Greytown Wastewater Treatment
At the Greytown Wastewater Treatment plant, sewage flows through an aerated facultative pond, a maturation pond and ultraviolet treatment. Discharge of the treated effluent is managed to either an adjacent block of land by irrigation or to the Papawhai Stream, depending on the season, river levels and conditions of the Resource Consents.
The plant was granted new consents on 11 February 2016. These consents will continue for 35 years (expire 11 February 2051).
In general, the consents allow SWDC:
- to discharge treated wastewater to land via an irrigation system where there is a soil moisture deficit that is greater than the depth of discharged wastewater.
- to discharge treated wastewater to the Papawai Stream at an annual average daily flow of up to 750 cubic meters per day and at a maximum daily rate of up to 1,500 cubic meters per day.
- to discharge treated wastewater to land via seepage from the oxidation ponds
- to discharge contaminants and odours from the oxidation ponds within the boundary
- to discharge contaminants and odours from irrigation of treated wastewater to land within the boundary.
Resource consents
Plant performance
Current Status: Non-compliant
Period: October 2025
Commentary:
In 2023, Greater Wellington Regional Council issued letters requesting explanations of non-compliance. Wellington Water is implementing the required corrective actions where possible within the plant and resource constraints.
The plant is currently non-compliant for effluent quality. The non-compliant parameters are Total Ammonia–Nitrogen and Total
Nitrogen. The consented limit allows no more than three non-compliant results within any 12 consecutive monthly tests for either parameter. The Plant has been non-compliant for both parameters since April. While the plant recorded compliant
effluent quality results in October, this single month did not bring overall compliance back within the consented limits. The overall compliance has not been within consented limits since April.
Capital delivery is with SWDC, major investment is required.
Items of significance:
With effect 01 July 2025, SWDC took back ownership of the Capital Delivery Programme and associated projects .
Wellington Water submitted a draft growth and capacity study to SWDC in December 2024; SWDC have taken ownership and need to consider the next steps.
Read the October 2025 Greytown wastewater treatment plant performance monthly report