The Wastewater Treatment Plant on Kioreroa Road is largest wastewater processor for Whangārei. It processes an average of 21,000 cubic metres per day of wastewater from homes and businesses and has a replacement value of $65 million.
It treats wastewater for Whangārei’s main urban area, from Kamo in the north , Maunu in the west, Raumanga in the south to Onerahi and Whangārei Heads in the east.
Cleaning up the city’s wastewater takes a lot of steps – it is strained, mixed, filtered, feasted on by live bacteria, dried and disinfected. The resulting solid waste is taken to landfill and the treated water is discharged into the Limeburners Creek Wetlands.
Wastewater is screened to remove paper and other debris.
Large settling tanks separate the wastewater – the solids (sludge) sink to the bottom and the fats and oils float to the top. The sludge, fats and oils are pumped to sludge digestors while the liquid flows to the basalt rock filters.
In our basalt rock trickling filters live millions of microbes that eat and digest the organic compounds in the wastewater. This is a 100% natural way to treat wastewater and these bugs are our heroes, doing all the hard work for us without the need for nasty chemicals. These bugs are very susceptible to chemicals which is why it is important not to flush things like paint down our drains.
The aerators are like two giant eggbeaters – adding oxygen into the wastewater to create a nutrient-rich soup for superbugs that consume microscopic particles in the water. This is the part of the process that causes the smells the plant sometimes produces.
Rotating filters remove any remaining fine particles from the water before it is disinfected by ultraviolet (UV) tubes that kill any remaining bugs.
The treated water receives a final filter through thousands of native plants in the Limeburner Creek Wetlands. In 2014, the wetlands had a major makeover and instead of the plants being planted in the ground they are now planted on floating mats, their roots extending down into the water. You can explore the wetlands, which provide a great habitat for birds, via a timber boardwalk.
Solid waste collected during the process is heated and dried in two large digestors which heat it and dry it out. The water that is removed is returned to the waste process and the sludge is taken away to landfill. Two biogas generators harness the poo power created by methane gas during the sludge treatment process and turn it into electricity.