The Ohakune Wastewater Network provides for the collection and treatment of wastewater generated from approximately 1893 properties within the Ohakune community.
The below schematic shows flow through the network:
Wastewater from Ohakune township is transported through 6.12km of pipelines to the Ohakune Wastewater Treatment Plant. A map of the collection network is provided in the link at the bottom of this page.
Raw sewage is also received directly at the Wastewater Treatment Plant from septic tank trucks which empty into a Septage Receiver.
Wastewater Treatment Plant
1. Primary Treatment
1.1 Step Screen: Raw wastewater arriving at the Wastewater Treatment Plant is passed through a screen with holes in it. Fluid wastewater and smaller solids pass through the holes and on to the next step in the treatment process. Larger solids, including wetwipes, rags, and other rubbish items that end up in our wastewater system, are retained by the screen as they are too big to fit through the holes (a bit like a large scale sieve). These items must be disposed of to landfill.
3. Tertiary Treatment
3.1 Stone Media Lagoon
Wastewater leaving the Secondary Oxidation Lagoon travels through a Stone Media Lagoon.
Stones (or gravel) act as a very basic filter, removing algae present in the wastewater and also removing smaller solids which are suspended in the wastewater. Algae and solids get caught in the stones as the wastewater passes through the stone media and remain behind while cleaner wastewater continues on its way to be disinfected by Ultra Violet irradiation.
3.2 Ultra Violet (UV) irradiation: Wastewater is further treated by exposure to Ultra Violet light. This kills any bacteria and viruses remaining in the wastewater by destroying their genetic core (DNA). It is also effective against many protozoa.
Discharge of treated wastewater to the environment
The treated wastewater from the Ohakune Wastewater Treatment Plant is discharged into the Mangawhero River.