Sydney
19.7 Wastewater discharge outside of region

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

This line item refers to the total metered volume of treated wastewater discharged to the sea or outside of the region. The discharge is from wastewater treatment plants and water recycling plants managed by Shoalhaven City Council and Sydney Water Corporation during the the 2012–13 year. The total volume is 402,455 ML (see the following table). 

Total wastewater discharged out of region

Managing authority	Plant type	Plant	Discharge volume to sea (ML)
Shoalhaven City Council	wastewater treatment	Culburra	170
		Shoalhaven Heads1	84
Sydney Water Corporation	wastewater treatment	Bellambi	594
		Port Kembla	748
		Warriewood	6,844
		Shellharbour	6,795
		Cronulla	20,059
		Bondi	47,438
		North Head	133,063
		Malabar	172,744
	water recycling plant	Gerroa	146
		Bombo	1,705
		Wollongong	13,178
Subtotal			403,568
Less untreated discharge to sea included in 19.20 Other urban water system decreases			1,113
Total			402,455

¹ Discharge occurs via sand dunes to the sea

New South Wales Office of Water, Water Supply and Sewerage Performance Monitoring Report.

Shoalhaven City Council.

Outflow volumes from Shoalhaven Heads wastewater treatment plant were measured using an Elster meter and a Parshall flume with a venturi flow meter.

Treated wastewater was discharged to the sea via sand dunes, which act as natural sand-bed filters.

The volume is based on measured data. Estimated uncertainty based on meter accuracy is +/– 5%.

Data managed and maintained in an internal data management system by Sydney Water Corporation's Service Delivery Division (Assurance and monitoring).

Sydney Water Corporation.

The number represents the total volume of treated wastewater discharged to the sea, based on flow meter readings from wastewater treatment plants and water recycling plants.

The flow of wastewater from the 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 an internal 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.

Nil.

The volume is based on measured data. Estimated uncertainty based on meter accuracy is +/– 2%.