD) Seniors Engineers’ Association has come up with a proposal to increase storage capacity of the existing tanks in Chennai metropolitan area that could be a cost-effective alternative to setting up desalination plants in future.
The association, which is a forum of retired engineers, has prepared a list of 507 tanks in 322 villages in the neighbouring districts to augment surface water resources and supply drinking water to Chennai.
The chosen tanks were from six taluks of Tambaram, Tiruvallur, Ponneri, Uthukottai, Sriperumbudur and Chengalpattu enlisted in the Chennai Metropolitan (Groundwater Regulation) Act 1987. These waterbodies have been shortlisted keeping in mind the feasibility of transferring the water through pipelines to the existing network.
A. Veerappan, former chief engineer and State secretary of the association, said an additional storage of nearly 3.75 tmcft. could be created by desilting tanks, the cost of which would work out to ₹500 crore, including conveyance through lorries. This was way cheaper than constructing new facilities such as the ₹5,000-crore desalination plant in Perur along the East Coast Road with a capacity to treat 400 million litres of water a day (mld).
Listing the demerits of desalination plants in the long run, he said brine waste from the plant could affect the ecosystem even far away from the facilities apart from the high energy cost. Steps to reduce environmental impact would mean additional cost. The reverse osmosis membranes, which contribute 7% to 10% of the desalination project cost, need to be replaced every seven years.
Even experts, including S. Janakarajan, former Professor of the Madras Institute of Development Studies, had opposed the move to build desalination plants, Mr. Veerappan said.
K. Nagarajan, former special chief engineer, WRD, who made the study, said, according to Desalination Association of India, the production cost of desalinated water would be 10 paise a litre while the cost of treating surface water would work out to one paisa per litre.
A viable option
Desilting and improving the capacity of the tanks would help conserve surplus floodwater draining into sea and create economically viable solution for city’s rising water needs. An additional storage can be created by deepening major reservoirs such as Chembarambakkam and Red Hills by a depth of one metre.
Chennai would get a minimum of 6.75 tmcft of additional resources with a project cost of ₹900 crore and the cost could be reduced by selling excavated soil. This would translate to nearly 524 mld to the city, Mr. Nagarajan added.
Enhanced storage capacity would replenish water table in the surrounding areas. The entire project, including laying pipelines, could be implemented at a cost of ₹1,000 crore, according to the association that plans to submit a proposal to the State government in this regard shortly.
The Water Resources Department recently submitted a proposal to the government to augment water supply under Chennai city partnership programme.
COMMents
SHARE