The Seine River in Paris has been closed to public swimming for more than 100 years, but it reopened to swimmers this summer. We talked to two people who took a dip.

Megan Hall: Welcome to Possibly, where we take on huge problems like the future of our planet and break them down into small questions with unexpected answers. I’m Megan Hall.

This summer, people in Paris got to do something that was illegal for more than 100 years: swim in the Seine.

The river was closed to public swimming in 1923 because of pollution and boat traffic. But now, after a massive clean-up effort, Paris officials say it’s safe to go back in. So, we decided to talk to some people who gave it a try.

Daniel: I’m Daniel

Megan Hall: That’s the nephew of our founder.

Nienke: And,my name is Nienke.

Megan Hall: That’s Daniel’s partner. They were working remotely in Paris this summer.

Daniel: We were just kind of, living our life, but in Paris.

Megan Hall: They just happened to be there when the city reopened the Seine for swimming. So they decided to check it out.

Daniel: We went to the area near the Eiffel Tower that was open for swimming.

Nienke: Eventually we waited maybe a half hour. Do you think that’s fair? Yeah.

Megan Hall: As they waited, they saw a man updating a sign with details about weather, wind speeds, and pollution in the river.

Daniel: He was this very sort of stern old man, not smiling, just writing numbers, and then

Nienke: He wrote, uh, in French, like happy swimming.

Daniel: Happy swimming.

Megan Hall: This happy swimming was made possible thanks to a push to clean up the river in time for the Paris Summer Olympics.

To do that, the city built large storage tanks for raw sewage. Before, when big storms happened, the sewers were overwhelmed and released everything straight into the river. They also worked hard to stop houseboats from dumping their waste into the water.

The end result for swimmers like Nienke and Daniel?

Daniel: Yeah, so the water, um, itself, um, was surprisingly clean.

Nienke: It was. Kind of chilly, but very, refreshing. The water looked almost a little bit blue. You could see some fish.

Megan Hall: Other Paris residents aren’t so sure about swimming in the Seine. They question whether the water is really clean enough.

Nienke: I certainly wondered, I hope this is as clean as they say, because I have no way of knowing if,  if there is something strange in here. But I think each of us also accidentally had a little taste of the water, and it seemed absolutely fine.

Daniel: It tasted delicious.

Megan Hall: Daniel says he hopes the Seine clean-up encourages other cities to make their rivers safe enough for swimming.

Daniel:  I grew up in New York and I always thought it would be cool to go swimming in the Hudson River and was always told, no, it’s too dirty. And I thought that was very strange, because I have access to parks, to the streets, and it’s just sort of another natural environment that’s accessible as something you can enjoy.

Nienke: I agree. I think it changes your relationship to the city. I think both Dan and I have been in, in cities abroad where if there’s a river we’re, we start asking people, oh, where can I go and swim? And then when the answer is like, you absolutely can’t, that would be dangerous, that’s a very depressing and strange realization, that there’s parts of the city that are so prominent, like the Seine, it’s right there, you see it all the time, I think being able to access it makes you more connected to the city and its resources.

Megan Hall: So far, the swimming program at the Seine has been a success, so much so that the mayor extended the season to the middle of September.

But if you can’t make it to Paris, there are cities in the US that have made these transformations too. Similar efforts to store sewage have made Narragansett Bay here in our home state of Rhode Island much cleaner. In fact, everywhere these kinds of improvements are made, it’s transformed water that was once filthy and dangerous.

That’s it for today. You can find more information, or ask a question about the way your choices affect our planet, at askpossibly.org. You can also subscribe to Possibly wherever you get your podcasts or follow us on Instagram, Facebook, LinkedIn, or Bluesky at  “askpossibly”

Possibly is a co-production of Brown University’s Institute for Environment and Society, Brown’s Climate Solutions Initiative, and The Public’s Radio.

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During heavy rain, Providence’s sewers used to get overwhelmed and dump untreated sewage into the Bay. But thanks to a project to increase the capacity of sewers, untreated sewage rarely makes it into our waterways anymore.

Megan Hall: Welcome to Possibly, where we take on huge problems like the future of our planet and break them down into small questions with unexpected answers. I’m Megan Hall.

