Seaview Wastewater Treatment Plant
The Seaview Wastewater Treatment Plant serves a population of about 160,000 in Upper Hutt, Lower Hutt and Wainuiomata. The wastewater is treated or cleaned through a series of screens, tanks, bioreactors, clarifiers and ultraviolet treatments before being discharged into the open sea near near Pencarrow Head / Te Raeakiaki where it is quickly diluted.
Seaview Dryer Shutdown - 3rd to 17th June
What work is happening, and why?
The dryer at Seaview Wastewater Treatment Plant is essentially coming to the end of its design life, and requires constant maintenance. Multiple components of the dryer need to be replaced to give the dryer the best chance of functioning reliably until the new dryer is commissioned.
In order to compete this work, the current dryer will be taken offline for two weeks, between Tuesday 3 June and Tuesday 17 June. Doing this work all at once aims to minimise disruption to the plant’s operations and increase efficiencies.
This work includes:
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replacement of the infeed screw and barrel
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replacement of the emergency transfer screw
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replacement of the rotary valve
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refurbishment of the acceptance bucket elevator
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replacement of the recycle transfer screw, and
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refurbishment of the shaker.
It is important to note that if this work is not completed as soon as possible, the risk of the dryer failing increases. This would in turn require a longer period of trucking de-watered sludge, and pose a real risk to the health and balance of the plant and the level of odour experienced by the community.
What can the community expect?
While this work is underway, we will need to transport de-watered sludge from the plant to Silverstream Landfill.
It’s possible there will be a temporary increase in the level of odour, which are working to mitigate as much as possible.
It is likely that another extended shutdown will be needed in the second half of 2025, and we will provide further information on this as planning progresses.
What are Wellington Water and Veolia doing to reduce the risk of odour?
Reducing the risk of odour impacting the community has been a top focus as we've planned for this work.
It's important to note that last year, the failure of the dryer was complicated by issues with other equipment at the plant. These issues meant that the biological process of the plant was compromised, with key parameters of the health and balance of the plant well out of the target range. The health and balance of the plant is vital to manage odour.
Real care is being taken to avoid any similar issues. Our risk mitigation plan includes:
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critical ‘control points’ to closely monitor and manage the biological process
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a heightened approach to operations and maintenance, including reducing sludge levels before the shutdown begins, and
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well-covered loads and deodorisers active onsite.
We will keep the community up to date as the work progresses.
Odour level indicators
The level of odour experienced by the community is influenced by many internal and external factors.
With all these variables, odour can't be forecast with a high level of confidence.
What we can do is monitor the internal factors at the plant which can give an indication of possible odour, and communicate these clearly.
The health and balance of the plant
Seaview Wastewater Treatment Plant uses a biological process to help treat wastewater, which we work to keep healthy and balanced. Two key indicators for the health and balance of the plant are Mixed Liquor Suspended Solids and Dissolved Oxygen levels.
When they are within target range, it is a good indication that we can expect odour to be at a minimum, unless there is an operational issue at the plant.
Plant maintenance and operations
Seaview is an aging plant, with routine operations and maintenance occurring every day, and unplanned urgent maintenance commonly needed to address issues as they crop up. Major project work is intermittent as we continue to address odour and work to upgrade the dryer.
All of these can affect the level of odour experienced by the community, so we work to keep people as up-to-date as possible with all the plant's maintenance and operations. You can find the latest information here under 'Updates'.
Odour Update
Did you know? The direction of the wind can impact where odour is experienced. Commonly, a northerly impacts residents of the southern suburbs, while a southerly can carry odour up the valley where it affects residents in the northern suburbs. The weather forecast can let you know what way the wind will be blowing.
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Seaview Newsletter
Find more information about plant activity and projects
Odour Project
Learn more about the ongoing works to reduce odour at Seaview Wastewater Treatment Plant
Making a complaint
If you have a complaint about Wellington Water directly, please call 04 912 4470 or email customer@wellingtonwater.co.nz to access our free complaints process.
After hours, please contact the Hutt City Council Call Centre on 04 570 6666 / 0800 488 824.
Greater Wellington Regional Council is the regulatory agency for reporting airborne discharges 0800 496 734.
Complaints to the Seaview Wastewater Treatment plant can be sent to the following contact details:
First point of contact: Veolia Duty Manager - Call 0800 928 371.
Veolia's Duty Manager contact number operates 24/7 as such complaints can be directly forwarded to them especially if the complaint is urgent and/or happened after office hours.
When a complaint is received, the following information will be recorded:
- Name
- Contact details of the customer
- Nature of the complaint
- Date and time
- Location
Complaints shall be actioned within 24 hours upon receipt and the records being written to the plant's operational incident log. Odour and/or wastewater discharge complaints will be forwarded to the regional council.
Plant performance
Current status: Non-compliant
Period: February 2025
Commentary:
The plant moved back into compliance for faecal coliforms on the 90-day geomean but remains non-compliant with the 80th percentile. This is trending to compliance in March. The plant remains compliant for Suspended Solids and Biochemical Oxygen Demand (BOD).
Discharges:
There were no unconsented discharges, or discharges into the Waiwhetū Stream in February.
Odour Complaints
The plant received 6 odour complaints in February, none of which were deemed offensive and objectionable by Greater Wellington Regional Council.
Items of significance:
Primary sedimentation tank refurbishments
Planned maintenance to the first of the final two primary sedimentation tanks will commence early March with the second tank following soon after. These works should further stabilise the plants biological process.
