Christchurch Wastewater Treatment Plant update

9 May 2024

Odour control system upgrade complete

We've recently replaced the odour control system's bio-bed material (photo below). The bio-beds are made out of biological material such as bark and seashells, which is home to millions of microorganisms that break down and filter out odorous gases such as hydrogen sulphide. This material needs to be replaced roughly every 5 - 10 years so it keeps working effectively.

We're also re-using the old material that has broken down over time. Through this process it becomes a highly effective soil conditioner and we've used it in our native planting areas surrounding the oxidation ponds as part of the midge control programme.

Secondary contact tank inlet chambers covered

The secondary contact tank inlet channels were identified as a source of odour during the on-site monitoring programme. We've recently completed work to cover these inlet chambers as they have the most surface disturbance. This will help contain the odour within the channels and will reduce the dispersal into the atmosphere.

Ponds operating in winter mode

We're now a few weeks into operating the oxidation ponds in winter mode in an effort to reduce odours.

Last year there was an increase in odour when temperatures dropped and the biology of the ponds changed. This hasn't happened yet this year, but with the cooler weather we've been having, we expect it will occur within the next few weeks.

As part of these changes, we're directing wastewater past the oxidation ponds nearest residential properties. This reduces the retention time within the pond system, which should reduce the duration and intensity of any odour event.

We won't know if this approach is successful until the biology of the ponds changes. We're keeping a close eye on the ponds and will be monitoring to see if the changes are effective in reducing odour.

Fencing at oxidation ponds 

Late last year a fence was installed around the perimeter of the oxidation ponds to improve safety and prevent unauthorised access to the ponds.

Unfortunately a couple of issues have arisen as a result of the more secure fence line, including the hemming in of birds between the fence line and the state highway, as well as catching more rubbish on the fence line, which was previously getting through the old fence and into the ponds. We've made some minor changes to the fence line to deter the birds from walking between the fence line and the state highway which appears to have some success, but we will be closely monitoring this.

This land is owned and maintained by NZ Transport Agency Waka Kotahi. We're working with them on an approach to rubbish collection going forward and will provide more information when we can. 

Funding approved to improve relationship with Eastern Communities. 

On Wednesday 1 May the Mayor and councillors approved a grant of $130,000 to resource a project with the goal of strengthening and sustaining effective and respectful relationships with Eastern Communities. The project will include:

• Appointment of an external facilitator to work to understand the needs of the community and to build social cohesion.
• Appointment of a project manager to facilitate an internal team within Council to assist with understanding the community’s needs, rebuild trust with the community and prioritise what matters most to them.
• Appointment of a coordinator to assist with the Wastewater Treatment Plant Response in order to improve the reach of the Council to communities that we have not been able to engage with.
• Prioritise two employees from the Civil Defence Team to focus on coastal response planning, community response planning for the Waitai Board area, tsunami warning and risk planning.
• Implement quick wins for the community to show that the Council is hearing and responding to their concerns.

The first step will be work with the Waitai Coastal-Burwood-Linwood Community Board, as they will be the governance oversight for the project. More information about this project will be made available in future, once the project gets underway.

Hydrogen sulphide monitor results

In certain winds hydrogen sulphide from the treatment plant has been detected at Mecca Place and Shortland Street. The levels for the past three weeks are lower than what has been detected recently. 

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.