19.1 Evaporation from urban water system
a. Discharge to surface water from wastewater system
The total wastewater volume collected was 38,429 ML during the 2011–12 year. Approximately 88% of the collected wastewater discharged to surface water after treatment (34,325 ML).
During the 2011–12 year, approximately 11% of treated wastewater was recycled; and the rest was the losses. The following figure shows all the inflows and outflows associated with the wastewater system.
For more detail on a particular flow associated with the recycled water system, refer to the line item notes. Note that volumes annotated with an * indicate flows between sub-components 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 during the 2011–12 year for Canberra's wastewater system. Line item numbers are provided in brackets.
b. Supporting information
This line item refers to the volume of water that was calculated as loss through evaporation at the Lower Molonglo Water Quality Control Centre (LMWQCC), Fyshwick Wastewater Treatment Plant (WWTP) and the Queanbeyan WWTP. The total volume reported in the 2012 Account is 3,838 ML.
|Treatment plant||Evaporation loss|
Reported volume is measured data retrieved from the ACTEW Water Water Data Warehouse. The calculated volume of water lost through evaporation in the treatment process at the LMWQCC, Fyshwick Wastewater, Urriara and Outward Bound treatment plants was calculated as the inflow to the plants, less the discharge to surface water, less the volume of recycled water.
|Calculation||Component||Fyshwick||LMWQCC||Urriara||Outward Bound||ACTEW Water TOTAL|
|minus||Discharge to surface water||–||31,255||9||–||31,264|
|minus||Discharge to sewer||616||–||–||–||616|
The calculated volume of evaporation and other system losses at the Queanbeyan WWTP was 752 ML. Evaporation was measured from four lagoons, two sludge lagoons and other smaller open water bodies such as aeration tanks. The moisture content of sludge was not included.
Assumptions, limitations, caveats and approximations
The uncertainty estimate was not quantified.