KALMUNAI, Sri Lanka, (AFP) - A Canadian soldier climbs a tank and opens the top; another kick-starts a pump that sends in precious freshly desalinated water.

They are part of a Canadian army Disaster Response Team (DART) operating a water purification plant that has become a lifeline for 80,000 survivors of December’s devastating tsunami disaster.

"We pump fresh but impure water out of the nearby lagoon... purify it in our two machines here and store it in eight rubber tanks to be distributed to the people," said Master Corporal Bob Levesqua, who heads the water unit.

The two Canadian-made reverse osmosis purification units produce 5,000 litres (1,300 gallons) of safe drinking water per hour and each rubber tank stores 11,000 litres.

The Canadian army has set up three such units on the island’s east coast.

"Dozens of tankers and vehicles take water from here each day. It is virtually a round-the-clock operation," said Levesqua as locals queued up with vessels to collect water.

A board nearby indicates Levesqua’s team had supplied one million litres of water by Wednesday.

"In the next 10 days we will hit the two-million-litre mark," he told AFP.

Producing clean drinking water is a critical part of the Canadian contingent’s relief operation in tsunami-battered Sri Lanka.

The 200-member contingent has been based in eastern Sri Lanka since the December 26 tsunamis that killed nearly 31,000 people and initially left a million homeless.

The east coast of the island was one of the areas worst affected by the giant waves that struck shores across the Indian Ocean, leaving more than 290,00 people dead.

"The water produced by these teams is distributed to around 80,000 tsunami survivors every day," said Major Steve Hewitt who heads the Canadian Disaster Response Team.

Their work had helped keep the region disease-free in the aftermath of the tsunamis, he said.

"When we arrived there was no assurance of good water," he said.

"Most of the wells, which were the prime source of drinking water to thousands in the villages, had turned saline after the waves hit. Our teams started producing pure water which is now used by the people."

In the first weeks after the tsunamis it was difficult to bring in supplies of drinking water because of the damage to road and rail networks.

The Canadians based here also have a separate medical team that runs mobile clinics to treat survivors suffering from post-tsunami trauma.

"A lot of people, especially children, are complaining of nightmares, lack of sleep and fear that another tsunami will attack," said captain Virginia Thomson, a medical team leader.

Many have tsunami flashbacks and report feeling angry or lacking in appetite, she said.

The Canadians have treated about 5,000 patients, with many reporting emotional and mental traumas apart from physical injuries.

"It is just over a month after the disaster... we are going to see more of such cases in the months to come," Thomson said.

"It is very essential that these are treated sensitively in the long run."

Thomson and her team have translated trauma-counselling booklets from English into local Sinhala and Tamil languages.

"We will be gone from here after a while, but we want the people to be looked after," she said.