Odour mitigation work underway

We recently submitted an odour mitigation plan to Environment Canterbury in response to issues raised in a Compliance Monitoring Report.

The plan outlines the many actions we’re taking to address odour at the Christchurch Wastewater Treatment Plant to address the issues, improve the performance of the plant and lessen the impact on the community.

We’ve provided an update below on some of the key actions currently underway at parts of the plant. We’ll continue to provide updates on this work and any additional actions that happen in future.

Screen room – a temporary ventilation system has been installed in the screen room and consultants are looking into a permanent system.

Primary settlement tanks – this is where the majority of odour is coming from and we have a range of work underway to improve their performance:

• We’ve reduced the number of tanks in service to move sewage through the system more quickly. Following an electrical failure we had to return one tank to service. We intend to get back down to four tanks as soon as possible.
• We’re doing manual daily scum removal.
• We’ve engaged a contractor to investigate the possibility of a containment system to address odour.
• We’re investigating covering chambers where there is significant surface disturbance.
• We’re investigating improving the automatic water spray scum removal system.

Temporary secondary treatment – a consultant is working over 18 weeks to improve this phase of treatment.

Odour control system – we have three bio-bed systems to address odour. We’ve rewired the system to get more fans working and are doing more proactive maintenance. We’re engaging a contractor to renew the remaining bed media.

Oxidation ponds – all aerators are in service and expected to remain so. On 8 March we briefly turned all aerators off to carry out critical maintenance work. This went well and didn’t cause additional odour. There is no further planned maintenance coming up and all aerators are available as we head into winter.

Digesters – investigations revealed the pipework is slightly too small. A project is in the final stages to upsize this. We’re also doing more proactive maintenance.

Odour monitoring – the intensive odour monitoring service is underway and continuing beyond the initial four weeks.

Transition to winter – we’ve developed a plan to minimise the odour from the ponds during the summer to winter transition. This is being checked over the next week and will be put in place by the end of the month.

Website changes – we’re working on making changes to our website so it’s easy to see what odour mitigation work is underway. We expect this to be available in the next week or so.
 

Hydrogen sulphide monitor results

The graph for 3 to 10 March continues to show that hydrogen sulphide is being detected in the Shortland Street area, and this occurs at times when the wind is coming from the treatment plant itself. This is particularly evident when wind conditions are light.

Our staff continue to do all they can to reduce the odour as quickly as possible and are making changes to processes at the plant. 

There are no readings for the dog shelter as that meter is being used at another site.

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.