And when fully commissioned in December, the system’s end product will be safe to swim in, the Queenstown Lakes District Council says.
Construction works for stage one of the Project Shotover upgrade should be finished next week, at which time a three-month commissioning process will begin.
Queenstown Mayor Vanessa Van Uden said the project had required a major investment, and future-proofed the town’s infrastructure for its expected rise in population.
"It also produces a much more environmentally friendly output, and I think everyone can agree this is a great step forward for Queenstown."
Once the plant is fully operational, it will treat two-thirds of the resort’s waste with a biological nutrient removal system that employs concrete tanks built at the plant’s site by the Shotover bridge during the past 12 months.
It will take wastewater from Queenstown, Frankton, Quail Rise, Arthurs Point, Shotover Country, Lake Hayes, Shotover Country and Arrowtown.
The end product will have E coli at a level accepted as safe for swimming under recreational bathing standards.
The remaining one-third will be processed through the existing pond treatment system.
The output from both treatment processes is UV-treated to kill bacteria and viruses before being discharged into the Shotover River.
Council senior project manager Lane Vermaas said the commissioning process involved circulating wastewater through a series of tanks to develop the bacteria needed for the system to function.
The bacteria enabled the plant to stabilise organic material in the wastewater, resulting in a much cleaner end product than the existing system.
"People may notice some foam and increased smell at the site over this time, but rest assured this is all expected and a perfectly typical part of the process."
Stage two of the upgrade is the construction of a land dispersal field between the plant and the Shotover delta, which will take the whole output of the plant by 2022.
The third stage involves the construction of more treatment facilities at the same site and the retiring of the pond-system, which is scheduled to occur between 2025 and 2031.
How it works
● Raw sewage screened then pumped through a series of tanks
● First tank breaks down elements in wastewater
● Second tank stabilises organic matter and reduces nitrogen concentration
● Settling tank further separates and clarifies the resulting liquid
● Processed clear water is UV-treated and pumped out of the system
● Some remaining solids are pumped back to the start of the process. The remainder are dried and disposed of off-site
