MOBILE PLANT: The experimental floating desalination plant, constructed by the National Institute of Ocean Technology, 40 km off the Ennore Port. — Photo: S. R. Raghunathan

CHENNAI: The National Institute of Ocean Technology (NIOT) has suggested a tie-up with the Tamil Nadu Electricity Board for setting up shore-based desalination plants using the low temperature thermal desalination (LTTD) method.

According to the NIOT proposal, warm water discharged from thermal power stations in and around Chennai will be used by the Institute to produce fresh water.

The LTTD method essentially makes use of temperature difference of water to produce potable water.

Recently, the institute commissioned an experimental one-MLD (million litres a day) floating barge-mounted desalination plant, situated about 40 km off the Ennore Port (25 km north of Chennai).

It utilised the difference in temperature of deep-sea water and surface seawater.

At present, TNEB authorities are required to bring down the temperature of hot water before letting it into the sea.

Two purposes

"Our proposal will achieve two purposes, tackling thermal pollution and producing fresh water," director of the institute S. Kathiroli told reporters who were taken around the experimental plant on Friday.

Normally, the temperature of warm water from the power plants after use is around 40-42 degree Celsius.

The NIOT would converting this into vapour by passing it through vacuum chambers and eventually condense it using surface seawater. The temperature of seawater at the surface level is in the range of 27 degree Celsius to 29 degree Celsius.

Talks on

"We have held discussions with the Chief Secretary and Energy Secretary of the State Government. Also, we are talking to the NTPC (which with the TNEB plans to establish a power plant in Ennore)," Dr. Kathiroli said, adding that the State Government's response was positive. Around 60 MLD of freshwater could be produced from the discharge of power stations located in and around the city.

Cost factor

On the cost of the production of water from the experimental plant, the director said it was six paise a litre.

If the NIOT's proposal materialised, the cost could come down to three-four paise.

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