Get the latest news and meeting reports on the wastewater treatment plant recovery. We'll be updating this page as required if the situation changes or there is new information.

Latest news and updates

Latest update

30 October 2023

Two of the vertical shaft aerators on Pond 1 have stopped running. The contractor is aware of the issue, but the windy conditions mean they're unable to inspect and repair the aerators until Wednesday when the wind is forecast to drop. 

At the same time the current windy conditions, and warmer, longer days mean the ponds remain in good health, and we don’t expect the aerator break-downs will result in the ponds producing odours.

The remaining 14 aerators on the pond continue to operate.

On the night of Tuesday 2 October 2023, the arms of one of our two clarifiers at the wastewater treatment plant stopped rotating and were out of action for several hours.

These arms sweep the activated sludge off the bottom of the tank, and play a vital part in the treatment process - our temporary activated sludge plant requires both clarifiers to be running to achieve the current maximum flow through the plant.

Divers found three pieces of rubbish at the bottom of the tank, and since these have been removed, the clarifier arm has continued working. 

The findings of an independent review into the Council’s response and recovery from the wastewater treatment plant fire, and the Council's draft improvement plan, have also just been published with the Council's agenda for next week.  

The review highlights aspects where the Council did well and provides recommendations and suggestions where the Council could improve so that it’s better prepared to face other significant events in the future.

The draft improvement action plan identifies the need to work collaboratively with the local community, key partners and the local Waitai Coastal-Burwood-Linwood Community Board.

Read the Council report(external link) or independent review [PDF, 750 KB].

An update on the oxidation ponds

30 May 2023

We've updated our situation(external link) page with an update on the oxidation ponds and the odours that are starting to get emitted from them as we head into the cooler winter period. We’re still trying to determine exactly what’s causing the smell, but we believe a combination of factors might be at play.

These include mechanical issues on the disc aerators, algae reducing considerably over the winter months, recent wet weather, and below-average settling floc earlier in the treatment process. Read more about each of these, and what our next steps are.(external link)

A return to all 'green' ponds

20 April 2023

The 16 aerators we have installed on Oxidation Pond #1 are already making a significant difference to the biological health of the pond system. The aerators performance is also exceeding the strict design criteria set by the Council staff.

Monitoring by both wastewater treatment plant operations staff and contractors is showing that all ponds are now recording higher dissolved oxygen levels, and visual observations are showing the ponds look healthier.

Observations of the aerators have also shown the initial sludge disturbance has settled down quicker than anticipated, with the water being aerated by the aerators running clear, with no ongoing sludge disturbance.

This has resulted in a negligible level of odours and hydrogen sulphide now being emitted by the ponds; recent monitoring had shown these levels were slowly beginning to increase over recent months.

All this means the ponds are now in a much healthier, robust position as we head into winter, and we’re able to turn all ponds to ‘green’ in the pond tracker(external link).

This rapid response in pond health, and the additional performance provided by the aerators, means the systems we’ve installed are more resilient, and the future risk of odours is now reduced compared to previous forecasts.

However, there will continue to be an underlying risk of odours present around the wastewater treatment plant until the permanent solution for the treatment process is completed.

Oxidation pond aerators are fully operational

 14 April 2023

A project to minimise odours coming from the Christchurch wastewater treatment plant oxidation ponds has been successfully completed, with all 16 aerators surging to life yesterday. Read more on Newsline.(external link)

FENZ fire investigation report published

16 December 2022

We have just received from FENZ their Fire Investigation Report – Shuttle Drive, Bromley, Christchurch City [PDF, 5.1 MB].

Consequently, we have not had an opportunity to consider it fully. Our own investigation is ongoing and we will not be commenting further.

Snapshot of hydrogen sulphide levels decrease

2 November 2022.

This graph shows how the hydrogen sulphide levels coming from the oxidation ponds has significantly decreased over the four months from 10 June to 10 October 2022.

The activated sludge plant was made operational on 28 July, with the biology reaching full maturity on 17 August, despite the challenges of growing the biology over the middle of winter. 

It took four weeks for the better-quality wastewater to flush through our network of six ponds, with the odour substantially reduced by mid-September. This was in line with the timeframes that we promised the community we'd work to.

Hold off from cleaning your house

30 September 2022.

With hydrogen sulphide levels dropping and the days warming up, it might be tempting to clean any discolouration off your house that might have been caused by a chemical reaction between lead paint and hydrogen sulphide. 

We ask that you keep waiting. Before we begin encouraging people to clean their homes, we'd like to see at least four weeks of low hydrogen sulphide levels and improved weather to get an idea of how any discolouration fades. 

We're about to start monitoring some 'test houses' and will provide updates on our website to show how the discolouration improves. 

If you absolutely must clean your house now, make sure you're familiar with our list of dos and don'ts that we published last month. 


  • Read the report findings and information(external link) on house discolouration. 
  • Wash your walls with a commercial chlorine-based solution, or warm, soapy water. This could help remove any organic dust, common moulds and some discolouration. The presence of these common moulds is not linked to the wastewater treatment plant fire.
  • Adhere to the manufacturers’ proprietary ratio recommendations if you use a commercial chlorine-based solution.
  • Several washes might be required.


  • Don't use a high-pressure washer to try and clean any staining or discolouration, as this could result in flakes of lead-based paint entering the environment.
  • Don't exceed the manufacturer’s proprietary ratio recommendations if you use a commercial chlorine-based solution.

The Ministry of Health(external link) has more information about lead-based paint.

Our team is keeping a register of homes that have reported paint discolouration. If your home has discolouration and you haven't let us know, or if you'd like more advice about what to do, email

Newsline stories

2023 Newsline stories

2022 Newsline stories

2021 Newsline stories


2023 Newsletters

2022 Newsletters

2021 Newsletters

Meetings and minutes

7 July 2022

Christchurch Wastewater Treatment Plant  meeting between CDHB, ECAN and Christchurch City Council.

Action points:

  • Proceed with the setting up of the continuous monitors at the agreed sites.
  • Work with comms regarding the best way to display data on website from continuous monitors.

30 June 2022

Christchurch Wastewater Treatment Plant  meeting between CDHB, ECAN and Christchurch City Council.

Action points:

  • Circulate notes for confirmation
  • Circulate report on SIFT – MS sampling when available
  • Prepare draft/updated information for Council website.

23 June 2022

Christchurch Wastewater Treatment Plant meeting between CDHB, ECAN and Christchurch City Council.

Action points:

  • Send invitations to Medical Officer of Health for the Council meeting on 30/06

21 June 2022

Wastewater Treatment Plant Communications Advisory Group minutes [PDF, 592 KB].

9 June 2022

Christchurch Wastewater Treatment Plant meeting between CDHB, ECAN and Christchurch City Council.

Action points:

  • Report on Summary of completed sampling to be prepared.
  • Continue deploying H2S meters.
  • Ecan make available information from SO2 and H2S monitoring when available.