Taumarunui Wastewater Scheme

The Taumarunui Wastewater Network provides for the collection and treatment of wastewater generated from approximately 2139 properties within the Taumarunui community.

The below schematic shows flow through the network:


The Pipelines

Wastewater from Taumarunui township is transported through approximately 49km of pipelines to the Taumarunui Wastewater Treatment Plant. The network consists of ten pumping stations (Bullians Avenue, Camp Ground, Golf Road, Huia Street, Matai Street Nos 1 and 2, Sunshine Road, Tubby Woods, Tuku Street and Victory Bridge).

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

Wastewater Treatment Plant 

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

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.


1.2  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.  

 1.3 Aerators: Four mechanical Aerators circulate air or oxygen through the water and help to make water flow around the lagoon. The chopping action of the Aerators also helps to physically break up blue algae on the surface of the wastewater, preventing algal bloom.


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 also present in this lagoon, but 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 to the Ultra Violet Irradiation system.

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


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.

The figure below shows a UV lamp cartridge taken out of the UV system for servicing.


The UV cartridge is slotted into the below UV system. Water flows through the system and is exposed to UV irradiation.


Discharge of Treated Wastewater to the Environment

The treated wastewater from the Taumarunui Wastewater Treatment Plant is discharged into the Whanganui River.

Page reviewed: 29 Apr 2017 6:01pm