Lime will be spread over Wanganui's wastewater treatment ponds from today to try and stifle the foul odour coming from the plant and drifting across most of the city.
A stench has been coming from ponds off and on since they were commissioned in 2007 but since last month the extent and strength of the smell has multiplied.
Mark Hughes, council's infrastructure manager, said consultants from BTO Cardno had looked at alternatives and suggested adding the slurry to the ponds.
A similar exercise in Nelson had been successful.
"We had equipment on site today and workmen will begin mixing the slurry from about 7am tomorrow," Mr Hughes said yesterday.