The upgrading of Wanganui's wastewater treatment plant could be the prime opportunity to get major industries on side with a comprehensive pre-treatment process.

That is the view of sources within the city's wet industries who have told the Chronicle such a move is vital to ensure the plant's problems are not repeated.

The plant in Airport Rd was commissioned in 2007 but almost from the beginning had problems. Now it has failed to the point that Wanganui District Council is facing a $24million upgrade. But one industry insider said the sensible solution was to approach the major players to get pre-treatment ponds in place with a dissolved air flotation (DAF) system.

In a DAF system air is pumped into the wastewater under pressure and then released at atmospheric pressure. The air forms bubbles which stick to the solids causing them to float so they can be skimmed off and not discharged into the city's system.

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"The council is going to say that they will handle everything because they have consultants standing in front of them that deflect their responsibility," the source said.

"I'd suggest they are the only major council taking totally untreated waste from wet industries and probably are the only one that isn't rating them accordingly," he said.

The source said Talleys (which owns AFFCO Imlay) and other major players should be approached to put in a joint venture pond and DAF plant "even if the council partially funded it and was then paid back through recoverables".

"If that was done, a cleaned-up version of the current ponds would probably suffice."

One council which has successfully gone down that path is Matamata-Piako with a scheme designed to improve the Morrinsville treatment system. That council and two major wet industries - Fonterra and Greenlea Premier Meats - joined forces to create a $19 million pre-treatment plant with the industries funding 40 per cent of it.

Don McLeod, Matamata-Piako DC chief executive, told the Chronicle that the funding split was not difficult to formulate.

"It was based on the difference between what we would have had to do without their discharge versus what we had to do with their discharge," Mr McLeod said.

The pre-treatment option was adopted because Morrinsville's system was being upgraded. Before the upgrade, industry waste had been directed into the town system.

"No system can cater for open-ended discharge levels, either in volume or in strength. Treatment plants are complex biological systems that can be destroyed in a couple of days with inappropriate discharge," Mr Mcleod said.

Wanganui Mayor Annette Main said the upgrade for Wanganui's plant was "a robust and well-proven process".

"The council is confident that the developed design is the best option to deal with our domestic and trade waste," she said.