Porirua Wastewater Treatment Plant upgrade programme
On behalf of Porirua City Council, we are completing a programme of work to upgrade and increase the capacity of the Porirua Wastewater Treatment Plant, so it is fit for purpose for the growing population.
If you have any questions about this work, please contact:
Wellington Water, 04 912 4400
Latest Updates
New UV system mechanical fault
New UV System up and running
We have replaced the corroded aeration manifold pipe which supplies air from the blowers to the aeration basin, a critical part of the wastewater treatment process.
Bypass discharges have been eliminated and the plant treatment capacity has increased, following Hydraulic Upgrade and Milliscreen Channel remediation works.
We have completed the upgrade of new ultra-violet (UV) disinfection equipment and related works including upgrading the powerlines and switchboard, and relocation of the security gate.
The Aeration Manifold renewal works are also complete, which will reduce power use at the plant.
Prior to this work the Porirua wastewater treatment plant could treat a peak of 1,000 litres per second. In heavy rain the amount of wastewater delivered by the network can reach up to 1,300 litres per second, meaning some partially treated wastewater is discharged off Rukutane Point.
When the upgrades are completed early in 2023 the peak capacity of the plant will be 1,500 litres per second.
This will mean the plant will be better able to fully treat all incoming wastewater, even after heavy rain. Combined with network upgrades it will also be able to handle a growing population over coming decades.
All Updates
New Porirua WWTP UV System:
Since the new system was commissioned there have been eight recorded discharges of fully treated but undisinfected wastewater, initially thought due to a faulty mechanical part in the new Duron unit. The last of these discharges occurred on 5 May 2023. A subsequent investigation of the discharges has ruled out mechanical issues as the main cause and a number of minor issues have been identified as likely causes of the discharges. Multiple steps have been implemented to prevent further wet weather discharges and these have proven to be successful to date. The new Duron unit is back in service as the main (duty) UV unit. Greater Wellington Regional Council is being regularly updated on progress. Wellington Water and Veolia continue to monitor the situation closely.
Porirua WWTP Hydraulic Upgrade and Milliscreen Channel Remediation:
The hydraulic upgrade and milliscreen channel corrosion project is almost complete. Two out of four milliscreens have been reinstated in the screening building while the other two require maintenance before returning them into service. This will then be followed by recommissioning of the milliscreens and associated pipework to take the plant’s full flow. The project is expected to be completed by June 2023 pending the full reinstatement of the milliscreens.
Porirua WWTP Aeration Manifold Renewal:
The aeration pipework renewal has been completed. The project team are currently collating the as-built documentation in preparation for the handover to the operations team.
Porirua WWTP Solids Handling Project:
The Porirua solids handling upgrade project is underway to upgrade the sludge thickening and disposal equipment and increase capacity for growth. The project has completed the planning and optioneering phase. It is currently under concept design phase.
Porirua WWTP Odour Control System Project:
The odour control system project for Porirua WWTP is ongoing. The project is currently in the investigation phase. An independent odour survey is being planned to inform the best practicable options report as a requirement of the plant’s upcoming new consent.
New Porirua WWTP UV System:
The Porirua new UV system is online and is capable of treating the current maximum flow delivered to the treatment plant.
Porirua WWTP Hydraulic Upgrade and Milliscreen Channel Remediation:
Enabling works for the Porirua WWTP Hydraulic Upgrade and Milliscreen Channel Remediation are complete. These works involved the installation of a bypass stepscreen and pipework connection to the aeration basin. The successful completion of this work allowed the project to meet the project outcomes in the short term by eliminating bypass discharges from the treatment plant and upgrading the plant treatment capacity to up to 1550 L/s. This has also allowed following works needed for the project to be undertaken offline. There have been no bypass discharges from the plant since September 2022.
The bypass step screen will remain after the completion of the hydraulic upgrade project to provide additional redundancy for the screening system.
Porirua WWTP Aeration Manifold Renewal:
The physical works for the aeration manifold renewal are complete. The project involves replacing the corroded aeration pipeline from the blowers which supply air to the aeration basin. The oxygen coming from the air supply is required by the bacteria to treat the wastewater and ensure that everything in the aeration basin is mixed. The upgrade is expected to reduce power use at the plant as the aeration process is one of biggest users of power at the plant.
