How helpful is it to find petrified human shit?

Treasury loo What our legacy reveals

The sewers of Karlsruhe

Just a few meters below the surface of the earth, 70 men in Karlsruhe have a not too fragrant and dangerous job: every day, the sewer workers descend into the “underworld” and ensure that the approximately 1,100 kilometer long sewer network works and that the city's drainage works.

Wastewater is tough: it contains bacteria and germs, and it can produce gases that are dangerous for workers. So you need to be well protected when cleaning the net. To do this, they use conventional technology, such as a sledge with two shields that pushes the dirt that has settled on. A high-pressure flushing vehicle is also used, which works with a pressure of up to 150 bar. The loosened dirt is sucked off so that nothing can clog.

The heart of the wastewater system of the Baden city is the Landgraben, which previously drained the city and was then used as a sewer. It was not until 1877 that the open, stinking water was provided with vaults - based on the model of the Roman Cloaka Maxima, which has been in operation under Rome for around 2000 years. Covering the sewer, as the Roman rulers recognized early on, protected the health of the population.

Viruses, drugs and medication in sewage

The municipalities make enormous efforts every year to remove pollution from the wastewater: In a multi-stage system, the wastewater is first freed of coarse residues; then bacteria eat the biodegradable substances. The important mineral phosphorus is removed. And yet there are still a lot of potentially dangerous substances left over. In Karlsruhe, active charcoal is to be used in a further cleaning stage to remove substances that come from cleaning agents, cosmetics or medication and that have so far been damaging to the environment.

In addition to the sewer workers, scientists are also interested in life in sewers, because human excretions contain pathogens or traces of drugs, even if they are very diluted. The Leipzig virologist René Kallies tracks down corona viruses: Even if only ten out of 100,000 inhabitants in a region are infected with SARS-CoV-2, Kallies can determine this using the wastewater. With the help of the data, regional outbreaks should be detected before many people are infected. And even after Corona, this extensive monitoring of wastewater could help: as an early warning system for pathogens before an infection becomes an epidemic.

Drug residues can also be found in wastewater. Cocaine consumption is particularly high in Dortmund and Zurich, while crystal meth dominates in Chemnitz. And ecstasy is a typical weekend drug, the Swiss researcher Christoph Ort has established. The results of the research network Score in 70 cities could help the police to get information on drug hot spots.

Archaeologists are at work, for example, to analyze centuries-old legacies in Freiburg: remains that have got caught in the remains of the wall despite all cleaning, or even earlier latrines provide information about everyday life as it must have looked in the city in the Middle Ages.

Correct posture in the loo

Sitting in a chair when defecating seems natural to us today. The sitting posture is not necessarily the healthiest, but an achievement of western civilization. The chair used to be reserved for the upper classes and remained so for a long time.

The squat position is actually the best position for relaxed emptying - the pelvic floor is relaxed, the bowel straight. It is different when seated: when the back and thighs are at right angles to each other, the last part of the intestine is curved. The bowel movement becomes more difficult and takes longer. And even hard pressing is by no means necessary or helpful. This knowledge is important for people who already have problems - incontinence or constipation, for example. But like many things to do with bowel movements, the subject of correct posture is still a taboo today.

Toilet habits: men and women

Women are very reluctant to sit on someone else's toilet seat, but men sometimes have a hard time if the neighbor's urinal is occupied while peeing. Prof. Mete Demiriz, sanitary scientist at the Westphalian University of Gelsenkirchen, is researching the different problems and solution strategies of the sexes in the quiet village. Every second man likes to make himself comfortable with a newspaper; Women tend to pick up a magazine. Even toilet poetry is different: men tend to scribble political issues, women tend to be more romantic.

The use of toilet paper is also important: every German uses an average of 20,000 sheets per year - men are much more economical here. Two percent of all men are satisfied with a single sheet of paper. Women, on the other hand, use a lot of paper, for example to lay out the toilet seat, and thus like to clog the toilet.

In order to make life easier for women when they go to the toilet, Prof. Demiriz has developed a special women's urinal. It should save them the hygiene problems on the way and make clothes handling easier. But so far the urinal has not been available to buy - women still have to use makeshift solutions.

History of the quiet place

There is a need for privacy: we like to be alone in the toilet. Until the beginning of the 20th century it was completely normal in Germany to do one's chores in public; in the field, on the street - women and men just let it go.

In Rome 2000 years ago, the toilet was even a sociable place. People met without any shame, talked, played games and did business. At least there were designated places for the toilet, because the streets had to be kept clean.

It was different in the Middle Ages: it was done literally everywhere - including in houses and castles, on the floor, on the stairs; Streets and streams stank to the sky. In the 16th century the toilets came up and the appropriate court regulations regulated their use. More order returned and the work shifted more into the private sphere. A well-known exception was France's Sun King Ludwig IVX. He went to the "throne" to perform in front of the court society.

It was not until the 19th century that the invention of the latrines spread in the cities - you went alone to the quiet place - it became a rather shameful process. And anyone who pees unabashedly in the great outdoors must expect a hefty fine.

The raw material wastewater provides energy and phosphorus

But excrement is not just rubbish - skilfully used it can contribute to the generation of electricity and heat. And they also contain real treasures: for example phosphorus, an important element that humans need to live.

In the Jenfelder Au, an eco-housing project in the east of Hamburg, the planners are relying on precisely this for the wastewater concept. They use what the residents flush down the toilet to generate energy and recycle the valuable phosphorus. The settlement, which will later be home to 2,000 people, uses the extremely economical wastewater concept “Hamburg Water Cycle”. The wastewater is treated in a biogas plant and comes back into the houses as electricity and heat. At the same time, the phosphorus, which is the basis for fertilizer and currently has to be imported at great expense, is recovered. The aim of the project: in the future, the settlement should be able to supply itself with energy completely independently, primarily thanks to the use of wastewater.

What prehistoric droppings reveal about us

For archaeologists, human legacies are a real treasure: What they nourished themselves on thousands of years ago and what their microbiome was made up of in the intestine can actually still be determined today: Researchers at the Max Planck Institute in Jena are studying prehistoric lumps of excrement, so-called coprolites . The remains provide information about the lifestyle of the people and their diet.

The researchers are particularly interested in the composition of the intestinal microbiome compared to today. Because changes could be an indication that certain illnesses such as depression or cancer are due to a change in food and lifestyle. The scientists have already found a difference: Modern humans lack a certain bacterium that digests plants. Probably because much less plant-based food is eaten today than in the past.

In the CoproID project, DNA analyzes are used to reconstruct the history of the human microbiome and to use the findings for our current health. Not an easy project, because the scientists have to process gigantic amounts of data to do this. There is human DNA with around three billion base pairs in a small pile of excrement alone.

Broadcast on