River discharge may switch to land-based

Palmerston North City Council's consent to discharge its treated sewage into the Manawatu River could be overhauled, forcing consideration of a switch to land-based disposal.

Horizons Regional Council has already instigated a review of the consent conditions in light of evidence the outfall from the Totara Rd wastewater treatment plant is harming the river.

Last night City Networks special projects manager Phil Walker told the city council meeting that it could bring forward a more comprehensive review of whether the city is using "the best practicable option".

Its 2003 consent includes a clause allowing a review in 2016 of whether it is using the best method for treating and discharging wastewater.

"It may also be appropriate to advance this review at the same time," Mr Walker said.

The city council is already working on an action plan to overcome the problems the wastewater discharge is causing.

A joint investigation last summer proved there was an overload of phosphorous downstream of the discharge causing algae to grow three and a half times faster than it does upstream.

The algae makes the riverbed hostile for sensitive mayflies and caddisflies that provide food for fish.

The significant adverse effect on aquatic life breaches the city's consent conditions.

Further studies are needed to find out why the phosphorous levels are much higher than what is entering the river at periods of low flows when the council doses with alum to remove the phosphorous.

The council is expected to pay to treat for phosphorous over longer periods this summer to test the theory that the river sediments absorb it during high flows, and release it when the river levels drop.

Cr Pat Kelly said he was pleased councillors were being informed and involved in plans to improve the river.

"But my concern is there no doubt will be major costs to the city."

Cr Chris Teo-Sherrell, who made a $21,000 Official Information Act search for evidence councillors were not being properly informed about problems with the plant, was also pleased the results of the research were being accepted and that there was a willingness to act on them.

The council voted unanimously to receive the scientific report on the effects of the discharge, to discuss an action plan to be presented to a workshop in late October, and note that the consent review is under way.

Manawatu Standard