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A sprinkler system is being installed over the smouldering trickling filters at the fire-damaged plant to help extinguish hot spots and reduce the smell.
"We are aware there are some odour issues around the plant because the plastic media housed within two trickling filters has partially melted and is giving off an acrid smell," said council head of three waters and waste Helen Beaumont.
"We hope to reduce the smell by putting a constant stream of water through the trickling filters so we are working through options for installing sprinklers over the structures."
Beaumont said the roof structure and the wastewater distribution system for the trickling filters has been destroyed, but it is still not clear how much of the plastic media housed within the filters has been damaged.
It is also not yet known whether the concrete housing has been structurally compromised, although external inspections indicate there is no immediate risk of collapse.
"To undertake a full internal inspection we will need to gain access to the interior of the trickling filters and remove most, if not all, of the material inside. This is going to a challenging logistical exercise," Beaumont says.
"There are still hot spots deeper within the filter media - it is about six metres deep. We are assessing options for gaining access so we can do a full inspection once the material has cooled sufficiently for us to safely enter."
Preliminary testing of the debris from the fire indicates none of the material contains asbestos.
Beaumont said while people can still use their toilets, bathrooms and kitchens as usual, the loss of the trickling filters at the wastewater plant is impacting on the wastewater treatment process.
"We are modifying the treatment process so that we can bypass the filters, however, doing that will impact on the quality of the effluent discharge.
"We have assured Environment Canterbury that we will make every effort to comply with the conditions of our discharge consents and that we will liaise with their compliance monitoring officers during the recovery effort."
Beaumont said it takes about 20 days for the wastewater that is piped into the plant to pass through the treatment process and to get discharged via the ocean outfall. So it will be some time before any changes in the quality of the discharge becomes evident.
"An adaptive management plan is being worked on with the objective of ensuring the best possible outcome with respect to the quality of the effluent discharge within the practical constraints of the plant," Beaumont says.