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Resources / The Network / Wastewater / Wastewater treatment plants / Western Wastewater Treatment Plant

Western Wastewater Treatment Plant

At the Western Treatment Plant, sewage travels through a series of screens, tanks, bioreactors, clarifiers and ultraviolet treatments before being discharged as liquid into Cook Strait in the vicinity of the Karori Stream Mouth.

The Western Treatment Plant was granted new consents on 28 July 2010. These consents will continue for 25 years (expire 28 July 2035).

In general, the consents allow Wellington City Council to:

  • discharge of treated and partially treated effluent through an existing outfall,
  • to discharge mixed disinfected, treated and milli-screened wastewater during and/or immediately after heavy rainfall,
  • the discharge of contaminants to the air,
  • and permission to occupy the coastal marine area with an outfall structure.

Resource consents

Resource consent reports

Plant performance

Current Status: Non-Compliant
Period: April 2024


The plant remains non-compliant for Biochemical Oxygen Demand (BOD) Geomean limit. The daily Effluent BOD results is still above the geomean limit. Process adjustments is being undertaken to resolve this issue.

The mechanical refurbishment of the plant’s clarifiers has also been completed which will improve the plant’s reliability.


No wet weather or plant failure discharges in April.

Odour complaints

No odour complaints in April.


Items of significance:

Outfall Repair:

Repairs to the main outfall pipe remain is now expected to resume in  May following the signed access agreement with the landowners. The repair works is anticipated to be completed by end of quarter 1 of next financial year.





Community Liaison Group Meetings