2024 Olympics - Seine Water Quality
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2024 Olympics - Seine Water Quality

Disclaimer and Copyright Notice

 

We point anyone using or referencing the data released under the Fluidion Open Data Initiative, regardless of the medium used (print, web, video, social media), that respecting our copyright is not an option but a legal obligation, including proper attribution of the data following our specific requirements. Find the full details at the bottom of this page.

Technical note

 

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Table of contents

Fluidion's 2024 Olympics Open Data Initiative

 

 

FLUIDION ALERT LAB One Alexandre III sml 

 

We believe that monitoring water quality is essential for ensuring safe water access for recreational and competitive activities. With the 2024 Olympics set to conduct its opening ceremony and host several water-based events in the Seine River, addressing water quality concerns has become crucial. As a leader in rapid microbiology instrumentation and a deep-tech company grounded in solid scientific expertise, Fluidion has developed the necessary technology and field knowledge to deliver up-to-date water quality insights for the Olympic venue.

 

The water quality data presented on this page are collected and reported by Fluidion in a dedicated effort to provide accurate, current, and accessible information on the Seine River's condition leading up to and during the Olympic events. This effort is self-funded and fully independent.

 

These data and associated graphs are regularly updated. These results incorporate samples gathered and analyzed by Fluidion's team and by trained community scientists under Fluidion's guidance. Sampling occurs at the Alexandre III bridge in Paris, the designated location for some of the 2024 Olympic aquatic events. We also collect samples at other locations, such as upstream of Paris on the Seine and Marne rivers.

 

Last three measurements (Seine River, Alexandre III bridge)

 

 

 

The dashboard below displays the results for the latest three days, illustrating both the values obtained using standard laboratory techniques and those provided by Fluidion® ALERT rapid microbiology instrumentation. Whenever multiple measurements were performed on a single day, their geometric mean is shown.

 

Standard culture-based laboratory methods for measuring E. coli, such as the most probable number method and membrane filtration and plating, cannot differentiate between individual bacteria and those clumped together in aggregates. In contrast, ALERT technology can accurately quantify both planktonic (free-floating) bacteria and those within aggregates. This capability provides a vital additional dimension of information for risk assessment, as fecal particles or aggregates loaded with pathogens and indicator bacteria can represent a substantially higher health risk. Thus, ALERT measurements report both planktonic and comprehensive E. coli counts.

 

Following the dashboard presenting the latest results, we provide graphs that plot the data across the entire intensive sampling period for 2024, beginning April 8, in both linear and logarithmic scales. Additionally, 95% confidence intervals are included to convey the uncertainty associated with the data. Relevant environmental factors, such as rainfall and river discharge, are also provided to aid in data interpretation.

 

Further details on how these data were collected can be found in the Methodology section below.

 

The data presented here undergo quality control by Fluidion scientists, which may lead to occasional delays in data availability. Any errors detected in the data are unintentional and corrected immediately.

 

The Fluidion Water Quality Color Chart

 

 

 

 

With our water quality color chart we are presenting water quality data in a new way that is highly visual and allows the reader to quickly grasp what the water quality was on any given day, without the need to study complicated charts or graphs. Our water quality color chart below shows water quality in shades of blue (when the E.coli count is below the Triathlon safety limit of 1000 E.coli/100 mL) or red (when the E.coli count is above the safety limit).

 

We also show the results obtained from two distinct ways of counting the bacteria using the Fluidion ALERT technology [for a brief methodology note please click here]. On the left we display the safety indication based on the comprehensive E.coli count, which counts all E.coli bacteria present in the sample (whether free floating or aggregated onto larger fecal or sedimant particles). On the right we display the safety indication based on the planktonic E.coli count (counting free-floating individual bacteria and small aggregates <5µm only).

 

Days when the water qualilty is acceptable as per the World Triathlon limit are shown in a shade of blue and are decorated with a chack mark ✓. On the other hand, days when water quality is unacceptable are shown in red and marked with a ✗ sign.

 

Seine Water Quality Colorchart

 

For example, on Wednesday July 31st, when the women's and men's World Triathlon events were held, the water quality was acceptable by the planktonic E.coli count, but was above the limit by the comprehensive E.coli count.

