Project Shotover upgrade close to completion

The 30 million dollar upgrade to Queenstown’s sewage treatment system, Project Shotover, is expected to be completed this month. It will then begin a commissioning period with the aim of being in full operation by mid-December 2016.

The upgrade will see two thirds of Queenstown’s waste treated in a new biological nutrient removal system in huge concrete tanks currently under construction on the Shotover Delta.

QLDC Senior Project Manager Lane Vermaas is pleased with how the project is tracking so far, “Downer have done a great job keeping everything on time and to budget. We’re looking forward to kicking off the commissioning process and getting the system completely online in December."

Commissioning Project Shotover is expected to begin mid-September. It involves circulating wastewater through the tanks in order to develop the bacteria needed for the treatment system to function. This bacterial culture will enable the biological nutrient removal plant to stabilize the organic material in the wastewater, resulting in a much cleaner end product than the current system.

During the commissioning period people may notice a layer of white foam sitting on top of the holding tanks. This is a normal part of the process and happens when the wastewater in the tanks is aerated in order to kick start the biological process. As the biomass of bacteria is still growing, the detergents in the wastewater from substances like soap and shampoo react to form this white foam layer for about the first week or so. At this stage additional odour is generated but will be mitigated with supplementary odour control units.

Mr. Vermaas says the commissioning period is expected to take around three months. “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.”

Queenstown Mayor, Vanessa Van Uden believes this is a significant advance for Queenstown’s infrastructure. “Project Shotover has involved a significant investment by QLDC and is part of ensuring the town’s infrastructure is future proofed for population increases in years to come. It also produces a much more environmentally friendly output and I think everyone can agree that this is a great step forward for Queenstown.”

How the new treatment system works

The treatment plant operates using the Modified Ludzack-Ettinger (MLE) process, where raw sewage is screened to remove the bulk of the non-degradable solids and then 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.

This upgrade has been designed with future growth in mind and can easily be expanded if the need arises. It will also offer a far cleaner end product, with E-coli at the levels accepted as safe for swimming under the recreational bathing standards

ENDS

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