3 Mar 2023

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Up to 16 new aerators will soon be installed on the Christchurch wastewater treatment plant oxidation ponds to mitigate odours over the coming winter months.

Contractors are currently installing the electrical cabling for the new aerators, with the project expected to be completed and operational before winter.

The locally-sourced aerators will churn more than 300kg of oxygen into the Pond 1 wastewater every hour and improve its biological health. This will see better-quality wastewater then flow through the pond network. 

Disc aerator

Five new disc aerators will push an abundance of oxygen to the water while also creating optimum flow patterns in the pond, and these should be installed in the coming weeks.

An additional 11 vertical shaft aerators, which can push very high levels of oxygen into the water, are due to arrive on site in the next two weeks. This is the style of aerator that was installed on the clarifiers last year, as part of the temporary treatment process.

Acting Head of Three Waters Brent Smith says this work is being completed early to avoid more odours coming off the ponds this winter.

“Last winter the ponds struggled with the higher load of solids after the treatment plant fire, and we’re proactively taking these steps now so we don’t see a repeat of those high hydrogen sulphide levels negatively impacting the community,” says Mr Smith.

“With the daylight hours shortening and recent calm wind conditions, wastewater treatment plant staff have noticed indicators that the ponds early in the treatment process are starting to show signs of changing. Indicators include a slow, trending increase in biological oxygen demand and slowly decreasing dissolved oxygen levels.

“Our temporary treatment process is still working well, and we’re doing everything we can to avoid the odours that plagued the eastern suburbs last winter. We’re installing these aerators while it’s still warm and the ponds are still generally healthy,” says Mr Smith.

Options around a permanent solution for the fire-damaged wastewater treatment plant will go before the Council once the insurance processes have been settled. This process could take some months.