Revealed: The icky reason behind build-up of forever chemicals in Sydney catchment

Sewage treatment plant outfalls are discharging dangerous forever chemicals into creeks and rivers in Sydney’s drinking water catchment, a new study has found, and the pollution is occurring without oversight from the environmental watchdog.

The news comes as the Australian Bureau of Statistics revealed that NSW has the highest proportion of residents with cancer-causing PFAS chemicals in their blood and urine in the country.

The study by researchers at Western Sydney University points to treated effluent as a significant contributor of PFAS contamination in rivers such as the Wingecarribee, Wollondilly and Coxs River that feed Warragamba Dam.

Professor Ian Wright and PhD candidate Katherine Warwick by the Wingecarribee River near Berrima sewage outfall, a known hotspot for platypus.Credit: Dominic Lorrimer

Lead author and PhD candidate Katherine Warwick said this study was the first to establish PFAS was present in sewage outfalls, since the NSW Environment Protection Authority did not require plant operators to test for the toxic chemicals.

“These contaminants are being discharged without anyone knowing about it, without authorisation, essentially,” she said.

Professor Ian Wright, Warwick’s supervisor and co-author, said the levels were modest – not like Medlow Bath where the dam had to be excluded from the Blue Mountains drinking water supply – and the risk to human health was minimal.

Professor Ian Wright taking water from the Wingecarribee River near the Berrima sewage treatment plant outfall. The river is running brown after heavy rainfall.Credit: Dominic Lorrimer

Sydney Water is testing drinking water for PFAS and publishing its results, a move Wright credited to this masthead’s reporting. Based on the testing, Wright said: “Dilution is winning here and the levels in Sydney’s main water supply are low”.

Wright said he was concerned about the fact that the Wingecarribee and Wollondilly Rivers were agricultural areas and the contaminated water was used to irrigate crops and drank by livestock.

The main risk was environmental, he said, because the carcinogenic chemicals released into the waterways accumulated in the bodies of wildlife, especially predators such as platypuses.

Warwick found last year that nine wild platypuses from across NSW had traces of PFAS in their livers, and the worst was a platypus found dead at Wingecarribee River near Berrima in the Southern Highlands with 390 micrograms of PFAS chemicals per kilogram in its liver.

The study, designed to find the source of the pollution, took samples from the water column and river sediment near sewage outfalls at five sites, including Goulburn, Lithgow and three in the Southern Highlands. The researchers also tested for nutrients that could cause algal blooms and heavy metals.

The PFAS contamination was higher at the sewage outfalls and then diluted downstream, which Warwick said was a strong indication that the outfalls were the source. The river sediment 50 to 100 metres downstream from the outfalls showed higher concentrations of PFAS, which Warwick said had probably accumulated over some time.

PFAS are a family of synthetic chemicals prized for their resistance to heat, grease, and water, and used in a wide range of everyday products such as stain-resistant fabrics, cleaning products and firefighting foams.

Warwick said PFAS in sewage could come from human waste and also household items and activities, such as being shed from clothing in the washing machine or non-stick cookware in the kitchen sink.

The worst results were for the Wingecarribee River at Bowral, with high concentration of PFAS chemicals – including the notorious carcinogen PFOS – at 2900 nanograms per kilogram, more than double the next worst at Lithgow.

The NSW EPA licenses operators of sewage treatment plants. A spokesperson confirmed there was no requirement to monitor PFAS levels, but said this was set to change under the revised PFAS National Environmental Management Plan.

The ABS released its first dataset on PFAS contamination in Australians over the age of 12 on Tuesday. Most of the population has exposure to at least some types of PFAS, and this is slightly higher for men. The concentration of the cancer-causing contaminants in people’s bodies rose with age, which the ABS explained was partly because the chemicals accumulated over time and partly because PFAS usage has reduced this century after a peak in the decades after 1970.

NSW had the highest proportion of its population exposed to PFOS – detected in the blood of 99.7 per cent of residents – and PFOA (96.8 per cent). The average level of PFOS contamination was 1.9 nanograms per millilitre of blood for NSW residents, on par with South Australia and second only to Tasmania.

The five wastewater treatment plants in the Western Sydney University study are owned by respective local councils. The water flows into the catchment managed by WaterNSW, and is then treated and supplied as drinking water by Sydney Water.

A WaterNSW spokesperson said the Australian drinking water guidelines referred to drinking water post-treatment, but the agency had been sampling untreated water in these dams to test for PFAS levels for several months.

“With the exception of Medlow and Greaves Creek dams, all results for untreated water from all Sydney dams, including Warragamba, are well within current and proposed drinking water guidelines,” the spokesperson said.

A Sydney Water spokesperson said: “Our monitoring indicates our drinking water is safe to drink and meets proposed Australian drinking water guidelines at all water filtration plants.”

Sydney Water also discharges highly treated sewage into rivers within its network. Like the other operators, it is not currently obliged to test for PFAS.

The EPA has started public consultation on its statutory five-year review of Sydney Water’s sewage treatment plant licences, including the level of treatment required. Public submissions close on June 12.

Wingecarribee Shire Council, which manages the sewage treatment plants at Mittagong, Moss Vale and Bowral, said it worked with the EPA to ensure it met all regulatory standards and would implement any future directives.

Lithgow City Council said in a statement it carried out regular testing of its effluent output as required under its EPA licence and was compliant across all sites.

The council said the discharge test point in the study also received urban stormwater that could contain PFAS, and it was awaiting the results for testing at its sewage treatment plants.

Goulburn Mulwaree Council was contacted for comment.

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