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Skulking through Brussel's Sewer Museum

Updated: May 24, 2023

FLUSH was delighted to visit Brussel's Sewer Museum recently! There, we learned a lot about how Brussel's sewer history works and its intimate relation with the Senne (not to be mistaken with France's river, The Seine).

The Brussels Sewer Museum's model sewer (Credit: FLUSH/K Worsham)

The museum had a very cheeky audio tour – available in several languages. Through that tour, guests learn a detailed history of the sewer system, how to construct and run sewers, what's in wastewater, working conditions for sanitation workers, and some essential sewer vocabulary. They even went into the evolution of different sewer system styles - from open gutters and pits to square underground drains to the modern egg-shaped sewers invented by sanitation engineer giant Baldwin Latham in 1867.

The museum had a bunch of small-sized models about building sewers (Credit: FLUSH/K Worsham)

History of Brussel's Sanitation System

Brussels (meaning "swamp land") is watery, making managing human excrement tricky. This has been a problem in the city even from when it was small nearly 700 years ago, particularly because it has 3 rivers where waste was being dumped – particularly the Senne. In 1341, Brussels banned throwing waste into the Senne to prevent odors. Instead, it mandated that residents manage open gutters on the streets while the city collected the fecal sludge. Seemingly, this didn't work out, and people continued to pour their wastewater into the Senne. Eventually, Brussels created the civil servant job of the moddermeyers ("mud masters"), who cleaned stoves, waterways, and sludge. What a way to make a living!

The Brussels moddenmeyer's pledge (Credit: FLUSH/K Worsham)

As Brussels grew over the centuries, the city became denser, and more efforts had to happen to address the growing filth. By 1640, the city had a storage basin called the mestback (literally the "poo basin") to store excrement and city debris before boats took them away to be used in the fields as fertilizer. By now, the city knew they needed a sewer network, but people continued to dispose of their waste into the Senne. So Brussels started putting together sewer systems for stormwater here and there in a disorganized fashion – an open gutter here, poorly-designed ones there…you get it.

A 19th-century map of Brussels and its waterways (Credit: FLUSH/K Worsham)

By 1835, the city's unsanitary conditions were getting worse. The city had some sewers – about 50km – but they didn't cover the whole city and were falling into disrepair. Moreover, private households couldn't connect to this meager sewer system until 1865, when Brussels combined the existing stormwater drains into a larger sewer network underground. As a result, the Senne was getting dirtier, working ostensibly as Brussel's sewer system. The smell was getting terrible, which terrified people (remember – this was when miasma theory was popular).

Around the same time, the city commissioned a project to manage the Senne. Over time, after much deliberation, Brussels decided to move the flow of the Senne with a canal to reduce flooding. They also vaulted the Senne underground to limit the smells, reduce city flooding, and stop spreading diseases (particularly cholera, from which 3,500 people died in 1866).

From left to right: A window in the sewer system, an old sewer train used to travel around the underground (Credit: FLUSH/K Worsham)

Where was the wastewater and sewage going? Oh, it was still going into the Senne, but it wasn't being seen. And that's what mattered. It wasn't until 2000 and 2007 that Brussels built its first two wastewater treatment plants. But we'll get into that a little further down.

What Lives in Brussel's Sewers?

In the Brussels sewers, some things lurk below with the vaulted river and incoming wastewater. First and foremost, Norwegian rats live in the sewers to optimize access to water and food. They infested the city so much that by 1964, they started running annual campaigns to poison rats quickly and manage their numbers.

From left to right: animal art in the Brussels sewer, a taxidermied Norwegian rat

(Credit: FLUSH/K Worsham)

But rats aren't the only occupants - slugs, mosquitoes, and frogs are also there! It depends on where you are in the sewers, though. For example, frogs like areas where the stormwater comes in, but not so much where there's a lot of sewage.

How Brussel's Current Sewers Work

How does Brussel's current sewer work now? We've got you.

Belgium uses only combined-sewer overflow (CSO) systems. As mentioned, that means the stormwater and wastewater (including sewage) come together in the same pipes. Brussels has 100 overflows across the city, working to address possible flooding. Its sewer system, like most others, uses gravity to allow the natural flow of water, and supplements it with pumping stations to hoist the water back up to higher altitudes and allow more gravity flow.

Left to right: An egg-shaped sewer and a mushroom-shaped underground area - both part of the walking sewer tour segment for the museum (Credit: FLUSH/K Worsham)

Of course, there are other underground networks that the sewers weave around, too, such as electric cables, tunnels, metro subways, etc. Finally, the sewer ends up further downhill to its two relatively new wastewater treatment plants, serving a combined 1.46 million people.

The museum had an example model of all of the underground systems competing with the sewer system (Credit: FLUSH/K Worsham)

Unfortunately, not all sewage ends up in the plants for treatment. The Senne continues to have up to 10 million cubic meters of raw sewage polluting its waterways annually. Unfortunately, the city's plants can't accommodate the rainfall (which isn't all that uncommon), making much of the combined wastewater fall into the riverway. The Senne continues to have a reputation for being the city's natural sewer system, and the current water quality of the river often doesn't meet EU standards.

Left to right: Signage about the Senne's altitude compared to sea level; the vaulted Senne and construction work (Credit: FLUSH/K Worsham)

There's work to fix that, but the infrastructure is expensive; it will take some time.

There's an old assumption that high-income countries have been pioneering sanitation and already "nailed it". The big lesson in the story of Brussels is that we can let go of that idea - sanitation is being figured out everywhere still.

A special thank you to the Brussels Sewer Museum team, who enthusiastically entered me into their museum and shared stories with us at the end of the tour!

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