Seaview Wastewater Treatment Plant
Seaview - Increased Odour Risk
Maintenance is required on the dryer drum, which is planned for Monday 1 to Saturday 6 December. This includes 2 days of contingency. This will bring forward some of the work planned for early 2026. This work is vital to keep the dryer functioning reliably, and reduce the risk of unplanned works.
Final update - December 5th - Works complete
Work has been completed, and sludge trucking has ended. We’ll be bringing the dryer back online over the weekend.
Thanks to the community for your patience and understanding as we completed this important work.
Reducing the risk of odour
To maintain the health and balance of the plant during these shutdowns, and reduce the risk of any ongoing odour issues, sludge will be trucked to Silverstream Landfill. This may result in a temporary increased risk of odour due to the loading of sludge onto trucks.
The same actions will be taken to reduce the risk of odour impacting the community as in the last shutdowns.
· Temporary shielding will be put up around the sludge load out area to act as a wind break
· The sludge will be well wrapped to reduce the risk of any odour getting out.
· The odour neutraliser will be used as needed
· Odour surveys are underway to monitor odour
Update - December 2nd
Maintenance on the dryer drum is progressing well and our timeline remains on track. This work is vital to keep the dryer functioning reliably and reduce the risk of unplanned works over the summer.
To maintain the health and balance of the plant during this shutdown and reduce the risk of any ongoing odour issues, we are closely monitoring the plant's biological process.
The most recent results indicate the process remains healthy, with no related risk of increased odour. The unloading and trucking of sludge remains the key odour risk during this shutdown.
The same actions are being taken to reduce the risk of odour impacting the community as in the last shutdowns.
- Temporary shielding has been put up around the sludge load out area to act as a wind break
- The sludge is being well wrapped to reduce the risk of any odour getting out.
- The odour neutraliser are being used as needed
- Odour surveys are monitoring odour
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.
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. This process is complex, with a number of factors. Two of these are Mixed Liquor Suspended Solids and Dissolved Oxygen levels. We use these to help give an insight into how the biological process is managed. We'll update these every month in the graphs below, where green indicates the standard target range for these factors at Seaview Wastewater Treatment Plant. Please note that these ranges are not the same at every treatment plant.
When they are within or close to the 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. However, some external factors (i.e. a weather event impacting the flow of wastewater into the plant) may require the team to make the levels higher or lower in order to keep the biological process balanced and healthy.
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 the Seaview Wastewater Treatment 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: October 2025
Commentary:
Faecal coliforms remain non-compliant for both the 90-day geomean and 80th percentile. Suspended solids and biochemical oxygen demand are compliant with consent parameters.
Discharges:
There were four consented wet weather discharges to the Waiwhetū Stream in October.
Odour Complaints
There were no odour complaints in October.
Items of significance:
Effluent Non-compliance: Unplanned maintenance to the thermal dryer in September is requiring dewatered sludge to be loaded out while repairs were carried out and negatively impacting the biological process. The recovery to the process has been slower than anticipated however trends and daily effluent results indicate the process is on the correct path to restoring compliance.
Community Odour Monitors:
Four of the five monitors have been installed in the designated locations, with one still to be installed. The community website platform is now expected to be available later in November.
Odour Treatment Project
What has been completed:
- Community Liaison Group Meeting – 22 October 2025
- New milliscreen odour treatment unit ducting is complete
What’s coming up:
- Installation of the final community odour monitor to be completed
- Complete and commission the new milliscreen odour treatment system
- Install and commission new Milliscreen and Biofilter fans (delayed due to manufacturing delays)
Read the full October 2025 Seaview wastewater treatment plant monthly performance report.
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 2024/25
Seaview Wastewater Treatment Plant Annual Resource Consents Report 2023-24
Seaview Wastewater Treatment Plant Annual Resource Consents Report 2022/ 23
Seaview Wastewater Treatment Plant Annual Resource Consents Report 2021/2022
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
Quarterly Reports:
Seaview Wastewater Treatment Plant - July - September 2025 - Quarterly Resource Consents Report
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:
Appendix IV - Annual Resource Consents Report - Hutt Valley Tradewaste Report 2024/25
Appendix V - Annual Resource Consents Report - AEE Waiwhetu Stream Wet Weather Discharges 2024/25
Appendix VI - Annual Resource Consents Report - AEE Non-compliant Discharges 2024/25
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
Seaview Wastewater Treatment Plant - Odour Deodoriser - Air Quality Assessment - October 2024
Seaview Wastewater Treatment Plant - Odour Investigation - June 2023
Seaview Wastewater Treatment Plant -Biofilter Flow Assessment -March 2024
Community Liaison Group
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.