Malabar wastewater plant discharges 5.4bn to 120bn microplastic particles each day, CSIRO report says, prompting calls for more advanced treatment processesFollow our Australia news live blog for latest updatesGet our breaking news email, free app or daily news podcastIt is not just human waste that is being pumped into the ocean off Sydney’s popular beaches due to the city’s unusual and archaic sewerage system – government scientists have confirmed billions of microplastics are also polluting the water.A CSIRO report, released in 2020 but not reported on until now, found the wastewater treatment plant (WWTP) at Malabar discharged an estimated 5.4bn to 120bn microplastic particles into the ocean each day.Sign up for Guardian Australia’s breaking news email Continue reading…Malabar wastewater plant discharges 5.4bn to 120bn microplastic particles each day, CSIRO report says, prompting calls for more advanced treatment processesFollow our Australia news live blog for latest updatesGet our breaking news email, free app or daily news podcastIt is not just human waste that is being pumped into the ocean off Sydney’s popular beaches due to the city’s unusual and archaic sewerage system – government scientists have confirmed billions of microplastics are also polluting the water.A CSIRO report, released in 2020 but not reported on until now, found the wastewater treatment plant (WWTP) at Malabar discharged an estimated 5.4bn to 120bn microplastic particles into the ocean each day.Sign up for Guardian Australia’s breaking news email Continue reading…
It is not just human waste that is being pumped into the ocean off Sydney’s popular beaches due to the city’s unusual and archaic sewerage system – government scientists have confirmed billions of microplastics are also polluting the water.
A CSIRO report, released in 2020 but not reported on until now, found the wastewater treatment plant (WWTP) at Malabar discharged an estimated 5.4bn to 120bn microplastic particles into the ocean each day.
By comparison, the report found the Cronulla plant – which uses more advanced techniques to treat wastewater – discharged an estimated 86m to 350m microplastic particles each day.
Guardian Australia has previously reported that Sydney Water planned to spend $32bn to improve the city’s sewerage system but would not upgrade the Malabar, Bondi and North Head treatment plants.
Instead, the water authority planned to send less waste through the three coastal plants once it overhauls the rest of the city’s water infrastructure over the next 15 years.
Some experts believe the treatment plants may be to blame for thousands of debris balls or “fatbergs” that have washed ashore over the past six months.
The New South Wales Environment Protection Authority (EPA) has said testing revealed the balls were consistent with human-generated waste such as grease and faecal matter.
The CSIRO report also identified Sydney’s wastewater treatment plants as a “significant” source of microplastic pollution in the ocean.
The report noted there was “increasing evidence” the ingestion of microplastics – any type of plastic less than 5mm in length – could cause “physical damage” to marine life.
Sydney’s sewage is only given “primary” treatment at the wastewater plants in Malabar, Bondi and North Head before it is pumped out to sea through “deepwater outfall” pipes that reach between 2km and 4km off the coast.
Environmentalists unsuccessfully campaigned to have “secondary” treatment added to the plants before the ocean outfall pipes were built in the 1990s.
Primary treatment involves physical processes such as pumping sewage through a screen to remove solid waste. Secondary treatment involves finer filtration and biological processing to break down the sewage.
Tertiary treatment – which is used at the Cronulla plant – involves further filtration as well as biological treatment and UV disinfectant before the effluent is released.
The CSIRO report found that at Malabar, anywhere between zero and 79% of microplastics were removed from wastewater during the primary treatment process, while the Cronulla plant removed more than 98% of microplastics.
“The Cronulla WWTP was more effective at removing microplastics from wastewater than the Malabar WWTP,” the report said.
The analysis was based on samples CSIRO collected over a 24-hour period for 10 months at the Cronulla and Malabar plants.
Dr Scott Wilson, the research director at the Australian Microplastic Assessment Project, said it had been known “for a while” that wastewater treatment plants were the main source of microplastics pollution.
“The greater the treatment process the better it is at reducing microplastics that are coming through,” he said.
“What is probably more amazing is the levels still coming out of a tertiary treated plant’s system [at Cronulla].”
Wilson said this should be remedied and Sydney Water should examine advanced tertiary treatment options.
“If you’re pumping billions of little particles into the environment, they’re bound to have effects over time, at least, if not straight away,” he said.
A Sydney Water spokesperson said the CSIRO study had concluded that the risk of contaminants from microplastics affecting marine organisms was “likely to be relatively low”.
“We have considered the findings of the report and are looking at potential treatment options, in consultation with our environmental and pricing regulators, to determine the best way forward,” they said.
The water policy expert Prof Stuart Khan previously told the Guardian the “vast majority” of Sydney’s wastewater went into the ocean through the Malabar, Bondi and North Head plants.
Khan, who heads the school of engineering at the University of Sydney, said it was “not sustainable” to continue discharging “80% of the sewage produced by 5 million people into the ocean after only primary treatment”.
Under its “long-term capital and operational plan”, Sydney Water intended to reduce its reliance on the coastal plants by processing more wastewater inland. New facilities would be built in Sydney stretching from Arncliffe to Quakers Hill.
An EPA spokesperson said microplastics were a “major threat” to the environment and it was analysing the results from its assessment of 120 waterways across NSW including Sydney Harbour and Parramatta River.
“This assessment, which was completed in mid-2024, will help us better understand what types of microplastics are out there and the scale and source of microplastics in our waterways,” they said. “A report on this work will be finalised by mid-2025.”
The spokesperson said previous work such as the CSIRO report had helped inform the bans on single-use plastic items such as plastic bags and straws introduced by the NSW government.
These bans had contributed to a 54% reduction in plastic litter in the environment since 2018, they said.
The CSIRO declined to comment.
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