City council approves river plan

The action plan to stop the Palmerston North City Council's wastewater discharge from harming the Manawatu River has been unanimously approved by councillors.

The plan of experiments, monitoring and an extra 22 days of phosphorus treatment that could cost an extra $1.127 million this year was adopted by 12 councillors present at last night's monthly meeting.

Chief executive Paddy Clifford is confident the costs can be met from savings elsewhere, particularly from staff vacancies and lower-than-budgeted interest costs.

Cr Bruce Wilson said while progress at the Totara Rd plant would not seem fast enough for some people, it was important to have quality science to support the changes proposed.

"It would be good if the community understood there is no shrinking from our commitment to do our part in cleaning up the river," he said.

And Cr Pat Kelly said the costs of improving the plant's performance suggested the "crisis" the media had given great attention to did not seem so serious after all.

The need for improvements was triggered by a Horizons Regional Council non-compliance assessment issued in July 2011, that councillors did not know about for three months.

It was followed by an abatement notice, an appeal by the city council, and eventual agreement to carry out water quality testing last summer to find out what was causing the significant adverse effect on mayflies and other sensitive river life downstream of the plant.

The results showed high levels of dissolved reactive phosphorus in the river were causing an overgrowth of algae, but the discharge at the time was not fully responsible for those levels.

Water and waste services manager Rob Green said further work would be done to investigate the suspected "sponge effect", where phosphorus discharged at high river flows settled in the river bed and was released when flows were low.

Another experiment would try to identify what "kick-started" algal growth quickly as flows dropped - a $17,000 task.

Alum treatment to remove phosphorus would continue for longer than usual as flows rose again. That could cost $120,000.

Research would also be done to monitor the load of contaminants coming in to the plant - $70,000.

The most expensive part of the action plan could be dredging out sludge from the aeration ponds, at $700,000.

However, the injection of bacteria into the sludge to help break it down was showing promising results, and could make that a less expensive project.

Deputy mayor Jim Jefferies said $15,000 earmarked for a public education programme was a particularly useful part of the plan.

It would highlight the significance of choosing household detergents containing no or low amounts of phosphorus.

"The cleaning up of the river is a total community matter to solve," said Cr Jefferies.

"If we can go back up the chain, each individual member of the community has an opportunity to make a difference."

Meantime, council staff will be considering changes to its discharge consent conditions that have just been presented by Horizons, and providing feedback before the consent review becomes formal next year.

Progress on the action plan, and any interim results, will be reported back to a city council committee every month.

The Manawatu Standard