How can an engineer bypass the epidemiologists and rid a city of outbreaks?

Posted by Derek Mason

2nd February 2021

Photo credit: Heidi Fin on Unsplash

Eradicating disease has long been a challenge for the human race. And people in authority have always questioned the science – and the scientists.

But surprisingly, it isn’t necessarily epidemiologists who make the biggest difference to a population suffering with disease. Looking back to another time – the 1800s – it was an engineer who saved London from repeated cholera outbreaks.

Even while the scientists and politicians couldn’t agree on how cholera was spreading, civil engineer Joseph Bazalgette was planning our modern networks of sewers.

The relatively new science of epidemiology was not universally trusted, and only a few “progressives” were suggesting that cholera was waterborne. The more mainstream medical view was that cholera was caused by miasma or “bad air”.

So while tonnes of sewage flowed into the Thames – the population’s drinking water supply – incredibly many did not make the link between the unsanitary conditions of the river and cholera.

But by 1858, the stench from the Thames was so great that parliament discussed moving to Oxford or St Albans to escape it. The foul smell created by the city’s inadequate drainage system forced the government to take action, and they passed an act that meant Bazalgette’s proposals could be enacted.

He planned an underground sewer network to divert waste downstream to the Thames Estuary and away from residential areas. This substantial project cost the equivalent of £1 billion in today’s money. It involved creating underground brick-lined sewers, that would be tasked with carrying away waste from thousands of miles of London’s streets. Waste that had previously been running along the streets themselves and into the Thames.

More than 320 million bricks were used in the scheme, along with Portland Cement – which was the first time this new material had been used on such a large project. Bazalgette ensured the construction of 1,300 miles of sewers and 82 miles of intercepting sewers – larger sewers that receive waste from surrounding networks.

One thing that those of us who live and work in London need to thank Bazalgette for is his forward thinking. He worked out a very generous figure for how much waste the sewers would need to carry, and then doubled it, meaning the sewers he built can still cope with waste levels today.

The population of London stood at around 3 million when he was making his calculations, and with 9 million people today, his system is still able to cope.

Taking the contaminated water out of the city had a huge impact and contributed to cholera outbreaks eventually ceasing in London and the UK – all thanks to one engineer. The Thames gradually lost its reputation as the dirtiest river in the entire world, and cholera has been eradicated in the city.

Sadly, there are still around 4 million cholera cases globally each year, and tens of thousands of deaths. But the Global Task Force on Cholera Control (GTFCC) has a target to reduce cholera deaths by 90% by 2030. Let’s hope there are some engineers involved.

And let’s also hope that we can see similar reductions in infection rates in the current global pandemic.

Meanwhile, I can’t promise to design a system to eradicate disease, but my team and I are working safely and with the right PPE, so do let me know if you need assistance with the structural elements of an upcoming project.

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