THE CHIEF MINISTER
followed that up by announcing allocation of Rs 2200 crore for setting two more plants of 150 MLD and 200 MLD capacities. So, finally, the state has woken to the needs of a city suffering from want of a perennial source for water.
Tucked away at the outskirts of the city, at Nemmeli, the 100 million litres per day (MLD) desalination plant boasts of being the first and largest sea water RO desalination plant on Design, Build and Operate (DBO) mode. Built over an area of 81,000 sq m, at a cost of Rs 908 crore, VA Tech Wabag, in consortium with IDE Technologies, is in charge of the operation and maintenance for seven years.
Established in 1996, VA Tech has become a total water solution company. Rajiv D Mittal, its CEO, heads the 800 strong workforce that has executed over 100 projects. “Indian desalination market is expected to grow at a CAGR of 30 per cent over 2013-18,” said Mittal. Tech Archival Research has forecast growth of 5350 MLD by 2018. The long coastline offers huge opportunity.
From sea to tap
In the plant at Nemmeli, sea water is taken in from a distance of 1.1 km from the shore through an intake pipe 12 meter below the sea surface. “We were cautious in placing the pipe as any alteration due to the tides will affect water flow,” said M S Srinivasan, Senior Vice President. The pipes had also been tested for stability when the Nilam cyclone struck and the pipes had stayed in tact.
The water from sea is collected in a sedimentation tank, from which all visible particles are removed. Then it is sent through series of filtration processes in which all suspended particles are removed.
At the reverse osmosis plant, the membranes repel salt and de-mineralised water oozes out. Later this water is sent though limestone filters and carbon-di-oxide absorbers and tested for potablility, before being connected to the Metrowater pipelines. After all treatments and processes, dissolved solids at the rate of 40,000 ppm are reduced to 300 ppm, making it potable. About 40 per cent of the intake water is converted to drinking water and the rest let out to the sea 642 metres from the shore.
Technology reduced plant size
The compact size and state-of-the-art treatment facilities occupy only 20 acres. “The energy recovery system and variable frequency systems ensure power optimisation. The full plant is fully automated by a distributed control system and requires only 20 persons per shift to monitor all parameters,” said Mittal.
The plant requires 3.6 units of power to produce 1 cubic metre of water and uses 400 million units of power per day.
Several developmental projects are hindered by problems of land acquisition. Srinivasan narrated an interesting story behind this 81,000 sq m of land. “All lands along the coast were owned by a single man called Alavandar, to whom it was handed over by the British. In his will, he had mentioned that no land under his control could be sold but only leased and the proceeds from the lease were to be used only for charity.” Thus Chennai Metrowater had leased the land for 30 years from the Alavandar trust.
Wabag and desalination
Targeting developing countries in Latin America and Asia, Wabag is also developing a strong base in Russia.
The proposal for the 150MLD desalination plant is planned right next to this plant and another of 200 MLD capacity which can be further expanded to 400 MLD has been decided at Pattipulam.
As we toured around the plant in the hot sun and neared the end, we gulped the RO treated desalinated water. It did quench our thirst and tasted as good as normal water.