How are we tracking?

Indicator: Ecosystems impacted downstream of inland wastewater treatment plant discharges

Macroinvertebrate monitoring

We monitor the diversity and abundance of freshwater macroinvertebrates upstream and downstream of WRP or WWTP discharges as a measure of ecosystem health. We sample macroinvertebrates twice a year, in autumn and spring, to gauge the health of receiving waters in the Nepean River, South Creek, Cattai Creek, Berowra Creek and the lower Hawkesbury River.

In 2011–12, our monitoring showed ecosystem health was maintained downstream of eight of the 12 inland WRPs and WWTPs. Although there were localised impacts in creeks downstream of Hornsby Heights WWTP, St Marys WRP, West Camden WRP and Winmalee WWTP, there was no evidence of impacts downstream in the Hawkesbury-Nepean River system to which these creeks flow.

Toxicity testing

We test the toxicity of treated wastewater from inland WRPs and WWTPs using the sensitive indicator organism Ceriodaphnia dubia (freshwater flea). We began pilot testing in 1998 and the EPA has included toxicity testing as a condition of licences since 2004.

In 2011–12, all inland WRPs and WWTPs met the toxicity licence limits. Our results showed five toxicity events at four plants, out of 167 tests conducted across the 14 inland plants. Three events were associated with high flow from rainfall in April 2012 at Wallacia, St Marys and West Hornsby. The two other events, at Wallacia and Richmond, could be because of rainfall or chlorine disinfection, which have accounted for some failures in the past. As these events were not followed by more toxicity events, we could not investigate them further.

There was no evidence of impacts to the environment from these events.

Indicator: Ecosystem impacts of deepwater ocean  discharges

We began regularly monitoring offshore marine sediments before Sydney’s deepwater ocean outfalls were commissioned in the early 1990s. Our ongoing program assesses long-term performance of the deepwater ocean outfalls. It monitors the toxicity of treated wastewater and the characteristics of ocean sediment. The EPA requires us to carry out the tests under our licences for wastewater treatment systems that discharge to the ocean.

Ocean sediment monitoring

The Ocean Sediment Program is a three-year cyclical program that assesses the impact of discharges from Malabar, Bondi and North Head WWTPs on the marine environment.

The program’s first year is the assessment year. We collect sediment samples from each site, identify and count the benthic macroinvertebrates (small animals that live on the ocean floor). We test sediments to determine levels of metals, organic compounds, nutrients and other physical characteristics.

In the second and third years (the surveillance years), we measure sediment samples at the Malabar deepwater ocean outfall for benthic macroinvertebrates, total organic carbon and particle size spread. If the results show discharges at Malabar are affecting the benthic macroinvertebrates or sediment quality, we then analyse samples from the North Head and Bondi sites.

In the current cycle, 2012 is a surveillance year. Results from the last assessment year, 2011, indicate that the deepwater ocean outfalls had no impact on ecosystem health. In the surveillance years, 2009 and 2010, there was also no impact on benthic macroinvertebrates or sediment quality at Malabar. We will report data from the Ocean Sediment Program in late 2012 as part of the Sewage Treatment System Impact Monitoring Program Annual Data Report 2011–12, which will be published on our website.

Toxicity testing

We test toxicity of treated wastewater from ocean plants using the sensitive indicator organism Heliocidaris tuberculata (sea urchin). The NSW EPA has set licence limits for toxicity since 2004.

All seven wastewater treatment plants, at Bombo, Bondi, Cronulla, Malabar, North Head, Shellharbour and Warriewood, met their toxicity licence limits in 2011–12.