A Brief History
1888 - Royal Commission into public health following cholera and typhoid outbreaks in Melbourne.
1890 - Melbourne and Metropolitan Board of Works (MMBW) established.
1897 - Western Treatment Plant (then known as Werribee Farm) began operations. First homes connected to Melbourne’s sewerage system.
1921 - Parts of Port Phillip Bay and Bellarine Peninsula including the Western Treatment Plant declared a sanctuary for native animals.
1982 - Western Treatment Plant declared a Ramsar site, internationally recognised for its wetland habitat especially for waterfowl.
1996 - Port Phillip Bay Environmental Study by CSIRO recommended reduction in nitrogen loads to the bay.
2004 - Plant upgraded to reduce nitrogen loads to the bay. Recycled water irrigation replaced sewage irrigation across the site. Land and grass filtration methods stop being used.
Melbourne's first sewage treatment plant
In 1888 a Royal Commission was carried out to come up with a solution to Melbourne’s waste problems. Prior to this, methods for disposing of human waste were very basic. Sewage had been collected in open channels that ran into the Yarra River and Hobsons Bay, and cholera and typhoid were rife.
The Commission’s findings led to an ambitious plan for the construction of a sewerage system – a system of pipes, sewers and drains built underground to carry sewage from homes and factories to a sewage treatment farm.
In 1892, the newly established Melbourne and Metropolitan Board of Works (MMBW) began buying land at Werribee, chosen for its low rainfall and suitable soils. Western Treatment Plant (then known as Werribee Farm) began operations in 1897.
How was sewage treated at the plant?
In the past the plant used three sewage treatment methods: land filtration, grass filtration and lagoon treatment.
Land filtration
The land filtration method dates back to 1897, and was the main sewage treatment method used during summer. In this method, an open paddock was flooded with sewage, up to a depth of 10cm. The land acted as a filter - rubbish and other solids were filtered by the land, while the filtered sewage seeped through the soil, and flowed out at the lower end of the paddock into an earthen drain. The earthen drain then carried treated effluent to Port Phillip Bay.
Nutrients from organic waste were used by the grass and pollutants were broken down by the bacteria in the soil.
The treatment process normally took about three weeks, and happened in cycles. It took about one to two days to flood the paddocks, and a further five days for the paddocks to dry out and for sewage to seep through the soil. Then, sheep and cattle grazed on the paddocks for about two weeks, before the land was flooded with sewage again.
Grass filtration
The grass filtration method was adopted in the 1930s as the main winter treatment method. There were two stages in this process:
- Pre-treatment, and
- Filtration in grass paddocks.
Large rubbish was first removed from the water in large concrete tanks through the process of sedimentation. Lighter rubbish floated to the top of the tank, while heavier rubbish sank to the bottom of the tank, leaving a middle layer of water called primary treated sewage.
The primary treated sewage then slowly flowed over sloping bays planted with a type of grass that was tolerant to continuous flooding. As sewage trickled through the grass, all other solids were filtered out. Pollutants in the water were removed by a film of bacteria which were present on the grass and in the soil. At the end of the bay, the filtered sewage flowed out into earthern drains which took the treated effluent to Port Phillip Bay.
Lagoon treatment
The first treatment lagoon was constructed in 1936. Lagoon treatment facilities have been continuously upgraded to meet the needs of Melbourne’s growing population. The first large, modern lagoon was installed in 1986.
Today all sewage at the Western Treatment Plant is treated in modern lagoons, replacing old lagoons and traditional land and grass filtration methods. The new methods remove large amounts of nitrogen, which would otherwise enter the bay, and generate high quality recycled water, which is a valuable resource for onsite and offsite use.
Cultural heritage and the township of Cocoroc
Cocoroc Town Hall, 1912
Aboriginal people have lived in Australia, including what is now Victoria, for more than 40,000 years. The rivers, creeks and land we manage today are places of spiritual and community activity of the past, present and future. Aboriginal sites, places and objects can be found all over Victoria, often near natural resources.
The Western Treatment Plant is a significant cultural landscape which has a rich history of Indigenous, Contact and European heritage. In particular, the area that is now the treatment plant is the traditional Country of the Wathaurang people. The workers township of Cocoroc was created onsite in 1894 to house workers employed at the Metropolitan Sewage Farm (as it was known then). The name 'Cocoroc' means 'frog' in the traditional language of the Wathaurang people.
An 1894 plan of the township shows there were 72 allotments. By 1897, there were 32 houses, a town hall, football ground (and team), swimming pool, tennis courts, four schools and a post office. By the early 1950s there were nearly 100 houses, and by the 1970s some 500 people were living in Cocoroc.
As it became too expensive for the Melbourne and Metropolitan Board of Works (MMBW) to subsidise, Cocoroc was abandoned. By 1973 most of the houses and other buildings were demolished or moved to Werribee.
All that is left now of Cocoroc are two small, empty, concrete swimming pools, a few weatherboard sheds and a big iron water tank.
The heritage listed water tank
Cocoroc comes back to life
The heritage listed water tank has been granted a new lease on life through an extensive restoration project.
The tank was originally located in East Melbourne and stored water from the Yarra River in Melbourne’s early days. It was moved to Cocoroc in 1893 as a back-up water supply for the workers. It was de-commissioned in 1925 after the township was connected to mains water, and finally drained in 1929.
For many years, soil used by the treatment plant’s tree nursery was stored beneath the tank.
The tank has been converted into an interpretive centre, which together with remnant buildings and structures from the former township will be used to house displays interpreting the rich cultural history of the site.
Preserving conservation values
The Western Treatment Plant contains a network of lagoons, wetlands, inter-tidal and shoreline areas that provide a haven for thousands of birds. The wetlands, attract an amazing array of birdlife including thousands of migratory waders that fly 12,000 kilometres south from Siberia to avoid the harsh northern winter.
In 1921 parts of Port Phillip Bay and Bellarine Peninsula including the Western Treatment Plant were declared a sanctuary for native animals. In 1983 the plant was declared a Ramsar site, internationally recognised for its wetland habitat especially for waterfowl.
Moving to a modern era
In 2004, Melbourne Water completed a $160 million upgrade of the plant. This work stemmed from a CSIRO study which found that Port Phillip Bay could be damaged if nitrogen loads entering its waters continued to increase.