Christchurch Wastewater Treatment Plant update

Monday 2 March

We said we’d be back in touch on Tuesday, but we’re sharing this update today because we have some positive progress to let you know about.

Our team has been working hard to find ways to reduce the odour from the ponds, and we're now looking at an interim option that could help take pressure off the pond system. You can read more about this below.

Council to investigate further odour mitigation method

To mitigate the ongoing stench coming from its Wastewater Treatment Plant, Christchurch City Council is investigating pumping a portion of treated wastewater straight to the existing ocean outfall pipe.   

Cooler temperatures and high levels of rain have reduced the oxygen and algae levels in the ponds, which has caused the current spikes in odour. 

Mayor Phil Mauger says the Council has been in discussions with Environment Canterbury and mana whenua about finding an interim solution.  

“Because the Wastewater Treatment Plant has been running on a knife edge since the fire, the ponds have been overloaded and are now in poor health,” Mayor Mauger says.  

“Anyone who lives nearby knows the odour issues have become more intense, and we’ve been looking at all ways to help alleviate the stench.” 

“Reducing the amount of wastewater entering the ponds would take the load off, give them space to recover, and – most importantly – address the current odour,” he said.  

“If we can reduce how much wastewater is going into them, it will help stabilise pond conditions while the longer-term rebuild of our new treatment plant continues.” 

This approach would also provide extra resilience across the treatment system through construction of the new activated sludge reactor and essential maintenance on one of the plant’s clarifiers.  

The wastewater diverted to the outfall would be partially treated, and the Council would add chlorine to ensure bacteria levels are safe before it reaches the ocean.  

There are a number of elements to work through to get this up and running. Staff are developing a plan as quickly as possible and will keep residents updated as this plan progresses.  

Mayor Mauger said the Council will continue to look at further actions to improve pond health and reduce odour.   

Latest hydrogen sulphide monitoring

The latest hydrogen sulphide graph shows that H₂S remains present at detectable levels. Our teams will continue to monitor readings closely and provide updates as trends develop.

Stay updated

We want everyone to be able to stay updated on what's happening at the Christchurch Wastewater Treatment Plant, and we regularly post new information on ccc.govt.nz/wastewaterfire 

You're welcome to send this update to your networks. If you know someone in the community who doesn’t have email or internet access, please print this newsletter off and pass it to them.

If you know of anyone who would like to receive this e-newsletter they can subscribe online. 

If you have any questions, or would like further information on the project, please call us on 03 941 8999 or 0800 800 169 or email wastewater@ccc.govt.nz  

Thanks for your patience and understanding. We’ll be in touch again soon.