Low Temperature Thermal Desalination: turning deep seawater into drinking water across eight islands

Background

Low Temperature Thermal Desalination (LTTD) is an indigenous technology developed by the National Institute of Ocean Technology (NIOT), an autonomous institute under the Ministry of Earth Sciences, to convert sea water to potable water.
Desalination plants based on LTTD technology are operational across eight islands of Lakshadweep, including Kavaratti, Minicoy, Agatti, Amini, Kalpeni, Kadamat, Chetlat and Kiltan.
The technology converts seawater into potable water by utilising the temperature difference between warm surface water and cold deep-sea water drawn from depths of around 350 to 400 metres. The warm seawater is flash-evaporated under low pressure and the vapour is condensed using cold seawater from the deep ocean.
The process needs no chemical additives and no high-pressure membranes, and it avoids the discharge of concentrated brine, which can affect fragile coral ecosystems.
The first LTTD plant in Lakshadweep was commissioned in Kavaratti in 2005. The first three plants, at Kavaratti, Agati and Minicoy, each had a capacity of 1 Lakh litre of potable water per day.
Six more plants, at Amini, Androth, Chetlet, Kadmat, Kalpeni and Kiltan, were taken up with a capacity of 1.5 lakhs litres/day, at a total cost of Rs. 187.75 cr.
The technology suits these islands because the temperature difference of about 15 degrees Celsius that it needs between sea surface water and deep-sea water is found in the vicinity of Lakshadweep coasts, where groundwater is limited and salinity intrusion is a standing problem.