Perth
19.7 Wastewater discharge outside of region
Supporting information
a. Supporting information
The volume reported in the water accounting statements (120,293 ML) represents the total volume of treated wastewater discharged to the sea from wastewater treatment plants within the Perth region during the 2012–13 year.
Total volume of treated wastewater discharged to the sea from each treatment plant during the 2012–13 year is given in the following table.
Wastewater treatment plant |
Discharge to sea (ML) |
Perth metropolitan area |
|
Alkimos |
2,602 |
Beenyup |
45,366 |
Point Peron |
6,720 |
Subiaco |
21,741 |
Woodman Point |
43,864 |
Total |
120,293 |
b. Wastewater system overview
The wastewater system is one of three subcomponents of Perth's urban water system. The three subcomponents 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 Wastewater collected) and transferred to wastewater treatment plants throughout the region.
During the 2012–13 year, approximately 8% of treated wastewater was recycled; 88% discharged to the sea (19.7 Wastewater discharge outside of region); and the rest discharged to rivers (part of 19.5 Discharge from urban water system to surface water) or infiltration lagoons (19.8 Other wastewater discharge). 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. Volumes in the figure annotated with an asterisk (*) indicate flows between urban subcomponents 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 2012–13 year for Perth's wastewater system; line item numbers are provided in brackets
Quantification approach
Data source
Provided by
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%.