'Fatbergs' are a modern menace. Can we stop them? |
'Fatbergs' are taking over city sewers - scientists are fighting back
Reeking coagulations of grease and debris are clotting sewers around the world on a colossal scale. Cities are deploying new technologies to control this modern menace.
Beneath the bustle of pedestrians and traffic on London's Whitechapel Road, something truly horrific was taking shape. It weighed more than 130 tonnes – the same as 11 of the city's famous red double decker buses – and breathed toxic fumes.
This subterranean monster had been growing unnoticed in the Victorian-era sewer running underneath the busy street, until workers carrying out a routine inspection bumped into its rock-hard flank. Now, a team wielding pickaxes, high-pressure water jets and clad head-to-toe in protective clothing, were preparing to tackle the putrid beast.
Their foe? A stomach-churning agglomeration of fat, oil, grease, wet wipes, sanitary products and condoms, known as a "fatberg".
This unholy concoction turns out to be "a magical mixture" that hardens like concrete, says Richard Martin, head of treatment improvement at Southern Water, a water company responsible for sewers in the southeast of England.
These hideous clogs menace cities around the world. Formed from material that householders and businesses flush down the drains, they block sewer systems, causing flooding and sewage pollution to spill out into nearby rivers. Homeowners and businesses can find sewage backing up into their property or the streets outside if the worst fatbergs are not tackled. They can form quickly and unpredictably.
It would take workers from Thames Water – the company responsible for London's sewer system – nine weeks to dig out the coagulated mass beneath Whitechapel in 2017. But at the end of 2025, sewage workers discovered it had returned, regrowing to more than 100 tonnes.
Water companies in the UK tackle an estimated 300,000 of these accumulations of coagulated fat, oil and grease every year. New York City – where 40% of sewer backups are due to grease – spends around $18.8m (£13.8m) annually degreasing and removing blockages from the sewers beneath its streets.
And behemoths rivalling the Whitechapel specimen raise their ugly heads with alarming frequency. Giant fatbergs have been discovered lurking beneath the suburbs of Detroit and Baltimore in the US, Liverpool and Oxford in the UK, and Melbourne and Sydney in Australia.
The challenge is detecting these fatty blockages before they reach such gargantuan proportions. Hidden in the dank netherworld of the sewer network, they form far out of sight – from materials we'd rather forget as soon as we flush them.
Now, water utilities are turning to new technology to help them in their subterranean battles with fatbergs, using artificial intelligence to help them spot the signs of a fatty build-up so they can act early.
In the UK, Southern Water has deployed around 34,000 sensors in its sewers. The sensors are attached to manhole covers and use radar, pinging out a signal that bounces off the water in the sewer below, to check the level.
These measurements are fed into a machine learning algorithm – a form of AI – which combines them with information on rainfall and weather data to produce estimates for what should be a normal water level on any given day. "If it pops outside of that band, that's when we react," says Martin.
Historically, water companies have relied on customer tip-offs or routine inspections to learn of the presence of fatbergs. With........