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Paihia Wastewater Treatment Plant

Paihia Wastewater Treatment Plant

Plant overview

The award-winning Paihia wastewater treatment plant is located within the Waitangi Forest northwest of Paihia. The plant serves approximately 5000 residents in the communities of Paihia, Waitangi, Opua and Haruru and in summer the serviced population can exceed 11,000.


Treating the wastewater

Wastewater from the communities of the communities of Paihia, Waitangi, Opua and Haruru is pumped to the wastewater treatment plant where solids are screened from the wastewater for landfill disposal. Wastewater is first treated in anaerobic ponds that are designed to be very deep so that at their base oxygen is not available within the wastewater. The absence of oxygen encourages the growth of bacteria that breaks down biodegradable matter.  The wastewater then flows to oxidation and maturation ponds which use aerators and bio-shells to promote oxygen in the ponds where nutrients are broken down.   Following treatment, the wastewater is sampled for testing and discharged to a tributary of the Kerikeri inlet.

About bioshells

The plant was upgraded in 2020 to better remove ammonia from the wastewater.  The oxidation pond now contains 553 large plastic shells, known as bioshells covering about 4000 square metres of the pond surface. The bioshells are secured to a concrete frame and submerged within the wastewater and each is pumped with oxygen with a dedicated air hose.  Within each shell are hundreds of small plastic spherical cogs that provide surface area which, along with the pumped oxygen, provide the optimum environment for bacterial growth. This bacteria removes nutrients, specifically ammonia, from the wastewater.


The bioshell upgrade to the Paihia wastewater treatment plant is the winner of the 2021 Institute of Public Works Engineering Australasia 'Excellence in Project Innovation' award.  You can read more about this project and the award here.


The discharges from the treatment plant are authorised by a resource consent. You can read the consent here.


Haruru Falls Road, Waitangi 0204  View Map

Last updated: 02 Apr 2024 4:34pm