Efforts continue to fix Tahuna odour

Dunedin (Wednesday, 10 February 2016) – The focus is shifting to another part of the process as the Dunedin City Council tries to solve odour problems at its major wastewater treatment plant.

Flushing and cleaning work carried out from late last week appeared to have the problem under control yesterday, but last night the “rotten egg” smell from the Tahuna Wastewater Treatment Plant resurfaced.

Tahuna Plant Operations and Maintenance Manager Chris Henderson says, “We thought the problem was with one part of the biological process, but now it appears it may be with another part so we are turning our attention to that.

“We know this is a real nuisance for people in the Tainui area. We apologise for the time it is taking to get the problem sorted and we thank residents for their patience.”

This part of the sewage treatment is a delicate biological process and staff are having to work through the different components to see what might be causing the smell.

“Unfortunately, this is not a mechanical or electrical issue where we can fit new equipment to fix the problem. A biological process is more complicated than that.”

The issue surfaced at the start of last week and the smell is coming from two of the plant’s four bio-filters. The other two bio-filters are working normally.

“This part of the treatment process relies on bacteria and it’s important to keep them happy. They can be very sensitive to changes in weather and other conditions so we are trying to make sure they have the best conditions possible so we get the best results.”

As part of the work carried out, distribution pipes have been water blasted and cleaned, and then inspected via remote camera. Moisture and pH levels have also been checked.

There was very little smell yesterday, but it returned in the evening and staff are trying to work out why. Mr Henderson says the bacteria should be operating effectively so it appears they are being overloaded.

In response, staff are trying to reduce the amount of gas generated. This will make sure the bacteria that consume the gas have the right conditions they need to thrive. It may take a few days to see if this helps.

The DCC is also seeking expert advice and continuing some of the flushing work to try to reduce odour levels in the meantime.

“We are doing our best to get this problem sorted as quickly as possible and we will keep residents informed about what’s happening.”

ENDS

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