 

This creates a contradiction, and for good reason. The answer is in the fact that the Seine river contains large quantities of aggregate-bound bacteria that are invisible to the laboratory methods and not included in the planktonic count. But the comprehensive count from our ALERT instrument accounts for all the E.coli present, including those on aggregates. It is easy to understand how the comprehensive count provides a more accurate assessment of risk: bacterial aggregates, such as E.coli-rich fecal or sediment particles. are powerful and resilient infectious vectors, in a way like vessels that transport and protect the E.coli bacteria and all the associated pathogens. The currently approved lab methods are inadequate for risk assessments in waters containing large amounts of aggregate-bound E.coli. This is the case of many urban rivers that are affected by sewer overflows.

 

For details about the water quality prior to and during the Olympic Triathlon, please click  here

 

 

All results (starting April 8, 2024)

 

 

 

The following figures provide the time-series data since early April, when our high-frequency monitoring efforts started. E. coli concentrations obtained from ALERT instrumentation (comprehensive - red triangles; planktonic - green inverted triangles) are juxtaposed with the MPN laboratory E. coli concentration (gold circle).  Local environmental factors are shown as well: daily precipitation (light blue line) and mean river discharge (dashed blue line). Standard deviation and 95% CI are shown as colored bands. Whenever multiple measurements were performed on a single day, their geometric mean is shown. 

 

The first time when the Austerlitz undeground water storage tank was operationally used is shown as a vertical gray line (during the rain event on June 17-18, 2024). The information regarding the Austerlitz tank usage was obtained from this page, maintained by the City of Paris.

 

Figures are plotted using both linear and logarithmic scales for the bacterial concentration axis. The linear scale provides better visibility of the water quality exceedances., while the logarithmic scale is typical for analyzing bacterial concentration data, which is best modeled by a log-normal distribution.

 

The juxtaposition of environmental factors allows observing their effect on water quality. This is particularly true of rainfall, which can generate river pollution by combined sewer overflows.

 

Thresholds

The horizontal solid red line represents 1000 E.coli/100mL, while the dashed line represents 500 E.coli/100mL. These correspond to the guidelines for good and, respectively, very good inland water quality for swimming, published by the World Triathlon.

 

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Focus on the latest three weeks of data

 

 

 

The latest three weeks of data are highlighted in the following graphs, allowing a focus on the most recent trends that were observed. The data update automatically. Figures are plotted using both linear and logarithmic scales for the bacterial concentration axis. Whenever multiple measurements were performed on a single day, their geometric mean is shown. 

 

The E. coli concentrations obtained from ALERT instrumentation (comprehensive - red triangles - and planktonic - green inverted triangles) are juxtaposed with the MPN laboratory E. coli concentration (gold circle). The error bars represent the 95% confidence interval for each measurement. The different data series were slightly offset for improved graph legibility.

 

Thresholds

The horizontal solid red line represents 1000 E.coli/100mL, while the dashed line representes 500 E.coli/100mL. These correspond to the guidelines for good inland water quality published by the World Triathlon.

 

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Women's and Men's Paratriathlon (September 2, 2024)

 

 

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September 2, 2024 (23:50 pm)

 

We are excited to announce that our measurements performed on the 10:00am samples, collected right at the end of the Paratriathlon event at the Alexandre III bridge, provided water quality results that are acceptable according to the Water Triathlon safety thresholds, for both the planktonic count (geometric mean: 316 E.coli/100 mL) and the comprehensive count (705 E.coli/100 mL).

 

This demonstrates that obtaining acceptable water quality in Paris is not a utopia, but that the right conditions need to be met - in this case, sunny weather, low river discharge and lack of disturbances from boat traffic. This allows for UV disinfection and sedimentation to take place, which reduces the planktonic and, respectively, the comprehensive count. This conclusion is reinforced by the Seine and the Marne rivers being significantly more polluted at their confluence at Alfortville, than at the downstream Alexandre III competition site.

 

All in all, this shows that good water quality is possible under the perfect conditions, and provided very careful monitoring to ensure the safety of users. So, could public swimming in Paris become a reality for next year? An optimistic thought for the end of the 2024 Olympics !

 

 

September 1, 2024 (20:20 pm)

 

Today's scheduled events were postponed to tomorrow, which was the correct decision in view of the poor water quality results that we observed. So, how about tomorrow? What do today's tests tell us?

