The NSW Environment Protection Authority (EPA) has confirmed that Sydney Water's sewage treatment network is the likely source of the black, sticky balls that have been washing up on beaches across New South Wales since late 2024.
The debris balls, found on beaches from Sydney’s eastern suburbs to the South Coast and Northern Beaches, were found to contain a complex mix of human faeces, cooking oils, drugs, cosmetics, and other urban waste. The EPA’s investigation, launched after the first balls appeared in October 2024, has now issued a formal investigation notice to Sydney Water following comparative testing of the debris with samples from major wastewater treatment plants at Malabar and Bondi.
“While we are yet to determine exactly what caused the pollution incidents to occur when they did, we can say the composition and the characteristics of the debris balls are consistent with a land-based sewage source,” said EPA Director of Operations Adam Gilligan.
The sticky spheres baffled scientists and beachgoers alike when they first appeared on Coogee Beach, with further discoveries sparking concern along the coastline. A multi-disciplinary team from UNSW, in collaboration with the EPA and other agencies, determined the debris was composed of hundreds of chemicals and compounds in November 2024, from fatty acids and diesel fuel residues to steroidal medications, PFAS, and even recreational drugs.
“At UNSW Science, we have been investigating the balls that appeared on Coogee Beach,” said Associate Professor Jon Beves, who led the analysis. “Our analyses show that the material is not natural and cannot be attributed solely to an oil spill. It is most consistent with human-generated waste.”
The debris balls, found on beaches from Sydney’s eastern suburbs to the South Coast and Northern Beaches, were found to contain a complex mix of human faeces, cooking oils, drugs, cosmetics, and other urban waste
Further analysis confirmed that the spheres were formed from a mixture of modern and fossil carbon, suggesting a blend of plant, animal, and industrial sources. The high calcium content also pointed toward a formation process similar to so-called FOG (fat, oil, and grease) blobs common in sewer systems, where fats bind with metal elements to form water-insoluble masses.
Despite the mounting evidence, Sydney Water maintains that its facilities are functioning as intended. “All coastal treatment facilities are operating normally, and we are compliant with regulatory standards,” said Louise Beer, Sydney Water’s acting executive general manager for water and environment services, to the media. The utility reported no faults in its system and suggested that multiple small discharges, more than ten in total, from different locations might be to blame.
In response to the EPA’s investigation notice, Sydney Water will be required to conduct oceanographic modelling to trace the dispersion of the balls, complete comprehensive sampling and analysis across its treatment network, and review its deep ocean outfall systems and sewer pipelines.
“This is a significant step forward in our investigation, but there is still work to do,” said Mr Gilligan. “The community has been eager for answers, and to assist in our ongoing investigation we’ve established a Wastewater Expert Panel to provide independent scientific advice.”
The EPA has advised the public not to touch any debris balls found on beaches and to report any sightings to local councils or the EPA’s Environment Line.
While Sydney Water denies any direct malfunction in its operations, the EPA and independent scientists are moving ahead with further testing to trace the exact origins of the pollution and determine how similar events can be prevented in the future.
