19.10 Discharge from urban water system to groundwater
a. Recycled water system overview
The recycled water 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, 8% of the treated wastewater from the wastewater system is recycled.
During the 2011–12 year, approximately 49% of the recycled water produced was resold for industrial use and local irrigation (part of 19.4). Approximately 24% of the recycled water was used on-site at the wastewater treatment plants throughout the region; the remaining 27% was used to recharge aquifers—via injection wells (19.9) or groundwater infiltration (19.10). The following figure shows all the inflows and outflows associated with the recycled water 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 recycled water system. Line item numbers are provided in brackets.
b. Supporting information
This line item volume (1,668 ML) represents the total volume of treated wastewater infiltrated to groundwater from the Kwinana Wastewater Treatment Plant during the 2011–12 year.
Treated wastewater from the Kwinana treatment plant is infiltrated to the groundwater store to assist in maintaining environmental values at the Spectacles Wetlands on the Swan Coastal Plain. The groundwater in this region is also extracted and recycled by Alcoa as part of the overall allocation of groundwater in the region.
Treated wastewater from the Kwinana Wastewater Treatment Plant is infiltrated to the groundwater store via infiltration ponds. The volume of treated wastewater infiltrated to groundwater is based on metered data at the treatment plant that is collected on an almost continuous basis.
Assumptions, limitations, caveats and approximations
Expected error for water meters is +/– 5%.
The Department of Water requires that all water meters, when tested under in situ conditions, must be within 5% accuracy across the full flow rate range (Guidelines for water meter installation 2009).
This line item corresponds to line item '19.10 Urban water discharge to groundwater' reported in the 2011 Account.