On the latest estimate, the plant to provide safe drinking water for the town will not be fully operational until the end of this year at the earliest.

Power and Water officials today told Katherine Times their earlier projections for the finish of the project were "overly optimistic".

They had told residents the plant would be ready by the end of 2019, but most of the construction work has not even started yet although preparation works on the site are done.

It is hoped the plant will be operating to about half its capacity by the middle of this year, officials said today.

The delays have been blamed on the world-first technology needed to remove the PFAS chemicals which were first identified as contaminating the town's drinking water almost four years ago.

PFAS was contained in firefighting foams used in training at the Tindal RAAF Base which continue to leach off the base and into the groundwater which flows directly under Katherine and into the river.

There is no other community the size of Katherine anywhere else in Australia which has been impacted by the PFAS crisis in this way.

Katherine remains the only Australian town to be forced onto water restrictions because of PFAS and the Government says those restrictions will likely stay even when the new plant is producing some of the best quality drinking water anywhere in Australia.

Some of the key pieces of the plant, which is being paid for by Defence, are a series of 21 carbon steel pressure vessels which are being shipped from the US.

It is hoped those big pieces will be delivered in Darwin in March and then be freighted by truck down the Stuart Highway.

A tender which was released for the construction of the building at the existing plant site to house the new equipment has been withdrawn.

Power and Water's senior water and waste water engineer Skefos Tsoukalis today said that tender would be launched again soon.

"We are moving forward about 100 miles an hour," Mr Tsoukalis said.

He said most of the delays are the result of the plant being a world first.

There were also niggling delays with Defence over payment for the plant and its running costs for years into the future.

The plant is designed around three series of tanks, or "trains" as they are called by water engineers.

Each train can remove PFAS from five megalitres of water every day.

The plant is designed to produced 10 megalitres of super clean water for Katherine each day, with the third train of five megalitres, as an added redundancy to allow for maintenance on the other trains.

The plant uses the same ECT2 technology being used in the emergency plant rushed to Katherine in August 2017 which treats just one megalitre of water a day.

There are two similar one megalitre plants already in operation at the Tindal RAAF Base trying to reduce the amount of PFAS still leaking off the base into the aquifer.

It is expected those plants will have to pump away from many years to make an appreciable difference given the size of the acquifer.

Mr Tsoukalis said the 2019 deadline for the new plant was impossible to meet.

More reading: PFAS in Katherine a timeline.

"They were more optimistic timelines than they should have been," he said today.

"We have full confidence that the technology works."

He said the existing plant had to be upscaled to a 10 megalitre town plant and he was not aware of any similar plant of that size providing drinking water anywhere in the world.

He said the re-release of the tender for the construction of the plant building would not cause any "critical delays" for the new plant.

The likelihood that Australia will follow the global rush to reduce the allowable PFAS contaminants in drinking water has also been considered in the design of the new plant.

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