Seaview Wastewater Treatment Plant Upgrades
We’re upgrading the Seaview Wastewater Treatment Plant on behalf of Hutt City Council and Upper Hutt City Council to reduce odour and discharges of untreated or partially treated wastewater and future-proof the plant, starting with odour improvement.
If you have any questions about this work, please contact:
Wellington Water, 04 912 4400
Latest Updates
It’s been a busy week at Seaview Wastewater Treatment Plant, with work completed on Primary Sedimentation Tank (PST) #1.
We have made good progress in the past month and the plant is now close to normal operations. Our recent monitoring has indicated that with the reduction in sludge levels at the plant, odour levels have also generally reduced.
The first step in improving odour treatment - replacing the biofilter media - was undertaken in December 2023. Find out more in the Updates section.
Odour treatment Renewal project
Work on the $13 million Odour Treatment Renewal Project is underway, with the initial planning phase complete. Detailed design and procurement are happening now in preparation for the physical works to commence this winter.
This project is prioritising areas for action that are most likely to make a significant impact on reducing odour escaping from the plant; the biofilter, milliscreening odour management and sludge drying odour management.
There’s more information on the project page. The work will be delivered in multiple packages. There are five high priority work packages in Phase 1 as follows:
The second phase includes two work packages; sludge dryer air treatment and further external ducting. Both will require an assessment of the effectiveness of the first phase in reducing odour issues. The sludge dryer air treatment also needs to be considered alongside plans to replace the sludge dryer.
The Seaview Wastewater Treatment Plant is aging. Much of the plant’s equipment and parts are nearing the end of their service life, which means it is more prone to service interruptions and needs more maintenance. Find more information about the plant’s performance and resource consents here
A multi-million-dollar programme of work is planned over the next six to 10 years to renew and upgrade equipment at the plant to improve its operation, subject to funding being confirmed. The current plan includes:
- Odour treatment renewal project (2024-2026)
- Sludge dryer replacement (2024 - 2028)
- Ultra-violet (UV) disinfection equipment renewal (2024 - 2026)
- Sludge pumps, aeration control system and aeration blowers (2024 - 2028)
- Clarifier ( 2026- 2028)
This work will contribute to reducing odour and discharges of untreated or partially treated wastewater, increasing capacity to handle population growth, and improving efficiency.
There is no quick fix, but Wellington Water is committed to short- and medium-term interventions to effectively manage operations of the treatment plant.
More detail on each area will be provided as planning progresses. Wellington Water is also considering options for reducing overflows to the Waiwhetū Stream and replacing the Main Outfall Pipeline.
FAQs
Is the plant meeting resource consent standards?
We are working hard to improve the current performance of the plant and the way we operate. Our focus is to meet the required standards and be compliant with the resource consents. The plant is aging, much of the equipment and parts are nearing the end of their service life, which means the plant is more prone to service interruptions and needs more maintenance.
Why are there no covers on the aeration or clarifier tanks at the Seaview plant?
Seaview’s aeration tanks do not pose a significant odour risk when they are operating according to design, as we are actively blowing air into a mixture of suspended aerobic microorganisms. The clarifier tanks which follow the aeration tanks also have a low odour risk. In the event of a breakdown in upstream treatment processes or a power failure, odour from the aeration tanks is possible. This risk is better addressed by ensuring we have effective equipment and systems, than by covering the tank. It is not common practice to cover tanks here or overseas, and not practicable at Seaview given the plant’s design.
Why are the treatment plants at Hastings, Gisborne and Napier totally covered?
Those plants use a different treatment technology and are constructed differently to the Seaview plant. It’s a bit like comparing diesel with petrol systems. The Hastings, Gisborne and Napier plants use trickling filter tanks and spray the wastewater over an open tank filled with algae that grows on plastic media. This does not happen at Seaview.
Why didn’t you replace the biofilter plenum (air distribution system) in December, when replacing the biofilter media??
During the works in December 2023 and following a condition inspection, it was discovered that the ‘plenum’ [biofilter structure] had degraded and should be replaced. It was necessary to proceed with the biofilter media replacement, as undertaking this additional work would delay the immediate objective of improving odour levels. Inspection of the plenum was only possible after we started removing the old biofilter media.