This will benefit not only the Porirua community but also the environment, provide better efficiency of the airflow to the process.
The temporary bypass screen has been in operation since late August 2022. This has performed well while we have been undertaking the permanent hydraulic upgrade and screen channel and chamber remediation.
As designed, the increased capacity of the temporary bypass has resulted in no screened or unscreened bypasses of the treatment plant since the temporary bypass was put into operation, even in high rainfall events.
The permanent hydraulic upgrade work is going well, with all new pipework in place. We are currently completing the screen channel and chamber remediation where the corroded concrete and reinforcing has been repaired or replaced.
We expect the project to be completed in March 2023.
Residents have the chance to have their say on plans to upgrade and operate the Porirua Wastewater Treatment Plant over the next 20 years, as set out in the Porirua City Council application for resource consent for the plant.
Porirua Mayor Anita Baker says this is an important step in the council’s continuing commitment to improve the health of our harbour and coastal waterways by upgrading the wastewater system.
“Porirua City Council and Wellington Water are working on a city-wide programme to look after our assets, support future growth, reduce water consumption, improve water quality, and reduce the impacts of climate change.
“The consent application outlines how we propose to increase the capacity of the plant to treat wastewater from 1,000 litres to 1,500 litres of wastewater per second and make other technical improvements, so that the plant is fit for purpose for a growing population,” says Mayor Baker.
Wellington Water Chief Wastewater Advisor Steve Hutchison explains that the network of pipes carries wastewater, or sewage, from homes and businesses throughout Porirua and North Wellington to the treatment plant.
“There, we treat and clean it so that it can be returned to the sea safely. We have to make sure the treatment plant can handle all the wastewater delivered to it, and we also have to fix leaks and blockages throughout the network, so that wastewater gets to the plant.”
The application proposes regular monitoring and measurement of the impact, including a new ecological survey and a full review of operations and future technology after 10 years.
These plans build on upgrades over the last 10 years, which have seen the quality of the discharge improve considerably.
Porirua City Council, Wellington Water and Ngāti Toa are working together to ensure mana whenua are at the table in future decision making on the plant.
The resource consent application is available on the GWRC website
Wellington Water is holding a public information meeting in Titahi Bay on Wednesday 9 June, at 7 pm at Titahi Bay School.
Background information is available here
The disinfection plant provides the final treatment, inactivating bacteria and viruses, prior to the discharge. The new Wedeco UV system which was supplied and commissioned by Xylem, provides an additional UV system to double the disinfection capacity at the Porirua WWTP.
Previously high flows during rainfall exceeded the capacity of the UV plant which caused treated but undisinfected effluent to discharge to the sea. The UV system now has the capacity to treat all the flows that come to the WWTP resulting in an improvement to bacterial water quality in the coastal area.
The upgrade involved a $2.7 million investment in the treatment plant which is being progressively upgraded to provide growth over the next 20 years.
A big thanks to the great number involved in the project including Wellington Electricity, Xylem, Connect Water, Veolia Water Services and subcontractors Fulton Hogan, Stewart Electrical, Ducare, and Acme.
The completed UV system
Ballast and control cabinets for the new UV plant
One of the four UV lamp modules which provides disinfection to the effluent
Work has begun to upgrade the Porirua Wastewater Treatment Plant, with the installation of new ultra-violet (UV) disinfection equipment that will increase the volume of wastewater that can be disinfected.
Porirua Mayor Anita Baker says this is a critical first step in increasing the capacity of the plant by 2023, to stop overflows of partially treated wastewater from the plant to the sea during heavy rain. “This is the first part of a multi-million upgrade that will be completed by 2023.”
Wellington Water Chief Advisor Wastewater Steve Hutchison says ultraviolet (UV) light disinfection is the final stage in treating wastewater. “It destroys remaining bacteria and viruses down to safe levels before the fully treated liquid is discharged to the sea,” says Mr Hutchinson.
Currently the Porirua wastewater treatment plant can treat a peak of 1,000 litres per second. In heavy rain the amount of wastewater delivered by the network can reach up to 1,300 litres per second, and so some partially treated wastewater is discharged off Rukutane Point, as happened during an extreme rainfall event at the end of November.
Steve Hutchison says by 2023 the peak capacity of the plant will be 1,500 litres per second.
