Warrnambool Sewage Treatment Plant Upgrade

Wannon Water’s Warrnambool Sewage Treatment Plant services Warrnambool, Allansford and Koroit and is currently operating at the limit of its treatment capacity.

We have announced a major project to upgrade the plant to meet the needs of housing and economic growth in the region. 

The project, estimated to cost $40 million, will be the largest ever single project undertaken by Wannon Water. It will ensure the plant has sufficient capacity for a projected increase in sewage volumes while continuing to protect the environment.

More details are available in this Information Sheet.

The plant currently discharges treated effluent to the Southern Ocean at Thunder Point via an onshore ocean outfall following treatment through an existing inlet screening facility and four intermittently decanted extended aeration (IDEA) tanks with a tertiary effluent screen. 

The upgrade is needed to increase capacity to manage demand for sewage and wastewater treatment now and until 2040, and foster growth in the south-west region. The upgrade will include installation of a new inlet screening facility, a new odour control system and the addition of two new IDEA tanks with a second tertiary effluent screen.

Wbool Stp Upgrade Draft Detailed Design June 2021

Project updates

On 29 July 2021, the EPA issued a Development Licence for the upgrade project. Further details are available at Engage Victoria.

Final design and approval is now underway with construction expected to start in 2021, taking two to three years to complete.

In order to finalise the structural design of the Warrnambool STP Upgrade Project, geotechnical investigations are now taking place. The geotechnical work is in the Thunder Point Reserve area, adjoining the plant, and will involve the removal of a small amount of vegetation, the drilling of bore holes and seismic studies. The area will be revegetated once the project is complete.

Access to the majority of walking and bike riding tracks will still be available, however there will be localised track closures and we urge users of the area to observe the signs and temporary fencing.

Warrnambool Stp Image01

In January 2021, we announced several changes to the project to improve environmental protections. The changes respond to feedback from the Environment Protection Authority (EPA) and community members and follow detailed analysis and modelling of the coastal environment.

The revised proposal ensures that we comply with the State Environment Protection Policy (Waters). You can read more in the Warrnambool Sewage Treatment Plant Upgrade Update 6.

In preparation for the project, we've also upgraded a section of the existing unsealed driveway off Elliott Street to an asphalt pavement.

The aim is to reduce noise, dust and other potential issues for surrounding residents while ensuring access for the ongoing operation of the sewage treatment plant throughout the upgrade work. The completed pavement has been undertaken in consultation with Warrnambool City Council.

Elliott Street driveway

Further information about the project is available in this video.

Wannon Water will tender the project through VicTenders and advertise in local papers. A briefing session will be held in advance of the tender being advertised.

The following project updates have been prepared in relation to the works:

Download the Warrnambool Sewage Treatment Plant Upgrade Update 6

Download the Warrnambool Sewage Treatment Plant Upgrade Update 5

Download the Warrnambool Sewage Treatment Plant Upgrade Update 4

Download the Warrnambool Sewage Treatment Plant Upgrade Update 3

Download the Warrnambool Sewage Treatment Plant Upgrade Update 2

Download the Warrnambool Sewage Treatment Plant Upgrade Update 1

Tertiary treatment and Class A water

We’re upgrading our Warrnambool Sewage Treatment Plant (STP) in a $40 million project that will enable us to support growth in south-west Victoria through to 2040.

The upgrade will increase the capacity of the plant by around 50 per cent and enable maintenance of treatment standards critical for environmental protection at the ocean outfall.

The project will:

  • Improve solids removal with the inclusion of a new inlet screening system as well as tertiary effluent screening
  • Expand existing secondary treatment, including nutrient removal, to manage environmental and public health risks
  • Include a foul air collection and treatment system.

This capacity upgrade is the first step as part of a long term strategy and will enable future improvements at the site, such as enhanced nutrient removal, tertiary treatment and/or the production of recycled water for commercial reuse when the timing is right.

The Warrnambool STP currently provides treatment of sewage and industrial wastewater by removing physical, chemical and biological contaminants. The aim is to produce treated effluent that is suitable for discharge to the ocean in accordance with our Environment Protection Authority (EPA) licence and State Environment Protection Policy (SEPP) requirements.

Each year the STP also produces around 60 million litres of recycled water of a quality suitable for reuse within the plant for process water e.g. equipment cleaning and hoses.

