Sewage crisis: Truth about British rivers and how2 clean
| Malcolm Blackmore |
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Tue 15 Aug 2023, 20:57 Sewage crisis: The truth about British rivers and how to clean them up Long article from the subscriber only pages of this weeks New Scientist which may be an important read for local people concerned about the condition of the Evenlode and tributaries. We were very distressed by the opacity, murkiness, of the river by the Millstream weir now compared to 2005 when we first came here with a young family. I remember clearly being in a couple of working parties for Riverside those decades past, wading the stream by the slipway looking for broken glass so that paddling kids wouldn't get slashed feet. The visible Trout seemed to be very curious. Or waiting to snaffle invertebrates stirred up.. It was clear enough water to see the bottom quite well. Now? Long article pasted in from the NS below the dotted line if you want to read this and the url link doesn't get access for you: ================================================= Sewage crisis: The truth about British rivers and how to clean them up There were at least 361,103 sewage spills into English rivers last year, but there are several things we can do to clean up the mess - as a society and from your own home Mandatory Credit: Photo by Maureen McLean/Shutterstock (12908462g) Pollution on the Jubilee River adjacent to Slough Sewage Treatment Works managed by Thames Water. The Jubilee River is used regularly by open water swimmers and is a haven for migrating birds. During 2021, water companies discharged raw sewage into rivers in England 372,533 times. By 2040 the sewage discharges into rivers is targetted to be reduced by 40%, however, many environmentalists say this is too little, too late and that the directors of polluting water companies should be imprisoned as fines alone are not stopping regular sewage discharges into rivers Pollution, Jubilee River, Eton Wick, Windsor, Berkshire, UK - 23 Apr 2022 Sewage flowing through the Jubilee river in Windsor, UK, threatening wildlife Maureen McLean/Shutterstock TENS of metres under central London a tunnel has been dug that stretches 25 kilometres at a cost of £4.3 billion. Boring was completed in April 2022 and the passage should start operation in 2025. The 7.2-metre-wide Thames Tideway won’t carry people or vehicles though, but sewage. This “super sewer” will collect the huge volumes of stormwater and waste that often overwhelm London’s ageing sewage system. Instead of being dumped into the Thames estuary, as happens now, the effluent will gush through the new tunnel to Europe’s largest sewage treatment works at Beckton, on the outskirts of the city. The Thames Tideway is the most conspicuous example of the UK’s attempts to stop dumping sewage into rivers, amid growing outrage towards the privatised water companies responsible for the waste system. But this new infrastructure is just the tip of the iceberg when it comes to solving this crisis, which is linked to wider issues of how water is managed and even climate change. The good news is that technical solutions already exist, many of which are win-wins: helping to solve sewage overflows as well as problems such as flooding and drought. While many forms of pollution foul Britain’s rivers, sewage has grabbed the limelight. News programmes have repeatedly shown footage of dirty slurry tumbling into pristine river waters. The main culprits are combined sewer overflows (CSOs), designed for when water from heavy rain is carried into the sewage system and must be discharged due to its high volume – taking waste with it. Sewage spills Campaign and conservation groups such as Surfers Against Sewage, The Rivers Trust and Top of the Poops have compiled data on CSOs in Britain. Their headline numbers don’t make pretty reading. Top of the Poops reports “at least 361,103 ‘sewage spills’ into English rivers in 2022, lasting an almost unbelievable 2,207,527 hours”. It is tempting to assume that rates of sewage dumping must have increased, but we have only had systematic data collection from CSOs for a few years. Water companies were encouraged to install monitors by a 2013 letter sent by Richard Benyon, the then UK minister for natural environment and fisheries. Benyon wanted “the vast majority” of CSOs to be monitored by 2020. As a result, coverage in England increased 14-fold between 2016 and 2020. In March this year, the UK government reported that more than 91 per cent of storm overflows in England now have monitors. This expansion of monitoring has revealed the current scale of sewage dumping. The issue has become strongly politicised. A common narrative