"The Seine has never been so clean."

For a long time, the idea of swimming in the Seine seemed unrealistic. It then became a goal, on the occasion of the 2024 Olympic GamesIt is now a reality: swimming is allowed on certain sites of the river, as well as on the Saint-Martin canal, during the summer period. “Never in 70 years has the Seine been so clean”, says Science and Future Vincent Rocher, Deputy Director for Innovation, Strategy and Environment at SIAAP (Interdepartmental Syndicate for Sanitation of the Paris Agglomeration).

“In 1970, the Seine was a polluted, biologically dead river”, he explains. At that time, sanitation capacities were much less developed than today, and a large part of the wastewater was still returned to the river without effective treatment. “We were putting too much organic matter in it, and that led to deoxygenation. There was little to no life.”"Today, the situation is completely different," continues Vincent Rocher. “We have succeeded, because we have made considerable efforts over the last few decades, in restoring exceptional quality and biodiversity to our rivers.”he insists. The wastewater treatment plants in the Île-de-France region process approximately 2.5 million cubic meters of wastewater every day. “That’s roughly equivalent to processing 30 cubic meters per second.”he explains.