It was in the media that the work to replace the biofilter should have started in 2021, why the delay?
The biofilter media replacement was never programmed to be replaced in 2021. This work started in November 2023 after condition assessment and lab testing of bark composition, and the availability of a specialist contractor. The replacement was completed ahead of schedule in December 2023.
Is the biofilter media replacement making a difference?
While the new biofilter media is establishing well, there are ongoing issues with odour levels. Replacement of the biofilter media is only one part of the solution. We are continuing independent odour scouting, as well as monitoring complaints from the public, as we continue to work on other issues contributing to odour.
What upgrades do you have planned, how much will it cost?
We are prioritising improvements in three key areas we know are causing significant odour issues: the biofilter system, the milliscreening building and the sludge drying building. Hutt City Council has budgeted $13 million for these works.
Is the odour issue ever going to be fixed?
Wellington Water and Hutt City Council are committed to resolving the issue, though this is not an overnight fix, and it will take time. We acknowledge this is concerning, frustrating, and upsetting for everyone given it has been a long-term issue that has got worse in recent years.
Are there any health implications with plant associated odour?
When odour levels are strong and unpleasant, it can make some people feel ill. We are not aware of any health implications (bacteria that can be inhaled) and are following standard health and safety guidelines with the maintenance works we are doing at the treatment plant.
Te Whatu Ora - Health New Zealand has done an assessment on the use of the deodoriser at the Seaview Wastewater Treatment Plant. Please find the statement and more information here
Given the projected long-term investment, is the plant's current design under review?
We have concluded the design of the plant remains appropriate but much of the equipment needs renewing and upgrading, because the plant is aging, and equipment has deteriorated more quickly than expected.
We have also considered projected population growth and the standards we are required to meet by current resource consents.
The odour treatment renewal project is the first workstream in this long-term plan, followed by the sludge dryer replacement. There are other proposed upgrades for the UV system, sludge pumps, aeration control and clarifier. In addition, there is ongoing planned maintenance such as the milliscreen replacement, and reactive renewals (replacing smaller items that fail).
There is no quick fix, but Wellington Water is committed to upgrading the plant so we can continue to protect the health of people and the environment, while catering for population growth.
What odour neutraliser spray is used at the plant?
Odour Neutraliser Plus (SCD 1100)
For more information about the odour control product being used at the Seaview Wastewater Treatment Plant > Odour Neutraliser Plus Assessment
Update November 2024
We have completed stage one of the odour treatment renewal project, improving the biofilter.
Design work is underway on the next stage, capturing and delivering odourous air to the biofilter from covered areas of the plant, primarily the milliscreening room.
About the odour treatment renewal project
We’re investing $13 million in work to improve systems to capture and remove odours at the Seaview Wastewater Treatment Plant to avoid odours reaching the community.
The objective of the odour treatment renewal project is to improve the management of odour to ensure the plant is a safe environment and is operating within its resource consent.
We’re aware odour continues to be a problem, based on community feedback and our own independent scouting.
In the short term, we are prioritising areas for action that will result in capturing more odourous air from the milliscreening process and ensuring that the biofilter system is working effectively to remove odours from this air.
In the medium term, we are assessing options to improve odour management from the sludge dryer area, noting the dryer is due for replacement.
As well as replacing equipment, we’ll continue with maintenance and operational activity that we expect to contribute to reducing odour.
Treating odour
The Seaview Wastewater Treatment Plant uses physical and biological processes that harness the action of bacteria and other microorganisms to clean the wastewater. One of the side-effects of this process can be odour. The plant is designed to treat odours.
Odourous air is pumped to the biofilter, where is passes through a bed of media (mainly bark, gravel and limestone chip) containing microbes that break down the odour-causing compounds.
The Seaview plant also uses an odour neutraliser, which sprays a safe chemical mix into the air to neutralise odours.
Priority work
1: Improving the biofilter
When the biofilter media was replaced in December 2023, a comprehensive mechanical and structural condition assessment was undertaken. It became evident that:
- The air distribution system (plenum) in all six biofilter cells needs replacing.
