WEBSITE 500 x 600 px 1
In this section
Resources / Topic / Wastewater / Wastewater treatment plants / Porirua Wastewater Treatment Plant

Porirua Wastewater Treatment Plant

At the Porirua Treatment Plant, sewage travels through a series of screens, bioreactors, clarifiers and ultraviolet treatments before being discharged as liquid into Rukutane Point. 

For more information on how wastewater is treated, go to the treatment process. 

The consent for the Porirua Wastewater Treatment Plant (WWTP) was recently renewed.

In general, the consents allow Porirua City Council to:

  • discharge treated and partially treated effluent at Rukutane Point through an existing outfall,
  • discharge contaminants to the air
  • and permission to occupy the coastal marine area with a concrete deflection wall and outfall structure.


Upgrades to the plant’s UV treatment system and hydraulic capacity were completed in mid-2023.  The plant is now able to treat a peak flow of 1,500 litres per second.   In heavy rain the amount of wastewater delivered by the network can reach up to 1,300 litres per second.

Planning Ahead

Over coming decades, we want to keep reducing the volume and number of overflows from the wastewater network.

Overflows happen when rainwater overwhelms the wastewater pipe network, causing untreated wastewater to flow over land or into freshwater. This is objectionable, and abhorrent to mana whenua. Overflows contain bacteria that may make people sick if they come into contact with contaminated water.

We know where and when overflows happen from our monitoring, incidents reported by the community, and network modelling. Wellington Water and Porirua City Council have a view of where work is needed to reduce overflows and have already started on improvements.   For example, the central wastewater storage tank will reduce overflows into Porirua Stream, and the Eastern Porirua regeneration project will reduce overflows into Kenepuru Stream.

Resource consents

Resource Consent Application 2020 - 2022

Independent Hearing Panel Decision Report (relating to the 2023 Resource Consent Applications: Renewal of existing consents for discharge of treated sewage to coastal water, and associated discharge to air from the Porirua Wastewater Treatment Plant)

WGN200229 [36816] Discharge to Coastal Marine Area (Porirua WWTP)

WGN200229 [36727] Contaminants Discharge to Air (Porirua WWTP)

WGN980083 [03] Land Occupation by Outfall Structure (Porirua WWTP)


Resource consent reports

Plant performance

Current Status: Compliant but with noted issue
Period: October 2023


The plant is compliant for effluent quality consent limits.


There was one unplanned discharge in October, originally reported as unconsented. 

Please explain letter issued:

GWRC requested an explanation for the discharge that occurred on 2 October. The sumo pump for the screenings press machine blocked causing a small overflow, which entered the common UV channel for disinfection. Sampling showed no adverse effects on the environment. A response was provided to GWRC within the required timeframe.


Four unverified odour complaints for October were received in November.

Items of significance:

UV Performance Issues:

An investigation into faults in the new UV treatment unit outlet penstock ruled out mechanical failure. The project team continue to implement process modifications to fine tune the system's operation. To date this has proven successful during high flows. The system will continue to be monitored while these changes are being implemented.

Odour Control:

The Weather Station at Pikarere Farm and the interim odour control measures are in place and fully commissioned, meeting the consent deadline of 12 October.





More Documents Here

Cawthron Institute Wastewater Treatment Plant Environmental Effects Assessment

Executive Summary - Porirua Wastewater Treatment Plant: Discharge of wastewater & discharge to air

Porirua Network Improvement Programme - Wastewater Overflow Reduction Master Plan Strategy November

Porirua Wastewater Network Improvements - Reports June 2021

Greater Wellington Regional Council Annual Compliance Monitoring Assessment

Incident Reports

Odour Control Best Practicable Option Review

Complaints Register

13 October - 5 November

Date of Complaint Submitted

Date of Incident

Complaint Description / Characteristics as per the complainant

Wind Direction

Ave Windspeed (km/h)

Inlet Tunnel Vent  Fan Operation

Plant Operations

1/11/2023 22:09


Musty Smell





1/11/2023 22:09


Musty Smell





1/11/2023 22:09


Musty Smell

SE (00:00 to 8:35)
NW(8:36 to 23:59)


On (00:00 to 8:35)
Off (8:36 to 23:59)


1/11/2023 22:09


poo smell



On (00:00 to 4:58)
Off (4:59 to 23:59)


1/11/2023 22:09


musty smell





5/11/2023 21:55

5/11/2023 21:55

the plant smell is now worse it used to be a musty smell it’s now got a poo smell



Off (00:00 to 23:06)
On ( 23:07 to 23:59)