• Overview
  • Who we are
  • Our sustainability approach
• 2006/07 in Review
• Chairman and MD’s report
• Water
  • Overview
  • Coping with drought
  • Protecting catchments from fire
  • Supply of drinking water
  • Key performance indicators
• Sewerage
  • Overview
  • Eastern Treatment Plant
  • Western Treatment Plant
  • Sewerage transfer
  • Managing biosolids
  • Statewide trade waste
  • Key performance indicators
• Waterways
  • Overview
  • Challenges of a very dry year
  • Improving river health
  • Drainage and flood protection
  • Other works and initiatives
  • Key performance indicators
• Recycled water
  • Overview
  • Recycling west of Melbourne
  • Recycling east of Melbourne
  • Key performance indicators
• Protecting our natural environment
  • Overview
  • Energy and greenhouse
  • Waste assessment
  • Biodiversity
  • Key performance indicators
• Our relationships
  • Overview
  • Protecting the past for the future
  • Metropolitan retail water partners
  • Getting to know communities
  • Educating and informing
  • Working with the community
  • Key performance indicators
• Our people, our workplace
  • Overview
  • Developing a preferred culture
  • A safe place to work
  • Encouraging sustainable behaviour
  • Other results and initiatives
  • Our workforce
  • Key performance indicators
• Our business
  • Overview
  • Sound financial performance
  • A triple bottom line approach
  • Best practice review
  • Business efficiency
  • Key performance indicators
• Governance and risk management
  • Our governance procedures
  • Risk management
  • Statement of obligations
  • Board of directors
  • Organisational structure
• Statutory information
  • Statement of Corporate Intent
  • Key performance indicators
  • Publications
  • Freedom of Information
  • Bulk entitlements
  • Committees
  • Whistleblowers' protection
  • Other statutory information
• GRI – content index
• Independent assurance statement
• Financial statements
  (PDF, 434kb)
• Feedback form
  (PDF, 1.8mb)

Waste assessment

Melbourne Water spent $1.87 million on waste disposal costs in 2006/07. During the year, we undertook an initial waste assessment across the business and identified the following waste streams:

Sewage treatment plant waste

• 198,431 million litres of treated effluent was discharged into the ocean from the Eastern and Western sewage treatment plants (treated effluent refers to sewage that is treated to a high standard at our sewage treatment plants and either discharged into the ocean or further treated for recycling purposes)
• 45,800 tonnes of biosolids were produced by the Eastern and Western treatment plants, contributing to the 2.87 million tonnes stored onsite at both treatment facilities (biosolids refers to the stable by-product of the sewage treatment process)
• 4936 tonnes of grit and screenings, collected from the Eastern Treatment Plant, was sent to landfill for disposal (grit and screenings refers to the litter, gravel, sand and other non-biodegradable material being collected by screens and grit removal tanks in a pre-treatment facility). There was less grit and screenings waste collected over the past year due to water restrictions and decreased rainfall, which reduced the sewage velocity needed to transport them to the sewage treatment facility. If any increased rainfall/water use occurs, it is expected that grit and screenings levels captured at the plant will increase. An upgrade of the grit and screenings facility is planned for 2012, which will significantly reduce the volumes sent to landfill and improve the quality.

Water treatment plant waste

Water treatment residuals (also known as sludges) are a by-product of the water treatment process. They are generally made up of clay minerals, organic matter, hydroxides of aluminium and polyelectrolytes.

In 2006/07, Melbourne Water produced 143,350 kilolitres of water treatment residuals mostly from Winneke Water Treatment Plant, with about 1% produced from the Frogley, Cresswell and Yarra Glen treatment plants. The Yan Yean Water Treatment Plant also produces water treatment residuals, which are currently stored in drying pans onsite.

Water treatment sludges are discharged to the sewer from the Winneke Water Treatment Plant under a trade waste agreement with Yarra Valley Water.

The amount of water treatment sludges discharged to the sewer has reduced over the last few years due to the reduction in water being treated.

Stormwater – litter/sediment traps

Litter and sediment are collected in traps located in the drainage, waterways and wetlands systems. There was a significant increase in litter and sediment collected in the past few years due to an increase in the number of traps installed (99 in 2004/05 to 135 in 2006/07) and improved data recording. Sediment traps are usually installed in new developments with wetlands, so it is expected that this number will continue to increase in the coming years.

Construction and maintenance waste

At this stage Melbourne Water does not collect construction waste figures or routine maintenance figures. However, wherever possible products are disposed of responsibly, including oil and lubricants from general maintenance, which are treated and reused by an external contractor.

(See office waste under Our people, our workplace)