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But this entire model of large centralised sewers and treatment plants is already starting to look outdated.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.


Which British cities have the bestest ultrafast broadband?

Oooh, fibre. Image: Getty.

The latest instalment of our series, in which we use the Centre for Cities’ data tools to crunch some of the numbers on Britain’s cities. 

Between the dark web, Breitbard News and Donald Trump's Twitter feed, it's abundantly clear that terrible things often happen on the internet. But good things happen here, too - like funny videos and kitten pictures and, though we say so ourselves, CityMetric. 

Anyway. The government clearly believes the internet is on balance a good thing, so it's investing more in improving Britain's broadband coverage. But which cities need the most work?

Luckily, those ultrafast cats at the Centre for Cities are on hand with a map of Britain's ultrafast broadband coverage, as it stood at the end of 2016. It shows the percentage of premises which have access to download speeds of 100Mbps or more. Dark green means loas, pale yellow means hardly any. Here's the map:

Some observations...

This doesn't quite fit the pattern we normally get with these exercises in which the south of England and a few other rich cities (Edinburgh, Aberdeen, York) look a lot healthier than the cities of the Midlands, South Wales and the North.

There are elements of that, sure: there are definitely more southern cities with good coverage, and more northern onse without it. But there are notable exceptions to the pattern, too. Those cities with very good coverage include Middlesbrough (88.0 per cent) and Dundee (89.4 per cent), not normally to be found near the top of anyone's rankings. 

Meanwhile, Milton Keynes - a positive boom town, on most measures - lingers right near the bottom of the chart, with just 12.9 per cent coverage. The only city with worse coverage is another city that normally ranks as rich and succesful: the Socttish oil capital Aberdeen, where coverage is just 0.13 per cent, a figure so low it rings alarm bells about the data. 

Here's a (slightly cramped) chart of the same data. 

Click to expand.

If you can spot a patten, you're a better nerd than I.

One thought I had was that perhaps there might be some correlation with population: perhaps bigger cities, being bigger markets, find it easier to get the requisite infrastructure built.

I removed London, Manchester and Birmingham from the data, purely because those three - especially the capital - are so much bgiger than the other cities that they make the graph almost unreadable. That don't, here's the result.

So, there goes that theory.

In all honesty, I'm not sure what could explain this disparity: why Sheffield and Southand should have half the broadband coverage of Middlesbrough or Brighton. But I suspect it's a tempory measure. 

All this talk of ultranfast broadband (100Mbps+), after all, superseded that of mere superfast broadband (just 24Mbps+). The figures in this dataset are 10 months old. It's possible that many of the left behind cities have caught up by now. But it's almost certain we'll be hearing about the need for, say, Hyperfast broadband before next year is out.

Jonn Elledge is the editor of CityMetric. He is on Twitter as @jonnelledge and also has a Facebook page now for some reason. 

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