Wastewater treatment plants

Our wastewater network carries a combination of residential and commercial (businesses) waste.

Wastewater contains 99% water and about 1% human and other waste.

Because the waste component contains many bacteria and viruses that could be harmful to human health, it’s important it is kept separate from the drinking water network. This is in accordance with the Health Act 1956.

All wastewater is carried along the wastewater network and treated at one of our four wastewater treatment plants, before being discharged out to sea, unlike the stormwater network which mostly flows straight out through streams and rivers before ending out at sea.

The Wastewater Treatment Plants are owned by Wellington City Council, Hutt City Council and Porirua City Council and are managed in accordance with the Resource Management Act 1991.

To find out more about our Wastewater Treatment Plants click the name of each plant below.

Featherston Treatment Plant

At the Featherston Wastewater Treatment plant, sewage flows through a facultative pond, a maturation pond, and ultraviolet treatment. Discharge of the treated effluent is managed to Donald’s Creek depending on the conditions of the Resource Consents.

The plant was granted new consents on 25 August 2009 with a variation granted on the 12 November 2010. These consents expired on the 25 August 2012. The plant is currently operating under this expired consent. An application for new consents is on-going.

In general, the consent allows SWDC:

to discharge treated wastewater to Donald’s creek at up to 9,000 cubic meters per day in dry weather and up to 12,000 cubic meters per day in wet weather.
to discharge odours and other contaminants from the treatment process within the boundary.

Greytown Treatment Plant

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 oxidations ponds within the boundary
to discharge contaminants and odours from irrigation of treated wastewater to land within the boundary.

Lake Ferry Treatment Plant

At Lake Ferry the wastewater treatment system consists of on-lot septic tanks with effluent filters and a community wastewater treatment plant. At the treatment plant, septic tank effluent flows through a packed bed reactor, a recirculation tank and ultraviolet treatment. Discharge of the treated effluent is managed to either an adjacent block of land by irrigation or to a constructed wetland, depending on the conditions of the Resource Consents.

The plant was granted new consents on 17 June 2005. A change of conditions was granted on the 10 January 2011. These consents will expire on the 30 September 2025.

In general, the consents allow SWDC:

to discharge treated wastewater to land via an irrigation system at up to a maximum daily flow rate of 200 cubic meters per day and a maximum weekly flow rate of 700 cubic meters per week.
to discharge treated wastewater to land at a maximum application rate of 3.0mm/day or up to the field capacity.
to discharge treated wastewater to water (wetland) when the field capacity of the irrigation field has been exceeded or when a discharge is required for emergency or maintenance purposes.
to discharge contaminants and odours from the collection, treatment and discharge facilities within the site boundary.

Martinborough Treatment Plant

At the Martinborough Wastewater Treatment plant, sewage flows through an aerated facultative pond, a series of maturation ponds and ultraviolet treatment. Discharge of the treated effluent is managed to either an adjacent block of land by irrigation or to the Ruamahanga River 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 at a flow rate of 795m3/day (Stage 1B) and 4300m3/d (Stages 2A and 2B)
to discharge treated wastewater to the Ruamahanga River at an annual average daily flow of up to 650 cubic meters per day and at a maximum daily rate of up to 4,300 cubic meters per day
to discharge treated wastewater to land via seepage from the oxidation ponds
to discharge odours from the oxidations ponds within the boundary
to discharge odours and other contaminants from irrigation of treated wastewater to land within the boundary.

Moa Point Treatment Plant

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

It was granted new consents on 11 May 2009. These consents will continue for 25 years (expire 11 May 2034).

In general, the consents allow WCC:

to continuously discharge up to 260,000 cubic meters per day of treated and disinfected wastewater into the coastal marine area via an existing submarine outfall,
to discharge up to 4500 litres per second of mixed disinfected, treated and milli-screened wastewater to the coastal marine area during and/or immediately after heavy rainfall, when the quantity of wastewater arriving at the Moa Point Wastewater Treatment Plant exceeds 3000 litres per second,
to occupy the foreshore and seabed of the coastal marine area with an existing submarine outfall pipeline,
to continuously discharge contaminants (including odour) to air from the Moa Point Wastewater Treatment Plan ventilation system.

Porirua 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 current consent for the Porirua Wastewater Treatment Plant (WWTP) expired in 2020. Prior to the expiry of this consent, Porirua City Council applied to Greater Wellington Regional Council for a new consent (a coastal permit) to discharge treated wastewater from the Porirua Wastewater Treatment Plant to coastal waters off Rukutane Point. While this process is underway, we continue to operate under the existing consents.

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.

Seaview Treatment Plant

At the Seaview Treatment Plant, sewage travels through a series of screens, tanks, bioreactors, clarifiers and ultraviolet treatments before being discharged as liquid into Bluff Point, south of the Pencarrow lighthouse.

The current consent ‘WGN120142 [33408] Discharge Treated Wastewater to Stream (Seaview WWTP)’ expired in 2018. Prior to the expiry of this consent, HCC applied to Greater Wellington Regional Council (GWRC) for a new consent to temporarily discharge treated wastewater from the Seaview WWTP to the Waiwhetu Stream. While this process is underway, we continue to operate under the existing consent.

In general, the consents allow HCC 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,
to discharge mixed disinfected, treated and milli-screened wastewater during maintenance,
the discharge of contaminants to the air,
and permission to occupy the stream and coastal marine area with an outfall structure.

Western 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 WCC 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.

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