Tour of Māngere Wastewater Treatment Plant

Dealing with wastewater for Auckland’s 1.7 million people is a big job. Every day Watercare collects over 400 million litres of wastewater, which runs through a network of 18 treatment plants, 518 pump stations and more than 8,000km of pipes.

Last Friday the Howick Local Board had the opportunity to tour the largest treatment plant at Māngere. This plant handles roughly 75% of Auckland’s wastewater (nearly ¼ of NZ’s wastewater) managing an average of 4.5 cubic metres a second and peaking at 12 cubic metres a second.

Sewage is treated through three stages – mechanical, biological, and filtration. The first stage involves separating solids from liquid using rotating filters and sedimentation tanks. The second stage is carried out in nine large reactors and clarifiers, each capable of holding 31.3 million litres (enough to serve 200,000 people). No chemicals are used, with special bacteria that eats nitrogen and ammonia. The final stage involves filtration and disinfection using powerful ultraviolet (UV) that kills any remaining pathogens. You can see the video showing almost perfectly clear water flowing out of this final stage.

Once processed, the water is discharged into the Manukau Harbour with the outgoing tide. This happens approximately 12 hours after the sewage enters the plant, showing the incredible efficiency of the operation.

Keeping the site going 24/7 requires a dedicated team of maintenance, operations, and management staff. It was great to have the opportunity to tour the site and understand this important process. Thank you to everyone who ensures that our wastewater is treated properly, looking after our environment and people.

You can help keep the pipes flowing by ensuring you only flush the three Ps down the toilet – pee, poo, and paper. Do not flush wet wipes – they block up the system!