'Stage 3' upgrades completed at Shotover wastewater facility

A significant upgrade at Shotover Wastewater Treatment Plant received its practical completion certificate this week, marking the end of the third stage of an upgrade programme being carried out at the facility since 2015. Work on 'Stage 3' has been underway since August 2023.

Improvements to the plant's treatment process have been operational for the last few months, and the announcement acknowledges the latest upgrades at Shotover Wastewater Treatment Plant are considered formally complete.

Queenstown Lakes District Council (QLDC) General Manager Property & Infrastructure, Tony Avery was pleased to share the news, saying work completed at the facility provides further improvements to the treatment of wastewater, more capacity, and the ability to meet future growth for approximately the next 20 years.

"We've introduced a second Modified Ludzack‑Ettinger (MLE) reactor and clarifier down at the facility to process wastewater, enhancing the quality of treated wastewater discharged from Shotover Wastewater Treatment Plant," said Mr Avery.

"These upgrades are essential to our long‑term wastewater management strategy as more people choose to make the Whakatipu Basin their home, helping to protect the environment and ensuring ongoing compliance with consent conditions for the quality of the treated wastewater discharged."

Completion of the new MLE reactor and clarifier means the oxidation ponds operating at the facility since 1974 are no longer required as part of the treatment process. All wastewater now receives a much higher standard of treatment through the MLE process, after which flows receive ultraviolet (UV) disinfection prior to being discharged from the plant.

The 'Stage 3' upgrade also included converting part of one of the old oxidation ponds into a calamity basin, which can be used to store wastewater in the event the treatment plant is unable to accept some or all the incoming flows for a period.

Mr Avery added that following this work, there was already a marked improvement in the quality of treated wastewater discharged from the facility, with the latest results from Council's thorough testing programme available in an online dashboard.

"Those interested can easily use the dashboard on QLDC's website to check how Shotover Wastewater Treatment Plant is performing, whether that's looking at treated wastewater at its point of discharge, or across multiple monitoring sites we've set up in Shotover and Kawarau rivers," said Mr Avery.

Separate to this project and associated with work on a long‑term disposal solution for Shotover Wastewater Treatment Plant, the remaining two oxidation ponds at the facility will be drained and have their sludge removed over the next two years.

One of those ponds will be turned into an additional emergency basin for treated wastewater in the event it isn't meeting discharge requirements, or if any issues are encountered at the end of the treatment process (for example, at the UV disinfection stage).

Shotover Wastewater Treatment Plant currently services Whakatipu Basin communities of Queenstown, Arthurs Point, Frankton, Kelvin Heights, Quail Rise, Shotover Country, Lake Hayes Estate, Lake Hayes, and Arrowtown.

Construction of the third stage of work on Shotover Wastewater Treatment Plant was carried out by McConnell Dowell.