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Eastern Treatment Plant

Treating sewage from Melbourne's south-eastern and eastern suburbs

The Eastern Treatment Plant in Bangholme treats sewage from about 1.5 million people in Melbourne’s south-eastern and eastern suburbs.

About 92% of the sewage that flows into the Eastern Treatment Plant each year is from residential and commercial sources, and the remaining 8% is from trade waste.

Sewage at the Eastern Treatment Plant is treated to secondary standard then disinfected, according to the EPA Victoria's licence requirements.

An increasing amount of fully treated effluent is recycled, and the rest is discharged into Bass Strait at Boags Rocks under an EPA Victoria licence.

Most sewage from the Mornington Peninsula is treated at South East Water's treatment plants at Mount Martha, Boneo and Somers, and this is also discharged to Bass Strait at Boags Rocks. These three plants discharge approximately 25 million litres a day of treated effluent.

When the Eastern Treatment Plant at Bangholme opened in 1975 it was a world leader in the secondary treatment of sewage.The plant is continually being improved to incorporate the latest technical equipment.

"The Eastern Treatment Plant is a key part of the essential public health service that Melbourne Water provides to the community. We maintain high standards in our operations but we are always looking for ways that we can improve our level of service."
Mike Smith, Manager, Eastern Treatment Plant.

Mike is a qualified mechanical engineer, who previously held roles in planning, asset management and capital projects delivery at Melbourne Water.

Map of the Eastern Treatment Plant and surrounds
How the Eastern Treatment Plant works

Sewage at the Eastern Treatment Plant is treated to secondary standard then disinfected, according to the EPA Victoria's licence requirements.

The sewage treatment process:

  • Sewage arrives at the Eastern Treatment Plant and is pumped through fine screens, removing objects such as sanitary products, cotton buds and other debris.
  • Sewage is aerated and grit is removed. The liquid waste passes to primary sedimentation tanks, and settled sludge and floating debris is pumped to larger tanks, known as digesters, where it is broken down.
  • The primary-treated water passes through the secondary treatment process, breaking down organic material in the plant's aeration tanks. The water passes to circular sedimentation tanks, which settle out more sludge and produce a final clarified effluent.
  • The treated effluent flows to large holding basins before it passes through three millimetre microscreens. It is then disinfected using a process called chlorination.
  • An increasing amount of fully treated effluent is recycled, and the rest is discharged into Bass Strait at Boags rocks under an EPA Victoria licence.
Aerial shot of the Eastern Treatment Plant

"The key way in which to describe what we’re doing here is that everything is focused on getting the impurities out of the water. The process we use to do that is essentially natural. We screen, allow settlement and then use bacteria and oxygen as the second part of the process. We’re not adding heaps of chemicals or anything, just some chlorine at the end to ensure disinfection, so that the water is ready to be discharged or re-used."
Annmarie Tracey, Process Engineer, Eastern Treatment Plant.

Having graduated with a degree in environmental engineering, Annmarie went on to complete a Masters in engineering in which she examined treatment processes for industrial wastewater. Annmarie has had five years of industry experience prior to her present appointment at Melbourne Water.

Download a diagram of the Eastern Treatment Plant treatment process (PDF 481 kb).

For more information visit the Eastern Treatment Plant Explorer.

Tertiary upgrade

In October 2006, the Victorian Government announced that a $300 million upgrade of the Eastern Treatment Plant to treat wastewater to Class A standard would begin in 2007 and would be completed in 2012. The upgrade is a key initiative in the Government's plan to secure our water future.

Recycled water is a precious resource, and the use of more recycled water for a range of purposes, will help us conserve our drinking water supplies.

This will mean that up to 135,000 million litres per year of treated water is potentially available for recycling in new housing estates, irrigation and industry, reducing flows into the ocean at Boags Rocks near Gunnamatta Beach.

A business case to confirm the estimated costs of the Eastern Recycling Proposal (to pump recycled water from the Eastern Treatment Plant to the Latrobe Valley for use by industry, instead of flowing into the ocean at Boags Rocks near Gunnamatta), the financial feasibility of the project, and the quality of water required by industry is being developed.

In accordance with the Eastern Treatment Plant upgrade works approval, Melbourne Water has completed a range of scientific studies into the impact of treated effluent discharges at Boags Rocks, taking into account a range of conditions including changes in treatment standards and possible future water recycling proposals including the Eastern Water Recycling Proposal.

A summary of these studies is available to download - ETP Works Approval Scientific Study.

Due to the size of the associated appended documents, we have not be able to add these to the website. They can be supplied on CD however by contacting Melbourne Water.

Tertiary Treatment Technology Research

In 2007, the next phase in the evolution of the Eastern Treatment Plant began with the construction beginning on a $10 million tertiary treatment technology trial facility at the site.

The construction of the trial facility is the first stage of the $300 million plant upgrade that will mean in future that all water leaving the plant will be processed to Class A quality - making it suitable for use in new housing estates, irrigation and industry.

In 2008, the new facility will examine a range of different treatment systems, to enable analysts to clearly assess the best possible tertiary treatment method to be constructed and commissioned by 2012. The trials will enable Melbourne Water to test different technologies for filtration and disinfection of recycled water, and will provide the ability to intensively monitor and analyse results using online instruments and in an onsite laboratory. Melbourne Water will work closely with EPA Victoria and the Department of Human Services to achieve a result that ensures a well-proven and validated process.

"Our high standard of secondary treatment - involving screening and settling of sewage, then further biological treatment using bacteria and oxygen, and final disinfection - will proceed unabated while the new research into tertiary treatment methods is conducted."
Chris Williams, Team Leader, Sewage Treatment and Strategy

View the tertiary technology trials fact sheet for more information.

Ammonia removal helps to protect the enviroment

Aeration tanks at the Eastern Treatment Plant are also being upgraded, to reduce the amount of ammonia in treated effluent being discharged into the marine environment at Boags Rocks.

A major two-year CSIRO study (PDF 1.6MB) examined the effect of treated effluent on the marine environment. The study found that ammonia levels and freshwater volumes were having a detrimental impact on the marine environment.

Reducing the amount of ammonia will help the marine ecology recover, and Melbourne Water is now well advanced with an $84 million project to cut levels by 75%.

In 2007, the first stage of this significant and complex project involves upgrading the existing aeration tanks at the plant. The construction of additional tanks will be completed in 2009.

In addition to the Eastern Treatment Plant upgrades, a number of upgrade works, at an estimated cost of $36 million, are currently in the advanced planning and construction phases at South East Water's Mount Martha, Boneo and Somers sewage treatment plants.For more information visit www.sewl.com.au.

Quality control measures

The Eastern Treatment Plant has been granted HACCP accreditation - it’s the largest sewage plant in Australia to achieve this.

HACCP (Hazard Analysis and Critical Control Point) is a quality control system that allows Melbourne Water to manage sewage treatment at a number of points along the treatment process rather than simply rely on testing the end product. The same strict procedure applies to food production.

"The emphasis on performance monitoring at the Eastern Treatment Plant is, in my experience, second to none. The HACCP approach drives process and stability, and as a result of the system, we can demonstrate what's happening."
Dr Mark Lynch, Team Leader, Process Management and Optimisation.

With a PhD is in waste water treatment, Mark worked and trained in both the United Kingdom and Hong Kong before taking up his current position at the Eastern Treatment Plant. He believes that it is the focus on quality control at the plant that makes the difference.