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.

Two new intermittently decanted extended aeration (IDEA) tanks will be constructed on the northern side of the facility to supplement the four existing tanks. The IDEA process has been in use at the plant for more than 20 years and is a robust and proven technology, both at the site and throughout the water industry. 


The project's design and approvals process is now underway with construction expected to start in 2019, taking two to three years to complete.

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

Screening strategy

Wannon Water is committed to protecting and enhancing the environment in line with community expectations.

The illegal dumping of nurdles through the plant and their subsequent spill into the ocean in November 2017 highlighted the global problem of plastic pollution on beaches.

At present, the sewage treatment plant has an inlet screening system that removes the majority of foreign material such as wet wipes, cotton buds, sanitary products and other objects that should never be flushed down the toilet or sink.

After the nurdle incident two additional effluent screens were installed at the outlet of the plant to further reduce the likelihood of microplastics being discharged into the ocean mixing zone. These screens need to be manually removed and cleaned at least once a day.

As part of the expansion project, Wannon Water will undertake substantial upgrades to the influent, effluent and septage screening systems at the plant.

We are investing in best practice technology that provides a safe, reliable and permanent solution to maximise screening performance and environmental protection.

Read more here: Warrnambool Sewage Treatment Plant Screening Strategy and Engagement Feedback Report

Warrnambool Sewage Treatment Plant concept design

A concept design of the expanded Warrnambool Sewage Treatment Plant showing the two new IDEA tanks, screening plant and septage receival facility.

The case for expansion

Unlike typical sewage treatment plants, wastewater in the Warrnambool system 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 plant cannot accept additional loads, which is limiting the capacity of existing industries to respond to market opportunities. Without the upgrade, major industrial development and investment in milk and meat processing cannot be expected to occur.

The project, which would expand the current capacity of the plant by 50 per cent, has strong industry and community support and financial commitments from industry.

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.

The statistics

• By 2040, the population served by the plant is expected to grow from 48,800 people to 59,300 people.

• The number of households in the same period is forecast to increase from the current 21,600 to 30,800.

• Dairying the south-west is an industry of national significance, producing 2.1 billion litres of milk each year (22 per cent of Australia’s supply).

• Industry expansion enabled by the upgrade would have the following economic spin-offs for the south-west:

  • 1512 full-time equivalent jobs.
  • $199 million in added economic value.
  • $196 million in exports.

Warrnamboolreclamationplant Aerial1web

The need for an upgrade

The region’s importance as a food industry hub means that demands on the Warrnambool Sewage Treatment Plant are much higher than would normally be expected based purely on population levels. While it is successfully meeting current demands, the plant is operating near capacity, treating around 15 million litres of sewage each day.

Residential and industrial development in Warrnambool is also expected to grow in the coming years. For example, the plant currently services nearly 15,000 houses, but this figure is expected to increase by more than 80 per cent to 25,000 properties in the next 50 years. Upgrading this plant will ensure we are doing all we can to protect and enhance the local environment and support the economic growth and prosperity of the Great South Coast region.

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Upgrade options

After a rigorous analysis of potential options for the future of sewage treatment in Warrnambool, engineering consultants provided a short list of options for the preferred approach of upgrading the existing Warrnambool Sewage Treatment Plant to increase its capacity by around 40 per cent. 

The preferred option, endorsed by the Wannon Water Board in May 2017, is the construction of two new intermittently decanted extended aeration (IDEA) tanks. The plan is to place them on the northern side of the facility to supplement the four existing IDEA tanks.

A Stakeholder Reference Group, consisting of residents, customers and representatives of key interest groups and major customers, was established to help decide the preferred upgrade option for the community and the region as a whole.

The IDEA process has been in use at the plant for more than 20 years and is a robust and proven technology, both at the site and throughout the water industry. 


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Community input

Wannon Water engaged with a Stakeholder Reference Group for the project in March and April 2017 to help decide on the best upgrade option based on balancing capital and operational costs, technical considerations, and environmental and social impacts.

Residents and representatives of recreational and environmental groups, aboriginal people, the EPA and the Department of Environment, Land, Water and Planning, members of our Community Advisory Committee and local business and industry were invited to participate through an expression of interest process.  The group met to help determine the criteria (and weightings) that were used to assess the shortlisted options presented to the board for a final decision.

Wannon Water has also consulted with nearby residents, local businesses, industries, recreational users and environmental groups about the project. This will continue throughout the entire design and construction stages.

We also briefed stakeholders, including government agencies, local government, regional groups, local Members of Parliament and our Community Advisory Committee.

Further information about the project is available by calling 1300 926 666 or emailing info@wannonwater.com.au

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Project timeline

March-April 2017 Stakeholder engagement & reference group meetings
May 2017 Wannon Water Board approves the preferred upgrade option
September 2017 Funding for preferred option listed in Wannon Water's five-year Price Submission to the Essential Services Commission (2018-23)
2017-19 Design and approvals process
2019-21 Construction and commissioning

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