Water  |  14 Apr 2023

A project to minimise odours coming from the Christchurch wastewater treatment plant oxidation ponds has been successfully completed, with all 16 aerators surging to life yesterday.

The 11 vertical shaft aerators and five disc aerators will churn more than 300kg of oxygen into the Pond 1 wastewater every hour and improve its biological health.

Operations Manager, Adam Twose, says although some localised, temporary odours had been expected as the aerators initially disturbed the sludge build-up at the bottom of the pond, the smells had been much less than anticipated.

Vertical shaft aerator on Pond 1.

“We waited for the optimal weather conditions before we turned on the aerators above the sludge blanket, and the odours were thankfully far from the worst-case scenario we had planned for,” says Mr Twose.

“The retention cycle for the water is three days, so we expect to start seeing an improvement in the pond’s dissolved oxygen and biological oxygen demand levels from next week. Better quality wastewater will then flow through the pond network.

“As the health of the pond improves, the minor localised smell that’s currently coming off the pond will also reduce, putting us in the best possible position to deal with odours from the pond network over the winter months.

“Longer term, these aerators will ensure the ponds continue to stay healthy and function well as they have done over summer.”

For more information on the wastewater fire recovery project, visit ccc.govt.nz/wastewaterfire.