Tonnes of melted material removed from fire-ravaged wastewater plant

Thursday, 9 December 2021

Christchurch City Council has released drone footage of the fire damage to two filter buildings at the Bromley wastewater treatment plant.

Excavation of tonnes of melted material from the fire-ravaged Christchurch wastewater treatment plant has revealed the state of the plant's filters, but the future of the site is still unclear.

Fire destroyed two trickling filters at the Bromley plant on November 1, causing residents to be evacuated and a public health warning because of the thick, black smoke.

The large filters played a crucial role in the wastewater process, and unpleasant smells have wafted across parts of the city since the fire, city council staff warning the odours could linger for years.

Council water boss Helen Beaumont said an excavator removed 2.2 tonnes of melted material from one of the destroyed filters on Thursday, providing “valuable information”.

**READ MORE:

The fire-ravaged site has created unpleasant smells which have been wafting across parts of the city since the fire and are expected to last for years to come.

* Odour from wastewater treatment plant could last months, council says

* Council ponders how to inspect burnt filters at wastewater plant without worsening odour

* Wastewater treatment blaze extinguished after burning for 19 days

Firefighters battle the massive blaze from the air.

“We now know the condition and state of the filter media, how easily it can be removed, and how much it packs down when it’s compressed.

The huge blaze led to residents being evacuated and a public health warning issued as thick, black smoke spread across the city.

“There’s quite a bit of open space between the filter media to provide room for the biological slime to grow and to allow air to pass up through the trickling filters. We will be compacting the media to make it easier to dispose of this material.”

She said damage assessments of the concrete trickling filter structures were under way and the results would determine if the structures need to be completely demolished.

“If the structures need to be demolished, that will require a much different deconstruction process than if the walls can be preserved.

“If we have to remove the filter media in the same way we undertook Friday’s trial, the process will be painstaking and will need to be done very carefully so that the trickling filter walls aren’t damaged.”

There was no notable increase in odours as they removed the media, Beaumont said, which was “encouraging”.

“Unfortunately we still have the ongoing smells coming from the secondary contact tanks and the oxidation ponds, and we’ll continue to treat the wastewater at these points.”

Monitoring had shown the quality of water being pumped into the ocean continues to meet consent conditions, which the council was “very pleased about,” Beaumont said,

The media in each of the trickling filters is estimated to be between six and seven metres deep, with a total volume of about 24,000 cubic metres.

This material is expected to compact down to 3000 cubic metres, which would weigh in the region of 500 tonnes.