Some Parisians save 'le pipi' to help the Seine (2024)

The plan for a swimmable Seine casts a spotlight on the state of sewage in our rivers – and on the people doing better things with Paris' waste, fertilising wheat for baguettes and biscuits.

It's cool in the sewers below Paris, and not as smelly as I thought it would be. The air is filled with the roaring sound of greyish-green sewage rushing beneath my feet, sped up by rainwater and the downward tilt of the pipes. A charming blue street sign on the sewer wall (Quai d'Orsay) reminds me where I am in the city: just downstream from the beautiful Pont Alexandre III bridge, where the Olympic and Paralympic triathlon events are planned to take place this summer.

Watching the health of the Seine, known as one of the world's most romantic rivers, has itself become a global spectator sport this year, with fans and media trying to guess if triathletes will really be ploughing through its water in July and August. One major problem is that heavy rainfall can overwhelm Paris' 19th-Century sewage system, which collects both sewage and rainwater, and spill wastewater into the Seine. Last year, a test event was cancelled due to poor water quality, after record rainfall. From early June, daily measurements of E. coli bacteria will determine if the river is safe to plunge into – including, as some athletes have emphasised, with an open mouth.

"Of course, I'm going to swim in the Seine as soon and as often as possible, when the water quality is good," Pierre Rabadan, deputyParismayor in charge of the Olympics, tells me a day after my visit to the sewers, adding that he's already swum in it once, for an official event. From 2025, the plan is to open three bathing sites to the public in the summer.

Rabadan says a €1.4bn ($1.5bn/£1.2bn) package of measures to boost water quality, including a giant, newly completed basin to collect wastewater during heavy rainfall, will help limit pollution for the Games. Given this year's heavy rain, however, he expects bacterial levels will "still be a bit over [what is considered safe] water quality" when daily measurements re-start in early June. But he then expects levels to improve due to drier weather and also the new basin, which is currently being tested. During the Games, levels of intestinal enterococci will also be measured, he adds.

The good news is that the river is cleaner than it used to be. In 1900, at the first Paris Olympics, "the swimming competition took place just upstream of a sewage discharge point", says Laurence Lestel, an environmental historian at Sorbonne University, who has analysed historical data and maps to trace the river's ecological state since the 1870s.

Speaking in her office on the university's campus by the Seine, she describes the 19th Century as a time of heated debate over issues that remain highly relevant: rising river pollution, a collapse of fish stocks due to weirs and declining levels of dissolved oxygen in the water. But also, a desire to use and enjoy the river.

"There was already an awareness that the Seine was very polluted," she says. "But at the same time, the Impressionists set up their easels by the Seine and painted this wonderful, extremely beautiful river. You wouldn't think the Seine was polluted from their paintings, and yet it was, at that time. And people continued to swim in it. It's a bit of a mystery."

Swimming in the river was banned from the 19th Century onwards, except for some designated sites – but the reason was to avoid clashes with river traffic, not concern over pollution, she says.

By the 1970s, the Seine downstream of Paris was considered ecologically dead. At the time, more than half of Paris' wastewater was discharged into the Seine without treatment, and the fish had disappeared from the river; irreversibly, it was thought at the time.

And yet, within a relatively short space of time, the river was brought back to life, largely thanks to the expansion of wastewater treatment plants, Lestel says. "By the 1990s, dissolved oxygen levels were actually acceptable for fish," which began returning to the river, says Lestel, who coordinates an interdisciplinary research projectstudying the Seineand its wider ecosystem.

For Fabien Esculier, a researcher at theLaboratory of Water, Environment and Urban Systems at Ecole des Ponts ParisTech and former head of the Seine's environmental river police, all these clean-up efforts still miss a basic question: why are we flushing our urine and faeces down the toilet and into the sewers in the first place – instead of seeing them as a precious resource?

"In Paris, urine and faecal matter used to be considered fertilisers," Esculier says during a stroll along the Seine – above ground, this time. He proudly wears a badge saying "L'urine c'est cool"("Urine is cool"). Research by Esculier and others shows that before the rise of artificial fertiliser, nitrogen-rich urine, which contains most of the nutrients we excrete, was in high demand to boost crops for a growing urban population. Around 1900, around 50% of nutrients from human urine and faeces were recycled, but with the rise of synthetic fertilisers, this fell to only around 5% today, according to Esculier's research.