 

The situation is a little better than yesterday, but not by a lot, unfortunately. E.coli levels recorded this morning at 9am at the Alexandre III bridge in Paris, which is the Olympic venue for the Paratriathlon, were of 868 E.coli/100 mL (planktonic count), which is just under the threshold of 1000 set by the World triathlon. However, the river continues to be highly polluted by E.coli-rich fecal particles, which cannot be measured using the standard methods used by the organizers. When taken into account, these raise the comprehensive E.coli count to 2119 E.coli/100 mL, which is over twice the limit, suggesting unsafe conditions.

 

Furthermore, both the Seine and Marne rivers just outside of Paris are also quite polluted. At Alfortville, just upstream of their confluence, the Seine river measured 1356 (planktonic) and 11,000 (comprehensive) E.coli/100 mL, whereas the Marne river (a smaller tributary) measured 565 (planktonic) and 2119 (comprehensive) E.coli/100 mL. This suggests that the City of Paris is polluted from sewer overflows occuring upstream, primarily in the Seine river, which cannot be cleaned up easily.

 

Tomorrow's event start under the threat of poor water quality. We can be almost confident that, should the events proceed tomorrow, the athletes will be competing in the same type of water that is in a "gray-zone" safety-wise. We hope their immune systems will be strong !

 

 
August 31, 2024 (20:00 pm)

 

We received the analysis results from that water samples collected earlier today, and they are unfortunately not promising. The planktonic count came in at 1012 E.coli/100 mL, just above the World Triathlon threshold for acceptable water quality. The comprehensive count, on the other hand, registered at 5173 E.coli/100 mL, a factor of 5 higher than the acceptable limit. This means that the river is quite loaded with E.coli-rich fecal and sediment particles, and today's water quality readings raise very serious questions about the safety of the river for tomorrow's scheduled Paratriathlon events. We know that the pollution with fecal particles, that we are witnessing now, takes significant longer to recover.

 

This pollution is the result of the rainfall yesterday (10.3mm), which has created a series of CSOs in the Seine and Marne rivers upstream of Paris, and possibly within the City of Paris as well. Since this was only a moderate rain event, smaller than the ones that disrupted the Olympic Opening Ceremony and Triathlon back in July, and since it came after a long dry period, we were expecting that the Austerlitz storage tank might have contained the pollution. Unfortunately, that does not seem to be the case.

 

 We will be monitoring the event tomorrow morning. so stay tuned. We are wishing that the organizers will take the measures required to protect the health of the athletes.

Men's Marathon Swim (August 9, 2024)

 

 

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August 9, 2024 (21:00 pm)

 

We received the results from four water samples taken earlier today during the Men's Marathon Swimming Event. The samples were collected at 7:30 AM, 8:30 AM, 9:00 AM, and 9:30 AM, yielding the following planktonic E.coli counts (per 100 mL): 243, 496, 371, and 496. All these values were below the World Triathlon threshold of 1000 E.coli/100 mL. However, comprehensive counts indicated slightly degraded water quality, with measurements of 867, 4132, 1338, and 650. Two of these samples exceeded the safety threshold, with a peak of contamination occurring shortly after the event began.

 

The geometric mean for all samples collected during the event was 386 E.coli/100 mL (planktonic) and 1329 E.coli/100 mL (comprehensive), indicating that the water quality remained in a risk-prone "gray zone." The water was contaminated with fecal E.coli-rich particles at certain points, reaching levels up to four times the World Triathlon threshold.

 

Congratulations to the athletes who competed, and let's hope that everybody stays healthy!!!

 

August 8, 2024 (22:00 pm)

 

The results from today's samples, collected during and just after the Women's Marathon Swimming event, have shown consistent good water quality for both planktonic and comprehensive E.coli counts, with geometric mean at 297 E.coli/100 mL (planktonic) and, respectively, 705 E.coli/100 mL (comprehensive).

 

The MPN laboratory count will arrive tomorrow morning, but based on today's samples so far, and provided stable weather conditions and no accidental pollution, water quality should be good for Men's Marathon Swimming event tomorrow! We'll be watching !

 

 

Women's Marathon Swim (August 8, 2024)

 

 

 

August 8, 2024 (22:00 pm)

 

The results from the competition this morning  have arrived, and are very reassuring. The planktonic and comprehensive counts for all four measurements performed showed values below the World Triathlon upper limit of 1000 E.coli/100 mL. This proves that the combination of good weather, low river discharge, and limited sewage discharge can actually create safe conditions for swimming in the Seine river. Attentive monitoring is key, as we have seen that this equilibrium is very unstable and water quality can be quite dynamic. 

