The organization of the Paris 2024 Olympic Games he decided to use the Seinethe great river that divides the city into two parts, for some aquatic disciplinestaking up an idea already exploited in 1900, the year of the first Paris Olympics. In order to compete, however, the river must be declared legally suitable for swimming. In addition to industrial waste, the biggest “enemy” to making the Seine suitable for swimming is theE. Colia bacterium naturally present in the intestinal flora of mammals and birds but which often causes bathing bans because it can cause gastrointestinal diseases or inflammation.
Efforts to clean up the Seine have been intense and seemingly successful, but the weather could still spoil the party for Parisians.
Why the Seine was not swimmable
European and national legislation provide for maximum concentrations of E. Coli for waters, revoking bathing conditions when the legal limit is exceeded.
In 2024, heavy rains affected Paris (and much of Europe) for several months; the “runoff” rainwater that ends up in the drains is treated together with the sewage water, since the paved ground of our cities cannot absorb it. This can lead, in the event of intense phenomena or floods, to exceeding the treatment capacity of purification systems citizens, who therefore therefore they pour into the river a part of the waste water that has not yet been treated.
In the case of the Seine, this problem is added to the discharges that happen “upstream” of the cityin areas where the use of floating houses or rural dwellings less served by sewage systems often leads to direct discharge into surface waters.
How the Seine was cleaned: the Austerlitz basin
L’most recent intervention and the construction of an enormous collection basin, the mammoth thing to make the Seine suitable for swimming, was Austerlitz Basininaugurated in spring 2024 after three and a half years of construction and a cost of 90 million euros.
With a volume of approximately 46,000 m3a height of 30 meters and a diameter of 50 meterscan contain the equivalent of 12 Olympic swimming pools. This structure allows for the retention of any excess water in the sewer systems and thus regulates the flows arriving at the treatment plants, avoiding unmanageable peaks due to extreme weather events.
These interventions have actually brought back the bacterial count of the Parisian river under the legal limitallowing the current mayor of Paris, Anne Hidalgoto dive and swim in the waters of the Seine on July 17, 2024 in front of the cameras. Unfortunately, however, on the days of heaviest rainfall, there were still exceeding the legal limits: for this reason the Olympic organization has already planned a possible transfer of the races (except in triathlon) in Nautical Stadium Olympic D’île-De-Francean area 30 km from the city that will already be hosting rowing competitions.
