The Western treatment plant

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Western Treatment Plant (Werribee)

The Werribee Treatment Plant at the west of Melbourne handles around 60% of Melbourne's sewage. The plant attends to around 1.6 million of the general public in the northern, central and western suburbs.

The development of the plant started in 1888 after a Royal Commission addressed at Melbourne's community wellbeing introduce a plan for the creation of a sewage treatment plant for Melbourne's waste water.

Beforehand, Melbourne's sewage remained stored in an exposed drain and directed into the Hobson's Bay and Yarra River. The facility is approximately 10,500 hectares and stands as frontrunner for the world in technical and environmental improvement.

A small amount of the treated waste is used by local customers as recycled water. What's left is released into Port Phillip Bay.

In 2005 a significant improvement of the facility was completed and has considerably lessoned the quantity of nitrogen in the treated waste that is sent to Port Phillip Bay and considerably improved the quantity of good quality water. Similarly it has enhanced its capacity to harness biogas to produce electrical energy, noticeably decreasing the greenhouse gas emissions and smell.

The Treatment Plant in Werribee is furthermore a refuge for a numerous number of birds and is one of the world's substantial wetlands.

Eastern Treatment Plant (Carrum)

The Treatment Plant in Carrum east of Melbourne handles around 40% of Melbourne's sewage. It attends around 1.5 million of the general public in Melbourne's eastern and south-eastern suburbs.

Approximately 92% of Melbourne's waste that enters the Carrum Treatment Plant is from households and the other 8% is from industries.

Sewage is treated and sterilized. A small amount of it is used by local customers as recycled water. What's left is pushed through a pipe for release into the South Eastern Outfall at Boags Rocks.

Types of waste inputs at Werribee and Carrum


At times named wastewater is all unwanted waste that goes through the laundry, kitchen and bathroom drainage system, also whatever you flush through the toilet pipes from our households and companies.

Sewage similarly contains filthy water from workshops that is sent into Melbourne's sewerage system. This is recognized as trade waste.


Wastewater that is flushed down the toilet is known as Blackwater.

Grey water

Wastewater from laundry, bathing and dishwashing is known as grey water. It does not consist of wastewater from the toilet.

Types of treatment originally used at Werribee

At one time or another treatment the plant at Werribee made use of three different sewage treatment approaches:

Land filtration

The process for land filtration was first used in 1897 and remained the leading sewage treatment process used throughout summertime. In this process, an exposed area of land was flooded with waste, up to about a height of 10cm. The open area of land performed like a strainer solids remained on the surface filtered by the land, as the sewage soaked into the earth, and streamed out at the lower part of the exposed area into a drain. This was then sent to Port Phillip Bay.

Because the sewage was high in nutrients it was used by the grass to grow while bacteria from the soil broke down any pollutants.

Undertaking the treatment of sewage in this method took around three weeks, and occurred in phases. It required around one to two days for flooding of the surface and an additional five days used for the sewage to soak into the soil. When the paddock is dried out the cattle and sheep grazed for around two weeks before the process begins again

Grass filtration

The process for grass filtration was first used in the 1930s and become the leading treatment process for the winter. Bulky trash is first thing that is removed from the sewage in big concrete vats by mean of the method sedimentation. The trash which is lighter floats to the highest part of the vat to the surface, while heavier rubbish dropped to the lowest part of the vat, giving the centre level of water in the vat named primary treated sewage.

The primary treated sewage then gradually ran through inclined channels planted with a kind of grass that was tolerant to nonstop flooding. As sewage filtered over the grass, all other solids were cleaned out. The bacteria in the soil removed out any pollutants in the water. In the last part of the channel, the filtered sewage flowed out into a drain which carried the treated sewage to Port Phillip Bay.

Lagoon treatment

The process for Lagoon treatment was first used in 1936. Due to Melbourne's increasing population the facilities for Lagoon treatment are incessantly being improved. The first major, modern lagoon was constructed in 1986.

These days at the Western Treatment Plant in Werribee all sewage is treated in modern lagoons switching from old lagoons and land and grass filtration process. The renewed approach eliminates enormous quantities of nitrogen, where previously would enter Port Phillip Bay, and now produces a higher quantity of quality recycled water, and can be used as a valuable source for off-site and on-site use.

