Queenstown council infrastructure operations manager Simon Mason said the new kit began treating wastewater at the end of August, and the commissioning process was completed last month.
It is now "operating within consent limits", Mr Mason said.
In an emailed response to questions, he said the second unit of the Modified Ludzack-Ettinger (MLE) system had roughly doubled the plant’s capacity, meaning it could now process an average daily flow of 20,600cu m of wastewater, a peak daily dry weather flow of 24,000cu m, and a peak wet weather flow of 39,800 cu m per day.
Although long-planned, the $37.5 million project aligns with a slew of Environment Court orders, made in June, that require the council to achieve a series of milestones in upgrading the plant — whose output has been discharged into the Shotover River for the past seven months — and replacing its failed land disposal system.
The Otago Regional Council (ORC) applied for the orders in January in response to breaches of the council’s consents for operating the plant, and a series of abatement and infringement notices the ORC has issued since 2021.
One of the court’s orders required the council to have a long-term disposal system for the plant’s output operating by the end of 2030.
Mr Mason said councillors would be briefed on the shortlisted options at a workshop before Christmas, with the preferred option to be presented for a decision early next year.
The conversion of part of Pond 1 into a "calamity basin" for raw wastewater, and another part for improving wastewater management at the site, is expected to be completed by the end of this month, he said.
Ponds 2 and 3 will remain full, but not operational, for the next 12 months in order for the wastewater to become "inert".
There will be occasional, planned discharges from the two ponds to control their water levels until their decommissioning, when they will be drained and dried out, before the end of 2027.
