To fight the fatbergs, we need to reinvent the sewers

Mmm, tasty. A flusher holds a piece of fatberg under London in 2014. Image: Getty.

A 250m-long, 130 tonne, “fatberg” was recently discovered clogging up the sewers below Whitechapel in east London. Fatbergs are made up of solidified fat and oils combined with wet wipes, nappies and sanitary products that are disposed of in sinks and toilets.

This wasn’t a unique find: another monstrous fatberg was found in a London suburb in 2013 and, a week after Whitechapel, a slightly smaller “berg” was found under the city’s Chinatown. No doubt there are many more fatbergs still out there, blocking up the sewage system and waiting to be discovered.

There is a simple way to avoid the build up of fatbergs and it relates to everything listed above: bin it, don’t flush it. But many people inevitably adopt the mentality of “out of sight out of mind” and assume it’s not their problem as someone else will sort it. The reality is that clogged-up sewers affect us all, sometimes even causing road closures and flooding.

The UK government has called on London to update its Victorian-era network of pipes and tunnels as, after heavy rainfall, lots of sewage is spilling out into the Thames. To help the capital’s creaky infrastructure cope with a growing population, Thames Water, the local utility, has started work on a huge £4.5bn pipeline that will follow the river through the heart of the city.

But this entire model of large centralised sewers and treatment plants is already starting to look outdated. London’s sewers don’t just need updating – the city needs an entirely new approach to reducing the strain on its sewers.

The problem with big sewers

The key flaw to standard sewers systems is they combine all different kinds of waste into one big mixing pot of chemicals, bacteria and organic waste. A typical household, for instance, has one wastewater stream from the toilet which contains dangerous pathogens, another from the kitchen sink with food waste, and a third from the dishwasher which contains chemicals. All of these require different types of treatment before it is safe to put the water back into the environment.

It’s actually relatively easy to treat one specific highly-concentrated waste stream. Dishwasher waste, for instance, will be around eight to 15 litres of water containing a variety of chemicals to make your cutlery sparkle and, in this concentrated form, UV or ozone treatment can be used to easily remove 99 per cent of them.

But when dishwasher water is combined with all other sorts of waste it then creates a complex cocktail that is much more difficult to treat. Currently, the next step is to dilute everything with rainwater, which vastly increases the volume of water that needs all these elements removed. By the time the waste reaches the treatment plant, dangerous chemicals or substances may make up just one part in a billion of water particles. For instance, a typical sewage works may have to identify and remove just a single raindrop’s worth of benzene, a known carcinogen commonly found in laundry detergents, from a tank of toilet waste the size of a swimming pool.

A sewage works near you

But if treatment was decentralised, with lots of smaller sewage works rather than one big one, most of the contaminants could be removed while they were still in high concentrations. This in turn means waste becomes more useful. Wastewater with lots of food and faeces contains high amounts of energy that can be extracted as “biomethane” gas which can be used for heating or cooking just like regular gas. But when this wastewater is combined with other sources, its energy content is diluted making it more difficult and less efficient to extract.

The solution is to build small treatment plants in new developments or renovations that service smaller areas. A variety of new technologies are being developed: some use electricity to combine different waste particles together into larger clumps so it can be extracted, while others use UV light to breakdown all the chemicals. Some designs let friendly bacteria breakdown the organic compounds producing methane or hydrogen, while others heat up the waste to extremely high temperatures turning it into a gas that can be used to produce electricity or to cook your dinner.

Depending on the needs of the site they could focus on recovering energy or removing chemicals and they could be designed to produce different qualities of water depending on its final use. These small plants could be completely sealed to stop the smell escaping, and quick treatment times would avoid large amounts of smelly waste being stored near the communities.

This way, waste wouldn’t need to travel for miles, mixing with other sources. Instead, it could be treated locally, providing both sustainable energy and clean water.

The ConversationSewage networks were invented by the Victorians and ultimately changed society for the better. But everything evolves and improves with time, and Britain’s water infrastructure should be no exception.

Thomas Philip Fudge is a PhD Researcher in sustainable wastewater treatment at Brunel University London.

This article was originally published on The Conversation. Read the original article.