- The biofilter cell isolation system needs redesign and upgrading to isolate each of the six cells individually, this would avoid odour discharge to the environment during routine maintenance events.
This work was completed in October 2024.
2: Capturing odours from the milliscreens
The wastewater screening room houses 10 inlet screens. These remove large solids from wastewater as it enters the plant. Find out more about the process here. This is typically the most odourous part of any wastewater treatment facility. The screens and channels are covered, with multiple ducts connected to the odour extraction system. This allows odourous air to be extracted with a fan and sent to the biofilter for treatment.
We know that there is an issue with the ducting from the milliscreens which is allowing odour to escape from the equipment into the building and then to outside. These ducts will be replaced to restore capacity.
We also plan to replace the fans that help extract odour around the plant.
3: Capturing and treating building air
While ducts capture air from the covered screens and channels, other air in the wastewater screening room vents directly to outside. We will upgrade the ventilation system to capture the building air for treatment before it is released. This is likely to involve installing new carbon air scrubbers in this building, subject to detailed design and planning being completed.
We are also looking at options for improving management of air from the sludge dryer building.
4: Repair External ducting
We know that some of the odour ducts running outside the buildings (external ducts) have leaks. This means that some of the captured odour escapes, and it also reduces the effectiveness of the fans in drawing out the odour from the different process areas. We have completed condition assessments on the external ducting and are planning how to repair leaks.
5: Process monitoring
Better monitoring of air flows will be built into all the above packages.
Phase 2
The second phase includes two work packages; sludge dryer air treatment and further external ducting, as required. Both of these would require an assessment of the effectiveness of the first phase in reducing odour issues. The sludge dryer air treatment also needs to be considered alongside plans to replace the sludge dryer.
Seaview Wastewater Treatment Plant Newsletter - December, 2024
Your latest news on what's happening at the Seaview Wastewater Treatment Plant
Kia ora koutou
This special edition of the newsletter provides a summary of the findings from Part 1 of the odour neutraliser shutdown trial which finished on 18 December. We also provide an update on the actions arising from the community meeting held on 25 November, together with details of the current status of the plant and operations over the Christmas/New Year holiday period.
Odour neutraliser shutdown trial
Thanks to everybody who’s completed the survey so far. Part 1 of the trial to shut down the odour neutraliser finished on 18 December and the odour neutraliser was turned back on at 8am Thursday 19 December. Part 2 of the trial is to leave the odour neutraliser running for another two weeks until 2January 2025.
Please continue to complete the survey until 2 January 2025. This will help us establish a ‘baseline’ from which we can assess the trial to help us understand whether the smell is better, worse or the same as it has been before the shutdown. We acknowledge the plant has not been in a normal operating state and will take that into account.
The odour survey is simple and very quick to complete. We appreciate your help with this.
We will continue to keep you updated on the progress throughout this next stage of the trial period via our interested parties’ email and our Facebook page - https://www.facebook.com/wellingtonwater.
Following the completion of the trial, we will undertake a process of review and assessment of the results. We will keep you informed as we work our way through this in the New Year. Feedback from the community will help Wellington Water and Hutt City Council determine our next steps.
A summary of the discussions at the meeting and issues raised, presentations from speakers alongside a Q&A document will be made available on our website over the next week. We will send out a link to this once it has been published.
Summary of responses so far from the trial
We received 241 responses to the survey over the period of Part 1 of the trial. Responses to the survey have been relatively low but we did receive a significant number of responses (119) on 6 December.
Odour levels during Part 1of the trial period confirm that odour remains an issue at the plant. The results show varying levels of impact based on location and weather conditions.
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Rate the smell between 1 and 5 |
How does the smell compare to previous months |
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Of responses rating the odour at 4 or 5, how did the odour compare to previous months |
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Odour levels were most frequently and strongly smelt at Seaview and Waiwhetu.
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Seaview |
Waiwhetu |
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83 respondents 56 rated odour at 4 or 5 |
60 respondents 28 rated odour at 4 or 5 |
During the trial, odour scouting was also undertaken daily. The findings of the odour scouts align with improvements in plant health and feedback received from the community. The winds were predominantly northerly meaning more odour was observed south of the plant than north. Odour levels were strongest in locations closest to the plant and in areas at the plant where work was being undertaken. Scouting is planned to continue 1-2 days per week in the New Year.
