Whanganui's mayor says he wants discussion around the city's wastewater treatment plant off the council table by Christmas so the council can focus on key issues such as economic growth.

Mayor Hamish McDouall told the Chronicle that the debate around the plant had been hanging over the council "like a veil" but this week's two-day workshop had answered a lot of questions for both returning and new councillors.

Mr McDouall said the workshop needed to be held and was well worthwhile.

"All councillors learned but especially so the seven new councillors. Not all the information had been available to them until now. I think it clarified a lot of thinking."


He said the wastewater treatment plant (WWTP) will be back on the council agenda when it meets on Tuesday next week but he expected that item to be held in committee.

But he is determined to have any outstanding questions around the plant sorted by Christmas.

"I want to start the New Year by gathering all the councillors together to focus on growing Whanganui's economy and pulling out the key strands for that. But we can't do that if key questions about the wastewater treatment plant are still out here," Mr McDouall said.

He said he was "very encouraged" by the presentations made at the workshops and was especially heartened by the message from Affco Imlay plant manager Troy Lambly.

Mr Lambly told the workshop that if the trade waste charges numbers stack up the company would be a part of the new treatment scheme.

Overall costs of the new plant have been put at more than $41 million, and initial forecasts had trade waste rates at $4.5 million annually. But the council's revised costs have come up with a figure of $2.8 million and that figure could track downward.

Mr Lambly said Affco was looking at treating its own waste and expected to have designs and costings done this month. Once that detail was together the company was keen to meet with the council to discuss future options.

One option could include higher-end treatment on-site but in partnership with the council.

Mr McDouall said the treatment plant "is the symptom. The actual issue is affordability and that's what the workshop dug down into".

"The figures from Mike Fermor (council finance manager) showed that we are getting closer to finding some sort of balance. We know the plant will work. We know that there will be a plant built by March 2019. Within those parameters we can explore everything but really it all comes down to the numbers."

But he said there was absolutely no question the new plant will be up and running by 2019. That's the timetable and that will be met."