Residents near the Christchurch Wastewater Treatment Plant may notice an increase in odour in the coming weeks due to environmental conditions affecting the oxidation ponds.

The Christchurch City Council has warned that the current stretch of dry and warm weather has led to more concentrated waste entering the ponds, placing additional pressure on the system and reducing dissolved oxygen levels. This, in turn, could lead to an increase in odours in surrounding areas.

Council staff have said they are actively monitoring the situation and responding swiftly to any changes that may exacerbate odour levels. Running the damaged treatment plant remains a challenge, but efforts are being made to mitigate the impact on nearby communities.

Large numbers of midges are still being recorded around the ponds, though reports indicate they are largely staying within the immediate area and not spreading into neighbouring suburbs.

Last week, the council trialled a new midge control method in Pond 2A, using a jetboat and midge dredge to disrupt the insect’s lifecycle. While the trial is ongoing, initial observations suggest that pond health has declined, which could contribute to further odour issues.

The midge season is expected to last until early April, and under certain weather conditions, midges may drift into nearby areas. However, council staff have reviewed the Midge Control Programme and are incorporating new recommendations into their efforts.

Additionally, a new Midge and Odour Monitoring and Control Project has been initiated as a high-priority initiative, with completion targeted for October 2025, ahead of the next midge season.

Complaint numbers regarding midges have significantly decreased, with only one reported since 24 January.