New methods have been introduced to try to reduce the smell coming from Wanganui's malfunctioning wastewater treatment plant.
Mayor Annette Main said intensive work was being done at the site that helped to gradually reduce the unpleasant odour, which has been wafting across Wanganui since early December.
The malfunction is believed to have been caused by a local industry dumping protein material, although the offender has not yet been identified.
"Staff and contractors have been working very long hours to try to combat the smell and we've had some encouraging news about the new odour neutralisation system which seems to be improving the smell from the site," she said.
"Unfortunately, there are some misconceptions from outside our district that the whole of Wanganui stinks all the time but it's only occasionally not constantly, and not in all areas.
"Those of us who live here know that wind direction makes all the difference to which parts of the district are affected by the smell - and some areas have not been affected at all.
"As a result of following up on smell complaints, we also know not all offensive smells are being caused by the treatment plant. Effluent from stock trucks and wet compost have been the cause of some odours reported to us.
"While there is a long way to go to fix the inherent problems with the treatment plant itself, I'm confident that we're on the way to reducing the offensive smell."
Wanganui District Council's infrastructure manager, Mark Hughes, said an atmospheric odour neutralisation system had been installed around the plant at 19 locations and went live on Thursday evening.
Stage two was installed last night and increased the number of locations to 30.
The spray will assist in addressing the odours coming from the ponds.
"It comprises a complex mix of plant extracts with no harmful chemicals and is environmentally friendly," Mr Hughes said.