Christchurch City Council has approved the installation of additional aerators in the city’s fire damaged wastewater treatment plant, in a move aimed at reducing ongoing odour issues affecting eastern suburbs.

The oxidation ponds have been under sustained pressure since a major fire in 2021, forcing the system to operate well above normal capacity.

Combined with periods of unusual weather, the strain has at times led to strong odours impacting nearby communities.

The council agreed to boost aeration in the ponds to increase oxygen levels and reduce the risk of odour.

The new aerators are expected to be up and running within 6 to 10 weeks.

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

“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.”

Councillors were presented with several options during a workshop last month, followed by a full cost and risk assessment by staff.

Increasing aeration was considered the most practical and effective solution. It is simpler to build and operate, carries a lower risk of failure, avoids discharging treated wastewater into the ocean, and can be delivered faster than other options.

Staff have also been given authority to install additional aerators immediately if conditions worsen.

Christchurch City Councillor Yani Johanson said “We cannot change the past, but we can change the future.”

Johanson said the issue had caused significant harm in parts of the east and needed to be treated as a serious public health concern.

“I’ve just been looking at an email from one of my constituents who’s talked about this being a public health issue, and that it really is something that needs to be given serious consideration.”

He said work was ongoing around psychosocial support and recovery, with further updates expected.

Christchurch City Councillor Celeste Donovan said, “This is something that has actually been a problem for decades, but the worst of it has been happening for what is nearly five years. And my maths is right, that’s 1773 days. So that’s a long time.”

“And when we talk about the stench, it’s all degrees. You have really bad days, you have terrible days, but it’s always there. So it’s not like it goes away.”

“What we’re looking at today is the worst of it, but there will still be a bad smell, and people have been living with this for far too long.”

“So I think when we talk about cost, and I know that that’s always a factor. We have to look at the cost of people’s lives, their health and their well being.”

Work is continuing on the long term fix, the activated sludge plant, which is expected to permanently resolve the odour problem once complete.