Christchurch wastewater treatment plant fire timeline

Emergency Services respond to a fire at the Wastewater Treatment Plant in Bromley. Both of the trickling roof filters collapse.

The damage can't be assessed properly until the fire is completely out.

The Council installs a sprinkler system to get rid of hot spots and help reduce the smell.

The Council also begins working on an adaptive management plan to figure out the best possible outcome for the discharge of wastewater from the plant.

The fire is officially completely extinguished by the fire service.

The Council identifies the need to remove the two trickling filters. Both filters store 13,000 cubic metres of material.

The Council starts using misters and poly aluminium chloride - an odourless powder that dissolves in water - to help suppress the smell.  Poly dosing also settles more of the suspended solids in the wastewater, improving the water quality as it progresses through the plants.

Hydrogen peroxide - a  compound that naturally breaks down into water and oxygen – starts to be added to the wastewater before it’s discharged into the oxidation ponds.

The Council completes a successful trial to remove a section of the fire-damaged media from the plant.

This means that the Council can begin assessing the stability of the structures.

Council staff plan to convert two of the plant’s four clarifier tanks (or secondary contact) into aeration tanks.

Installing four aerators in each of the two tanks will help decrease the bad smells and improve the quality of the wastewater being discharged.

The Council anticipates that it will be years before the trickling filters can be replaced or rebuilt.

Aeration components begin to arrive and we're able to implement our interim plan to minimise odours from the fire-damaged plant.

Eight aerators are installed in two of the plant’s four clarifiers.

Soon afterward, increased odours from the trickling filters are detected after wet weather. It's determined that the acute stench is caused by the material inside the trickling filters rotting and drying out.

The aerators installed in March are turned on.

The Council decides to fast-track the appointment of a contractor to remove the burnt filter material from the Bromley Wastewater Treatment Plant.

Independent testing to better understand the odours from around the fire-damaged Christchurch Wastewater Treatment Plant detects small amounts of hydrogen sulphide and methyl mercaptan.

Filter media removal work starts

Council confirms community support package for 3,380 of the most-affected residents.

Southern Demolition and Salvage Limited conduct a test run, removing and transporting the burnt trickling filter material on Friday 3 and Saturday 4 June.

Work to remove the trickling filter begins.

New activated sludge treatment process becomes fully operational at the plant. This new system pumps wastewater from the converted aeration basins to the clarifiers, which will greatly improve the quality of the wastewater over the coming weeks.

Trickling filters are emptied one month ahead of schedule.

Odours from the oxidation ponds are expected to reduce from September, although it's likely some odours will remain for most of the month. these will progressively reduce as the pond health improves.

A project to increase the biological health of Pond 1 is completed after 16 aerators are installed and turned on, churning more than 300kg of oxygen into the pond every hour.

Longer term, these aerators will ensure the entire pond continues to stay healthy and function well as they have done over summer.

In May 2023 the disc aerators on Pond 1 failed and are in the process of getting repaired.

Insurance negotiations are continuing. Once completed we will provide an update on the timing to restore the full treatment capacity of the plant.