That was “the likely source of odour that periodically affects businesses around the wastewater treatment plant and airport surrounds”, the report said.
Langford told the Chronicle a wet scrubber or a bio-filter would likely be installed for the air to be passed through.
“We can bring the budget forward without having an impact on rates.”
A wet scrubber removes pollutants from air streams by bringing them in contact with a scrubbing liquid, usually water, while a biofilter contains bacteria that treat air before it is released into the environment.
The plant’s thermal dryer removes water from the sludge that settles in its primary pond.
Langford said the budget was in the 2026/27 year as a provision, while staff investigated the odour issues.
The council has battled odour in the area for years, at the former wastewater plant and the new one – which cost nearly $40 million and went fully operational in 2019.
In 2013, a deodorising fence was installed around the old facility in an attempt to stifle the smell.
It was turned off a year later, saving ratepayers $5000 a day.
After multiple complaints from Mid West Helicopters in 2023, staff identified two parts of the new plant that were causing smells – the vent from the dryer building and foul air escaping from a pond cover.
A 2024 report from Hooper said media in the dryer’s bio-filter had been replaced, but that did not stop foul air from escaping and contaminating the building, with the air then extracted outside.
Seventeen small holes were found in the pond cover, but repairing them had little impact on the odour and neither did replacing the rubber seals around the dryer’s doors to try to prevent air escaping, it said.
“We are confident that once the issue is accurately understood the matter will be resolved.
“The challenge is in getting to that point, which ultimately requires a ‘trial-and-error’ approach.”
There were nine odour complaints reported to the council in February this year, with council staff meeting with complainants at the Wanganui Pistol Club site.
Langford’s report said installing the wet scrubber or bio-filter was expected to provide health and safety benefits to workers by reducing the airborne biological hazards they were “otherwise exposed to”.
Speaking to the Chronicle, he said council staff were working through a technical assessment to see which device would be most appropriate.
Mike Tweed is a multimedia journalist at the Whanganui Chronicle. Since starting in March 2020, he has dabbled in everything from sport to music. At present his focus is local government, primarily the Whanganui District Council.
