Sydney Water’s Malabar Wastewater Treatment System has been identified as the likely source of debris balls that washed up on Coogee and other NSW beaches between October 2024 and February 2025.
Background and Findings
The NSW Environment Protection Authority (EPA) confirmed the findings following an investigation that traced the origin of the debris to the Malabar system. The determination was based on evidence collected by Sydney Water under a Preliminary Investigation Notice. An independent wastewater expert panel reviewed the findings in September 2025 and advised further studies to identify specific sources within the system.
Scientific Explanation
A scientific report obtained by other media found that fats, oils and greases had accumulated inside sewer pipes before being dislodged by heavy rainfall and expelled through the Malabar ocean outfall. These materials later formed the debris balls that appeared on beaches, including Coogee.
Wave action and ocean conditions allowed the debris to move across several beaches between October 2024 and February 2025.
Composition and Contributing Factors
Tests indicated that the debris balls contained soap scum, cosmetics, human hair, petroleum hydrocarbons, fatty acids, and bacteria linked to wastewater. The main cause was the build-up of fats, oils and grease within the network. Population growth and an increasing number of food outlets were identified as contributing factors.
Preventive Measures and Upgrades
Sydney Water said investigations are continuing to shape short-, medium-, and long-term measures to prevent future incidents, with completion expected by the end of 2025.
The utility is implementing new programs to reduce fats, oils and grease entering the wastewater system and upgrading infrastructure across Sydney. Planned projects include upgrades to the Malabar, Bondi, and Georges River systems, improvements at North Head, and a new facility at Camellia by 2031.
Support for Local Councils
Sydney Water has acknowledged the financial impact of clean-up operations and committed to assisting local councils with related costs. Claims between Palm Beach and Gerroa will be reviewed based on wind and tide data.
Community Awareness and Next Steps
Residents are urged not to touch debris balls and to report sightings immediately through Sydney Water’s 24-hour hotline. The EPA will continue working with Sydney Water as investigations progress and will update the public when new information becomes available.
Published 3-Nov-2025