During the period of the trial, work has continued to bring the plant back to optimal operational performance and reduce the risk of increased odour levels over the holiday period. We appreciate this makes it challenging to make an accurate assessment of the effectiveness of the odour neutralisers. This means the results of the survey and odour monitoring need to be considered in the context of work at the plant that may lead to increased odour levels (e.g. transporting dewatered sludge to landfill) and other changes to processes at the plant to increase solids processing (e.g. Dissolved Air Flotation optimisation trial). Further details about this work and the current status of the plant are provided further in this newsletter.
A summary of the responses received from Part 1 of the trial (4-18 December) is available on our website – see https://www.wellingtonwater.co.nz/assets/The-Network/Wastewater/Wastewater-Treatment-Plants/Seaview/Odour-neutraliser-trial-survey-results_Part-1_website.pdf
Plant performance and operations
Current status of the plant
We have made good progress in the past month and the plant is now close to normal operations. Our recent monitoring has indicated that with the reduction in sludge levels at the plant, odour levels have also generally reduced.
Two key indicators of the health and balance of the biological process at the plant are levels of Mixed Liquor Suspended Solids (MLSS) and Dissolved Oxygen (DO). MLSS measure the volume of solids in the aeration tanks where bacteria feed on organic material in the wastewater. Providing the right range of Dissolved Oxygen (target range 1 to 3), gives the bacteria the best conditions to grow.
Below is a summary of how these indicators have been tracking since the outages with the dryer in September and October.
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Mixed Liquor Suspended Solids (MLSS) |
Dissolved oxygen (DO) |
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9 October |
5,760 |
0.69 |
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23 October |
5,070 |
0.67 |
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5 November |
5,230 |
0.83 |
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19 November |
4,800 |
0.67 |
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4 December |
4,350 |
0.69 |
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18 December |
2,560 |
2.11 |
While there is still some work to do to return the plant to the level that it was operating at before the incidents with the dryer, we are pleased to see a marked improvement in both indicators.
Operations over the holiday period
Preliminary cleaning of Primary Sedimentation Tank #2 has been completed in advance of repairs to be undertaken after parts arrive in mid-January. Work on the repair to Blower #2 has also been completed.
To keep the plant stable and minimise odour, we will be limiting planned maintenance and pausing non-critical work at the plant over the holiday period. The trucking of dewatered sludge to landfill will also stop from end of day Friday 20 December.
Routine operation of the plant and dryer will continue. Veolia, our plant operators will be monitoring key process points of the plant during the holiday period. Work has been undertaken to build resilience to plant operations, with resources on call and escalation processes in place to respond to any incidents that may arise.
The weekly updates on odour levels and plant operations recently provided will stop over the holiday period. We will follow our usual procedures for notification to the community of any unplanned outages, maintenance or operational incidents at the plant.
Actions from the community meeting
A summary of the notes from the community meeting held on 25 November, as well as a copy of the presentation on plant operations has been published on our website – Seaview Wastewater Treatment Plant Community Meeting Notes, Actions, and Presentation Slides.
Increased odour monitoring
We are continuing to investigate the right type of monitors that we could use to increase our monitoring of odour from the plant. We have met with the team at Christchurch City Council about the monitors that they have used. Our engineering team are completing their initial evaluation, and we will provide a further update in the New Year.
Updates on potential for high odour levels
We have continued to provide weekly communications to the community about operations at the plant that could impact on odour levels via our interested parties email list and posted updates on our website and Facebook page.
We are committed to making this information as accessible and transparent as possible so are looking at other formats to present these updates and to increase visibility on our website. We acknowledge that wind direction impacts odour levels and will explore how we can provide this as an added layer of information on our website.
We will keep you updated on progress with this work which requires further investigation and changes to our website.
Keep in touch
You are receiving this email because you have expressed an interest in the plant. Please feel free to share this with others who may be interested.
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Join the mailing list for plant notifications and this monthly update at customer.notifications@wellingtonwater.co.nz.
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If you have any questions relating to this newsletter email community@wellingtonwater.co.nz.
