Odour from the oxidation ponds is most likely during seasonal change.
Odour at the Christchurch Wastewater Treatment Plant doesn’t stay the same all year. It follows a seasonal cycle driven by temperature, sunlight and biology in the ponds.
The oxidation ponds receive a high volume of wastewater, meaning there is a lot of organic material for bacteria to break down, which uses up oxygen.
In summer, sunlight helps algae grow and produce oxygen, keeping conditions healthy, while in winter both algae and bacteria slow down, so oxygen demand remains low.
However, during spring and autumn this balance can shift – bacteria may use oxygen faster than algae can produce it. Because the ponds are already working hard under high loads, they are more sensitive to these seasonal changes, and oxygen levels can temporarily drop, leading to short-term odour events.
Explore the points below to learn what factors influence odour throughout the year.