Officials are hoping to reduce pollution levels in the Seine to make it safe to swim in ahead of an Olympic river race in 2024. However high levels of e.coli, sewage and industrial dumping pose huge challenges.
With just over a year to go before the Paris Olympic Games, the Seine is the focus of attention. Two swimming contests are to be held in the river, between the Alexandre III Bridge and the Eiffel Tower off the 7th arrondissement.
However, swimming in the Seine is banned due to high levels of bacteria, e.coli and pollution. It was formally banned in 1923 and those caught breaking the rules are subject to fines but public authorities have decided to launch a €1.4 billion plan to change this.
Rainwater poses the greatest challenge, heavy rainfall causes sewers in the capital to overflow into the river.
Several projects, such as the construction of a 50,000 m3 retention pond are underway.
Samuel Colin-Canivez, who heads major works for the Paris sewerage system said: "The aim of the basin is to fill it up thanks to an interceptor which will block the rainwater before it is discharged into the Seine. And after the rain, it will be emptied using a pumping system towards the purification station.
"This will prevent volumes of polluted water from flowing into the Seine and because this water is polluted with a bacteriological load, we will be able to meet the sanitary criteria, not environmental but sanitary, for bathing" he added.
A European directive sets the maximum quantity of faecal bacteria - an indicator of water quality - for safe bathing. While levels in Paris are too high, one scientist, Jean-Marie Mouchel, a hydrologist and Professor at Sorbonne University, is optimistic: "I think it's pretty good, given the number of inhabitants in the Seine basin and the low flow. So obviously, there are still things to be done, we're talking about faecal bacteria, there are things going to be done and there are also some chemical products.
"But there were decades when we didn't really care about the quality of the Seine. It was only in the 1970s that efforts were much greater and today we have almost reached this breathable state".
Talks are underway on how swimmers and boaters can coexist in the Seine, twenty beaches will also be constructed.
The Paris City Hall is aiming to lift the swimming ban by 2025 if all projects go to plan.