The blaze on November 1 destroyed two trickling filters at the Bromley plant and led to nearby residents being evacuated and a public health warning over the smoke.
Since then, unpleasant odours from the plant have been wafting across the city, especially in the west during the easterly wind.
Christchurch City Council head of three waters Helen Beaumont said six aerators are being flown in from the United States, and two more have been sourced in New Zealand, as part of its medium-term plan to minimise odours from the plant.
The motors are coming from Brazil and specialised submersible electrical cabling from Australia.
She said work was already under way to convert two of the four clarifier tanks into aeration basins, but the aerators are a "vital component of the interim solution".
"Installing four aerators in each of the two tanks will pump more oxygen into the wastewater, which should help decrease the unpleasant odours and improve the wastewater quality before it enters the oxidation ponds," Beaumont said.
"We aim to have the aerators functional by the end of March.
"The November 1 fire destroyed the two trickling filters at the plant, and these were very important to the wastewater treatment process.
"We’re very aware of the smells that residents have been subjected to since the fire. We expect the new system, which should be in place by the end of next month, will help improve this situation, as it’s likely to be years before we’re able to fully rebuild or replace the trickling filters."
To convert the clarifiers into aeration basins, a crane will lift four 75kw mixer aerators into each clarifier. An additional 600kw power supply will enable the aerators to continuously operate.
New submersible pumps will push the wastewater from the new aeration basins through to the remaining two clarifier tanks.
After the clarifier conversion is completed, detailed design will begin on a way to provide additional aeration into the oxidation ponds.
Beaumont said poly aluminium chloride will continue to be added to the wastewater at two key points in the process.
This "poly-dosing" settles more of the suspended solids and reduces the organic loading of the supernatant wastewater - the clear liquid from the top - that now bypasses the trickling filters and goes on to the secondary contact tanks," Beaumont said.
She said hydrogen peroxide – a compound that naturally breaks down into water and oxygen – is being added to the wastewater before it’s discharged into the oxidation ponds.
Beaumont said council staff also submitted its incident report to WorkSafe this week. The report will be made public once all insurance claims are settled.
