South East Queensland
19.5 Discharge from urban water system to surface water

The volume for the line item during the 2012–13 year was 39,413 ML. This line item consists of discharges to surface water from the urban water supply system, wastewater system, recycled water system and advanced water treatment  within the South East Queensland (SEQ) region.

Discharge from urban water supply system

Discharges from the urban water supply system could not be quantified in a way that is complete, neutral, and free from material error, but are expected to be minor compared to wastewater and recycled water discharges. Discharges may include supply system flushing, air valve releases, and tank cleaning.

Discharge from wastewater system

A number of wastewater treatment plants (WWTPs) discharge treated wastewater to rivers and creeks within the SEQ region. This line item includes discharges to freshwater rivers and creeks that form part of the surface water system. Discharges to estuarine rivers, creeks, inlets and the sea are reported in line item 19.7 Wastewater discharge outside of region. A number of WWTPs that discharge to the Brisbane River are included in line item 19.7 Wastewater discharge outside of region, as the Brisbane River is estuarine through much of the urban Brisbane area.

Discharge from recycled water system

The recycled water volumes discharged to surface water for environmental purposes or to augment potable water supplies are included in this line item. These uses are not reported in the SEQ region in 2012-13.  

Discharge from advanced water treatment

Reverse osmosis brine concentrate from the Bundamba advanced water treatment plant (AWTP) was discharged to the Bremer River as part of the Western Corridor Recycled Water Scheme treatment process.

Excess purified recycled water discharges occurred from the Gibson Island and Luggage Point AWTPs, but as the Brisbane River is estuarine at the discharge point, these discharges were reported in line item 19.7 Wastewater discharge outside of region. No excess purified recycled water discharges to surface water occurred from Bundamba AWTP.

There is potential for recycled water discharges from the Western Corridor Recycled Water Scheme to Lake Wivenhoe in accordance with the current SEQ System Operating Plan v. 3.1 when the SEQ water grid storages fall below 40%. When the total volume of water stored by key water grid storages falls below 40% of the total water storage capacity of these storages, the supply of purified recycled water to Lake Wivenhoe from the Western Corridor Recycled Water Scheme is to be maximised, subject to appropriate approvals. If and when purified recycled water is introduced into Lake Wivenhoe, this water will then be available for use throughout the entire SEQ region via the SEQ water grid. 

 Table Notes:

1. No discharge of wastewater effluent was to surface water within the SEQ water supply region from either Crow's Nest or Yarraman (Toowoomba Regional Council); discharge to land as per licence at Yarraman WWTP is included in line item 19.8 Other wastewater discharge, and  recycled water use at Crow's Nest is included in line item 19.4 Delivery to urban water system users.

2. – = not available.

The volume of wastewater collected by the wastewater system during the 2012–13 year (11.4 Wastewater collected) was 244,668 ML.  The majority of the outflow from the wastewater system (74%) was treated wastewater discharged to sea (19.7 Wastewater discharge outside of region); approximately 16% was discharged to surface water (19.5 Urban water discharge to surface water) and approximately 9 % was recycled. The remainder (1%) comprised a small volume of treated wastewater discharged to landscape and losses from the wastewater system.

The following figure shows all the inflows and outflows associated with the wastewater system. There was some unaccounted flow in the wastewater system that produced an error of  0.4% of total wastewater system inflows. 

For more detail on a particular flow associated with the recycled water system, refer to the line item notes. Note that volumes annotated with asterisk (*) 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 2012–13 year for South East Queensland's wastewater system; line item numbers are provided in brackets

About 7% of urban water consumption (236,941 ML) came from the recycled water system and from advanced water treatment.

During the 2012–13 year, approximately 55% of the recycled water produced (23,241 ML) was supplied to urban users. Approximately 13% of the recycled water was used on-site at wastewater treatment plants (WWTPs) throughout the region; about 20% was used in-process (recirculated) and the rest was delivered for advanced water treatment. There was some unaccounted flow in the recycled water system inflows that produced an error of (1%) of total recycled water supply system inflows.The following figure shows all the inflows and outflows associated with the recycled water system and advanced water treatment.

For more detail on a particular flow associated with the recycled water system and advanced water treatment, refer to the line item notes. Note that volumes annotated with an asterisk (*) 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 2012–13 year for South East Queensland's recycled water system and advanced water treatment; line item numbers are provided in brackets

 * due to data discrepancies, it was assumed that inflow into recycled system equalled to the recycled water usage.

Seqwater: WaterHub database, Western Corridor Recycled Water Scheme dataset;

Queensland Urban Utilities (QUU), Redland City Council: datasheets via Queensland Water Directorate (Qldwater);

South Burnett Regional Council: datasheet;

Unitywater: Bureau of Meteorology code data;

The Department of Environment and Heritage Protection (EHP) via the WaTERS database.

QUU; Redland City Council; Seqwater; South Burnett Regional Council; Unitywater; Queensland Department of Science, Information Technology, Innovation and the Arts (DSITIA) on behalf of WaTERS.

Discharge from wastewater system

The metered and estimated volume of treated wastewater discharged to surface water as reported by water authorities.  Where necessary, clarification were obtained from the water authorities on the discharge points to confirm discharges to surface water. When the treated water discharged to estuary, it was considered as discharge to sea and included as part of line item 19.7 Wastewater discharge outside of region.  

Discharge from advanced water treatment

Annual advanced water treatment plant (AWTP) discharge data for reverse osmosis concentrate was obtained from Seqwater datasets for Bundamba AWTP. 

Nil.

The uncertainty was not quantified.