Gazing at the turbulent, rain-swollen river, Esculier highlights what he sees as a curious paradox: as a society, we are spending energy on treating our nitrogen-rich wastewater and destroying reactive nitrogen, while also, spending energy on making synthetic nitrogen fertiliser (whose production and use account for around 2% to 5% of greenhouse gas emissions). Treatment facilities capture around 10% of nitrogen from our sewage to be spread on crops, while 50% goes into the air, he says - and the remainder, into the river. Given a greater Paris population of 10 million people, this means "nitrogen from four million people goes into the Seine every day".

If we used all the urine from greater Paris to fertilise wheat instead, it would be enough to produce more than 25 million baguettes a day," Esculier calculates.

Over the past decade, Esculier has tried to put some of those findings into practice, trialling ways to collect urine and use it as fertiliser. In its simplest form, he was familiar with this from his own family history: "One of my grandmothers used to tell her children to go and pee on the rhubarb," he says, which gave the plant a boost of natural fertiliser.

Under a research programme called Ocapi, which Esculier leads, he and his team have organised various pilot projects aimed at collecting urine in cities which is then used by farmers to fertilise their crops. In one project, 20 volunteers collect their own urine and bring it to a drop-off point, where a farmer then collects it, stores it and uses it as fertiliser.

Esculier hands me a packet of biscuits produced as part of the Ocapi project. As the label proudly states, the Biscodor (or "Golden Biscuits") are made with flour from "wheat cultivated with a fertiliser based on human urine". I put them in my bag, curious to see what my colleagues in London would think of them.

The idea of separating urine at source is attracting interest on a larger scale.

Saint-Vincent-de-Paul, a planned new neighbourhood in Paris in the grounds of an old hospital, will feature urine-separating toilets as part of a recycling pilot programme by the City of Paris.

"It's fairly rare in Paris to have a new neighbourhood, given that the city is essentially already built, so we don't have many opportunities to test these kinds of things," says Antoine Guillou, deputymayor ofParis in charge of waste management, recycling and sanitation. He adds: "The idea is to test the separation of urine, and to see if it can be collected and used as fertiliser."

The new neighbourhood in Paris' 14th arrondissem*nt will comprise around 600 households, "which is quite a considerable size for an experiment but is small compared to the whole of Paris", Guillou points out.

"It's not a solution that's easy to implement in existing buildings, so it's not necessarily something we can use in all of Paris in the coming years," he says, of urine-recycling toilets. "But it could have a very important role for new neighbourhoods elsewhere in France, and globally."

Guillou does highlight another way of lightening the load on Paris' sewage system: reducing the amount of rainwater than runs into the sewers.

"In the long term, this is about greening the city and making it less sealed, so water can be absorbed by the soil," he says.

This, too, is constrained by Paris' historic architecture, he points out – all those quays and squares made of stone. One successful example, he says, is Place de Catalogne, a sealed square that was turned into an urban forest. "It's about reconciling Paris' heritage and this vision for a greener city, which is necessary for heavy rainfall but also in confronting climate change. And we know the city's residents really appreciate trees."

Lestel emphasises that truly reviving the Seine involves research and action far beyond Paris. She gives the example of fish, such as eel, sea lamprey and some salmon, which have made some recovery thanks to the improved oxygen levels. Research suggests that weirs are still limiting that return – along with threats from pollutants other than sewage, and rising water temperatures.

Despite the debate around the Seine's water quality, Rabadan is confident that Parisians will embrace the idea of swimming in their river once the sites open to the public – especially since similar existing bathing sites in areas off the main river have proven popular. "Once people see that you can swim in there, and it's authorised because the measurements are good, everyone will go," he says.

Esculier hopes the vision of a swimmable Seine – for the public, not just the Olympics – can spark bigger change, also in terms of our own habits. "If you swim in the river, you're going to want to protect it, and you're going to start asking yourself: why am I pooing into the water? Why am I peeing into the water?"

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