Rangataua Wastewater Scheme

The Pipelines

Wastewater from Rangataua township is transported through 4.1km of pipelines to the Rangataua Wastewater Treatment Plant. A map of the collection network is provided in the link at the bottom of this page.

Wastewater Treatment Plant

The Rangataua 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 pond. This sludge is colonised by anaerobic bugs 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 Basic 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.