“This will mean the plant will be better able to treat all incoming wastewater, even after heavy rain. Combined with network upgrades it will also be able to handle a growing population over coming decades,” he says.
Mr Hutchison says Porirua City Council and Wellington Water have a range of work under way to address wider network issues, including:
- Identifying and repairing cross-connections where stormwater gets into the wastewater (sewage) pipes overloading their capacity
- Setting up regional drainage inspection crews to investigate faults on public and private drainage
- Plans for a city centre wastewater storage tank, enabling better management of peak flows to the wastewater treatment plant and reducing the frequency of overflows to the environment
- Longer term programme of wastewater pipe and pump station renewals and upgrades across the network.
At the Wastewater Treatment Plant, the UV upgrade works will happen over the summer. Most of the activity will be inside the plant boundary, apart from traffic to and from the site.
Overview of how the treatment plant works
Meanwhile the council’s application to Greater Wellington Regional Council for a consent to continue operating the wastewater treatment plant for the next 20 years is expected to be notified for public submissions between March and June 2021.
For more on the consent application see below:
Porirua City Council today formally lodged plans to upgrade and improve the Porirua wastewater treatment plant, taking the next step towards improving the health of Porirua’s coastal waters.
These plans are set out in the council’s application to Greater Wellington Regional Council for consent to continue operating the wastewater treatment plant for the next 20 years.
“The consent application outlines how we propose to increase the capacity of the plant from 1,000 litres to 1,500 litres of wastewater per second and make other technical improvements, so that the plant is fit for purpose for a growing population,” says Porirua Mayor Anita Baker.
The consent application has been developed for Porirua City Council by Wellington Water in discussion with Ngāti Toa. Community views were also sought late last year.
“We value Ngāti Toa’s contribution as we work towards our shared goal of improving the health of our harbour and coastal areas,” says Mayor Baker.
“We will continue to work in partnership with Ngāti Toa on the future of the wastewater treatment plant and our wider plans to improve the Porirua wastewater network.”
Ngāti Toa Manager – Resource Management & Communications Naomi Solomon says the iwi looks forward to continuing the work with Wellington Water and Porirua City Council around the matters raised in the Cultural Impact Assessment that forms part of the consent application.
“The ongoing management of wastewater is vital to the health and wellbeing of our waterways, and Ngāti Toa would like to see that this managed in an appropriate way,” says Naomi Solomon.
Greater Wellington Regional Council will hear public submissions, likely later this year, before making decisions.
The consent application outlines plans to invest $5 million in capacity and technical upgrades that will be in place by 2023, which will further improve the quality of the discharge and reduce the number of times there is contamination from high rainfall events.
These plans build on upgrades over the last seven years, which have seen the quality of the discharge improve considerably in recent years.
Alongside plans to improve the treatment plant, Wellington Water, on behalf of Porirua City Council, is also improving the network of wastewater pipes leading to the plant.
“We have made a number of improvements to pumping stations and the network in recent years, and this work continues to be a long-term priority,” says Steve Hutchison Chief Advisor - Wastewater.
Editors note:
The wastewater treatment plant is funded by Porirua and Wellington City residents and Wellington Water is responsible for operating and maintaining it. It’s located near Rukutane Point, just south of Titahi Bay, and treats wastewater from Porirua City and northern Wellington suburbs.
Background information on the consent is attached.
For more details on broader plans for the wastewater network, visit https://www.wellingtonwater.co.nz/pwp/
Background information on the Porirua wastewater treatment plant consent application
Under New Zealand law (the Resource Management Act), special permission is required to discharge treated wastewater. This permission takes the form of a resource consent, issued by a regional council. The consent can include conditions that require steps to be taken to minimise the impact of the discharge, and to monitor and report on the impact.
The current consent for the Porirua wastewater treatment plant (WWTP) expires later this year (2020) and needs to be replaced.
Porirua City Council (PCC) is applying to Greater Wellington Regional Council for a new consent (a coastal permit) to discharge treated wastewater from the Porirua WWTP to coastal waters off Rukutane Point.
Greater Wellington Regional Council will now review the application and may seek further information before making it public. It is expected that the regional council will publicise the consent application documents and ask the public for their views in coming months. There will be a public hearing of submissions.
What’s PCC asking for?
