Every year, up to 12.9 billion litres of wastewater is collected from 31,700 connections around the city.
Forty pumping stations help move the wastewater along a network of pipes that, if laid on end, would stretch from Palmerston North to Hamilton (405km).
When it arrives at our treatment plant in Tōtara Road the first thing we do is remove things that shouldn’t have gone down a drain – like wetwipes, condoms and tampons. These need to go in your bin.
The wastewater is then pumped with air to remove grit or sand, before passing onto our sedimentation tanks. Here, the solid material sinks and the cleaner material moves on. Solid material isn’t just poos – it includes fat and oil and food scraps from your sink.
It then goes to lagoons where air is pumped into the water allowing microorganisms to grow and eat any remaining solid material.
Then we remove phosphorus from the water and blast it with UV light. By the time the water reaches our small wetland, 99.9% of bacteria has been removed. The water then passes through the wetland into the river after about four days of treatment.
The remaining solids stay on site for 20 days, where bacteria help break it down before it’s removed offsite.