The plant began operating before Christmas, but would not be fully operational until next week, Queenstown Lakes District Council senior project manager Lane Vermaas said.
Commissioning had been expected to be completed last month, three months after construction works ended.
The plant would be officially opened on February 27, by which time roading, security fencing and some landscaping would be completed.
Designed and built by Downer — which would also operate the plant for its first five years — it was based on a "tried and true" biological nutrient removal process.
But its high-tech control system was highly automated, including automatic sampling and online sensors, which meant it could be monitored by one person working on-site.
Located by the State Highway 6 bridge across the Shotover River, the plant treats wastewater from central Queenstown, Frankton, Quail Rise, Arthurs Point, Shotover Country, Lake Hayes, and Arrowtown.
Mr Vermaas said it treated two-thirds of the resort’s waste, and the remaining third was processed through existing treatment ponds.
The output from both processes was UV-treated to kill bacteria and viruses before being discharged into the Shotover.
The second stage of the project was scheduled to occur between 2028 and 2030.
It would involve the construction of another main tank as well as a clarifying tank and also the retiring of the pond system.
However, in the meantime the council was moving ahead with its plans to dispose of the plant’s entire output on council land between the plant and the Shotover delta.
Although the council had until 2022 to complete the project, it had already lodged resource consents with the Otago Regional Council and could start building the land dispersal field as early as this year, he said.