is that privatised water companies have siphoned off profits while failing to invest enough in infrastructure. In England, the companies have paid shareholder dividends averaging £2.1 billion a year and have £54 billion of debt. Yet Scottish Water remains publicly owned and it allowed sewage to overflow 54,289 times between 2017 and 2021. It also lags behind English companies in installing CSO monitors. Instead, the problem of sewage dumping can be traced to Britain’s antiquated water management infrastructure. Many of its sewers date to the 19th century and carry both sewage and excess rainwater. “Our stormwater and wastewater are collected by a single drainage system,” says Luiza Campos at University College London. The aim was to reduce the risk of flooding. “When it rains hard, rather than your property being flooded, it’ll go into a sewer and be taken away,” says Tom Stephenson at Cranfield University in the UK. The sewers transport the mix of municipal sewage and rainwater to wastewater plants (see “How sewage treatment works”). The downside of this combined system is that heavy rainfall can overwhelm the wastewater treatment plants. If too much water flows into the system, the sewers back up, risking raw waste welling up into people’s homes. Thames Water Utilities sewer cleaning team inspects the Fleet River's Victorian-built storm sewer of Blackfriars, beneath the streets of the City of London. Discarded fats from restaurants congeal in sewer networks leading to blocked pipework. Sewer men are shovel the deposits and bring them in vats to the surface. In the early 19th century the River Thames was practically an open sewer, with disastrous consequences for public health in London, including numerous cholera epidemics with the The Great Stink of 1858 a turning point. Intercepting sewers constructed between 1859 and 1865 were fed by 450 miles (720 km) of main sewers that in turn conveyed the contents of some 13,000 miles (21,000 km) of smaller local sewers using 318m bricks, 880,000 cubic yards of concrete and mortar and excavation of over 3.5m tonnes of earth. (Photo by In Pictures Ltd./Corbis via Getty Images) Many of the UK’s sewers were built in the 19th century and are unfit for modern Britain In Pictures Ltd./Corbis via Getty Images Two major things have been done to reduce this threat. First, engineers estimate how big a flow a treatment plant might experience and design it to cope. “You have to build the sewage works bigger than you might do for the average flow,” says Stephenson. Second, plants are fitted with an overflow system. When too much water enters, some is diverted into overflow pipes and out into rivers and other waterways. Inevitably, some sewage goes too. “They [CSOs] are deliberately discharged so you haven’t got sewage bubbling up into your toilet,” he says. “You’re protecting properties, people and businesses from being flooded.” In other words, CSOs are an inherent part of a combined sewer, but they are supposed to be a rarely-used backstop. Furthermore, if they are operating properly, they are relatively safe. That is because overflows should only happen at times of really heavy rain, when rivers are running high. This waters down the discharged sewage to the levels seen after treatment. Yet the system clearly isn’t working properly. In the past few years, several water companies have been prosecuted for polluting rivers and other water bodies in the absence of rain. Read more: Most of England's sewage systems are overwhelmed, finds analysis As well as this, the idea of CSOs as a last-resort system is difficult to reconcile with the hundreds of thousands of dumping events every year. In the Netherlands, they only happen “once or twice a year”, says Mark van Loosdrecht at Delft University of Technology in the Netherlands. “If it’s more often, yes that’s a problem.” While sewage isn’t the biggest source of pollution in Britain’s rivers (the leading cause is the runoff of slurry and sludge from farms), it is a threat to our health and the environment. Combined sewage and stormwater can include “high levels of bacteria, pathogens, pharmaceuticals and personal care products, heavy metals, sediments, microplastics and tyre wear particles”, says Campos. “Pathogens present in the untreated sewage can cause illnesses such as gastroenteritis, hepatitis and other waterborne diseases.” Not safe for swimming The upshot is that Britain’s rivers aren’t reliably safe to swim in. Of 1500 rivers, only stretches of three are designated bathing sites – and even these aren’t judged to be safe for swimmers. There has also been a change in attitudes. “I think people, quite rightly, are less tolerant of having a filthy stream running