Smelly problem set to linger on

Consultants work on long-term solution Until a long-term solution is found for Wanganui city's ailing wastewater treatment ponds, the community should steel itself to cop more of the foul odours from the ponds.

The Wanganui District Council's infrastructure and property committee yesterday heard first-hand from consultants Cardno BTO about the condition of the ponds and efforts to stop the stench.

Mike McCoy, business unit manager for the Wellington firm, said while short-term measures were having an effect on the odour, it would only be fixed with a long-term solution.

Mr McCoy said his team was investigating long-term options and a report to the council should be ready within two months.

Adding lime slurry and pre-treating waste at Beach Rd before it got to the ponds were short-term solutions, while using aerators to oxygenate the ponds were medium-term options.

Mr McCoy said major investigation would determine whether the plant was flawed in its design. While lots of ideas had been floated, nothing would be gained by diverting some partially treated waste directly out to sea, bypassing the ponds altogether.

"In the short term, that will not work, because the odour problem is within the ponds themselves," he said.

While solutions being tried now, including applying lime, provided short-term respite, the stench kept coming.

Replying to councillors' questions, he said removing some or all of the sludge that was causing the stench would help but would take months. Then it had to be dried out before being dumped at a landfill, which would require a whole new set of resource consents.

Problems at the ponds were "very complex" and council and the community needed to be reminded that solutions being tried now were not the final answer.

"It's not that simple. Having more aerators in the ponds would help, but in my opinion it wouldn't solve the odour or the consent issues," Mr McCoy said.

He said his team could not say at this stage what caused the spike in the smell from December.

"We're evaluating that right now. But we know summer temperatures are another influence as the sludge layer increases," he said.

Mayor Annette Main said knowing the consultants were working toward a long-term solution was heartening.

"But I'm really uncomfortable and concerned that we'll continue to have smells like we've experienced in the weekend and that there isn't a simple fix to fix all the smells right now," she said.