If you’ve lived in Rhode Island for a while, you may have noticed that the Narragansett Bay is a whole lot cleaner than it was in the past. We’re here with Possibly reporters Will Malloy and Juliana Merullo to find out why.

Will Malloy: Hi Megan!

Juliana Merullo: Hiya!

Megan Hall: So, is the bay really that much cleaner?

Will Malloy: Legend has it – that back in the day, if you fell into the upper parts of the Narragansett Bay you’d get sent to the hospital for antibiotics. It’s definitely not that bad anymore.

Juliana Merullo: In fact, in recent years, the Bay has gotten so much cleaner that the state has reopened shellfishing grounds that were closed for over 70 years!

Will Malloy: And water quality overall has improved so much that in 2021, parts of the Narragansett Bay were officially taken off the EPA’s list of waterbodies that are so dirty that they don’t comply with the Clean Water Act.

Megan Hall: Wow! That’s great! But how did that happen?

Will Malloy: To find out, we took a trip to the Field’s Point Wastewater Treatment Facility.

Megan Hall: What’s that?

Juliana Merullo: It is the main facility that cleans the water from our sewers before it gets let back into the Bay. It’s under those big windmills we can see from around Providence as we look down the Bay.

Megan Hall: Ok, but why are you going there to figure out why the Bay is cleaner?

Will Malloy: That’s a great question – Jim McCaughey, the Deputy Director of the Narragansett Bay Commission, which operates the Field’s Point facility, says it all goes back to our sewer systems:

Jim McCaughey: Older cities when they built their sewer systems, they were designed to collect both wastewater from homes and businesses, but also stormwater. So the systems are designed to collect both.

Juliana Merullo: The sewers in Providence are that older kind, which means they have to handle both the stuff we flush down the toilet or the drain and our rainwater – all mixed up in the same pipes!

Will Malloy: That makes the system more likely to get overwhelmed if it rains a lot.

Juliana Merullo: And if the system gets overwhelmed the extra water will get stuck in the pipes and back up into people’s homes if it’s not released somehow.

Will Malloy: So the system is designed with release valves that let all that extra water flow out into our waterways, untreated.

Jim McCaughey:  So you’d be getting raw wastewater being discharged during a storm into the rivers and the bay. No good.

Megan Hall: Gross!

Will Malloy: Super gross. All that untreated sewage in our waterways made the Bay really unhealthy for people and animals.

Juliana Merullo: Which is why, the Clean Water Act required states across the country to phase out those release valves – which are called “combined sewer overflows”  or “CSOs”.

Will Malloy: Because of the Clean Water Act, the EPA said that Providence, and the Field’s Point Facility in particular, had to do something to stop those overflows from overflowing.

Juliana Merullo: So the Narragansett Bay Commission designed a decades-long project to fix the problem.

Will Malloy: Which included  building a huge tunnel under the city of Providence!

Jim McCaughey: During rain events there was CSOs that would have gone into the rivers and the bay are discharged into this tunnel, where we can pump out and treat that wastewater.

Juliana Merullo: And that big tunnel holds onto the water until the system is less stressed and can deal with the excess water from the storm.

Megan Hall: That works?

Will Malloy: Yes! Those improvements we talked about earlier – the reopened fishing grounds, the better water quality – are largely thanks to fixing the overflow problem.

Jim McCaughey: When we solved these CSO problems, we’re really servicing the whole state, because this helps anybody that uses the bay, and the rivers.

Megan Hall: That’s great!

Will Malloy: It is – but it’s also worth noting that there are more ways to tackle these kinds of problems, like building infrastructure that prevents water from going into the sewer system in the first place. But that’s for another episode…

Megan Hall: Something to look forward to!

That’s it for today. For more information, or to ask a question about the way your choices affect our planet, go to askpossibly.org Or subscribe to us wherever you get your podcasts.

You can also follow us on Instagram, Facebook, LinkedIn or X at  “askpossibly”

Possibly is a co-production of The Public’s Radio, Brown University’s Institute for Environment and Society and Brown’s Climate Solutions Initiative.

