Rāwene Wastewater Treatment Plant

The Rāwene wastewater treatment plant is located on Rāwene Road, south of the Rāwene township in the Hokianga. The township was reticulated in 1982 to mitigate the impact of leaky septic tanks on the water quality of the Hokianga Harbour. The treatment plant was built at this time to receive and treat the sewage flows. Today the plant serves a population of approximately 590, and receives septage from the surrounding areas including Kohukohu, Whirinaki and Ōpononi. On average the plant treats 250 cubic meters of wastewater a day.

Treating the wastewater

Solids are removed from the wastewater before entering the large oxidation ponds and then two maturation ponds. In these ponds a combination of sunlight, algae, and microbes perform biological processes which clean the wastewater. Sunlight and time naturally kill off harmful bacteria, while the algae and microbes consume the organic matter in the wastewater.

The treated wastewater is then pumped to a series of constructed wetlands. Wetland plants use the nutrients in the water to grow at the same time removing nutrients from the wastewater. The treated wastewater is discharged into a drainage ditch where it eventually discharges to the Ōmanaia River estuary via tidal floodgate.

Monitoring

The discharges from the treatment plant are authorised by a resource consent. Consent conditions require regular monitoring of the wastewater quality along the treatment process. Consent conditions also limit the volume and quality of the treated wastewater discharged. You can read a copy of the resource consent here.