Christchurch Wastewater Treatment Plant update

Wednesday 7 January 

What we're doing to keep odour to a minimum

Over the last month there have been short-term spikes in odour. This is a result of seasonal and weather conditions which result in more highly concentrated waste entering the ponds. However, the most recent results (included at the bottom of this newsletter) indicate signs of recovery. This is something we have to deal with each summer and we are doing what we can to address odour. 

Keeping the plant running in its damaged state is challenging and there will always be an element of unpredictability, but our team is experienced and quick to respond to any changes that can lead to an increase in odour. Here's what we've been doing:

• Adjusting for summer conditions (lower flows, higher wastewater strength).
• Temporarily taking some primary settling tanks offline to improve process stability.
• Monitoring odour at five community locations.
• Installing three new aerators in oxidation ponds to improve circulation and reduce odour (two installed in December, one to be installed this month).
• Regular water quality sampling and sludge surveys to inform operational adjustments.
• Using aerial imagery and bird monitoring to assess pond health.
• Operating an algae transfer pump to improve pond performance.
• Engaging an international odour specialist for an in-depth assessment, with findings to inform further mitigation.
• Continuously reviewing monitoring data and adjusting operations as conditions change.

Once the new facility is operational, it will provide a long-term solution to the odour issues experienced since the fire, and until then we’ll keep doing what we can to keep the plant operating while keeping odour to a minimum.

Activated Sludge Plant update 

Our contractors have started setting up the construction village, which will be the team's home over the next couple of years. They're aiming to have everything ready for the main construction by the end of January.

Property survey reminder

A quick reminder for our neighbours on Shortland Street who received a letter about a pre-construction property survey. If you're keen to proceed with a survey please use the details provided in the letter to contact the Council's Project Manager Thomas Fietzko.

Pest control on Shortland Street Parks Depot boundary 

We continue to monitor bait stations along the property boundaries of Shortland Street. Our contractor hasn’t noticed a visible increase in the bait uptake since the additional stations were installed in April 2025 to manage the situation. We’re continuing to monitor these and will increase the number of stations if needed.

In 2024 the Council brought all park maintenance services in-house and the depot was built to store the wide range of equipment used to carry out this work.

Latest hydrogen sulphide monitoring 

Over the last month there have been short-term spikes in odour. This is a result of seasonal and weather conditions which result in more highly concentrated waste entering the ponds. However, the most recent results indicate signs of recovery. 

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.