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Projects / Seaview Wastewater Treatment Plant Biofilter Media Replacement

Seaview Wastewater Treatment Plant Biofilter Media Replacement

Current status
All Updates

This project was completed in December 2023

Start Date
End Date

If you have any questions about this work, please contact:

Wellington Water, 04 912 4400

Latest Updates

3 January 2024

The biofilter media replacement works have been completed ahead of schedule.

21 December 2023

We’ve made great progress with the biofilter media replacement at the Seaview plant.

18 December 2023

We're making excellent progress after replacing the biofilter media in cells 3 & 4.

The biofilter media replacement was completed ahead of schedule in late December 2023.

Please see the 'Background' tab for more detailed information and 'All Updates' 

Why was this work needed? 

The biofilter receives air and gases from the most odorous wastewater treatment processes which are extracted through a ventilation system and blown through an active biological bed of bark and other organic material.

The bark mix which is part of the biofilter media at the Seaview Wastewater Treatment Plant was replaced to enable improved odour management at the plant.

What did this involve? 

The work involved replacement of six media cells . The old media was carefully excavated and disposed at landfill.

While the cells were being replaced, the condition of the pipework below the biofilter media was assessed to determine its performance at evenly distributing the odorous gases across the cell.

Summary of Seaview Wastewater Treatment Plant Community Meeting - 6 December 2023 

At the community meeting, Council and Wellington Water acknowledged that it's been unpleasant, inconvenient, and distressful for many who live in the vicinity, and discussed plans to address the odour issue at the Seaview wastewater treatment plant. 

Te Rūnanganui o Te Āti Awa ki te Upoko o Te Ika a Māui, Waiwhetu marae and Wellington Tenths Trust/Palmerston North Māori Reserve Trust were in attendance as were many residents. The Hutt Park Holiday Village (Top 10) also attended. Deputy Mayor Lewis, Councillors Edwards, Brown, Dyer and Mike Fisher Petone Community Board Chair also attended along with staff from HCC, WW and GWRC. Seaview Marina and other businesses were also in attendance.

The presentation from Wellington Water explained the investigation undertaken to date and its outcome that biofilter media had reached the end of its lifespan and requires replacing. It was explained that an attempt to isolate and contain the first section of the biofilter as it was removed had not worked as hoped and resulted in the recent offensive odour.

Assurances were given by Council that we would do all we can to address the odour issue in the short and medium term.

Council is considering the draft Long Term Plan, which now has a significant investment of $13 million, to significantly improve the situation with replacement of aged equipment at the plant. This investment has been brought forward to the next three years.

Mana Whenua present requested a separate briefing and for improved communications with them. Residents and businesses expressed frustration with the time it is taking to address the issue and, in the meantime, having to live with the offensive smell.

Hutt Park Holiday Village was critical the work is being undertaken during their busiest period, reporting a significant number of negative online reviews and direct complaints from customers about the smell.

Wellington Water expects this work will be completed by 25 January by which time the odour is expected to have significantly abated.

Councillors recommended that residents continue to log complaints via when they notice the smell and encouraged them to make submissions to the Long Term Plan process currently before Council. An online survey to gather feedback will appear on Hutt City Council's Annual Plans and Long Term Plans page on 2 April 2024 and remain open throughout April.


The plant manager Veolia completed the biofilter media replacement in December 2023.


Relevant documents

Seaview community meeting presentation - 6 December 2023

Frequently Asked Questions

Why are you doing this work in summer, shouldn’t you be doing it in winter? 

We had hoped to do it earlier in the year, unfortunately, that was not possible. There is no ideal time to do this type of work. It wouldn’t necessarily make a difference if we had done the work in summer or winter, as the wind can affect odour levels. 

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. There was general maintenance work undertaken to the existing biofilter media in 2021, which was published on the Wellington Water website. The biofilter media replacement was delayed earlier this year, due to condition assessment and lab testing of bark composition, and the availability of a specialist contractor to undertake what is complex works. 

Will the biofilter media replacement make a difference? 

We do expect the new biofilter media will improve odour levels. This will not be immediate as the biofiltration process is biological and it takes time for the new composition of bark and shell to become settled and established. 

What upgrades do you have planned, how much will it cost? 