In brief, PCC is asking for permission to discharge wastewater that has been treated and disinfected through the existing outlet at Rukutane Point for the next 20 years. The application proposes regular monitoring and measurement of the impact, including a new ecological survey and a full review of operations after 10 years.
PCC and Wellington Water are continuing to work with Ngāti Toa to develop mitigation measures to adequately address adverse effects on their cultural values. This will be presented at the public hearing.
For the next three years, there would continue to be intermittent, partially treated discharges during heavy rain events until capacity upgrades of the treatment plant are completed by 30 June 2023.
The consent application sets out plans to increase the capacity of the plant, so that it can manage a maximum peak daily discharge volume of 129,600 cubic metres (m3) per day, which equates to 1,500 l/s operating continuously for 24 hours.
This capacity has been designed to cover projected population growth over the next 20 years.
Alongside the capacity increase, PCC is investing in new ultra-violet (UV) equipment that will provide a higher level of disinfection and will ensure projected population growth can be adequately disinfected.
The consent application includes an assessment of the effects on
- Marine ecology
- Public health
- Recreation
- Impacts on Ngāti Toa’s cultural values
- Natural character & landscape
The application includes specialist reports on each of these topics and how potential adverse effects will be minimised. It proposes a monitor, review and respond approach; that is, if monitoring shows that contamination is above a trigger point, the treatment process would be reviewed and, where necessary, changes would be made. PCC and Wellington Water are proposing a series of legally binding conditions to give effect to this approach.
Next steps
The next step is for Greater Wellington Regional Council to consider the application. This will include making documents available to the public, calling for submissions and holding a public hearing. The exact timing for these steps is yet to be determined.
Here's a look at the programme of work underway to improve Porirua’s wastewater network, that will help reduce pollution on the coast at Titahi Bay and in the Harbour.
Wastewater treatment plant consent application
Porirua City Council is in the process of seeking a consent to continue operating the wastewater treatment plant for the next 20 years, as set out here.
There will be an opportunity for people to comment later this year. The new consent will have different rules/requirements from the current one. The consent application is based on plans to invest $5 million in capacity and technical upgrades that will be in place by 2023, which will further improve the quality of the discharge and reduce the number of times there is contamination from high rainfall events. These plans build on upgrades over the last seven years, which have seen the quality of the discharge improve considerably in recent years.
The treatment plant generally treats wastewater to higher than the required standard, and the discharge from the plant has been scientifically assessed to be appropriate for the location.
Overflows and bypass
The current consent recognises that from time to time there will be a need to discharge some partially treated (screened) sewage along with the fully treated wastewater, in particular when there is heavy rainfall and volumes are above the capacity of the treatment plant. As the city has grown, the frequency of these discharges has increased. The next planned upgrades will address this issue.
We acknowledge the need to invest in upgrading the wastewater and stormwater infrastructure that serves the community.
Find out more about our plans here.
Porirua City Council today formally lodged plans to upgrade and improve the Porirua wastewater treatment plant, taking the next step towards improving the health of Porirua’s coastal waters.
These plans are set out in the council’s application to Greater Wellington Regional Council for consent to continue operating the wastewater treatment plant for the next 20 years.
“The consent application outlines how we propose to increase the capacity of the plant from 1,000 litres to 1,500 litres of wastewater per second and make other technical improvements, so that the plant is fit for purpose for a growing population,” says Porirua Mayor Anita Baker.
The consent application has been developed for Porirua City Council by Wellington Water in discussion with Ngāti Toa. Community views were also sought late last year.
“We value Ngāti Toa’s contribution as we work towards our shared goal of improving the health of our harbour and coastal areas,” says Mayor Baker.
“We will continue to work in partnership with Ngāti Toa on the future of the wastewater treatment plant and our wider plans to improve the Porirua wastewater network.”
Ngāti Toa Manager – Resource Management & Communications Naomi Solomon says the iwi looks forward to continuing the work with Wellington Water and Porirua City Council around the matters raised in the Cultural Impact Assessment that forms part of the consent application.
“The ongoing management of wastewater is vital to the health and wellbeing of our waterways, and Ngāti Toa would like to see that this managed in an appropriate way,” says Naomi Solomon.
Greater Wellington Regional Council will hear public submissions, likely later this year, before making decisions.
The consent application outlines plans to invest $5 million in capacity and technical upgrades that will be in place by 2023, which will further improve the quality of the discharge and reduce the number of times there is contamination from high rainfall events.
