Prepare to be shocked! A massive fatberg, the size of four buses, has been lurking in Sydney's ocean sewer, and it's causing quite the stink! This giant mass of fats, oils, and grease has led to the closure of Sydney's beloved beaches, and the situation is far from simple.
The fatberg, located in the Malabar deepwater ocean sewer, is believed to be the culprit behind the mysterious 'debris balls' that washed up on Sydney's shores a year ago. Sydney Water, the responsible authority, is facing a challenging task as they cannot easily access the fatberg's location, making it difficult to assess its true size.
But here's where it gets controversial... Fixing this issue would require shutting down the outfall, which extends a whopping 2.3km offshore, for maintenance. This would divert sewage to an alternative discharge point, potentially closing Sydney's beaches for months. A secret report obtained by Guardian Australia reveals that this approach has never been attempted before and is now considered unacceptable.
The report, dated August 30, 2025, was prepared for the New South Wales Environment Protection Authority, which has been investigating the debris ball incidents. It concludes that the accumulation of FOG (fats, oils, and grease) in an inaccessible area has likely caused the release of these debris balls. The chamber, not designed for routine maintenance, can only be accessed by shutting down the entire system, an operation that would disrupt Sydney's beaches for an extended period.
And this is the part most people miss... The first poo balls that appeared on Coogee Beach in October 2024 were likely triggered by a power outage at the treatment plant, causing a temporary halt in raw sewage pumping. The sudden restart could have dislodged part of the fatberg, leading to the debris ball incident. A similar pressure drop and increase, this time due to wet weather, occurred in January 2025, potentially causing the January debris ball landings.
Sydney Water initially denied responsibility, stating that their wastewater treatment plants were operating normally. However, evidence collected by the EPA and Sydney Water has now narrowed down the origin of the debris to within the Malabar system.
The latest report reveals that a significant amount of FOG has accumulated over time in the intersection chamber between the Doof bulkhead stopboards and the ocean outfall tunnel. The bulkhead door, usually submerged, can only be accessed during low tide and low system flows. It is believed that the fatberg is located in a 300 cubic metre chamber beyond the stopboards, making it extremely difficult to reach and clean.
Sydney Water is now regularly cleaning the accessible part, a risky operation, and in April 2025, they removed an impressive 53 tonnes of accumulated FOG, including debris balls. The report notes that the FOG had not consolidated into a single large mass but rather remained breakable. However, the potential for further accumulation remains high.
The cause of the debris balls is likely due to the buildup of FOG on the landward side of the intersection chamber, where it was trapped in a quiescent zone. The sudden drop and increase in flow then drew this material into the main flow path, pushing it through the Doof and out through various openings.
Sydney's sewage treatment process is unique, as it only involves primary treatment, straining out solids. Most cities employ secondary treatment, using settlement tanks and disinfection techniques before releasing or recycling the wastewater. For example, Singapore treats its sewage to such a high standard that it can be reused in the drinking water system.
The August report highlights a concerning rise in FOG and volatile organic compounds in the Malabar wastewater system over the past decade. Concentrations are so high that FOG is now escaping wherever possible, often during wet weather events, through hydraulic relief structures in the network.
Fatbergs have caused issues in other cities too, but in different ways. In London, a massive fatberg, weighing the same as 11 double-decker buses, was found blocking a section of the sewage network. New York City spends a significant amount, around $19 million annually, on removing fatbergs from its sewers.
Sydney Water's options for dealing with this potential fatberg crisis are limited. They plan to continue cleaning the accessible part of the bulkhead and launch campaigns to discourage Sydneysiders from putting FOG down the drain. They also aim to initiate a trade waste program for food businesses, as many operate without waste approvals, contributing to the Malabar system's issues.
The state water minister, Rose Jackson, has announced a $3 billion investment program over the next 10 years to address the Malabar system's issues. This program aims to reduce the volume of wastewater discharged via the deep ocean outfall.
However, some experts, like Jeff Angel from the Total Environment Centre, argue for a fundamental shift in thinking. They believe the outfalls represent outdated technology and that Sydney's sewerage system needs modernization, including higher levels of treatment and increased recycling to conserve water resources.
As Sydney Water works to address this complex issue, the question remains: How can we ensure the protection of our beloved beaches and the environment while managing the challenges posed by our sewage systems? Share your thoughts in the comments below!
