The world is abuzz with the upcoming Summer Olympic and Paralympic Games, set to begin in Paris, France, on July 26th with a spectacular Seine River-based opening ceremony. The Seine is expected to be a major player in this year’s Olympics as it will also host three swimming events such as the swimming portion of the triathlon. In fact, the sustainable aspect of using the Seine for events was a key component of Paris’s Olympic bid. Yet despite spending $1.5 billion on cleaning up the river just to make it swimmable after more than a century’s ban, tests in the last week have shown unsafe levels of E. coli and enterococci bacteria still in the water.  

E. Coli and other bacterial organisms exist in naturally occurring bodies of water, known as nature water, to one degree or another, and it is inevitable that a person will encounter some. The goal from a water quality management perspective is to keep those risk factors under control and the water safe. Paris went to great lengths to mitigate the risks and provide athletes with a healthy competitive environment; however, heavy rains and their related runoff have washed bacteria from the city’s industrial and residential activities into the Seine, causing today’s Olympic challenge.

The 2024 Paris Olympic Games are set to be the first competition since 1923 that will allow swimming in the Seine River. Before the introduction of pools to the games early last century, all swimming events occurred in rivers and natural sources. While modern swimming pools utilize chemicals and technology to prevent bacterial populations from rapidly multiplying, natural water typically houses a few hundred colony-forming units of E. Coli, which are a naturally occurring part of that ecosystem with or without human impact. Paris compounded these naturally occurring organisms with its 19th-century activity of directly discharging factory and human waste into the Seine through its revolutionary sewer system. 

Last week there was cause for alarm in Paris as the most recent wave of E. Coli screenings, attributed to high rainfall within the city, came back positive and above the 900 CFU threshold set forth by the Olympic Committee. As of writing, there is no known backup plan to host the three swimming events this August. Paris, a truly ancient city, has always bordered the Seine; therefore, the river has been impacted by heavy pollution for centuries that has contributed to the destruction of the habitat for much of the local wildlife. After the European Union passed legislation to address urban wastewater, The Greater Paris Sanitation Authority put forth a massive effort to improve the treatment infrastructure and, thereby, the overall health of the river. In 2015, the City launched its plan baignade, or swimming plan, to clean up the Seine ahead of this year’s Olympics. In addition to other measures, the plan connected 23,000 residences and houseboats that had previously dumped their untreated waste into the river to the City’s municipal sewer system. The efforts continued and just last month a large holding tank was installed to collect excessive rainwater runoff to further combat the possibility of toxic sewage spilling into the river. 

Paris’s efforts to clean up the Seine have been so intense that the recent results have angered residents. A delay in Paris Mayor Anne Hidalgo’s promotional swim in the Seine led residents to threaten a protest poo in the river.  The hashtag call to action, #JeChieDansLaSeineLe23Juin, which translates as "I s*** in the Seine on 23 June,” has been pervasive across social media channels.

Although these recent rounds of testing are certainly a valid cause for caution, the river's water quality has seen dramatic improvements. The most recent wave of testing was likely impacted by heavy rainstorms in the Paris area. In a large metropolis where there are sewer systems collecting wastewater, a massive storm event can lead to the sewers overfilling with rain runoff and then spilling into the neighboring rivers and streams. This trend of sewage spilling would lead to a toxic situation that would only cease as the waters recede. 

It is hard to sift through all the potential factors contributing to the E. coli spike in these recent river tests. However, the fact remains that without the infrastructure to treat our wastewater, swimming in the Seine would be the least of our concerns. Wastewater management is a balancing act that improves not only public health but also maintains the “natural equilibrium with our surrounding environment.” 

Now, the question is what the Olympic Committee will decide in the face of the Seine's test results. As with the rest of the world, we will be watching to see what happens in a few weeks when the Olympics begin.