Sydney
19.5 Discharge from urban water system to surface water
Supporting information
a. Recycled water system overview
The recycled water system is one of three subcomponents of Sydney's urban water system. The three subcomponents are the:
- urban water supply system
- wastewater system
- recycled water system.
In the Sydney region, around 98% of the recycled water used was produced at wastewater treatment plants within the region and a small volume was imported.
During the 2012–13 year, approximately 44% of the recycled water was supplied for to private users for residential, industrial, agricultural, or commercial use (19.4 Delivery to urban water system users); about 29% was used for environmental purposes (19.5 Urban water discharge to surface water); and the remainder was used for on-site in-process.
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 recycled water system, refer to the line item notes. Note that volumes annotated with an asterisk (*) indicate flows between subcomponents 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 Sydney's recycled water system; line item numbers are provided in brackets
b. Wastewater system overview
The wastewater system is one of three subcomponents of Sydney's urban water system. The three subcomponents are the:
- urban water supply system
- wastewater system
- recycled water system.
The Sydney region has several urban utilities responsible for managing wastewater in the region. Sydney Water Corporation, Shoalhaven City Council, Goulburn Mulwaree Council, Lithgow City Council, and Wingecarribee Shire Council all collect wastewater from users (11.4 Wastewater collected) and treat this wastewater at a number of wastewater treatment plants throughout the region.
During the 2012–13 year, a total of 507,638 ML was collected by the wastewater system. The majority of the outflow from the wastewater system (around 77%) was discharged to the sea (19.7 Wastewater discharge outside of region); around 10% was discharged to inland surface water (19.5 Urban water discharge to surface water) and a further 10% of that wastewater was recycled and the remainder was losses from the system (see 19.1 Evaporation from urban water system and 19.20 Other urban water decreases). The following figure shows all the inflows and outflows associated with the wastewater system.
For more detail on a particular flow associated with the wastewater system, refer to the line item notes. Note that volumes annotated with an asterisk (*) indicate flows between subcomponents 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 Sydney's wastewater system; line item numbers are provided in brackets
Urban water discharge to surface water
The volume of water discharged from urban wastewater systems during the 2012–13 year was 68,523 ML. This line item consists of two components;
- treated wastewater discharge; and
- recycled water discharge to surface water for environmental purposes.
A breakdown of treated water from wastewater treatment plants and water recycling plants discharged to the streams is provided in the following table. The discharged volume is a decrease to the water distribution system store.
Plant operator and description of wastewater discharge | Plant | Discharging to watercourse | Volume discharged during 2012–13 (ML) |
Goulburn Mulwaree Council—treated wastewater from wastewater treatment plants | Goulburn |
not applicable | 34 |
Lithgow City Council—treated wastewater from wastewater treatment plants | Lithgow | a tributary of the Coxs River | 1,537 |
Wallerawang | Coxs River | 139 | |
Palerang Council—treated wastewater from wastewater treatment plants | Braidwood | a tributary of the Shoalhaven River | 128 |
Shoalhaven City Council—treated wastewater from wastewater treatment plants | Berry | Broughton Creek | 206 |
Bomaderry | Abernathys Creek | 746 | |
Nowra | Shoalhaven River | 1,716 | |
Sydney Water Corporation—treated wastewater and recycled water from water recycling plants | Castle Hill | Cattai Creek | 2,123 |
Glenfield | Georges River | 689 | |
Liverpool | Georges River | 2,684 | |
Penrith | Boundary Creek | 1,322 | |
Picton | Stonequarry Creek | 330 | |
Quakers Hill | Breakfast Creek | 8,931 | |
Richmond | Rickabys Creek | 704 | |
Rouse Hill | Second Ponds Creek | 4,461 | |
St Marys | Boundary Creek | 15,1421 | |
St Marys | South Creek | 6,485 | |
West Camden | Matahil Creek | 4,306 | |
Sydney Water Corporation—treated wastewater from wastewater treatment plants | Brooklyn | Hawkesbury River | 85 |
Fairfield | Orphan School Creek | 1,905 | |
Hornsby Heights | Calna Creek | 2,112 | |
North Richmond | Redbank Creek | 316 | |
Riverstone | Eastern Creek | 590 | |
Wallacia | Warragamba River | 273 | |
West Hornsby | Waitara Creek | 5,052 | |
Winmalee | Nepean River | 7,181 | |
Wingecarribee Shire Council—treated wastewater from wastewater treatment plants | Berrima | Olbury Creek | 104 |
Bowral | Wingecarribee River | 1,342 | |
Braemar | Iron Mines Creek | 1,115 | |
Bundanoon | Reedy Creek | 217 | |
Moss Vale | Whites Creek | 1,007 | |
Subtotal | 72,982 | ||
Less agricultural releases | West Camden | 1,825 | |
St Marys (South Creek) |
2,269 | ||
Quakers Hill | 365 | ||
Total | 68,523 |
1 Sydney Water Corporation released 15,142 ML of recycled water from St Marys Water Recycling Plant to Boundary Creek (a tributary of the Nepean River). These releases are intended to replace outflows released for environmental purposes from Lake Burragorang (Warragamba Dam) to the river.
