National Park Wastewater Scheme

The National Park Wastewater Network provides for the collection and treatment of wastewater generated from approximately 526 properties within the National Park community.

The below schematic shows flow through the network:


The Pipelines

The wastewater reticulation network is 6.12km long and is entirely gravity fed.

A map of the reticulation network is provided in the link at the bottom of this page.

Wastewater Treatment Plant

Wastewater is transported through the National Park Wastewater Network to the National Park Wastewater Treatment Plant, where it is treated prior to discharge. The National Park Wastewater Treatment Plant (WWTP) was commissioned in 1985.

The National Park Wastewater Treatment Plant provides treatment of wastewater through the following steps:

1.      Primary Treatment

1.1 Primary Oxidation Lagoon: Wastewater is piped into a Primary Oxidation Lagoon where heavier solids separate from the wastewater through settling as sludge to the bottom of the lagoon. This sludge is colonised by anaerobic bugs (bacteria that don't need oxygen to survive) which help to break it down by using it as a food source. Bugs also live suspended in the wastewater and use up organic matter “food” throughout the lagoon. 


2.     Secondary Treatment

2.1 Secondary Oxidation Lagoon: Wastewater remaining at the top of the Primary lagoon contains less solids and is piped to the Secondary Oxidation Lagoon where further settling and removal of organic solids takes place. Bugs are present in this lagoon in lower numbers and need oxygen to survive.


3.     Tertiary Treatment

3.1 Wetland: Treated wastewater is trickled into a planted area called a 'Wetland'. Plants in the wetland act as a very basic filter, removing colour caused by algae present in the wastewater and also smaller solids which are suspended in the wastewater. Algae and solids get caught in the plants as the wastewater passes through the wetland and remain behind while cleaner wastewater continues its way through the wetland.

 Wetlands are also thought to help remove pollutants present in wastewater, such as heavy metals (eg, mercury, lead and iron) and nutrients such as Nitrogen and Phosphorus. Scientists are still learning about this and understanding how it works. 

The National Park wetland system consists of six small weirs or dams and a plant system which works particularly well.

Discharge of Treated Wastewater to the Environment

The treated wastewater from the Wastewater Treatment Plant is discharged into an unnamed tributary of the Makaretu Stream.

Page reviewed: 16 May 2017 8:35am