Melbourne
19.8 Other wastewater discharge

Supporting information

a. Other wastewater discharge

The volume presented (0 ML) represents the volume of treated wastewater discharged to the landscape at the Whittlesea sewage treatment plant (STP) when the recycled water storage dam is full.

b. Wastewater system overview

The wastewater system is one of three subcomponents of Melbourne's urban water system. The three subcomponents are the:

  • urban water supply system
  • wastewater system
  • recycled water system.

In the Melbourne region, wastewater is collected (line item 11.4) from users by the four retail water authorities within the region:

  • City West Water
  • South East Water
  • Western Water
  • Yarra Valley Water.

Following collection, wastewater is either delivered to smaller, local wastewater treatment plants operated by the authorities, or delivered to one of the major wastewater treatment plants: Melbourne Water Eastern Treatment Plant or Melbourne Water Western Treatment Plant. During the 2012–13 year, Melbourne Water received and treated almost 90% of the wastewater collected within the region.

During the 2012–13 year the majority 75% (line item 19.7) of wastewater system outflows was treated wastewater discharged to sea; approximately 17% was recycled (an increase from 11% in 2011–12); discharge to surface water was < 3% (line item 19.5 ), evaporative losses and other accounted for about 5% (line item 19.1).

The following figure shows all the inflows and outflows associated with the wastewater system. The small misbalance shown (< 1%) can be attributed to metering inaccuracies, unaccounted losses, and inaccuracies in the estimation of the recycled water on-site in process use.

For more detail on a particular flow associated with the wastewater system, refer to the line item notes. Note that volumes annotated with an asterick (*) indicate flows between subcomponents and are not reported in the account. As such, these flows do not have an associated line item number.

Schematic diagram of water inflows and outflows for Melbourne's wastewater system during the 2012–13 year; line item numbers are provided in brackets
Schematic diagram of water inflows and outflows for Melbourne's wastewater system during the 2012–13 year; line item numbers are provided in brackets

Quantification approach

Data source

Local treatment plants flow database.

Provided by

Yarra Valley Water.

Method

Yarra Valley Water meters the volume of wastewater discharged from the local treatment plant on a monthly basis.

Assumptions, limitations, caveats and approximations

Nil.

Uncertainty information

The uncertainty is estimated to be +/– 5% based on meter specifications.