There’s a lot of poop in London and not enough places to put it. Designed the late 1800s, the city’s sprawling, spluttering sewer network spans more than 1,100 miles, but was only built to serve 2.5 million people. With almost nine million people now flushing and washing, the system has reached breaking point. Or, to put it more bluntly, there’s shit everywhere. Around 39 million tonnes of sewage flows into the River Thames each year. And, finally, something is being done about it.
It’s about time. Other than the very obvious downsides of flushing toilets into the Thames, bacteria in sewage can also absorb the dissolved oxygen from the water, killing off fish and water-dwelling plants. Ammonia in urine is poisonous to aquatic life. If you were unlucky enough to find yourself swimming in the Thames, you would get ill.
In most of London, the sewage system is comprised of combined sewers that carry wastewater from sinks, toilets, washing machines and fat runoff from takeaways and restaurants alongside rainwater runoff. Not only has the population of London increased since Bazalgette’s original design, but the accessibility of piped water in households and public spaces has meant there’s larger volumes of the wet stuff sloshing around than in the late 1800s. So when there’s a small amount of rainfall, the sewer system can’t cope.
When that happens, all of that water only has one place to go. Valves are opened that release the combined wastewater, untreated sewage and runoff into the Thames. These are called combined sewer overflows, or CSOs, and around 50 of the epic dumps are thought to happen each year in London. “The releases of human waste from CSOs are probably the last great source of pollution entering the Thames,” says Filip Babovic, who researches water resources at Imperial College London. “By reducing CSOs, the Thames should have a much healthier ecology.” Solutions are few and far between – London’s current infrastructure is so wide-ranging and deeply entrenched that any renovation would be expensive and impossible.
The solution? Another, even bigger, sewer. In 2014, work started on the UK’s largest ever water infrastructure project. Thames Tideway, which will come into full operation in 2023, is essentially a giant tunnel, dug right through the heart of London and stalking the path of the Thames, which will capture, store and move vast quantities of raw sewage and rainwater across London. The 7.2-metre wide tunnel will run for 25 kilometres across the city and connect to 34 of the most polluting CSOs, taking sewage that would normally be pumped into the Thames and sending it instead to a treatment facility at Abbey Mills. “It’s a really unique project, and there will be nothing similar to it in the UK,” says Babovic. “Even globally, there will be very few projects which can compare to the Thames Tideway.”
The ultimate goal of the project is to reduce the amount of overflow water and sewage being pumped into the Thames by 94 per cent. “The reason that London is situated here is because of the river,” explains Ray Cantwell, an engineer on the project. “It should be a lovely piece of natural land to be enjoyed by all. I don’t think it serves that purpose.”
A project on this scale will inevitably have an environmental impact – more than 840,000 tonnes of concrete will be used in the construction of the tunnels, all of which will have to be moved through central London. Thankfully, that’s where the poop-filled Thames comes in handy. “We’ve tried to utilise the river as much as possible, to alleviate the traffic on the roads in the current planning route,” says Cantwell. “We use barges and boats to transport 90 percent of our material to and from the site, which is something that has never been done before.”
The super-sewer is designed to last for 120 years. But there’s a danger that the same problem could crop up again then, or even sooner. Tse-Hui Teh, a lecturer at the Bartlett School of Planning at University College London, says we have to plan even further into the future – and think differently about how we approach waste water . “It’s the same solution which was given in the Victorian era,” says Teh. “It’s the same logic, and I don’t think it chimes well with our ecological systems. The way that the structure of the water utilities and sewage utilities are regulated in the UK drove the super sewer to be the preferred option,” she says. Teh explains that water infrastructure is about a lot more than just pipes. One example, she says, is people paving over their front gardens, replacing absorbent grass with hard concrete. “People don’t think of that as water infrastructure, because it’s so dispersed,” Teh says.
Even Tideway’s own estimates suggest that around two million tonnes of sewage are still likely to be dumped into the Thames each year. Some of the cost of the £4.2 billion project will also be passed onto the public: many Thames Water customers have already seen an increase of £13, on average, to their annual water bill as a result (this figure, by Tideway’s own estimates, could rise to £25 before inflation by the end of the project). Tideway said these increases in price would apply for the foreseeable future, although there may be fluctuations depending on how many people live in the areas that Thames Water services. One of the original assessors who recommended the construction of the super sewer has since said that the cost of the project might outweigh its benefits.
“The Thames Tideway Tunnel will one day need to be replaced or have its capacity augmented,” says Babovic. “As it’s augmenting the current sewage system, it’s fair to say that there’s a general consensus in the water resources community that we cannot build ever larger and deeper sewers, that’s just too impractical and costly.”
So what can be done? Well, Thames Water doesn’t have the power to force customers to start making big changes in their own homes. But many small solutions to the problem already exist – and while it might seem like a pain, a lot of it is common sense. Items like wet wipes, are often labelled as flushable, but they’re often not biodegradable, which is a key difference. Other items that can’t be flushed, like condoms, tampons and wet wipes, are often responsible for creating blockages. The simple solution? Only flush toilet paper, poop, pee and other bodily fluids. Everything else needs to go in the bin, and if you’re unsure, check your local council website.
To get a grip on the problem, look no further than the Whitechapel fatberg. At 250 metres long and weighing 13 tonnes, this hulking lump of fat, oil, faeces, hypodermic needles and nappies, is a stark reminder of what we absentmindedly flush or wash down the drain. If you put items into the sewer which don’t break down, it usually ends up calcifying (so reacting with calcium present in the sewer environment) and solidifying with other substances. And stopping monstrosities like this from clogging up our over-burdened sewers doesn’t require fancy technology.Aside from the obvious solutions, there are three main culprits – fats, oils, greases. Pouring hot oil and fat down drains might be easier for you individually, but it just solidifies within the sewers instead.
So what if you work in a restaurant kitchen and are on a tight schedule, but still don’t want to contribute to the Whitechapel fatberg? Buy a grease trap, which will make your life easier in the long run. You can also wait for pots and pans to cool and scoop out solidified muck. If you’re cooking from home, do the same - but a lot of councils ask that you pour cooled oil or fat into containers and then just put them in the bin. But the problem doesn’t stop at your kitchen or bathroom.
If you’re not so sure that this problem applies to you, or even that you need to do something about it, it might be time to install a water meter, which are easy to find online. This will help you figure out how much water you’re using and identify areas where you can cut down. Separating rainwater from wastewater will make a huge difference. If you’ve got access to a garden, put in a water butt to collect rainwater runoff from your gutters and redirect it to plants in your garden. Got paved areas? Put in planting containers or replace concrete or paving slabs with gravel or grass. If you’re thinking of carrying out construction in the near future, porous asphalt is an environmentally friendly material that retains water. Resources like The Renewable Energy Hub help explain whether your home or your workplace, are good locations for rainwater harvesting.
And there’s more cities can do, too. Some cities in the US have installed giant industrial grease traps underground, which collect all of the oil and grease dumped at once. Closer to home, in Bradford, a scheme is being trialled where this cooled fat or oil is actually turned into fuel. Yorkshire Water teamed up with local energy companies and various councils to set up an oil collection scheme, which they say has completely transformed their sewer system (they were only called to a “jetting” job on blocked drains once in 2017). Such changes might seem small – almost inconsequential – but in the long run, our struggling sewer system is going to need all the help it can get.
This article is part of our WIRED on Climate Change series. From the urgent race to make cows fart less to the battle over deep sea mining, we're taking an in depth look at the technologies and ideas at the forefront of our crucial mission to reverse the effects of global warming.
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This article was originally published by WIRED UK
