Lime will be spread over Wanganui's wastewater treatment ponds from 7am today to try and stifle the foul odour emitting from the plant and drifting across most of the city.
A stench has been coming from ponds intermittently 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, told the Chronicle 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.
"A helicopter will drop loads of slurry over the ponds until the treatment is complete."
Mr Hughes told the council on Monday that the lime option was not expected to interfere with the bio-augmentation programme under way but would cover a thick layer of sludge at the bottom of the ponds.
It was the sludge that was creating the foul-smelling hydrogen sulphide gases which were bubbling to the surface of the ponds.
Horizons Regional Council had served an abatement notice on council, giving it until February 7 to sort out the odour problem.