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The Great Stink of 1858 cleared the Houses of Parliament and led to London’s first great sewage treatment project. Today, London’s bottoms are threatening the safety of our capital once more. Water engineer Dr Brian Mathew asks just how much shit can London take.



“‘No Shit Sherlock,’ Dr Watson commented to Sherlock Holmes, while gazing over the parapet to the Thames below, its usual putrid smell now a thing of the past.”

Following the ‘Great Stink’ of 1858 some 17 years earlier, when Parliament had at last been forced to act, civil engineer Joseph Bazalgette was commissioned to design and build a vast series of sewers, tunnels and pumping stations to shift the sewage of London away to the east. Now the Thames had at last started to recover and the city could breathe again.

Bazalgette’s solution was a simple one: to effectively turn the beds of the small rivers and streams that drained the capital, and had become open channels of filth, into sewers and then catch the effluent as it reached the Thames with two great sewer tunnels that ran along the northern and southern banks. These tunnels were built into what became known as The Embankments. Through these, London’s sewage could be transported miles out of the city, before being pumped to a higher level where it could flow into the Thames Estuary. Later, sewage works were added to treat the effluent.

Today that system, wonderfully over-engineered for its day, is being upgraded with the construction of the Thames Tideway scheme. In the years since the virtual Holmes and Watson wandered along London’s Embankment, the population has risen from around three million to over eight million today and rising, and the tide of effluent with it.

The quantity of shit produced by your average person every day is 0.14 litres, which when added to their urine amounts to 1.5 litres. Multiply this by the population of London and that is 5.2 full-size Olympic swimming pools of the stuff each day, or around 1,900 Olympic swimming pools of bodily waste each year… lovely.

Piss and shit are not the only things that end up in London’s sewers, of course. In 2013, the Guardian newspaper reported that a 15 tonne ‘fatberg’, twice the length of a London bus, comprising congealed fat, wet wipes, condoms and other sanitary and household waste was removed from the sewer at Kingston… even more lovely.

Stuart Turkington/Thames Water/PA


The sewers also carry a great deal of ‘grey’ water from London every day. This is the water that is flushed down the toilet each time we use it, water from our baths, washing machines, and from what simply goes down the plug hole. This is one hundred times more in volume than the poop and wee. The British-based charity WaterAid estimates that the average UK person uses 160 litres of water per day, of which only two litres is actually consumed. So for London, that is 1.4 million cubic metres of water a day in addition to all the brown and yellow stuff.

Industrial wastewater from London’s remaining industries, breweries and so on, accounts for around twice this amount, but the biggest quantity of all comes from rainwater which, during storms, flows in torrents down into the sewer system in search of a route to the sea. Bazalgette knew that there would be times when these storms would reach and exceed his sewer network’s capacity. So he planned for this with a system of ‘Combined Sewer Outflow’ (CSO) ‘valves’. These would open at critical times to prevent the system from back-flushing into people’s houses and the streets. They would instead allow, on an exceptional basis, the storm water/sewage mix to exit directly into the Thames.

In Holmes and Watson’s day this would have happened once or maybe twice a year. Now it happens as much as fifty times a year. This is due to a number of factors. The increased population plays its part but, largely due to the concreting and tarmacing of driveways and gardens, there is much more run-off than in the past, when more rainwater could soak away into the ground. Increased numbers and intensity of rainfall events have also added to the load on London’s sewers and these are likely to get worse as climate change starts to bite. With combined storm water and sewerage outflows becoming more frequent, and raw sewage flowing directly into the Thames on a much more regular basis, the danger to London’s environmental health is once again starting to raise concerns.

This is where the Thames Tideway project comes in. It is a scheme for a tunnel under the Thames to intercept the 34 most polluting of these CSOs to catch the overflow when it happens and to transport the contents out to the existing five major sewage treatment works at Beckton, Moyden, Crossness, Riverside and Long Reach. All of these are also being upgraded to take the extra flow, and thus keep the sewage out of the Thames.


The cost of this scheme, which will be carried by customers of Thames Water, is estimated to be £4.6 billion and rising, up from £1.7 billion in 2004 when it was first proposed. The current estimate means an addition to water bills of between £20 and £25 per Londoner per year at 2011 prices from 2019 onwards.

The Thames Tideway project does have its objectors. Their arguments come in three broad categories: first, the financial mechanisms; second, the cost and the disruption to those living in the area; and third, because more environmentally friendly alternatives might be possible.

The financing of the scheme has troubled some as no one likes to see their water bills go up, and it seems some rather opaque and convoluted debit mechanisms are being used to help finance the project. Nothing new here, some might say, but there is a degree of dispute over how the numbers stack up, as was made clear as sewage in a House of Lords debate on 16 January 2013. During the debate, the suggestion that Thames Water should pay no dividends to its shareholders until the Thames Tideway project was completed did not go down too well with Environment Minister, who suggested that if this was the case Thames Water’s investors, many of whom were pension funds, would have a problem paying pensions if they had no income, and furthermore would have difficulty in attracting new investors.

To get over the problems of disruption and noise, Thames Water put forward a Code of Construction Practice to cover the works, although the Planning Inspectorate, in its June 2014 report, had a problem with it and claims that Thames Water underestimated the impacts including those on health and quality of life from noise.


Perhaps the most interesting opposition to the Thames Tideway scheme, however, comes from the environmental lobby, which argues that if London was to be itself transformed with roof gardens and permeable roads and pavements, more of the rainfall would soak in and thereby never actually enter the sewer system in the first place.

This idea, sometimes referred to as sustainable urban drainage, is one that has found favour at Oxford Services in Wheatley. A feature of the design is the capture of rainwater in water reclamation lagoons for flushing toilets, although the high nitrate levels have led to discolouration that some apparently find off-putting.

This approach has something to be said for it. But the Department of the Environment report of October 2015 suggests that the increase in population alone means the CSOs could soon overflow even on dry days. Given the huge task of transforming London involved, and the pressing need to do something, the coalition government in September 2014 overruled objections and gave the Thames Tideway project the go-ahead. An investment company was created for the project, Bazalgette Tunnel Ltd in deference to the 19th century engineer who saved London from the Great Stink over 150 years earlier.

Bradley Garrett


If government has a role it is surely to protect the people, in this case from their own crap. This is not just from the sight or smell of turds rolling backwards and forwards with the tides, and it can take between one and three months for an item dropped in the river at Teddington to reach the sea. If sewage flows untreated into the rivers and the sea in large enough quantities, the nutrients it carries, such as nitrogen, phosphates and potassium, can reach such quantities as to create great toxic plumes of dead water where nothing survives.

The Thames has not reached this state yet, indeed seals and dolphins have been spotted close to the centre of the capital. However, the situation must not be allowed to get worse for the sake of Londoners present and future. For this and the future prosperity of the city, money will need to be spent.

Current UK and EU law requires that sewage has to be treated before it is released into the sea. In the early 1980s, Greenpeace activists aboard the Beluga were involved in monitoring water quality around the UK’s shores and beaches, finding them at that time among the filthiest in Europe. Today, we can boast some of Europe’s cleanest beaches but we must still do better.

And anyway, shit might be bad for our rivers but it does have value. London and many other UK cities extract bio-solids at the sewage works and these are turned into a useful fertiliser/soil conditioner. Used on 3,000 farms in the UK, the saving to farmers is around £450 per hectare in fertiliser costs, or nationally around £300 million a year. Indeed, if a charge was added for the use of this sewage fertiliser, it could help to pay for the extension to the system itself. As the old Yorkshire saying goes, “Where there’s muck there’s brass”. No shit, Sherlock.


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