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.

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.