Christchurch Wastewater Treatment Plant update

Friday 28 November 

Seasonal conditions result in odour and midge increase

Algae pump in action

Increase in odour around the plant

We’ve recently noticed an increase in odour around the plant. Our team is actively monitoring conditions, and an odour specialist has visited the site to help us identify solutions.

We've taken action already by reducing the number of primary sedimentation tanks in operation - this helps them deal better with the lower flow of sewage during summer in dry weather conditions. 

When there’s an increase in odour we take action straight away but it can take a bit of time for this to have an impact. This is due to how long it takes for sewage to pass through the treatment plant and ponds.

We’re working on steps to minimise any impact and will keep you updated as improvements are made.

Midge numbers up 

Midge numbers around the ponds are higher than usual for this time of year and have appeared earlier than last season.

To help control the population, our team dredged the ponds twice in November. This disrupts the midge life cycle and reduces their numbers over time. We carried out the most recent dredging on 20 November. 

We'll keep monitoring midge numbers and consider what actions we can take. With the recent increase in odour we're unlikely to dredge again until conditions stabilise as dredging can exacerbate odour. 

Algae pump back in service

Algae play an important role in keeping ponds healthy by introducing oxygen, which helps prevent anaerobic conditions that can result in odour. To support this, we brought the algae pump back into service in Pond 1 at the beginning of November.

Algae pump in action

Thank you for your understanding as we manage these seasonal challenges. We’ll continue to monitor conditions closely and share updates with you via this newsletter. 

We're finalising a date for a community meeting 

We're in the final stages of confirming a date and location for a community meeting where Council and HEB Construction staff will give an update on everything happening at the Christchurch Wastewater Treatment Plant this summer and beyond. You'll be able to speak to the team and ask any questions you have about the work. 

HEB Construction has been awarded the contract to build the Activated Sludge Reactor project, which will kick off in the new year. On top of that there is also important clarifier repair work planned for the plant this summer.

We expect to confirm a date early next week and will publish information via this newsletter, our website and social media. We'll also drop flyers to properties neighbouring the plant. 

Hydrogen sulphide (H2S) monitoring 

The latest graph from our hydrogen sulphide monitors shows the biological health of the ponds is still fragile. Intermittent low levels of odour are being detected at community monitoring sites. 

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.