The 23.5 million dollar upgrade to Queenstown’s sewage treatment system is well underway and expected to be completed in September. It will then begin a commissioning period of around three months with the aim of being fully operational by mid-December
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, just after the Shotover Bridge on the way into town.
The new biological nutrient removal plant uses bacteria to transform the organic material in wastewater into simple substances that will not decompose further, resulting in a much cleaner end product.
This is achieved using the Modified Ludzack-Ettinger (MLE) process where raw sewage is screened to remove the bulk of the 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 waste. The second tank then feeds the waste with an oversupply of oxygen, causing biological processes that further treat the material.
The material is then pumped into a settling tank 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.
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