Thousands of mystery balls that washed up on Sydney beaches last month were gunk globules made of products such as motor oil, hair, food waste, animal matter and wastewater bacteria – but their source is yet to be traced.
A statement from the New South Wales Environment Protection Authority on Wednesday confirmed the balls comprised fatty acids, petroleum hydrocarbons and other organic and inorganic materials – and were not tar balls as previously theorised.
Tests were conducted by the Department of Climate Change, Environment, Energy and Water, and scientists from the University of NSW.
The balls were found to contain hundreds to thousands of different materials, including hair and “various fibres”, which suggests they originated from a source that releases mixed waste.
But testing has not been able to confirm their exact origin “due to the complex composition of the balls and the time they have spent in the water”.
“Authorities have so far been unable to trace the source,” the EPA said. Final results were expected in the coming weeks.
In October, Guardian Australia reported the team of scientists analysing the debris was investigating whether the balls had come from a nearby water treatment plant.
The EPA on Wednesday said Sydney Water had stated when the balls were first reported that “there were no issues with the operation or maintenance of the Bondi or Malabar water resource recovery facilities”.
There was also nothing conclusive yet from NSW Maritime’s examination of weather patterns in the days leading up to the balls washing up on beaches.
“They are disgusting and they smell revolting,” UNSW Associate Prof Jon Beves said on Thursday. He coordinated the testing of the balls with the EPA.
“Every ball was slightly different,” Beves said. “They are a complex mixture of different things … but it looks consistent with human-generated waste, like the types of things you would find from domestic waste in a regular sewer.”
Testing found materials including cooking oil, soap scum, diesel, human hair, bits of plastic, THC and methamphetamine, prescription drugs, heart medication and markers of faecal matter, Beves said.
They were “definitely not consistent with an oil spill” – which would be mostly fossil fuels.
“The question is, essentially, would you like to go and swim in the sewer?” the chemist said, adding some components could be toxic.
Beves suggested the collection of fats, oils and grease accumulated “somewhere in a pipe … somewhere which has been discharged into the ocean, possibly through an overflow into stormwater”. “But we don’t know exactly where it has come from.”
Oils and fats in products such as cooking oils, soaps and skincare items make up fatty acids, the EPA said. Petroleum hydrocarbons are chemicals from oil and gas products such as gasoline, motor oil and diesel fuel.
Organic materials are substances that can naturally decompose, such as hair, food waste and other plant and animal matter. Inorganic matter includes sand, calcium salt and bacteria associated with wastewater.
Beves and UNSW Prof William Donald wrote in the Conversation on Wednesday that “the mysterious black balls that washed up on Sydney’s beaches in mid-October were likely lumps of ‘fatberg’ containing traces of human faeces, methamphetamine and PFAS”.
Fatbergs form in sewers from material that does not dissolve in water – including oil and grease – piling up and sticking together.
“Initial reports suggested the ominous lumps were probably tar balls from an oil spill. However, analysis with a barrage of scientific tests has revealed a more complicated picture,” Beves and Donald wrote.
“This is consistent with contamination from sewage and industrial runoff.”