through the middle of their town than they used to be,” says Stephenson. England’s water companies are at least alive to the problem. In May, they apologised for the pollution and pledged to spend £10 billion this decade to clean up their act. Industry body Water UK says this amounts to a tripling of existing investment plans and should cut spills in England by up to 140,000 per year by 2030 compared with the 400,000 in 2020. The money is likely to come from water bills, which might need to rise by more than £50 per year to cover the costs. B2KBGN Sewage overflow outlet into the river Thames, London city, England, UK. A sewage overflow outlet pouring polluted water into the river Thames, in London. Steve Atkins/Alamy So far, the companies haven’t given any details of their plans. What will it take to stop sewage flowing into Britain’s rivers? Cleaning up Britain’s rivers Britain’s wastewater treatment plants are perfectly capable of handling the volumes of sewage they receive and the technology is constantly improving. “I’ve been at this for roughly five decades and the pace of change is faster than it’s ever been,” says Glen Daigger at the University of Michigan. Instead, the problem is that the sewers can’t cope with the amount of water they receive at certain times and this indirectly causes the sewage to escape. “You have to deal with this volume,” says van Loosdrecht. The obvious solution is to stop using combined sewers, but that is far from trivial. New housing estates are already built with separate sewers and rainwater drainage. However, that still leaves much of the country with the old, combined set-up. Replacing it would be a huge, expensive project. “You’ve got hundreds of billions of pounds of infrastructure built like that,” says Stephenson. It also isn’t a perfect solution. “Even the rainwater itself flushes all kinds of dirt from the streets”, including animal faeces, says van Loosdrecht. Large volumes of this contaminated water can still cause harm if regularly discharged into a river, so the rainwater may still need to be sent to a treatment plant – recreating the problem. P6761N Barking Creek Flood Barrier, Warpools Reach, River Thames, East London, UK The Barking Creek flood barrier on the Thames, one of the UK’s polluted rivers Avalon/Construction Photography/Alamy A better approach is to take a step back and consider the full range of problems facing Britain’s water. “What are the things that we can do that address the system as a whole?” says Daigger. This holistic method, advocated by the United Nations, is called Integrated Water Resources Management and is based on the premise that water is a vital resource for both people and ecosystems. In the UK, this points to a simple truth. “We have two problems: too much water or too [little] water,” says Campos. While Britain is famously rainy, the water isn’t evenly spread in time or space. South-east England is particularly prone to droughts. Other regions, like the south-west, can receive intense rainfall from the Atlantic, leading to floods. Read more: Climate change is turning snow to rain and raising risk of floods Global warming will worsen both problems. “Climate change is increasing the frequency and severity of storms,” says Daigger. It will also make droughts more frequent and intense. As the weather becomes more changeable and extreme, more sewage will be forced out of combined sewers by extreme rains. “These overflows, which are a designed component of the system, are occurring more frequently and with higher volume.” In this context, says Campos, we need to collect more rainwater where it falls. “Avoid the stormwater being discharged into the drains,” she says. That way, we can delay it entering the sewers, reducing the risk of overflows. The water can either be used immediately or stored to help with subsequent droughts. How to store water There are many ways to do this. We can collect the stormwater in tanks or artificial lakes that become amenities for communities. On a smaller scale, many more homes could have water butts attached to their drainpipes, with the water used for gardening. “San Francisco is one of the best examples of how a significant metropolitan area is addressing this,” says Daigger. New rules enable developers to install rainwater collectors and for the captured water to be put to use – often for non-drinking purposes like flushing toilets. “This gets down into things like plumbing codes and the building trades and so forth,” says Daigger. “Here’s quite a significant international city that’s moving very systematically in a water-short area.” Alternatively, we can harness nature. Buildings with green roofs naturally absorb some rainwater. Many