Matarangi Wastewater Treatment Plant Upgrade

Matarangi Treated Wastewater Discharge Consent Renewal

The Matarangi Wastewater Treatment Plant (WwTP) is owned and operated by our Council with resource consents from Waikato Regional Council (WRC) that authorise the discharge of treated wastewater from the plant, through a discharge drainage and filtration system, which eventually flows out to the Whangapoua Harbour.

Since the treatment plant was built in 1988 it’s been upgraded and modified to optimise wastewater treatment processes, meet the needs of the growing community and remain compliant with the resource consents. As the township of Matarangi is experiencing significant growth with more subdivisions, it is now necessary to upgrade the plant to meet increasing demand.

Following a four-year community working group process, we’ve lodged an application with WRC to renew the treated wastewater discharge resource consent for the WwTP. The application was publicly notified by WRC on 6 November 2021.  The public notice and application documents can be found on the WRC website www.waikatoregion.govt.nz/community/whats-happening/have-your-say/rc-applications/tcdc-app141878/

In our 2021-2031 Long Term Plan we allocated approximately $18.5 million to invest in the WwTP by 2026. The exact timing is dependent on the outcome of the resource consent process. The improved facility will also improve the effluent quality of the treated wastewater.

Existing Plant Processes

The existing WwTP targets the removal of solids,  organic, nutrients and pathogens from wastewater. The treatment process includes:

  • Inlet screening;
  • Treatment through three ponds;
  • Membrane filtration;
  • UV disinfection.

Following UV disinfection, treated wastewater is discharged to gravel trenches and flows toward a discharge drain. The drain joins an unnamed tributary of the Mapauriki Stream and eventually flows into the Whangapoua Harbour (see below). This treated wastewater meets the water quality requirements of the existing consent.

Matarangi Wastewater Treatment Plant

Matarangi Working Group

From 2016-2020 the Matarangi Wastewater Project Working Group, including representatives from iwi, community and environmental groups and agencies, considered a wide range of future wastewater treatment options and disposal alternatives for the community. 

The working group determined that the best option at Matarangi was to upgrade the existing plant at the current location, in the next five years.  The upgrades will further improve treatment processes and therefore improve the quality of the WwTP discharge to the environment.  

Resource Consent Renewal Application

The application is to renew the resource consent to discharge treated wastewater within treated wastewater quality limits, from the Matarangi WwTP to gravel trenches until the upgraded plant is commissioned. Treated wastewater flows from the gravel trenches to the Mapauriki Stream and Whangapoua Harbour.

After the upgraded plant is commissioned, treated wastewater will be from the plant to a constructed wetland and then to the Mapauriki Stream and Whangapoua Harbour. 

Environmental Effects

The effects of the discharge of treated wastewater on freshwater, coastal water and associated ecosystems were assessed as part of the application. The assessments considered the effects of the current and future discharge volumes and nutrient loads on freshwater, coastal water, cultural values, ecosystems, amenity values and public health.  The assessments concluded that the effects of the discharged treated water following WwTP upgrades will be minor and that, before upgrades, attention needed to focus on methods for further reducing nutrients.  Since the environmental assessments were made and the resource consent renewal application lodged, we’ve completed an upgrade of the membrane filtration unit and pond desludging.  This has improved the quality of the treated wastewater that is discharged and reduced nutrient levels.

Upgrades

The Matarangi working group looked at future option for the WwTP including plant upgrades or a new WwTP to further improve treatment quality and to provide for community growth. 

The planned upgrade will focus on increasing the capacity of the plant to cater for growth and improving the removal of nutrients (nitrogen and phosphorus).  The current concept design aims to achieve this by installing a Biological Nutrient Removal (BNR) plant, which is a more modern and effective treatment technology than the existing pond treatment process. 

The final wastewater treatment process design, however, will depend on the new resource consent conditions. Assuming the notified resource consent process does not take too long, our current goal is to have the upgraded treatment plant operational by 2026. The upgraded facility will include new wastewater treatment processes and parts of the existing system.

Further Information

The Matarangi WwTP resource consent renewal application, further information and notification details can be found on the Waikato Regional Council website www.waikatoregion.govt.nz/community/whats-happening/have-your-say/rc-applications/tcdc-app141878/. 

WRC is taking submissions on the application until 2 December.

Our Council’s contact for the application is Ian Smith ian.smith@tcdc.govt.nz or phone 07 868 0200