Perth
19.7 Wastewater discharge outside of region

Supporting information

a. Wastewater system overview

The wastewater system is one of three sub-components of Perth's urban water system. The three sub-components are the:

  • Urban water supply system
  • Wastewater system
  • Recycled water system.

In the Perth region, wastewater is collected from users by the Water Corporation (11.4) and transferred to wastewater treatment plants throughout the region.

During the 2011–12 year, 8% of treated wastewater was recycled; 88% discharged to the sea (19.7); and the rest discharged to rivers (part of 19.5) or infiltration lagoons (19.8). The following figure shows all the inflows and outflows associated with the wastewater system.

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


Schematic diagram of water inflows and outflows during the 2011–12 year for Perth's wastewater system. Line item numbers are provided in brackets.
Schematic diagram of water inflows and outflows during the 2011–12 year for Perth's wastewater system. Line item numbers are provided in brackets.


b. Supporting information

The volume reported in the water accounting statements (118,952 ML) represents the total volume of treated wastewater discharged to the sea from wastewater treatment plants within the Perth region during the 2011–12 year.

Total volume of treated wastewater discharged to the sea from each treatment plant during the 2011–12 year is given in the following table.

 

Volume of treated wastewater discharged to the sea from each treatment plant during the 2011–12 year

Wastewater treatment plant

Discharge to sea

(ML)

Perth city area

 

Alkimos

2,437

Beenyup

44,433

Point Peron

6,451

Subiaco

22,522

Woodman Point

43,109

Total

118,952

 

Quantification approach

Data source

Operational Data Storage System.

Provided by

Water Corporation.

Method

The total volume of wastewater discharged into the sea is not metered and is estimated as total inflow of wastewater into the treatment plant minus the volume of water recycled.

Assumptions, limitations, caveats and approximations

Outflows from these treatment plants are not measured. It is assumed that the volume of wastewater discharged into the sea is simply the total inflow of wastewater into the treatment plant minus the volume of water recycled and there are no other losses.

Uncertainty information

This value is estimated to be in the range of +/– 5–10%.