Wallerawang Wastewater Treatment Plant receives wastewater generated from supplies made to the Lithgow City Council's distribution system from the Fish River Water Supply Scheme. Lithgow Wastewater Treatment Plant receives wastewater generated from supplies made to the distribution system from Oakey Park Water Treatment Plant. Wastewater received at these wastewater treatment plants includes inflow and infiltration resulting from stormwater.
Treated water released from some of the wastewater treatment plants included in the above table becomes inflow to downstream storages (counted in line item 9.4 Runoff to surface water) as shown in the following table. The volume of water that has become inflow to downstream storages (5,589 ML) is deducted from line item 9.4 Runoff to surface water.
Wastewater treatment plants releasing treated water |
Reservoir receiving treated water |
Wastewater treatment plant operator |
Reservoir managing authority |
Lithgow |
Lake Lyell |
Lithgow City Council |
Delta Electricity |
Wallerawang |
Lake Wallace |
Lithgow City Council |
Delta Electricity |
Berrima, Bowral, Braemar and Bundanoon |
Lake Burragorang (Warragamba Dam) |
Wingecarribee Shire Council |
Sydney Catchment Authority |
Moss Vale |
Medway |
Wingecarribee Shire Council |
Wingecarribee Shire Council |
Braidwood |
Lake Yarrunga (Tallowa Dam) |
Palerang Council |
Sydney Catchment Authority |
Quantification approach
Goulburn Mulwaree Council
Data source
Provided by
Method
Assumptions, limitations, caveats and approximations
Uncertainty information
The volume is based on metered data. Estimated accuracy based on meter accuracy and professional judgement is +/– 20%.
Lithgow City Council
Data source
Provided by
Method
Flows were measured by water channel and height sensors, and converting water level to a volume in a spreadsheet using a rating table.
Assumptions, limitations, caveats and approximations
Wastewater received at Lithgow and Wallerawang wastewater treatment plants includes inflow and infiltration resulting from stormwater, in addition to wastewater generated from potable water supplies made to the water distribution system. Therefore, all of these sources contribute to the volume of treated wastewater released from the plants to the streams.
Uncertainty information
The volume was estimated from measured data. The uncertainty was not quantified.
Palerang Council
Data source
Provided by
Method
For 2012–13, the wastewater treatment plant (now decommissioned) did not have any dedicated flow measurement at the outlet. The outflow from the plant was from a tertiary pond system. Measurement was made at the inlet to the plant only and this was done by an ABB Magmaster-type flow meter. The inflow measured from the flow meter has been approximated to the outflow, disregarding any inflow that may be lost through evaporation, or that may be supplemented through rainfall or infiltration to the pond system.
Assumptions, limitations, caveats and approximations
Uncertainty information
The volume was estimated from measured data. Estimated uncertainty based on meter accuracy and professional judgment is +/– 10%.
Shoalhaven City Council
Data source
Provided by
Method
Outflows from wastewater treatment plants were measured as follows:
- Berry Wastewater Treatment Plant: Vega-type ultrasonic flow meter
- Bomaderry and Nowra wastewater treatment plants: a Parshall flume with a venturi flow meter at each site.
Assumptions, limitations, caveats and approximations
Uncertainty information
The volume is based on measured data. Estimated uncertainty based on meter accuracy is +/– 5%.
Sydney Water Corporation
Data source
Data managed and maintained in an internal data management system.
Provided by
Method
Total metered volume of treated wastewater discharge to surface water from Sydney Water Corporation's wastewater treatment plants and water recycling plants is provided. Details on recycled water discharge including water from St Marys recycling plant can be found in the Water Efficiency Report 2012–13.
The flow of wastewater and recycled water from plants was measured using flow meters. These measured data are continually monitored and recorded using the Integrated Instrumentation Control Automation and Telemetry System (IICATS). The data are stored within a complex data management system. Adjustments are made to the data (if necessary) to correct any interruptions, errors and so on. Data have been extracted for the 2012–13 year from the data management system.
Assumptions, limitations, caveats and approximations
The main difference between treated wastewater and recycled water produced by Sydney Water Corporation is quality, which is determined by the level of treatment. Recycled water is produced by treating water generated from sewage, greywater or stormwater systems to achieve high quality as required. Information on wastewater treatment levels in producing recycled water is available at Sydney Water Corporations website.
Uncertainty information
The volume is based on measured data. Estimated uncertainty based on meter accuracy is +/– 2%.
Wingecarribee Shire Council
Data source
Provided by
Method
The value represents the total volume of treated wastewater discharge to surface water from wastewater treatment plants.
The flow of wastewater from the plants was measured using ABB Magmaster flow meters installed on-site. The data from the flow meters are continually monitored and recorded.
Assumptions, limitations, caveats and approximations
Uncertainty information
The volume is based on measured data. Estimated uncertainty based on meter accuracy and professional judgement is +/– 7%. External flow verification audits for the flow meters are conducted annually by Hydrometric Consulting Services.