Melbourne
19.7 Wastewater discharge outside of region

Supporting Information

The volume presented in the water accounting statements (304,745 ML) represents the volume of wastewater discharged from water authorities in the Melbourne region to Port Phillip Bay and Bass Strait.

The following table shows the breakdown of wastewater discharged from each treatment plant by organisations in the Melbourne region during the 2010–11 year.

Wastewater discharged outside of region
Organisation Discharge location  Volume (ML)
Melbourne Water  Western Treatment Plant discharge to Port Phillip Bay  146,632
Eastern Treatment Plant discharge to Bass Strait  142,419
Melbourne Water subtotal  289,051
City West Water  Altona Sewage Treatment Plant discharge to Port Phillip Bay  5,675
City West Water subtotal  5,675
South East Water  Somers Sewage Treatment Plant discharge to South East Outfall  1,915
Mt Martha Sewage Treatment Plant discharge to South East Outfall  4,861
Boneo Sewage Treatment Plant discharge to South East Outfall  3,243
South East Water subtotal  10,019
Total 304,745

Quantification Approach

City West Water

Data Source

City West Water supervisory control and data acquisition (SCADA) database.

Provided by

City West Water.

Method

This item represents the metered volume of treated wastewater discharged from the Altona Wastewater Treatment Plant into Port Phillip Bay. Meters are located at the Altona plant and are read on a daily basis. The line item is calculated by deducting the metered volume of water used in-process within the treatment plant from the metered wastewater discharge value.

Assumptions, Limitations, Caveats and Approximations

Nil.

Uncertainty Information

Uncertainty is +/– 5%

Melbourne Water

Data Source

Melbourne Water: derived from metered data.

Provided by

Melbourne Water.

Method

This item represents the volume of wastewater discharged to sea (including Port Phillip Bay) from Melbourne Water's Western Treatment Plant and Eastern Treatment Plant.

The volume is determined using a mass-balance calculation of all wastewater collected, treated, stored and recycled.

Assumptions, Limitations, Caveats and Approximations

Nil.

Uncertainty Information

The uncertainty estimate was not quantified.

South East Water

Data Source

South East Water database.

Provided by

South East Water.

Method

This item represents the daily metered volume of treated wastewater discharged to the sea via the South East Outfall.

 

Assumptions, Limitations, Caveats and Approximations

  • Assumes meters and readings are accurate.
  • This item only refers to wastewater volumes directly managed by South East Water

 

Uncertainty Information

Uncertainty is +/– 5% in accordance with the Water Industry Regulatory Audits 2011 independent annual audit report.

 

Comparative year

This item corresponds to line item 20.4.2 Wastewater discharge out of region reported in the 2010 Account. There was no change to the volume reported in the 2010 Account. The comparative year volume is 208,934 ML.