South East Queensland
19.7 Wastewater discharge outside of region

Supporting Information

This line item consists of wastewater collection system and recycled water supply system discharges to the sea, estuaries and inlets outside of the South East Queensland (SEQ) region.

Wastewater collection system discharges

A number of wastewater treatment plants (WWTPs) discharge treated wastewater to the sea, estuaries and inlets outside of the SEQ region. Discharges to freshwater rivers, creeks and other surface water are reported in line item 19.5 Urban water discharge to surface water. A number of WWTPs that discharge to the Brisbane River are included in this line item, as the Brisbane River is estuarine through much of the urban Brisbane area.

Recycled water supply system discharges

Reverse osmosis brine concentrate and excess purified recycled water from the Gibson Island and Luggage Point advanced water treatment plants was discharged to the Brisbane River Estuary as part of the Western Corridor Recycled Water Scheme treatment process delivery process.

Wastewater and recycled water discharges outside of region
Discharge description Volume

(ML)
Treated wastewater discharge     170,188
Excess recycled water discharge        8,139
Reverse osmosis concentrate discharge        2,540
Total SEQ region     180,867

Quantification Approach

Data Source

Queensland Department of Environment and Resource Management (DERM) licensed discharge data from the Point Source Database. Qldwater Statewide Water Information Management (SWIM) system indicator WA71 (wastewater discharge) for Queensland Urban Utilities, and indicators WA20, 21 and 22 (recycled water supplied) for Queensland Urban Utilities and Unitywater. Allconnex Water and Unitywater internal database of WWTP discharge volumes. Allconnex Water, Unitywater and Queensland Urban Utilities internal database of WWTP influent Seqwater Western Corridor Recycled Water Scheme dataset.

Provided by

Bureau of Meteorology.

Method

Wastewater collection system discharges

Annual WWTP discharge volumes obtained from DERM's Point Source Database, Qldwater SWIM indicators and urban utility databases were compared with each other and with WWTP influent data and recycled water supply data. Where discrepancies between datasets occurred, the closest discharge to the influent minus the recycled water supplied was chosen. This resulted in Point Source Database data being chosen for some WWTP, SWIM data for others and urban utility data for yet others. Where the recycled water supplied was the same as the influent, the WWTP discharge was assumed to be zero.

Each WWTP discharge point was then identified and WWTP that discharge to sea, inlets, and estuaries were selected and summed.

Recycled water supply system discharges

Annual advanced WWTP discharge data for reverse osmosis concentrate and excess purified recycled water was obtained from Seqwater datasets for Gibson Island and Luggage Point advanced WWTPs.

Assumptions, Limitations, Caveats and Approximations

It was assumed that the WWTP discharge data that most closely represented the influent minus the recycled water supplied were the most accurate value. Despite this being the best choice from a water balance point of view, inaccuracies in WWTP discharge data may have occurred.

Uncertainty Information

The uncertainty estimate was not quantified.

Comparative year

This line item corresponds to line item 20.4.2 Wastewater discharge out of entity reported in the 2010 Account. The understanding of discharge points for WWTP in the SEQ region has developed since 2010 Account publication. Despite this, the 2011 Account comparison year uses the volume reported in the 2010 Account, as a breakdown of WWTP discharges for the 2010 Account data were not available.

In the 2010 Account, a breakdown of discharge by WWTP was not available and a number of WWTP discharging to estuaries were not included in this line item. With a more accurate understanding of the discharge locations and individual WWTP discharge data, a number of WWTP discharges were moved to this line item from line item 19.5 Urban water discharge to surface water for the 2011 Account. This was particularly prevalent in the Brisbane River, as the estuary extends through most of the urban Brisbane area.