Severe weather conditions from Wednesday 30 April to Friday 2 May may impact the network
Severe weather conditions may impact the network

Due to severe weather conditions forecasted from today, 30 April until Friday 2 May, there may be impacts on the network, 

Heavy rain increases the chance of excess stormwater entering the wastewater network, which it doesn’t have capacity for. This means there is a higher risk of wastewater overflows during wet weather events or emergencies such as major power cuts.

Our operations team are checking known risk areas and working to ensure that the stormwater network will be running as smoothly as possible. 

 

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Knowledge Hub / The Network / Wastewater / Wastewater treatment plants / Seaview Wastewater Treatment Plant

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.

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.  

 

Internal factors

External factors

  • the health and balance of the plant 

  • wind

  • plant maintenance and operations

  • weather

 

  • location

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.

Scheduled Works   Some Risk 23 Apr

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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

Resource consent reports

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

_________________________________

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:

  • discharge treated and partially treated effluent through an existing outfall,

  • discharge mixed disinfected, treated and milli-screened wastewater during and/or immediately after heavy rainfall,

  • discharge mixed disinfected, treated and milli-screened wastewater during maintenance,

  • discharge of contaminants to the air, and

  • to occupy the stream and coastal marine area with an outfall structure.