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Kawakawa Wastewater Treatment Plant

Plant overview

The Kawakawa wastewater treatment plant is located off State Highway 1, about 1 kilometre north of Kawakawa. The Kawakawa wastewater treatment plant treats wastewater from the Kawakawa township, including the Bay of Islands college and hospital. There are approximately 550 connections to this scheme.

Treating the wastewater

Wastewater flows from Kawakawa are pumped to the wastewater treatment plant where solids are screened from the wastewater. These solids are pressed to remove a high percentage of liquid. The pressed solids are then taken to a landfill site.

The screened wastewater is then pumped to a bioreactor which uses bacteria to treat the wastewater. A filter removes solids down to a size of 10 µm before the treated wastewater is disinfected by passing through an ultra-violet light (UV light) unit. UV light mimics the natural process that sunlight provides by destroying the DNA of bacteria and viruses so that they cannot replicate in the receiving environment. The treated wastewater is then discharged to a constructed wetland, which acts as a filter before being discharged into the Kawakawa River.

Solids that fall out of suspension during the treatment process, known as sludge, flow by gravity to the sludge ponds. Sludge is removed from these ponds as required and stored in bunded areas onsite.

Monitoring

The discharges from the treatment plant are authorised by a resource consent. Consent conditions also limit the volume and quality of the treated wastewater discharged to the Kawakawa River. You can read a copy of the resource consent here.