Perth

This line item refers to the treated wastewater discharged to the sea.

The total volume of treated wastewater discharged to the sea from each treatment plant during 2009-10 is given below.

(1) Based on measured data

Data source

Water Corporation: Operational Data Storage System.

Data provider

Water Corporation.

Method

There are 14 wastewater treatment plants within the Perth region, only five of which discharge treated wastewater into the sea (Woodman Point, Beenyup, Point Peron, Subiaco and Yanchep).

The outflow volume from Woodman Point and Point Peron treatment plants are based on measured discharge data collected by flow meters installed at each site.

For the remaining three treatment plants, outflow data are not collected and, therefore, the total volume of wastewater discharged into the sea is estimated as total inflow of wastewater into the treatment plant minus the volume of water recycled. Both inflow and recycled volume data are based on measured discharge data collected at each site.

Uncertainty

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

Approximations, assumptions, caveats/limitations

At the treatment plants where outflow data 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 that there are no other losses.