Coming soon: CityMetric will relaunch as City Monitor, a new publication dedicated to the future of cities

Coming soon!

Later this month, CityMetric will be relaunching with an entirely new look and identity, as well as an expanded editorial mission. We’ll become City Monitor, a name that reflects both a ramping up of our ambitions as well as our membership in a network of like-minded publications coming soon from New Statesman Media Group. We can’t wait to share the new website with you, but in the meantime, here’s what CityMetric readers should know about what to expect from this exciting transition.  

Regular CityMetric readers may have already noticed a few changes around here since the spring. CityMetric’s beloved founding editor, Jonn Elledge, has moved on to some new adventures, and a new team has formed to take the site into the future. It’s led by yours truly – I’m Sommer Mathis, the editor-in-chief of City Monitor. Hello!

My background includes having served as the founding editor of CityLab, editor-in-chief of Atlas Obscura, and editor-in-chief of DCist, a local news publication in the District of Columbia. I’ve been reporting on and writing about cities in one way or another for the past 15 years. To me, there is no more important story in the world right now than how cities are changing and adapting to an increasingly challenging global landscape. The majority of the world’s population lives in cities, and if we’re ever going to be able to tackle the most pressing issues currently facing our planet – the climate emergency, rising inequality, the Covid-19 pandemic ­­­– cities are going to have to lead the way.

That’s why City Monitor is going to be a global publication dedicated to the future of cities everywhere – not just in the UK (nor for that matter just in the US, where I live). Our mission will be to help our readers, many of whom are in leadership positions around the globe, navigate how cities are changing and discover what’s next in the world of urban policy. We’ll do that through original reporting, expert opinion and most crucially, a data-driven approach that emphasises evidence and rigorous analysis. We want to arm local decision-makers and those they work in concert with – whether that’s elected officials, bureaucratic leaders, policy advocates, neighbourhood activists, academics and researchers, entrepreneurs, or plain-old engaged citizens – with real insights and potential answers to tough problems. Subjects we’ll cover include transportation, infrastructure, housing, urban design, public safety, the environment, the economy, and much more.

The City Monitor team is made up of some of the most experienced urban policy journalists in the world. Our managing editor is Adam Sneed, also a CityLab alum where he served as a senior associate editor. Before that he was a technology reporter at Politico. Allison Arieff is City Monitor’s senior editor. She was previously editorial director of the urban planning and policy think tank SPUR, as well as a contributing columnist for The New York Times. Staff writer Jake Blumgart most recently covered development, housing, and politics for WHYY, the local public radio station in Philadelphia. And our data reporter is Alexandra Kanik, whose previous roles include data reporting for Louisville Public Media in Kentucky and PublicSource in Pittsburgh, Pennsylvania.

Our team will continue to grow in the coming weeks, and we’ll also be collaborating closely with our editorial colleagues across New Statesman Media Group. In fact, we’re launching a whole network of new publications this fall, covering topics such as the clean energy transition, foreign direct investment, technology, banks and more. Many of these sectors will frequently overlap with our cities coverage, and a key part of our plan is make the most of the expertise that all of these newsrooms combined will bring to bear on our journalism.

City Monitor will go live later this month. In the meantime, please visit to sign up for our forthcoming email newsletter.

As for CityMetric, some of its archives have already been moved over to the new website, and the rest will follow not long after. If you’re looking for a favourite piece from CityMetric’s past, for a time you’ll still be able to find it here, but before long the whole archive will move over to City Monitor.

On behalf of the City Monitor team, I’m thrilled to invite you to come along for the ride at our forthcoming digs. You can already follow City Monitor on LinkedIn, and on Twitter, sign up or keep following our existing account, which will switch over to our new name shortly. If you’re interested in learning more about the potential for a commercial partnership with City Monitor, please get in touch with our director of partnerships, Joe Maughan.

I want to thank and congratulate Jonn Elledge on a brilliant run. Everything we do from here on out will be building on the legacy of his work, and the community that he built here at CityMetric. Cheers, Jonn!

In the meantime, stay tuned, and thank you from all of us for being a loyal CityMetric reader. We couldn’t have done any of this without you.

Sommer Mathis is editor-in-chief of City Monitor.