Odour
Following the incident at Moa Point Wastewater Treatment Plant, there is a higher risk of odour.
We appreciate the significant impact that odour can have on the community, and do not take this lightly. Managing and reducing odour is a top priority for us, every step of the way.
27 March
Moa Point’s odour treatment systems are not working following the flooding on February 4th.
Restoring odour treatment at the plant is a top priority for Wellington Water, and we are working on a solution as quickly as we can. However, it will not be a quick fix – and it’s important that we continue to be upfront with the community around the ongoing risk of intermittent odour as we move through recovery of the plant.
What’s the current situation?
Ventilation at the plant has been partially reinstated, to reduce the risk that hydrogen sulphide poses to workers inside the plant building. Hydrogen sulphide is an odour compound commonly observed at wastewater treatment plants, which smells like rotten eggs. In confined spaces, and at high levels, it can pose a significant health and safety risk. Health and safety risks on site also impact how quickly and efficiently work can be completed.
The partial ventilation that has been set up as an interim measure vents air from the plant to the atmosphere through a large stack (or chimney). This helps any odourous air get picked up quickly by the wind and dispersed. However, on a still day, odour may linger.
Ventilation is something which we are continuing to improve onsite. If there is any change to the risk of odour related to this work, we will advise the community.
We appreciate the significant impact odour can have, and do not take this lightly. We'll keep you up to date on our progress to restore full odour treatment at the plant.
What happens when there is an increased risk of odour related to works onsite?
As recovery works progress, there may be specific pieces of work that increase the risk of odour. Wherever possible, we will provide the community with advance notice of these works via this mailing list, the Moa Point newsletter, the Wellington Water website and Wellington Water social media. We will also complete letter drops to the surrounding neighbourhoods wherever practicable.
Clarifier works
These works will continue until late April. There is a very low risk of intermittent odour while these works are underway. If the risk increases, or odour from these works is observed onsite, we will advise you directly.
Reducing the risk of odour
While we continue work to bring odour treatment back online, to reduce the risk of odour impacting the community, odour neutralisers are onsite and being used as needed. Odour scouts are monitoring odour onsite and in the community.
Frequently asked questions
Why is there a higher risk of odour?
There are three key things which may cause more odour:
- When the plant stopped operating, the wastewater treatment process also stopped. This left wastewater inside the plant at various stages of treatment, including sludge (wastewater solids). One of our top priorities has been to remove this sludge as soon as possible before it becomes septic, which could cause significant odour and a health and safety risk to workers onsite.
- The plant is receiving, screening and discharging wastewater out the long outfall pipe. This process can produce odour that would normally be managed by onsite odour treatment systems, however these were also impacted by the flooding and not currently operating.
- Removing sludge and screened material (i.e. wet wipes) from the plant may temporarily increase odour, as it is loaded out.
What are we doing to reduce the risk of odour impacting the community?
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We are clearing wastewater and sludge from the plant as quickly as possible. This work has been going well, and we expect the plant to be cleared by early March.
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Odour neutralisers and odour monitors are being brought onsite. Odour scouts are also regularly assessing odour levels within the plant boundary and in the community. We are working to restore odour treatment systems as quickly as possible, however we cannot provide a timeframe for this.
Does this pose a risk to public health?
No. Hydrogen sulphide, which tends to smell like rotten eggs, is odorous at much lower concentrations than the levels that can cause adverse human health effects. Reducing odour is important to protect community wellbeing, rather than physical health. High concentrations of hydrogen sulphide can pose a health and safety risk to workers onsite in enclosed spaces, and we have specific health and safety requirements and activities onsite to address this.
How do I get more information or lodge a complaint?
If you have any questions or feedback, please reach out to customer@wellingtonwater.co.nz or call 04 912 4400 and we’ll get back to you as soon as possible.
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Complaints can be made directly to Greater Wellington, by phoning 0800 496 734.