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Rotorua Wastewater Treatment Plant upgrade

Finding a solution to prepare for the future

Rotorua's Wastewater Treatment Plant is being upgraded to cater for future growth and ensure we manage our waste responsibly, in a way that:

  • Protects people's health
  • Is environmentally sustainable; and
  • Is culturally appropriate.

The objectives are inspired by the Lakes Water Quality programme - (PDF, 11.4MB) and align to the Council Vision 2030 goals of creating a vibrant and sustainable future for Rotorua and its residents.

November 2024 update

Progress is advancing on the Rotorua Wastewater Treatment Plant upgrade. Contractors from TRILITY have completed the earthworks and bioreactor shutdowns. These shutdowns support the installation of upgraded aeration pipework which will enhance air flows into the bioreactor for better nitrogen and phosphorus removal.

Works started in December 2022 and are planned to be complete in 2027. The design includes:

  • New inlet screening systems
  • Modifying existing Bardenpho unit to improve phosphorus and nitrogen removal
  • Installing new membrane reactor units to further clean wastewater and remove nutrients
  • Ultraviolet treatment to remove all remaining pathogens
  • Addition of wastewater storage capacity to prevent spills from large in-flows that are typically caused by stormwater entering the sewer system.

Background

Rotorua's current plant has to date been the most successful initiative in reducing nitrogen going into Lake Rotorua. Our treatment plant is among the best in the country, treating wastewater to a very high standard. But it is in need of future-proofing to meet higher projected demand and to continue to reduce and maintain nutrient levels below the targets agreed under the Lakes Water Quality programme - (PDF, 11.4MB).

Discharging into Whakarewarewa Forest is no longer viable as a sustainable option for several reasons including cultural concerns. It is also resulting in ground over-saturation that's detrimental to trees, making it an unreliable filtering system and adding to pollutants entering the Puarenga Bay.

The proposed upgrade would treat wastewater to an extremely high standard, removing pollutants like nitrogen and phosphorus and disinfect bacteria like E. Coli.

How is wastewater in the city is currently treated?

Current wastewater treatment service

Rotorua's wastewater (sewage) is treated daily at a central Wastewater Treatment Plant on Te Ngae Rd, using a 5-stage Bardenpho process. This was the first full biological nitrogen and phosphorus process used for municipal wastewater in New Zealand, and in terms of nitrogen, the discharge water is already one of the best in the country. The sludge produced (biosolids) is blended with wood pulp and vermi-composted, then cultivated into land that is used to grow a fodder crop.

To protect the quality of the water in Lake Rotorua, the treated water from the plant is currently irrigated to pass through the land in Whakarewarewa Forest before the groundwater discharges to Lake Rotorua.

The Rotorua Wastewater Treatment Plant currently serves a population of approximately 60 000 people residing in the city.

  • We treat an average of about 20 000 m3 (20 000 000 litres) of wastewater each day. We have the capacity to treat and discharge up to 44 000 m3
  • Most of Rotorua's wastewater is generated by domestic use. A small percentage is from industrial use

What the upgrade entails

With leadership from the community-led group, the Rotorua Project Steering Committee and other key rōpū (groups) including cultural expertise, Council endorsed the committee's preferred option to upgrade the Wastewater Treatment Plant.

The upgrade will include:

  • Increasing its flow capacity
  • Stormflow storage
  • Additional phosphorus removal
  • Ultra-filtration
  • UV treatment

Here's how the upgrade will treat wastewater

The Lakes Programme Integrated Framework - (PDF, 11.4MB) applies the current consent limit to urban land.

For more information visit:

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