27 Jul 2022

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The final part of the interim solution is in place at the wastewater treatment plant, with the new activated sludge treatment system made fully operational.

Head of Three Waters, Helen Beaumont, says the new system pumps wastewater from the converted aeration basins to the clarifiers, which will greatly improve the quality of the wastewater.

“This new system will significantly improve the wastewater being treated at the plant over the next three weeks, before the wastewater begins moving through the oxidation ponds from mid-August,” says Ms Beaumont.

“Depending on the weather, it then takes another three to six weeks for that better quality wastewater to flush through the six ponds.

“The unpleasant smells are coming from these oxidation ponds, but we’re on track to see major improvements in the health and odours from these ponds by mid-September.”

The November 2021 fire that destroyed the two trickling filters at the wastewater treatment plant reduced the plant’s ability to effectively treat wastewater by about 60 per cent. As a result, and despite the Council’s best efforts, poorer-quality wastewater has entered the oxidation ponds since.

The increased organic load on the ponds led to higher levels of an odorous gas called hydrogen sulphide, which has caused ongoing distress and affected the well-being of nearby residents over the past eight months.

“Living with the stench and dealing with this situation has been extremely hard for residents in the east, but the good news is we can now see the light at the end of the tunnel,” Ms Beaumont says.

“However, until a permanent solution is found and established, we still expect the ponds to produce smells from time-to-time.

“Our interim system has very little margin for error, so if there’s a breakdown, a major power outage or a natural disaster, the quality of the wastewater entering the oxidation ponds could again be compromised.”

The interim solution has a design life of five years and is expected to be in place for two to five years, depending on the time taken to rebuild or replace the trickling filters. Staff are working on options now, with a decision expected by the end of the year.