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Megan Hall: Welcome to Possibly, where we take on huge problems like the future of our planet and break them down into small questions with unexpected answers. I’m Megan Hall. 

Today we’re answering a question from listener Alexandra Hahn, who saw something a bit unusual: 

Alexandra Hahn: I wrote to you guys, because last spring, I saw a bunch of dead fish in a river downtown. And I was wondering what they were doing there, what kind of fish they were? How did they die? 

Megan Hall: Reporter Will Malloy talked to Possibly’s co-founder Professor Stephen Porder to tell us what’s going on. Hi Will!

Will Malloy: Hi Megan! 

Megan Hall: So, why were there a bunch of dead fish in the river? 

Will Malloy: There’s actually a name for the phenomenon Alexandra noticed – it’s called a fish kill. A fish kill is when a large number of fish die over a short period of time in the same area. 

Megan Hall: That sounds smelly! But why does that happen? 

Will Malloy: Like people, fish need oxygen to live – only instead of getting it from the air, like us, they breathe oxygen gas that’s dissolved in the water.

Stephen Porder: So they are actually breathing oxygen underwater the same way we’re breathing oxygen out here in the air. 

Will Malloy: And basically, a fish kill can happen when the amount of oxygen in the water drops and there isn’t enough for fish to survive. 

Stephen Porder: If you consume all that oxygen in the water, the fish will die. Just as if you consume all the oxygen in the air. We will die.

Megan Hall: Ok, that makes sense. But why would there be less oxygen in the water all of a sudden? 

Will Malloy: It’s a bit of a complicated process, but one thing that can take oxygen out of the water is actually dead seaweed and algae decomposing. 

Stephen Porder: If a dead piece of seaweed falls to the bottom of the bay, it gets decomposed, that consumes oxygen. 

Will Malloy: You can think of it like the opposite of photosynthesis – when plants photosynthesize, there is a reaction that produces oxygen. When dead stuff breaks down, there are reactions that use up oxygen. 

Megan Hall: Ok, sure, but isn’t stuff dying in the bay all the time? 

Stephen Porder: So there’s always algae and seaweed in the water. But in order to get a fish kill, you need sort of a burst of growth of stuff followed by a die off

Will Malloy: So if there’s a surge of more life – more seaweed, more algae – after a little bit, you’ll actually see more death as some of these plants die, which eats up a bunch of oxygen. 

Megan Hall: What causes this “surge of life’?

Will Malloy: It can come from a lot of factors, but often it comes after something like a big rainstorm. 

Megan Hall: Why would rain create more algae and seaweed in the water? 

Will Malloy: I wasn’t kidding when I said it was complicated! When there is a big rainstorm, the rain can wash fertilizer off of people’s lawns and down into storm drains.  

Stephen Porder: If there’s too much rainfall, our sewage system can’t handle it. 

Will Malloy: Meaning that the sewers overflow. And when some sewers overflow, they can spill out into bodies of water, like rivers, bays, or even the ocean. And that means all that fertilizer and the rest of our sewage ends up in the water. 

Stephen Porder: And so you got a flush of sewage, all of that is nutrients. And those nutrients provide that bursts of life, of growth of stuff in the water

Megan Hall: And after that fertilizer encourages more stuff to grow in the water, those plants eventually die, which eats up the oxygen that fish need to live? 

Will Malloy: Exactly! Now, this doesn’t happen every time it rains. I mean, the conditions have to be just right,  but in general, it’s one big chain reaction that starts with a bunch of rain and ends with a bunch of dead fish. 

Megan Hall: So, what can we do to prevent this from happening?

Will Malloy: In your own garden, try planting things that don’t need fertilizer. And in general, cities and towns can create more green spaces to break up paved surfaces. That way, stormwater can go into the soil instead of the bay. 

Megan Hall: Thanks, Will! That’s it for today. For more information, or to ask a question about the way your choices affect our planet, go to thepublicsradio.org/possibly. Or subscribe to us wherever you get your podcasts. 

You can also follow us on Instagram, Facebook, LinkedIn or X at  “askpossibly”

Possibly is a co-production of The Public’s Radio, Brown University’s Institute for Environment and Society and Brown’s Climate Solutions Initiative.

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