9h ago

Share this story

Christchurch City Council has approved the installation of additional aerators in the ponds at the fire-damaged Wastewater Treatment Plant to reduce the risk of odour.

The plant’s oxidation ponds have been operating under increased pressure since a major fire in 2021, forcing them to function well above their usual capacity. Combined with periods of unusual weather, this sustained strain has at times resulted in offensive odours impacting nearby communities.

To help reduce the odour, the Council has approved increasing aeration in the ponds to increase oxygen levels to a level that reduces the risk of odour. The new aerators are expected to be operating within six to ten weeks.

“We’ve been committed to finding a solution for the people of the east who have been affected by the stench,” Mayor Phil Mauger said.

“We needed to look at all possible solutions, so people know we are doing the very best for the community. Now we’ve made a decision we can get on with it as quickly as possible.”

At a workshop last month Councillors were presented with a range of potential solutions with Staff then doing a full cost and risk assessment of these options.

Increasing aeration was considered the most effective and practical solution. The option is simpler to build and operate, carries a low risk of failure, avoids discharging treated wastewater directly into the ocean, and can be delivered more quickly than alternative approaches.

Staff have also been given authority to add more aerators straight away if pond conditions worsen and they are required.

Work is also well underway on the long-term solution, the activated sludge plant, which is expected to permanently resolve odour issues once operational.

During construction of the new plant, the oxidation ponds are expected to face periods of additional pressure.

Increased aeration will also help the system cope during this transitional phase, reducing the likelihood of odour while the new plant is built.