What’s the story: Christchurch Wastewater Treatment Plant odour

You may have noticed an increase in unpleasant odour around east Ōtautahi Christchurch, coming from the Christchurch Wastewater Treatment Plant in Bromley this week.  

We know that these odours and the impacts residents are experiencing are very real, and we are committed to ensuring any required action is taken to reduce the likelihood of odour, wherever possible.

The facts - what’s happening right now 

This week, our team is working closely with Christchurch City Council (CCC) to resolve the current problem operationally at the treatment plant and get a solution in place.

CCC has advised us that heavy rainfall this month has significantly affected the health of several oxidation ponds. Monitoring on 26 January showed a drop in dissolved oxygen (DO) levels across the system. Low oxygen conditions make odour far more likely, particularly in Ponds one, two, and three, which are currently the most affected.

The ponds are also under extra pressure from higher than usual loading and patches of sludge rising to the surface, further increasing the chance of odour escaping into nearby communities. 

Based on these conditions, CCC expects stronger odours to continue for at least the next week. 

Christchurch Wastewater Treatment Plant operations teams are closely monitoring conditions and responding wherever possible to improve pond health and minimise odour.

This includes: 

• Adjusting flows through the ponds to stabilise loading.
• Regular monitoring so we can react quickly to changes.
• Using all available operational tools to support oxygen levels and improve pond performance.  

You can stay up to date on what’s happening at the treatment plant on ccc.govt.nz/wastewaterfire, or subscribe online to receive regular community updates. 

What we are doing  

Managing and monitoring discharges to air in our region, including odour, is part of our responsibilities as a regulator under the Resource Management Act (RMA) and the Canterbury Air Regional Plan. 

Our compliance team has been actively responding to complaints and carrying out regular proactive odour monitoring around the Bromley area over the past month.  

In this case, we are confident that CCC is taking the correct steps to reduce the impact to the community as quickly as possible.  

As the plant is a critical piece of public infrastructure, our current enforcement approach is to work with CCC on improving odour as soon as possible.  This approach doesn’t lessen our commitment to expecting compliance, and the issue continues to be under investigation.   

What happens next 

We will continue to work closely with CCC to ensure they are meeting their consent conditions and putting odour mitigation measures in place wherever practicable.

Your reports are an essential part of this work. They help us understand what you’re experiencing in real-time and guide the timing and location of our monitoring.

Report odour: If you notice strong, unusual, or unpleasant odour, please continue to report it through the SmeltIt app, or on 0800 765 588 (24 hours)