A recent condition inspection of the biofilter has shown the air distribution base (plenum) is in poor condition and an upgrade is under design. The odour ducting pipework at the site is also under review for replacement as the next significant step. In addition, odour treatment to the milliscreen and dryer buildings is another remedy under review. A budget for these works of $13M is proposed in the 2024 Hutt City Council Long Term Plan, but the exact scope of work is still being investigated and costed. 

Is the odour issue ever going to be fixed? 
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. Wellington Water and Hutt City Council are committed to resolving the issue, though this is not an overnight fix, and it will take time.  

Are there any health implications with the 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 on the Seaview Wastewater Treatment Plant page.

Is it true the treatment plant was never designed to keep odour within the plant boundary? 

The plant was built in the late 1990s when the surrounding area was more industrial than today. It was not designed to eliminate all odours but to mitigate the levels of odour from the plant below an “offensive or objectionable” level, as judged by regional council enforcement officers, a standard we expect would apply today. We acknowledge the odour levels recently have been particularly offensive and we’re looking at how we can improve this situation. The biofilter media replacement is first step in that process. 

Has Wellington Water ever been fined for not meeting the consents for odour management? 

Yes, Wellington Water, plant operator Veolia, Hutt City Council, and Upper Hutt City Council were recently fined a combined total of $70,000 dollars relating to offensive and objectionable odour beyond the boundary of the plant.

You aren’t transparent about consents; we have not been consulted recently… 

The resource consent in place is a long-term and expires in 2031. We have a community liaison group which meets at least once a year to review treatment plant consent reports and issues and have held several meetings with local groups in the past few years.  

Where can I get more information or ask any questions about the plant and the odour? 
We have dedicated website page with all the details about the works and future upgrades. If you have any questions or feedback, please email


All Updates

3 January 2024

The works were initially expected to be completed by late January  but the project team managed to reinstate the biofilter media prior to the Christmas break.

All the six cells of biofilter media are replaced and now commissioned.

Please note, While the biofilter media has been replaced, it will take a short period of time to bed in and become fully functional and 100 percent effective.  

These works are a small first step to improve odour management, Hutt City Council has also included $13 million of proposed upgrades and improvements in the draft Long Term Plant. 

This investment will support the long-term solution to odour management at the treatment plant.




21 December 2023

We’ve made great progress with the biofilter media replacement at the Seaview plant.

These important works to improve odour management at the plant are ahead of schedule and we’re on track to complete the works by January 25.

From tomorrow, December 22, works will stop for the holidays and resume on January 10, 2024.

We acknowledge the patience of the local community and businesses, we look forward to completing the works for better odour management at the plant.

18 December 2023

The team have made excellent progress after managing to replace the biofilter media in both cells 3  and 4.

This means 4 of the 6 cells of the biofilter media are replaced and commissioned. 

The team have now moved to cell 5 to begin the process of excavation and inspection, before installing the new media.

 Further updates will be provided as the project progresses.

Biofilter media - cells 2 &3 completed

Biofilter media - cell 4 completed

8 December 2023

Thank you to everyone who turned up at the Seaview community meeting on Wednesday night, your attendance and views were much appreciated.

We are committed to resolving the odour issue and will be working with Hutt City Council to get the necessary upgrades prioritised.

We know you want us to keep investing in the local wastewater system. Hutt City Council will be considering odour control upgrades as part of their long-term plan meeting next Tuesday.

Hutt City Council has proposed $13 million dollars to be spent over the next 3 years on the odour control upgrade work, along with other significant upgrades for the Seaview Wastewater Treatment Plant.


8 December 2023

The team have successfully commissioned Cells 1  and 2 today. This means that both Cells are now operational and treating the odorous gases as designed (Image 1).

The team have moved the digger into Cell 3 and commenced excavation of the old media this afternoon (Image 2). Next week Cell 3 will be excavated and inspections will be performed before installing the new media.

Further updates will be provided as the project progresses.


Image 1 - Cells 1  and 2 complete                                                                                     Image 2 – Cell 2 complete and digger in Cell 3


5 December 2023

Works to replace the biofilter media are progressing well with the contractor successfully installing the new media into Cell 1 last week. (Image 1)

The digger has now been moved to Cell 2 (Image 2) and will begin removing the old media which will then be transported to landfill for disposal.

The replacement media for Cell 2 will be delivered this week and the team are optimistic of installing this ahead of schedule to fully commission cells 1 & 2 next week.

Further updates will be provided as the project progresses.


Image 1 - New media installed into Cell 1.                                                                                                       Image 2 - Digger operating in Cell 2.