Western Treatment Plant Upgrade
Port Phillip Bay is Melbourne's playground - and one of Victoria's most precious natural assets. About three and a half million people live around the Bay, which is one of Australia's busiest ports and the focus of a burgeoning tourism industry.
In the late 1980s and early 1990s, Melbourne was growing quickly. Melbourne Water decided it needed to better understand how population increases would affect the Bay's capacity to assimilate treated effluent and urban run-off.
In 1992, Melbourne Water initiated a landmark, four-year study to identify ways of protecting the long-term health of the Bay.
The $12 million Port Phillip Bay Environmental Study, sponsored by Melbourne Water and managed by the CSIRO, consisted of more than 40 projects carried out by 29 research institutions - government agencies, private consultants and universities in four states, as well as the University of Southern California.
The study found the Bay was healthy by world standards, with good water quality, productive fisheries and healthy populations of dolphins and seals. It was, however, recognised that unchecked nutrient loads, particularly nitrogen, would take the Bay close to the point where significant ecological changes would occur through increased algal blooms and, eventually, eutrophication.
The study recommended reducing nitrogen loads to the Bay by 1000 tonnes a year (13%), focusing on stormwater and catchment inputs and the Western Treatment Plant in Werribee. Effluent discharged from the sewage treatment plant is a major source (approximately half) of nitrogen entering Port Phillip Bay, and a major $160 million upgrade of the plant was proposed to increase nitrogen removal, maximise water recycling and capture methane gas from the sewage treatment process to generate power for the plant.
The Western Treatment Plant is one of the largest sewage treatment plants in the world, and processes about 485 million litres of sewage and industrial waste a day - more than half Melbourne's total. The plant relies partly on lagoon-based processes, in which naturally-occurring bacteria and sunlight digest sewage. Under the major upgrade, these natural processes have been complemented by new technology to increase nitrogen removal. By 2006, nitrogen inputs entering the Bay will be reduced by 500 tonnes a year.
As part of the $160 million upgrade, massive membrane covers trap about 30 million cubic metres a year of methane gas from the sewage treatment process, helping to generate electricity for the plant's operations. Eventually, the plant will be close to energy neutral, with almost 80% of the electricity required being generated on-site, and capturing this methane gas will more than halve greenhouse gas emissions from the plant. This will contribute to Melbourne Water's target to reduce greenhouse gas emissions by 35 per cent by 2007.
The upgrade also enables a significant increase in the amount of on-site and off-site water recycling. Water recycling studies continue to be conducted in the Werribee region and beyond, which will assist Melbourne Water to achieve its commitment to recycle 20 per cent of Melbourne's effluent by 2010.
Other key benefits of the upgrade are:
- Improved public amenity through odour control
- Protection of the site's environmental values, as the wetlands are internationally recognised and home to a number of different bird species - some of which are extremely rare and highly endangered, such as the Orange-bellied parrot.
Downloads
- Western Treatment Plant Upgrade (PDF, 79kb)