Upgrades Scheduled For Shotover Wastewater Treatment Plant

A planned third stage of work to upgrade Shotover Wastewater Treatment Plant is set to start in August 2023.

Queenstown Lakes District Council (QLDC) General Manager Property & Infrastructure, Tony Avery said the $37.5M project would further improve wastewater capacity in the district and provide for future growth through to the year 2048.

“These upgrades will see the construction of a second Modified Ludzack-Ettinger (MLE) reactor and clarifier down by Shotover Delta, and a range of new equipment, technology and supporting infrastructure to help keep the district’s pipes flowing,” said Mr Avery.

The current treatment process using residual oxidation pond systems will no longer be required once work is complete, with the new process handled by the two MLE reactors.

Mr Avery said treating wastewater with the reactors would ensure long-term compliance as more people chose to make the Whakatipu Basin their home, helping to protect the environment and meeting tighter effluent consent limits if required by Otago Regional Council (ORC) in the future.

“Furthermore, one of the existing oxidation ponds on site will be repurposed as part of the works, with a portion to be used as a basin for improved stormwater management on site. Another area will be converted to act as a calamity storage pond for the extremely rare occasion when the treatment plant might go offline unexpectedly,” said Mr Avery.

The 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.

Once complete, these upgrades will allow the plant to receive additional wastewater flows from Jacks Point Village, Hanley Farm, Ladies Mile and an extension of the Quail Rise residential development area.

The construction contract for the third stage of work on Shotover Wastewater Treatment Plant was awarded to McConnell Dowell.

McConnell Dowell plans to reduce the project’s estimated carbon footprint by reusing spoil from the site, reducing transport emissions, using sustainable materials, and reducing the amount of steel and concrete used where possible.

Mr Avery added the contractor would put in place measures to mitigate any potential stormwater, dust, noise, and odour effects during construction.

Construction will typically occur between 7.30am and 6.00pm on weekdays, with the project expected to be complete in late 2025 before commissioning of the new plant infrastructure follows in early 2026.

About The Modified Ludzack-Ettinger process:
The Modified Ludzack-Ettinger (MLE) process sees raw sewage screened to remove the bulk of the non-degradable solids before it’s pumped through a series of tanks. The first tank starves the bacteria of oxygen, causing them to begin to break down elements in the wastewater in order to produce the oxygen they need to survive. The second tank then feeds the wastewater with an oversupply of oxygen, causing further biological processes that complete the stabilization of the organic matter, reducing the nitrogen concentration in the end product.

The material is then pumped into a settling tank (a clarifier) that further separates and clarifies the resulting liquid. The processed clear water is then UV treated and pumped out of the system. Some of the remaining solids are then pumped back to the start of the process to begin it all over again, while the rest is pumped into a dewatering plant where it is dried out and removed, to be disposed of at an approved off-site location.