"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.