How are we tracking?
Indicator: Total mass of phosphorus and nitrogen discharged to streams/rivers from inland wastewater treatment plants
The total masses of nitrogen and phosphorus we discharged increased in 2011–12 due to higher inflows to the treatment plants from severe wet weather conditions. The amount of nitrogen and phosphorus we remove during the treatment process continues to be high at around 90% and 98%.
The amount of nutrients we discharge to waterways is influenced by wet weather, population growth and the capacity of our treatment plants. Our inland plants provide additional treatment so that discharged water contains low levels of phosphorus and nitrogen.
In wet weather, wastewater inflows can exceed the capacity of wastewater treatment plants (WWTPs) and bypass some treatment processes for short periods. This is permitted under the Environment Protection Licence conditions. Please see the Office of Environment and Heritage website and public register at www.environment.nsw.gov.au/licensing/
Table 31 – Total mass discharged to streams/rivers from inland WWTPs 2007–08 to 2011–12
Indicator: Total mass of suspended solids and grease discharged from ocean wastewater treatment plants
We treat about 76% of Sydney’s wastewater at the North Head, Bondi and Malabar ocean WWTPs and discharge it through the deepwater outfalls. We discharged 98% of the suspended solids and 99% of the grease loads from these plants in 2011–12. The year’s loads were well within the limits permitted under the Environment Protection Licences. Our monitoring shows no evidence of environmental impacts from these discharges or any build-up of metal concentrations.
Loads are influenced by population growth and wet weather events. Over the past five years, we focused on maintaining the performance and reliability of water recycling plants (WRPs) and WWTPs to continue to serve Sydney’s growing population.
Table 32 – Total mass discharged from ocean WWTPs 2007–08 to 2011–12