Christchurch Wastewater Treatment Plant update

14 June 2024

Product trial gets underway 

Since the wastewater treatment plant fire we've heard from a number of suppliers of technological, biological and chemical products that address odours. 

We've considered these options and a number were ruled out for various reasons including incompatibility with plant processes and downstream effects.

We're about to start a trial with a small number of suppliers whose products may have value. We've engaged an independent external consultant to assess the products applicability and likelihood of success. 

We're currently in the first phase of the trial, which includes confirming the product information to ensure it's compatible with the treatment plant processes, safe to use in New Zealand and to assess downstream effects.  

We will then proceed to the next stage with eligible suppliers, which will include small and medium scale trials. Based on these results we'll then consider a full-scale month-long trial. 

Temporary activated sludge plant upgrade

A project to see if the temporary activated sludge plant can be optimised further is underway. Site staff have been working with process specialists to undertake a trial to vary the parameters of the activated sludge plant to see if it can be improved. The project has started and will continue for the next 20 weeks.

Pond flow returned to normal

The oxidation ponds have now stabilised in winter mode with algae having died off for the winter. During this period we had a flow path in place to mitigate odours from the ponds during the summer–to-winter transition. 

The image on the left shows the temporary flow path during the transition period. The ponds have now been returned to their normal flow path, shown in the image on the right. 

15 of 16 aerators are currently in service. 

Hydrogen sulphide monitor results

We are continuing to monitor levels of hydrogen sulphide at residential locations around the wastewater treatment plant. Monitoring results have shown that levels over the past month have been decreasing and are now well below the health guideline of 0.03ppm. At times light winds still carry hydrogen sulphide, and other odours, to nearby residential areas but the levels are below 0.01pmm.

Where to get help

If you need health support, we have information available on our website. This includes information on Pegasus Health's Partnership Community Workers and contact numbers for Healthline and counselling services.

Stay updated

We want everyone to be able to stay updated on our response and recovery from the treatment plant fire, and we regularly post new information and reports 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.