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: November 2024
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.
Major investment is required, and current approved funding levels do not meet this requirement.
A project is currently underway to develop a second stage of land irrigation (excluding growth). The plant is already operating beyond its design loading capacity and so new connections have been paused. The degree of desludging that will be achieved at Greytown is not yet determined. Further funding may be required to complete. The earthworks consent for the desludging activity at Greytown has been approved by GWRC.
Items of significance:
The 2023-2024 Annual Report was submitted to GWRC. Current plant design and processes are inadequate for the connected population, resulting in non-compliance (specifically related to nutrient concentrations in the effluent).
New connections have been paused while a Growth-Capacity study is undertaken to determine how to ensure the WWTP can operate compliantly with new connections.
Wellington Water has repaired the Greytown WWTP pond leak and confirms that all flows are being treated and discharged via the consented discharge route. Existing public health advice remains in place along the Papawai Stream.