Milliscreen repairs
The plant is operating with a reduced number of milliscreens due to increased age-related failures. These screens are the originals installed and are past their service life. Urgent repairs are currently taking place on some of these units to return them to operation in April. A project to replace all 10 milliscreens over a number of years, is in the design phase. This project will strengthen the plants processing resilience into the future.
What has been completed:
The design for Stage 2 works has been completed and approved.
The request for tender information has been completed and the tender put out in line with the procurement strategy.
The final report for the Stage 1 Biofilter works was provided to GWRC showing the Biofilter achieving >99.9% removal of H2S from the odorous air it treats. The report will be shared on the Seaview project page for public perusal.
What is currently in progress:
Contractors are currently working to respond to our request for tender stage 2 works, this closes in March. Odour scouting in the community continues.
Resource consents
WGN050359 [24539] Discharge Treated Wastewater to Coastal Marine Area (Seaview WWTP)
WGN120142 [31740] Construction to Coastal Marine Area Maintenance (Seaview WWTP)
WGN120142 [33406] Discharge of Treated WW to Fresh Water Wet Weather (Seaview WWTP)
WGN120142 [33407] Discharge of Treated WW to Coastal Marine Area Maintenance (Seaview WWTP)
WGN120142 [33408] Discharge Treated Wastewater to Stream (Seaview WWTP)
WGN930193 [1] Contaminants Discharge to Air Outfall Structure (Seaview WWTP)
WGN930193 [2] Contaminants Discharge to Air Venting Structure (Seaview WWTP)
WGN950162 [1] Contaminants Discharge to Air WWTP (Seaview WWTP)
WGN930194 Land Occupation by Outfall Pipeline and Structures (Seaview WWTP)
Compliance reports
Seaview Wastewater Treatment Plant - 2021 2022 Compliance Report
Seaview Wastewater Treatment Plant - Consent Compliance Report 2022 - 2023
Seaview Wastewater Treatment Plant - Consent Compliance Report 2023 - 2024
Resource consent reports
Annual Reports:
Seaview Wastewater Treatment Plant Annual Resource Consents Report 2023-24
Seaview Wastewater Treatment Plant Annual Resource Consents Report 2020/2021
Seaview Wastewater Treatment Plant and HCC/UHCC Trunk Main Annual Resource Consents Report 2019/2020
Seaview Wastewater Treatment Plant Annual Report 2021/2022
Seaview WWTP 2022/ 23 Annual Consents Report
Quarterly Reports:
Seaview Wastewater Treatment Plant - January - March 2025 - Quarterly Resource Consents Report
Seaview Wastewater Treatment Plant October - December 2024 - Quarterly Resource Consents Report
Seaview Wastewater Treatment Plant July - September 2024 - Quarterly Resource Consents Report
Seaview Wastewater Treatment Plant January - March 2023 - Quarterly Resource Consents Report
Appendices:
Seaview Wastewater Treatment Plant Annual Consents Report 2023-24 - Appendix ||| Trade Waste
Public health statements on the use of the treatment plant odour neutraliser
Summary
Potential health concerns associated with exposure to quaternary ammonium compounds are most likely associated with direct contact with undiluted product i.e. the staff preparing the solution. Staff exposure risk is managed by following the correct health and safety procedures. Quaternary ammonium compounds are often part of household cleaning and disinfection products and so exposure to the public is relatively common. Given the level of dilution of the product used in the cannon, and the distance between the placement of the cannon and potential locations for public exposure (typically this type of cannon dispersal method has an estimated droplet range of 50-100 metres) that effectively dilutes the strength further, we would not expect this to represent a health risk for the general public.
Te Whatu Ora - Health NZ - April 2023
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In May 2024, The plant operator, Veolia, switched to a new product Odour Neutraliser Plus (SCD1100) which is manufactured by biOx Environmental. This is a stabilised chlorine dioxide product that oxidises odour molecules such as Hydrogen Sulfide. The product is safe when used as directed and is utilised in wastewater treatment plants, landfills and transfer stations throughout New Zealand. While the previous product Hi Chem Disinfectant Reodorant presented no public health risks (see above) we decided to act on complaints from the community about the odour it generates and changed to Odour Neutraliser Plus (SCD1100). More information about this product
Independent assessment on the impact of the odour neutralisers
Regarding any impact of the odour neutralisers, an independent assessment has been undertaken and the report concluded that the potential health risks regarding the use of the odour deodorisers are low and acceptable in accordance with New Zealand Guidelines. A copy of the report can be found here.
Odour Investigation Reports
Consents
One of the nine resource consents permitting the operation of the plant, consent ‘WGN120142 [33408] Discharge Treated Wastewater to Stream ' expired in 2018.
Prior to the expiry of this consent, Hutt City Council applied to Greater Wellington Regional Council (GWRC) for a new consent to temporarily discharge treated wastewater to the Waiwhetū Stream.
While the reconsenting is underway, we continue to operate under the existing consent.
In general, the consents allow Hutt City Council to:
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discharge treated and partially treated effluent through an existing outfall,
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discharge mixed disinfected, treated and milli-screened wastewater during and/or immediately after heavy rainfall,
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discharge mixed disinfected, treated and milli-screened wastewater during maintenance,
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discharge of contaminants to the air, and
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to occupy the stream and coastal marine area with an outfall structure.