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For complaints relating to specific incidents or properties go to customer@wellingtonwater.co.nz.
Thank you!
Blair Johnson
Head of Wastewater Contracts
Seaview Wastewater Treatment Plant Upgrades - November 2024
Seaview Wastewater Treatment Plant Newsletter - November/December, 2024
Your latest news on what's happening at the Seaview Wastewater Treatment Plant
Kia ora koutou,
Welcome to the regular update about the operation of the Seaview Wastewater Treatment Plant and the programme of upgrade work. This is the last newsletter for 2024 but email updates will continue, and you can find the latest information on the website.
In this issue
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Community meeting update
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Next steps
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Update on work at plant
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Wastewater Treatment Plants Treatment Services contract review
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Plant performance update
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Keep in touch
Community meeting update
Thank you to those who attended the community liaison meeting on Monday 25 November.
We know it has been an extremely stressful time for the community. We appreciated the opportunity to have a face-to-face conversation to discuss recent issues that have resulted in increased odour from the plant.
The Mayor of Lower Hutt, Wellington Water Chief Executive and staff, and senior management from plant operators, Veolia, spoke at the meeting. Chief Executive, Hutt City Council Jo Miller was also in attendance. They all reiterated that the Seaview Wastewater Treatment Plant is a top priority and that the level of odour is completely unacceptable. However, all speakers also emphasised that there is no quick fix or silver bullet to reducing the odour from the plant. It is likely there will be intermittent occurrences of increased odour at the plant for a while as we work to replace and upgrade aging equipment at the plant.
Community members spoke about the emotional toll of the stench and the ongoing impact on their wellbeing, their businesses, and their house prices.
All speakers acknowledged the huge impact on the community. Mayor Campbell Barry said what the council can do is give people confidence that everything possible is being done to fix the problem.
Wellington Water's CE Pat Dougherty assured the community that Wellington Water and Veolia would be doing all they could to minimise odour over the holiday period. This included avoiding any maintenance or upgrades that might cause odour levels to increase.
We were especially grateful that the meeting was conducted respectfully, with a safe space for all speakers to talk freely and share information without interruption. We appreciate all the questions and comments from the community which have given us some things to take away and review.
In response to the concerns raised by the community at the meeting, we are working on three key actions/next steps:
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Turning off the odour neutralisers to see if this reduces the impact on the community, without increasing odour effects.
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Increase monitoring of odour from the plant.
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Providing the community with more timely and frequent information about the likelihood of high odour levels from the plant so people can plan.
A summary of the discussions at the meeting and issues raised, presentations from speakers alongside a Q&A document will be made available on our website over the next week. We will send out a link to this once it has been published.
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Next steps
To help us to assess the impact and effectiveness of the trial, we are asking the community to fill in a quick online odour survey daily to let us know of your experience of odour levels. You can fill in this survey up to three times a day – morning, noon, and evening or whenever you notice a smell.
If there is significant negative impact experienced by the community during the trial, it will be shut down earlier than planned. We will be monitoring feedback, odour scouting results and complaints very closely throughout the trial.
Increased odour monitoring
We need to consider the types of monitoring that will be fit-for-purpose for our environment, and this may take us a bit of time. We are working on this, and we have our engineering team exploring options.
Once we have further information and options to do this, we will seek community feedback and input.
More timely and frequent updates on potential for high odour levels
As this requires further investigation and changes to our website, this is not something we can do immediately. We will keep you updated on progress via email.
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Update on work at the plant
The recent sludge dryer outages caused a backlog of sludge in the system, throwing the biological waste treatment process out of balance. This contributed to the odour, as did the need to truck sludge that had not been dried to the landfill.
The dryer is now back online, and we are making progress with clearing the backlog. However, we will need to keep intermittently trucking some sludge to the landfill to help clear the backlog as quickly as possible. This is scheduled to resume on Tuesday, 3 December. We have erected scaffolding and cover in the area where sludge is being loaded to reduce the odour when this process is being undertaken.
Improvements in the biological process have been noted and we are doing all we can to get the process back into balance with the plant operating at design levels as soon as possible.
The reports on the fire and mechanical failure will be made available on our website when completed.
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