To keep up with a rising population and meet emissions targets, Melbourne Water is upgrading its Western Treatment Plant with a new resource recovery complex.
Having been established more than 120 years ago, Melbourne Water’s Western Treatment Plant (WTP) handles more than half of the city’s wastewater.
The plant, which is approximately the same size as Phillip Island, doubles as a working farm and its lagoons, grasslands and coastline provide an ideal and varied habitat that is internationally recognised as a prime birdwatching location.
The WTP supports Melbourne’s international reputation as one of the world’s most liveable cities by being a major agriculture and biodiversity hub, while also delivering resource recovery, education and ecotourism.
An essential process
The plant’s sewage treatment facilities provide an essential service that protects the health of the city’s public, waterways and Port Phillip Bay.
Having grown over its lifetime, the plant now treats more than 182,500ML of sewage every year using a low-cost, low-energy treatment process.
The process involves sewage slowly flowing through a series of lagoons – the largest of which can hold 600ML – where bacteria gradually break down the organic material in the water.
The process takes 30–35 days to turn wastewater into class C recycled water, which can then undergo further treatment in other parts of the facility, turning it into class A water – the highest standard of recycled water.
Anaerobic lagoons
The first lagoons in the process are contained beneath large plastic covers designed to keep out oxygen. This creates an anaerobic (oxygen-free) environment, perfect for certain types of bacteria to thrive.
As these bacteria decompose the organic material in the sewage, methane gas – also called biogas – is released. The plastic covers then serve a second purpose; to catch this gas, reducing the odour of the facility and preventing excessive emissions. The captured biogas is then repurposed to provide power for the site.
Aerobic lagoons
Sewage then flows into the uncovered aerobic lagoons, where aerator machines pump oxygen into the water, making it suitable for a different type of bacteria. These bacteria remove nitrogen from the water and cause remaining waste products to clump together.
This waste is then easily separated out in settling tanks called clarifiers before being dried and stored or reused as biosolids.
Release or recycle
Once the water has reached this stage of the process, it has been thoroughly cleaned and is categorised as class C recycled water.
Under strict conditions set by EPA Victoria, it can now be released into Port Phillip Bay.
Alternatively, it can be further disinfected using ultraviolet light and chlorine to produce class A recycled water, which can be reused in agricultural irrigation or residential water networks.
The plant is a vital part of the circular economy, turning waste into valuable resources that can be reused. These include:
- Biogas (methane) – used to generate enough renewable energy to power the plant
- Recycled water – used to irrigate the plant’s farmland and wetlands, and the nearby food growing district
- Biosolids – soil-like material rich in nutrients, used in farmland
Melbourne’s continued growth means sewage flows are expected to almost double by 2050. Together with innovative initiatives – like ‘co-digesting’ business food waste to reduce landfill and harness more biogas – this creates an opportunity for the WTP to make an even greater contribution to the circular economy.
Recovery and re-use
Melbourne Water Senior Manager Major Projects, Major Capital Delivery, Mark Lawrence, said that the WTP’s Resource Recovery and Re-Use Complex (RRRC) upgrade will ensure the plant remains up to the task of servicing the city’s population.
Image: Melbourne Water
“The RRRC will deliver an integrated environmentally sustainable solution at the WTP, decarbonising our existing process and reducing greenhouse gas emissions and odour,” Mr Lawrence said.
“The upgrade will increase resilience to accommodate Melbourne’s growing population, enabling improved resource recovery and potential renewable energy production.
“Additionally, the RRRC will reduce the load on existing and downstream processes, providing indirect benefits to ensure that the WTP continues to support a thriving Port Phillip Bay.”
The project is set to modernise the way Melbourne Water treats incoming sewage and return the existing lagoon‑based assets at the plant to a more sustainable mode of operation.
The RRRC consists of four projects that will:
- Reduce the load on the existing anaerobic lagoons and lower the frequency of odour-intensive maintenance works by introducing new treatment processes
- Improve solids handling and anaerobic digestion to divert sludge away from the overloaded aerated ponds
- Develop a new facility to receive and treat waste delivered by tanker from Melbourne Water’s customers, better managing environmental risk and helping Melbourne Water fulfill its obligations under the Environmental Protection Act
- Deliver a new liquid food waste facility to receive waste from industrial customers for co-digestion, which will generate renewable energy
- The WTP already treats approximately 60 per cent of Melbourne’s sewage, and the new complex is expected to increase its current capacity of almost 200ML per annum by nearly 50 per cent. This will ensure Melbourne Water’s ability to service the city through the projected doubling of its population by 2050.
In addition to improving delivery efficiency, bundling the four new plant assets into one major project has aided in technical innovation, allowing developers to modernise the way incoming sewage will be treated. This is expected to reduce greenhouse gas emissions, allow for better integration of liquid food waste digestion and enhance the plant’s biomethane production, which in turn will enable greater renewable energy generation. The RRRC project marks a major milestone for the future of the WTP. As part of the project, Melbourne Water is investing significantly in digital resources and academic collaborations that will help it to monitor and reduce its Scope 1, 2 and 3 emissions. The utility will seek to reduce its Scope 3 emissions by at least 20 per cent during works to the develop the RRRC, using a range of sustainability initiatives and practices.
The RRRC is being developed through a partnership between Melbourne Water and John Holland Group and is expected to be complete and fully operational in 2029.
Featured image: turning the first sod of Melbourne Water’s Resource Recovery and Re-Use Complex at the Western Treatment Plant.
