The "terrible saga" of Whanganui's wastewater treatment plant attracted about 130 people to a public meeting last night.

Called by the Ratepayers' Association, the meeting reflected community unease at the district council's March 9 resolution to build a new treatment plant - now costed at $41 million - to replace the failed facility.

Association chairman Graham Adams hosted the meeting and introduced civil engineer Colin Hovey, who worked for the council for more than 20 years and was closely involved in the MWH-designed Airport Rd plant which was commissioned in 2007 and which failed soon afterwards.

His version of what went wrong was the "terrible saga" as he recounted how the tornado aerators - which supplied oxygen crucial to the treatment process - were set to the wrong frequency by the United States suppliers.


They failed and were replaced by twister aerators, with Mr Hovey saying he was "shocked' that the council would accept twister aerators.

"MWH suggested council should install directional aerators, but that was not done," he said.

The twister aerators operated for six months and in that period the plant was functioning as required, he said. But when they, too, failed and were not replaced, the plant ground to a halt and Whanganui was left with a horrendous smell.

Mr Hovey maintains the MWH plant could have worked if operated properly with the correct aerators. However, that account has been rejected by council, which has had advice that the plant, as designed, could never have done the job.

The Ratepayers' Association had a petition under way last night, calling for an independent public inquiry into the failure of the plant and for any expenditure on the new plant to be suspended until the outcome of the inquiry is known.