Ask Onix
Sewers worldwide clogged by massive fatbergs
Cities across the globe are grappling with colossal blockages in their sewer systems, formed from congealed fat, wet wipes, and other flushed debris. These so-called fatbergs, some weighing over 100 tonnes, pose severe risks to public health and infrastructure.
The Whitechapel fatberg: A recurring nightmare
In London, a 130-tonne fatberg-equivalent to the weight of 11 double-decker buses-was discovered beneath Whitechapel Road in 2017. Workers took nine weeks to remove the concrete-like mass, only for it to reappear in late 2025, regrowing to over 100 tonnes. Thames Water, the company managing London's sewers, faces an ongoing battle against these subterranean monsters.
Richard Martin, head of treatment improvement at Southern Water, describes fatbergs as a "magical mixture" that hardens like concrete. These blockages cause sewage backups, flooding streets and contaminating rivers. In the UK alone, water companies tackle an estimated 300,000 such accumulations annually.
Global fatberg hotspots and costs
New York City spends approximately $18.8 million (£13.8 million) each year to degrease and clear sewer blockages, with grease responsible for 40% of backups. Similar fatbergs have been found in Detroit, Baltimore, Liverpool, Oxford, Melbourne, and Sydney, often growing undetected until they reach gargantuan sizes.
A 300-tonne fatberg in Birmingham, excavated in 2021, stretched nearly a kilometer underground. Another in Sydney recently ejected foul-smelling "poo balls" that washed up on local beaches, highlighting the environmental hazards.
AI and sensors: Early detection tools
To combat fatbergs, water utilities are turning to artificial intelligence and advanced sensors. Southern Water has installed 34,000 sensors in UK sewers, using radar to monitor water levels. Machine learning algorithms analyze this data alongside weather patterns to detect abnormal buildups before they harden.
"If levels spike outside expected ranges, we act immediately," Martin said. This proactive approach has helped Southern Water clear 700 blockages using AI this year, reducing sewage spills by 47% compared to 2024. However, the company still reported over 15,500 spills in 2025 due to overwhelmed sewers.
Robots and autonomous systems
Researchers are developing autonomous robots to inspect and remove fatbergs, minimizing human exposure to toxic sewer environments. An €8 million (£7 million/$9 million) EU-funded project, led by Tallinn University and the University of Sheffield, is designing a tardigrade-inspired robot equipped with cameras, LiDAR, and acoustic sensors.
"The robot can self-localize, detect blockages, and even remove them with an attached arm," said Lyudmila Mihaylova, professor of signal processing and control at the University of Sheffield.
In the U.S., companies like SewerAI use AI to analyze sewer footage, automating the detection of defects and blockages. Eric Sullivan, director of strategic development at SewerAI, compared the process to radiology, where AI interprets images for signs of trouble.
The science behind fatberg formation
Raffaella Villa, head of engineering at Lancaster University, studies fatberg chemistry. She suspects milk, poured down drains in coffee shops, may contribute to coagulation, similar to cheese-making. "Fatbergs start soft but harden over time," she said, crumbling a dried sample from the Whitechapel fatberg between her fingers.
Villa is seeking funding to use machine learning to identify the hardest, most mature fatbergs, prioritizing their removal. Meanwhile, kebab alleys and takeaway joints remain hotspots due to improper disposal of cooking oil.
Future solutions and worker safety
Autonomous robots could revolutionize sewer maintenance, reducing the need for workers to enter hazardous environments. Mihaylova emphasized the importance of resilience, noting that robots must withstand corrosive waste, high pressure, and communication challenges underground.
"Protecting workers from harmful sewer conditions is a major benefit," she said. With AI and robotics, the days of humans hacking through fatbergs with pickaxes may soon be over.