The capital cost of building a treatment facility that would produce high quality recycled water for toilet flushing, garden watering etc (Class A) is estimated to be more than $1 million per million litres of wastewater treated. For 2040 flows through the Warrnambool STP, this equates to an estimated $30 to 40 million on top of the $40 million already committed for the current upgrade.

In addition to the capital cost, the annual operating cost to run a tertiary treatment facility is expensive and would need to be shared by Wannon Water’s domestic and industrial customers on an ongoing basis each year resulting in higher bills. Our customers tell us that maintaining bill affordability is important.

We’ve previously commissioned investigations into possible large-scale reuse applications, and sought expressions of interest from third parties for recycled water. However, these processes have not identified any feasible applications, meaning there is currently no driver to produce recycled water.

Another key constraint is the high salt content originating from major industries in the region. The current salt concentration in the Warrnambool STP effluent is too high for sustainable irrigation systems or for residential reuse schemes without the use of a desalination process to reduce the level to a more suitable concentration.

The inclusion of a salt reduction plant would further increase the capital and operating cost of a Class A plant at the Warrnambool STP, while significantly increasing the STP’s environmental footprint through electricity consumption and waste by-products.

This Information Sheet provides further details about tertiary treatment and Class A recycled water.

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Screening Strategy

In an Australian first, Wannon Water responded to an illegal dumping of nurdles through the plant and their subsequent spill into the ocean in November 2017, by commissioning a screening strategy and subsequently constructing a one-millimetre fine effluent screen.

An automated band screen was successfully installed on the existing four IDEA tanks and it began operating on 24 April 2020. The commissioning results showed that particles of less than one millimetre were passing through, with all other particles being captured for disposal with other plant waste. The automated screen will now operate as the primary screen with the improved manual screen as a back-up.


As part of the proposed upgrade project, Wannon Water will be investing $4.2 million to construct a new inlet screening facility. The new facility will replace the existing outdated infrastructure located to the north of the main plant and provide an increase of 40-50% in the capture rate of solids in the raw influent. The facility will consist of two five-millimetre band screens upstream of a vortex grit chamber, along with associated waste handling facilities.


Read more here: Warrnambool Sewage Treatment Plant Screening Strategy

Wannon Water is committed to protecting and enhancing the environment in line with community expectations. Read more about the community's work to reduce marine plastic here: Clean Oceans Collective.

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The case for expansion

Unlike typical sewage treatment plants, wastewater in the Warrnambool system has a unique chemistry because it is predominantly fed by industrial activity.

Around 50 per cent of the current flow is sourced from three major industrial users, meaning organic and nutrient contaminant loads treated by the plant are much higher than those typically derived from domestic sources.

The existing plant has tight licensing requirements set by the Environment Protection Authority (EPA) governing the quality of effluent produced. The plant has nearly reached its capacity in being able to treat wastewater to the required quality, and for the approved discharge volume of 16.4 megalitres/day. As such, the Warrnambool system cannot accept additional new sources, which is limiting the capacity of existing industries to respond to market opportunities and the greater community to grow. Without the upgrade, major industrial development and investment in milk and meat processing cannot be expected to occur.

The project has strong industry and community support and financial commitments from industry. Licensing amendments from the EPA are being sought for the project which will see the effluent discharge licence increase to 27.9ML/d while maintaining existing water quality parameters.

Projections show that by 2040, the major industrial users could account for between 65 to 70 per cent of the treatment plant’s capacity. This is an abnormal, once-in-a-generation upgrade project, designed to support the growth of a nationally-significant industry.

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Key project challenges

Like any major key infrastructure project, this upgrade project is not without risks and challenges. Prior to construction, a whole range of potential issues must be worked though and solutions found to ensure the project can reach its construction phase. Some of these have been:

  • Designing a project of this size and nature – 294 drawings have been prepared
  • Funding a $40 million project – the most significant project Wannon Water has ever embarked on
  • Permits and approvals – a strategic project requires sign off from many organisations including the Department of Environment, Land, Water and Planning, Warrnambool City Council and the EPA.

Once the project advances to construction phases, new risks are faced:

  • Construction alongside an existing operational plant
  • Large excavation works in coastal sandy ground conditions
  • Minimising disruption to the surrounding community
  • Shutdowns and connections to live sewers and/or existing plant infrastructure
  • Commissioning the new plant once completed.



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