Gisborne city’s wastewater treatment plant in Banks Street treats domestic wastewater to a far higher standard than previously.
The plant was commissioned in December 2010, as required by a condition of the resource consents granted in September 2007.
All domestic wastewater is processed through a new biological trickling filter system before being discharged through the existing 1.8km outfall to the sea.
The trickling filter system enables fine wastewater solids to be transformed into plant-like matter in a process known as biotransformation.
How the treatment plant works
Domestic wastewater is screened by one of 2 rotating drum screens (one is on duty, one on standby) and then passed through a vortex grit removal chamber. Two more drum screens are used for industrial wastewater.
The screenings and grit removed from these stages will have the water pressed from them before being bagged and trucked to a landfill at Paeroa.
The screened and de-gritted wastewater gravitates into a biological trickling filter pump station before being pumped up through the tank’s central column to a height of 8m, then distributed through 6 rotating arms to trickle slowly through many different channels in 10 layers of large plastic media blocks.
In so doing, very fine screened and degritted wastewater solids are transformed into plant-like matter. The resulting treated wastewater is pumped via a new outfall pump station to the existing marine outfall, 1.8km out to sea.