Investigations have confirmed that Sydney Water’s sewage network was the source of thousands of tar balls, containing bacteria including E. coli, which forced closures at Bondi Beach and other Sydney coastlines.
Investigation Narrows Source
The mystery surrounding the thousands of small, dark debris balls that washed ashore on Sydney beaches between October 2024 and January 2025 appears to be solved. The NSW Environment Protection Authority (EPA) concluded its investigation, pointing towards Sydney Water’s wastewater network as the origin.
This finding came after the composition of balls collected from beaches matched samples taken from several wastewater treatment plants. The balls, mostly marble-sized and black or grey, contained household fats, oils, grease, human hair, fibres, and some petroleum hydrocarbons.
Their appearance forced the closure of seventeen beaches, starting in the eastern suburbs at locations like Bondi Beach, Coogee, and Bronte, later appearing at Kurnell, and then across the Northern Beaches, including Manly and Dee Why. Given the EPA’s findings, initial thoughts that a passing ship might be responsible seem less likely.
Health Concerns and Bacteria Identified
Concerns were raised about the potential health risks associated with the tar balls. Testing revealed the presence of bacteria commonly found in sewage, including Enterococci, E. coli, and thermotolerant E. coli. These bacteria are known indicators of faecal contamination and can be linked to various illnesses like diarrhea and infections.
In addition, Northern Beaches Council organised its own independent tests on balls found on its shores, which also identified faecal matter and E. coli. The council alerted the public to its findings and shared the results with the EPA.
Communication Questions Raised
Documents released under freedom of information laws indicated that the EPA’s testing identified the presence of specific bacteria like E. coli shortly after the first incidents in October 2024. However, Randwick Council stated it was unaware of these specific bacterial findings when it deemed its beaches safe to reopen several days later, although it stressed that it acted cautiously by closing beaches and organising cleanups while awaiting results.
The EPA responded to these points, stating it had advised relevant authorities, including councils within the response team, of early analyses that indicated bacteria, but emphasised these results were not fully verified at that stage. The agency maintained that more comprehensive analysis was needed and that the public was consistently advised not to touch the debris balls. In December, an official EPA media release mentioned the balls contained “bacteria commonly associated with wastewater”.
Sydney Water Response and Prevention
Sydney Water acknowledged that an independent expert it commissioned also identified its network or facilities as the probable source. A Sydney Water manager stated that their coastal treatment facilities were operating normally and meeting regulatory standards, and no specific faults were found in the system.
Investigations suggested the tar balls may have formed over time due to an increased load of fats, oils, and grease entering the system, combined with specific oceanographic factors and weather conditions leading to potentially ten or more separate discharge events. Sydney Water stated it would contribute to the clean-up costs and consider long-term infrastructure upgrades where needed.
It also highlighted the community’s role in prevention, urging residents and businesses to dispose of fats, oils, and greases in the bin, not down the drain.
Public Advised to Remain Cautious
While experts have assessed the balls as a low threat to public health, the EPA’s official advice remains consistent: people should avoid touching debris balls found on beaches. Any new discoveries should be reported immediately to the local council or the EPA’s Environment Line on 131 555. The EPA confirmed that its team of pollution experts and investigators is continuing work related to the incidents.
Published Date 16-April-2025
