Council is considering how to inspect burnt filters in a wastewater treatment plant without making odors worse

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The Christchurch sewage treatment plant fire on November 1.

Tobi Wheeler / Supplied

The Christchurch sewage treatment plant fire on November 1.

Christchurch Council is trying to figure out how to inspect its fire-damaged wastewater filters without making odor problems worse for residents.

On November 1, the trickle filters at the Bromley sewage treatment plant burned down in a fire that spread thick black smoke across the town.

The fire resulted in the evacuation of residents and a public health warning, as both filter roofs collapsed. Eight fire trucks tackled the blaze and one person was treated for minor injuries at the scene.

Jane Davis, city council director of infrastructure, planning and regulatory services, said they would remove a small amount of material from the filters in early December on a trial basis.

READ MORE:
* Efforts to cool wastewater treatment plant hot spots continue more than a week after the fire
* A sprinkler should be installed in a damaged sewage treatment plant to dispel the lingering smell of smoke
* The Council is not yet in a position to assess the damage after the fire at the wastewater treatment plant

Smoldering trickle filters, four days after the start of the fire.

CCC Information Line / Provided

Smoldering trickle filters, four days after the start of the fire.

“The result of this will help determine the best approach to remove the material and the likely time frame,” said Davis.

The Council’s approach should “take into account the wider impact on the community,” as removing the material could make odors worse, she said.

“The trickle filters have been inspected from the air and outside, but we will not be able to do a full interior inspection of the structures until the filter material has been removed. “

The Christchurch Wastewater Treatment Plant in Bromley treats wastewater from across the city of Christchurch.  The roof of two trickle filters collapsed in a fire on November 11.  City council says it can bypass filters.

Christchurch City Council

The Christchurch Wastewater Treatment Plant in Bromley treats wastewater from across the city of Christchurch. The roof of two trickle filters collapsed in a fire on November 11. City council says it can bypass filters.

Council has received a few formal complaints about the smell. He was also made aware of community concerns through social media and complaints through Environment Canterbury’s “Smelt It” app.

“Unfortunately, the fire suppressed an important step in our wastewater treatment process. As a result, we are getting an increase in plant odors and that should continue, ”Davis said.

Trickle filters are part of the wastewater treatment process. The water from the settling ponds is pumped to the top of the filters where it is evenly distributed over the surface of the filters.

CCC Information Line

Christchurch City Council has released drone footage of fire damage to two filtration buildings at the Bromley Sewage Treatment Plant.

The bacterial sludge grown inside the filters consumes the nutrients contained in the wastewater. As the flow is pumped through the filters, the sludge is washed away as a floating solid.

The council has managed to bypass filters since the fire, which is being investigated by an independent investigator.

Davis said that to suppress the odor, the council continues to use water foggers and add polyaluminum chloride to deposit suspended solids in the wastewater.

The first of a number of aerators will soon be installed in the oxidation ponds, she said.

The Council’s tests have shown that although the composition of its treated effluent has changed since the fire, it remains clean enough to be discharged into the ocean under the terms of its resource consent, Davis said.

“We are working with Environment Canterbury and will continue to monitor this closely. “


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