Method of treatment currently used at Werribee

The current lagoon process is usually made up of 10 big pools side by side, every one of which can hold approximately 600 million litres of sewage. It runs gradually over these ponds, letting the bacteria in the ponds to breakdown the organic solids. The wastewater gets clearer and clearer as it travels over every one of the pools.

The process sewage under goes at the Western Treatment Plant

  • Untreated sewage enters into lagoon structure at the Treatment Plant in Werribee.
  • Enormous shelters diminish the smells, and cut out almost halve the greenhouse emissions that are released and the methane gas is collected.
  • The methane gas that is collected is recycled to generate electrical energy which powers the aerators and different other parts of the facility.
  • The oxygen is dissolved into the wastewater by the Aerators.
  • The nitrogen is removed from the wastewater by the activated sludge process.
  • The treated sewage takes 30 to 35 days in the lagoon system, is either recycled or is released into Port Phillip Bay.
  • The water which is recycled by the plant is delivered to a variety of offsite clients, which include the pumping station at Hoppers Crossing in Melbourne, and used on-site upkeep and for irrigation.

The lagoon treatment process has two main kinds of ponds the aerobic which uses oxygen and the anaerobic which does not use oxygen. Aerobic and the anaerobic processes create to diverse types of bacteria in its ponds where the two types of bacteria are needed to breakdown the waste. Anaerobic process is the first phase the pond has bacteria that consumes the oxygen that break down the waste in the sewage. During this process the bacteria releases strong and unpleasant smells also it gives off hazardous greenhouse emissions, therefore the ponds are enclosed with shelters that capture and remove the unpleasant smells and hazardous greenhouse emissions. The removed gases are known as biogas which is used as fuel to produce electrical energy to run the facility.

As the waste becomes more treated, a bigger quantity of oxygen becomes presented in the water. In the first phase though, it's needed to force oxygen into the water with the use of aerators which decreases the unpleasant odours. In the rest of the ponds, the oxygen in the water becomes presented naturally therefore the odours become not as much of an issue.

Method of treatment currently used at Carrum

The treatment method currently used at the facility at Carrum is treated to a secondary standard, where this method refers to two phases of waste treatment.

Primary treatment

Primary treatment consists of cleaning out bulky items like cotton buds and other garbage via fine filters. Ventilating the waste takes away finer contaminates similar to sand type particles, and the heavy substances drop to the bottom developing a film named sludge. The developed sludge and bulky items floating at the surface is then sent to bigger vats, called digesters, which then bacteria brakes it down later on.

Secondary treatment

In secondary treatment, the same bacteria that is in the Lagoon treatment process exist alongside each other in the same vat, which breaks down the organic substances and removes it from the facilities aeration vats.

The wastewater then goes in sedimentation vats and for a second time sludge drops to the bottom of the vats which creates, cleaner effluent. The treated effluent goes into big ponds which hold it before it goes into a final screening procedure. After the final screening procedure the treated effluent from the plant is released to the environment after its disinfected with chlorine or recycled.

Tertiary treatment

There are plans for an upgrade to a tertiary standard of treatment to be finished by the end of 2012.

What are the major problems in the treatment of sewage from a major city

The major problem that the cities come across is the shear amount of sewage that needs to be processed. Due to the major portion of the treated waste form the plants end up in the waterways. Even with the improved processing methods it still creates a major problem in huge quantities.

Why is the Werribee area an ideal location for the sewage facility

The Werribee treatment plant location provides lagoons, Lakes, creeks and saltmarsh and creates Australia's most popular locations for recreational birding. It's been recorded that there is around 270 different types of bird species. The facility also provide a good vantage point for bird watching by permits only which can be gained from Melbourne Water

The major environmental impacts of the facility at Werribee

There was an issue at the Werribee facility back when they using the old treatment processes at the plant. When those processes were in affect there was too much nitrogen entering into Port Phillip Bay also the odours from the plant were considerably more. As of late the Werribee treatment plant has considerably lessoned the greenhouse gas emissions, using the gases for electrical power generation and the capture of the methane has lessened the smells coming out of the plant.

Problems with the location of the site at Carrum

There was environmental impact on the aquatic environment by the treated effluent at the present time are dedicated to decreasing the problem, by introducing a major scheme to decrease the ammonia levels in treated effluent.