In late 2021, the Zoological Society of London released a report [PDF] on the status of the River Thames. It found that seals, sharks, and seahorses had returned, thanks to improvements in the water quality of the tidal river. Increasing populations of harbor and gray seals were spotted laying on the foreshore, drawn to the nutritious fish that the cleaner environment supports.
The future of the river had not always looked so promising. Stretches of the Thames were declared biologically dead in 1957, and a century earlier, it had served as London’s dumping ground. “Through the heart of the town a deadly sewer ebbed and flowed, in the place of a fine fresh river,” Charles Dickens lamented in his novel Little Dorrit. In the hot summer of 1858, when temperatures reached 94.5°F—a singularly unpleasant season that became known as “the Great Stink’”—conditions in the river were especially abysmal. All kinds of refuse ended up in the Thames, including rotten food, human excrement, waste from abattoirs, and industrial chemicals. Chancellor of the Exchequer Benjamin Disraeli described the Thames as “a Stygian pool, reeking with ineffable and intolerable horrors.” Nearly all life in the river had been destroyed, he said, and London’s health was at risk.
This wasn’t the first time that contaminated water had put the well-being of Londoners in jeopardy. The city suffered cholera outbreaks in 1831 and 1832, and in 1854—just four years before the Great Stink—physician John Snow identified cholera as a water-borne disease, after findings that cholera cases centered around a particular water pump. Later, a sewer was found to be leaking near to the well that the water was drawn from.
Despite Snow’s discovery, some Londoners alive during the Great Stink still believed the miasma theory of the Middle Ages: that the disease was caused by poisonous vapors in the air. The smell of rotting waste was unbearable, particularly in the House of Commons in Westminster, in the rooms overlooking the river. In an attempt to protect themselves from the stench, they tried disinfecting curtains with a compound called chloride of lime. But it did little to protect the MPs from the revolting odor coming from the Thames.
The intensity of the stink in 1858 accelerated long-overdue measures to improve sanitation in the city, whose population had more than doubled between 1801 and 1851. Disraeli proposed a bill that MPs debated and passed within 18 days. It called for the desperate situation to be remedied, passing control and funding to the Metropolitan Board of Works, and Joseph Bazalgette served as its chief engineer.
Bazalgette’s background as a railway engineer and his experience with land drainage made him an ideal candidate for the enormous task at hand. Before Bazalgette’s new network, the increasing use of flushing toilets was wreaking havoc for the city, causing waste to seep from inadequate sewers into the river. His plan was to build a new subterranean network, including 1100 miles of drains and 82 miles of sewers, along with pumping stations, which helped to manage the sewage from low-laying areas, for discharge well beyond the city limits. The job was immense and required thousands of laborers to work on digging out the tunnels by hand.
The project cost £4.2 million (roughly $592 million in today’s dollars) and took approximately nine years. By the time of Bazalgette’s death toward the end of the century, his network was working harder than ever, supporting a population more than twice the size as when he built it. The sewer system proved to be money well spent, and it even ended up sparing most of the city from a cholera outbreak in 1866. Part of East End of London—the only area not yet connected to Bazalgette’s sewer system—was affected by the epidemic.
Bazalgette was the engineering mastermind that Victorian London needed, and his system had a positive impact on public health. Now, though, the brick-lined sewer network is struggling to keep up with London’s population of 9 million and counting. “The State of the Thames 2021” found that “storm events cause excess sewage to overflow into the tidal Thames, posing a major threat to water quality.” And earlier this year, 2 billion liters of raw sewage were dumped into the river over just two days.
Help is on the way for London, but it will take a while. The new Thames Tideway tunnel, dubbed the “super sewer,” is due to be completed in 2025 at a staggering cost of £3.9 billion (roughly $5.2 billion). With any luck, the super sewer will come just in time to save modern London from a new Great Stink, and ensure a good habitat for the recently returned sharks and seals for many more decades.