Ministry updates India's low-temperature desalination plans

India's Ministry of Earth Sciences (MES) released an update on 29 August 2011 about its program for development of Low Temperature Thermal Desalination (LTTD).

To date, four LTTD plants have been successfully commissioned in the country, one each in the Lakshadweep island communities of Kavaratti, Minicoy and Agatti, and one at the Northern Chennai Thermal Power Station, Chennai.

The National Institute of Ocean Technology - an autonomous body within the MES - started work on LTTD applications in 2004 with a laboratory-scale model with a capacity of 5  m³/d.

Work then moved on to a 100 m³/d capacity land-based plant in Kavaratti in 2005. Two years later, a 1000 m³/d capacity barge-mounted experimental/pilot plant was set up off the Chennai coast.

The MES now says it is working to set up six more plants, funded by the Lakshadweep administration, in each of its islands: Amini, Chetlet, Kadamath, Kalpeni, Kiltan and Andrott.

The ministry says that LTTD is a process by which warm surface seawater is flash- evaporated at low pressure and the vapour condensed with cold deep seawater. The technology does not require any chemical pre- and post-treatment of seawater, and thus the pollution problems are minimal and suitable for island territories.

Since no effluent treatment is required, it gives less operational maintenance problems compared with other desalination processes. The LTTD technology is completely indigenous, robust and environment friendly.

The cost per liter of desalination would depend on the technology used and cost of electricity, which varies from place to place. According to estimates made recently by an independent agency for LTTD technology, the operational cost per litre of bottled quality fresh water currently works out at 19 paise (US$ 4/m³).

Since the LTTD technology is not matured for coastal regions of mainland India, except in thermal power plants located very near to the coast, so far no attempt has been made to introduce such plants in Andhra Pradesh, says the MES. The coastal areas would require offshore plants with larger capacity, which are yet to develop.

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