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. The Western Treatment Plant (then known as Werribee Farm) began operating 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.
The land filtration method dates back to 1897, and was the main sewage treatment method used during summer. This method involved the following stages:
An open paddock was flooded with sewage, up to a depth of 10 centimetres
The land filtered rubbish and other solids – the grass used nutrients from organic waste, and bacteria in the soil broke down pollutants
Filtered sewage seeped through the soil and flowed out at the lower end of the paddock into an earthen drain
The earthen drain carried treated effluent to Port Phillip Bay
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.
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.
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.
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.
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.