new housing estates in the UK now have a swale: a wide, shallow ditch that captures rainwater. A swale enables this water to slowly drain away, rather than flowing quickly over paved surfaces straight into the nearest sewer or river. Swales are just one example of a sustainable drainage system. “We can also implement ‘rain gardens’ in urban areas,” says Campos. These are planted areas of ground that collect runoff. For example, in many British towns and cities, roundabouts that were once made solely of concrete have been turned into miniature gardens. There are plenty of other hard, paved areas that can be planted and this would lead to leafier cities as well as helping to control the flow of water. Thames Tideway Pr Image The Thames Tideway is a “super sewer” running under central London Patricia Rayner/Image 2 Photography Where space is available, artificial wetlands can also control water flow. The best designs have a layer of gravel or sand, which filters muck out of the water as it drains through, says Campos. The water can then trickle out into a river. Projects like these are being attempted in the UK. In May, South West Water announced it would pay farmers in Devon and Cornwall to store water on their land, variously using ponds, woodlands and wetlands. The company has been given £1 million of funding for the scheme by Ofwat, the UK regulator for water and sewerage firms. Campos emphasises that there is no one-size-fits-all solution. Wetlands probably aren’t viable in a densely-populated city like London, which is why the Thames Tideway tunnel has been built. But in smaller towns and rural areas, such huge infrastructure projects would be unsuitable. The challenge will be running Britain’s water system in a joined-up way. “The technical solutions are there,” says van Loosdrecht. “The main issue is in the governance and the political decisions.” It remains to be seen whether the UK government will enact the kind of joined-up thinking needed to tackle not only the sewage problem, but wider issues of water resources. Last month, a handful of Londoners went on a subterranean journey to see the kind of interventions needed, venturing into the Thames Tideway before it comes into use. For the occasion, a stretch of the tunnel had been turned into a garden-like art installation. However, wastewater will shortly take its place – and the sooner we face up to the reality of the disposal of our sewage, the better. New Scientist audio You can now listen to many articles – look for the headphones icon in our app newscientist.com/app How sewage treatment works The aim of a sewage treatment plant is to clean water sufficiently for it to be safely discharged into a body of water like a river. This treated water doesn't have to be as crisp and pure as a mountain spring, but it must be clean enough that it doesn't harm the ecosystem or pose a significant risk to people's health. A wastewater treatment plant works in stages. First, filters remove "the gross solids, in both senses of the word: the nasty stuff, but also the big stuff", says Tom Stephenson at Cranfield University in the UK. This includes items such as condoms and supposedly flushable wet wipes, which shouldn't be flushed down toilets, but often are. A second step filters out small, but dense, particles like grit and sand. The core challenge is the stuff that comes directly from the body, which forms the bulk of the pollution. "The big problem is the poo and the wee," says Stephenson. "You've got to remove the organic matter, you've got to remove the ammonia." As a first step towards this, the sewage is stored in tanks. Here, gravity drags the denser organic particles to the bottom, where they form a sludge. This is treated separately: sometimes it is used to produce methane, which can be burned to generate energy, or it may become a soil improver. Meanwhile, the bulk of the water is still contaminated with organic chemicals like fats and proteins, and with ammonia. Here, the trick is to harness microbes that break down the waste and get them to work quickly and efficiently. "You blow air or you provide oxygen and bacteria grow," says Stephenson. "They degrade the organic matter and, if you get the conditions right, you can also convert ammonia to nitrate, which is far less toxic." Most people have never set foot in a wastewater treatment plant and so have a lot of misconceptions, says Stephenson. People imagine "a horrible brown water with lots of turds floating in it", he says. "It isn't. It's a slightly muddy river." And while the microbial processes do smell, the whiff resembles "strong earth" rather than a broken toilet. Michael Marshall is a freelance writer based in Devon, UK |