1. Primary Treatment
Primary treatment of wastewater in Pipiriki is undertaken in septic tanks.
The network is a STEDS (Septic Tank Effluent Discharge Scheme), which collects and treats effluent discharge from septic tanks located on the individual properties.
Three main processes take place in the septic tank:
(i) The heavier, solid particles settle to the bottom of the tank, forming a sludge layer;
(ii) Lighter materials such as fat and grease float to the surface, forming a scum layer, and
(iii) Within the septic tank there is little or no oxygen, and anaerobic bacteria (bugs that can live without
oxygen) break down some of the solids. This helps reduce the build-up of sludge in the tank.
The clearer liquid (supernatant) lying above the solid 'sludge' layer in the septic tanks throughout the village has been treated to a Primary level and contains only smaller particles. This supernatant gravity feeds through pipelines to the Pipiriki Wastewater Pump Station (WWPS).
Wastewater Treatment Plant
Each sand filter is used for a two week period while the other is rested. Effluent from the pump station is discharged onto the top of the filter bed and then works its way through the sand bed at a high rate.
Sand acts as a very basic filter, removing algae present in the wastewater and also smaller solids which are suspended in the wastewater. Algae and solids get caught in the sand as the wastewater passes through the media and remain behind while cleaner wastewater continues on its way.
The Wastewater Pump Station collects effluent from the sand filters via a second pump sump and discharges to an irrigation field for land disposal.
Discharge of treated wastewater to the environment