These plans build on upgrades over the last seven years, which have seen the quality of the discharge improve considerably in recent years.
Alongside plans to improve the treatment plant, Wellington Water, on behalf of Porirua City Council, is also improving the network of wastewater pipes leading to the plant.
“We have made a number of improvements to pumping stations and the network in recent years, and this work continues to be a long-term priority,” says Steve Hutchison Chief Advisor - Wastewater.
Editors note:
The wastewater treatment plant is funded by Porirua and Wellington City residents and Wellington Water is responsible for operating and maintaining it. It’s located near Rukutane Point, just south of Titahi Bay, and treats wastewater from Porirua City and northern Wellington suburbs.
Background information on the consent is attached.
For more details on broader plans for the wastewater network, visit https://www.wellingtonwater.co.nz/pwp/
Background information on the Porirua wastewater treatment plant consent application
Under New Zealand law (the Resource Management Act), special permission is required to discharge treated wastewater. This permission takes the form of a resource consent, issued by a regional council. The consent can include conditions that require steps to be taken to minimise the impact of the discharge, and to monitor and report on the impact.
The current consent for the Porirua wastewater treatment plant (WWTP) expires later this year (2020) and needs to be replaced.
Porirua City Council (PCC) is applying to Greater Wellington Regional Council for a new consent (a coastal permit) to discharge treated wastewater from the Porirua WWTP to coastal waters off Rukutane Point.
Greater Wellington Regional Council will now review the application and may seek further information before making it public. It is expected that the regional council will publicise the consent application documents and ask the public for their views in coming months. There will be a public hearing of submissions.
What’s PCC asking for?
In brief, PCC is asking for permission to discharge wastewater that has been treated and disinfected through the existing outlet at Rukutane Point for the next 20 years. The application proposes regular monitoring and measurement of the impact, including a new ecological survey and a full review of operations after 10 years.
PCC and Wellington Water are continuing to work with Ngāti Toa to develop mitigation measures to adequately address adverse effects on their cultural values. This will be presented at the public hearing.
For the next three years, there would continue to be intermittent, partially treated discharges during heavy rain events until capacity upgrades of the treatment plant are completed by 30 June 2023.
The consent application sets out plans to increase the capacity of the plant, so that it can manage a maximum peak daily discharge volume of 129,600 cubic metres (m3) per day, which equates to 1,500 l/s operating continuously for 24 hours.
This capacity has been designed to cover projected population growth over the next 20 years.
Alongside the capacity increase, PCC is investing in new ultra-violet (UV) equipment that will provide a higher level of disinfection and will ensure projected population growth can be adequately disinfected.
The consent application includes an assessment of the effects on
- Marine ecology
- Public health
- Recreation
- Impacts on Ngāti Toa’s cultural values
- Natural character & landscape
The application includes specialist reports on each of these topics and how potential adverse effects will be minimised. It proposes a monitor, review and respond approach; that is, if monitoring shows that contamination is above a trigger point, the treatment process would be reviewed and, where necessary, changes would be made. PCC and Wellington Water are proposing a series of legally binding conditions to give effect to this approach.
Next steps
The next step is for Greater Wellington Regional Council to consider the application. This will include making documents available to the public, calling for submissions and holding a public hearing. The exact timing for these steps is yet to be determined.
It was great to see more than 100 locals turn up to our open days this month to learn more about and share their views on planned improvements to Porirua’s wastewater system - and to experience a guided tour of the wastewater treatment plant.
The open days focused on plans to upgrade the capacity of the wastewater treatment plant and how that will fit into bigger plans to address issues with the wastewater network.
Many attendees wanted to find out what is being done to protect Titahi Bay, the ocean and surrounding environment. Others were interested in learning about Porirua’s ‘three waters’ system of drinking water, stormwater and wastewater, and the role of the wastewater treatment plant.
For those who took one of the three guided tours of the treatment plant – it was a real eye opener. Many people were surprised to learn about how it operates, and learn what has already been done through recent upgrades to improve the plant’s performance.
We really value connecting with the community, so people can better understand what we do and we can find out what matters to you. We'll now be considering the community's feedback as we finalise the application for the wastewater treatment plant consent renewal, which will be lodged with Greater Wellington Regional Council in April next year.
Thanks to all those who attended.