In a bid to ease its water woes, Chennai may just be on its way to becoming the first in India to set up an off-shore desalination plant. To facilitate the same, a deep-sea site that is 40 km from the Ennore coast has been finalised.
Under the ₹ 10,000-crore Deep Sea Mission to be launched in March 2018, a detailed project report (DPR) on the off-shore desalination project has already been submitted by the National Institute of Ocean Technology (NIOT) for the consideration of the Union Government.
A significant difference between this off-shore desalination plant as against the existing desalination plants in Nemmeli and Minjur is that it will move away from the traditional reverse osmosis (RO) technology to separate fresh water from seawater.
Instead, the offshore plant will use the indigenously developed, environment-friendly technology of low-temperature thermal desalination (LTTD), which harnesses the temperature difference available between surface water and deep seawater, reported the New Indian Express.
Under this technology, the warmer surface seawater is made to evaporate at low pressures. The vapour obtained is then condensed using the colder deep sea water, thereby resulting in safe and potable drinking water.
This technology is the answer to the pollution caused by the existing RO-based plants, which release chemicals and highly concentrated brine into the ocean during desalination. This brine later settles on the surface of the water body and disconnects oxygen causing oxygen deficiency in the ocean floor area, which threatens marine life.
Ocean scientists are meticulously researching if the proposed desalination plant could be powered by electricity using ocean thermal energy conversion (OTEC), then the existing practice of using diesel.
If the use of OTEC for the plant becomes a reality, it could bring down operation costs to a great extent.
Speaking to the publication, M Rajeevan Nair, secretary, Ministry of Earth Sciences revealed that the according to the design submitted under the DPR by NIOT, the plant will have a 10-MLD (million litres per day) capacity and may cost up to ₹ 2,000 crores.
He also expressed that the plant is a massive challenge for ocean engineers because of its sophisticated design. Considering the city is characterised by shallow waters, the project will require them to travel about 40 km into the sea for the depth necessary to take in deep sea cold water.
Dr Satheesh C Shenoi, the Director of NIOT, expressed that the off-shore desalination plant by itself is a first of its kind.
“In the DPR submitted, the use of OTEC to power the plant is not included. But, the NIOT is optimising the technology at a laboratory scale for which an OTEC test lab has been commissioned on the NIOT campus on Monday. Next, we will be setting up India’s first OTEC powered desalination plant at Kavaratti in Lakshadweep Islands for which tendering process is on. Then, we will bring the best of technology to the proposed Chennai plant that will go a long way in solving the water crisis in the city,” he told the publication.