In an effort to achieve sustainable and eco-friendly desalination solutions, the National Institute of Ocean Technology (NIOT) is exploring technologies that are both low-cost and low-maintenance, and suitable for various geographical terrains.
Low temperature thermal desalination (LTTD) is a prominent technology, considered an alternative to the largely-used seawater reverse osmosis membrane technology.
An offshore plant
There are plans to launch an offshore plant, either on a ship or a barge based near Chennai, as LTTD technology is not advanced enough to be installed in the coastal region, NIOT officials said. NIOT has set up three LTTD plants in the Lakshadweep islands.
In this technology, the temperature difference is used to produce potable water. Surface sea water is evaporated at low pressure and the vapour is condensed with cold sea water to obtain freshwater.
M.A. Atmanand, director, NIOT, said the LTTD-based desalination plant, with a capacity to generate 2-3 lakh litres of freshwater daily, was operated at the north Chennai thermal power plant, five years ago. The demonstration facility used waste heat or the coolant water discharge for producing freshwater.
It is an eco-friendly technology, as it does not require pre-treatment or post-treatment of seawater, and has only a few units, compared to reverse osmosis. However, it also has limitations, as freshwater recovery is only 10% now, compared to the reverse osmosis (RO) technology, that has upto 60% recovery, he said.
‘Site-specific conditions’
M.V. Ramanamurthy, director, National Centre for Coastal Research, said: “A solar-based desalination plant in Kanniyakumari was recently set up with IIT-Madras. We are exploring economically-viable technologies suitable for coastal areas, especially using solar energy. Each technology has its merits and de-merits, and has to be implemented according to site-specific conditions.”
NIOT is setting up six more LTTD-based plants in Lakshadweep, as it is more suited for the island. Moreover, a similar plant of 2-mld capacity has also been proposed at the Thoothukudi power plant to minimise environmental pollution.
On the LTTD technology, he said power consumption was slightly more than the RO technology.
But with advancement in technology, such issues could be overcome in time, he said, adding that it is more eco-friendly and did not discharge brine of high salinity.