 

Time                  Planktonic (E.coli/100 mL)                  Comprehensive (E.coli/100 mL)

07:30am            139                                                       867

08:36am            496                                                       867

09:30am            425                                                       650

10:15am             267                                                        506

 

August 8, 2024 (7:00 am)

 

The results from the second sample from August 8 (collected 12:22pm) are in, and are good: planktonic count 308, comprehensive count 642 E.coli/100mL This confirms the results published last night, bringing the geometric mean for planktonic E.coli to 338, and the comprehensive mean to 483 E.coli/100 mL., and indicate that, in the current good weather stability conditions, the results are likely to be good this morning as well. We will have that confirmation a little bit later !

 

August 7, 2024 (23:50 pm)

 

The results have arrived from the 11:50am sample today, and are rather reassuring - looks like water quality is finally stable, with low planktonic and comprehensive counts (371 and, respectively, 364 E.coli/100 mL - the inversion is just a matter of noise in the data). This suggests that sunny weather, low river discharge, lack of rain, and the expensive capture infrastructure built for the Games finally got it right, and the water seems to have been of good quality today!

 

We will have results arriving from one additional sample later in the night, but given the stable weather and the calm river, we do not expect it to be too different.

 

And you know that you can count on us for sampling during the event tomorrow! Watch the data coming.

 

 

 

 

 

Olympic Mixed Relay Triathlon (August 5, 2024)

 

 

 

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August 5, 2024 (23:30 pm)

 

We have the results for the 9:12 AM sample collected during the Olympic Mixed Relay Triathlon event. The planktonic count came in at 418 E.coli/100 mL, and the comprehensive count was at 1001 E.coli/100 mL. The laboratory MPN count is expected to be just slightly higher than the planktonic count, and we'll update with that result in the morning. These results indicate marginally acceptable water quality according to the World Triathlon safety threshold. It's a notable milestone, though the precise count of 1001 E.coli/100 mL serves as a reminder that this discussion is far from being over!

 

 

August 5, 2024 (21:31 pm)

 

We have just received the results from the measurement performed at 12:00pm today, which is indicative of the water quality at the Alexandre III bridge in Paris, just a couple of hours after the end of the Olympic Mixed Relay. The planktonic count came in at 506 E.coli/100 mL, which is below the World Triathlon threshold of 1000 E.coli/100 mL. But again, the comprehensive count was high, at 1338 E.coli/100 mL, which is above the limit. This is relatively consistent with what was measured yesterday, and places the water quality in the gray zone, with contradicting risk indications provided by the planktonic and comprehensive counts.

 

We will soon provide results from the morning sample, collected at 9:12am during the actual Mixed Relay Triathlon. A small communication issue slowed down the data retrieval, but it is coming in now and it will be posted soon. The laboratory MPN count from this morning's sample will only be availble tomorrow and it will be posted as an update to this live water quality blog.

 

Congratulations to the athletes, who were at their best this morning!

 

August 5, 2024 (07:59 pm)

 

It is happening ! The Fluidion team is all set to measure water quality for the 2024 Olympic Mixed Relay Triathlon, starting in just five minutes! Wishing all athletes an amazing competition and safe waters! 

 

August 4, 2024 (23:59 pm)

 

We're sharing today's (August 4, 2024, 2:15 PM CET) latest water quality measurements for the venue of tomorrow's Mixed Relay Triathlon.

- Planktonic E.coli Count: 228 E.coli/100 mL (well below the World Triathlon threshold of 1000 E.coli/100 mL)

- Comprehensive E.coli Count: 1862 E.coli/100 mL (continues to be high)

- The laboratory MPN count would likely align closer to the planktonic count.

 

These results place us once again in the same gray zone observed during the Triathlon events on July 31st. While the risk associated with presence of planktonic E.coli is low, there is a significant risk related to E.coli-rich fecal or sediment particles floating in the water column. Since these E.coli bacteria are not visible to the standard laboratory methods, this risk is not captured and is therefore unknown.

 

Today's findings further highlight the inadequacy of the current regulatory methods to assess public health risk in waters like the Seine, which contain large amounts of suspended matter carrying clumps of E.coli bacteria and associated pathogens.

 

Click on this link to understand the difference between the laboratory count, and the planktonic and comprehensive counts we provide. Click here to understand the science.

 

August 3, 2024 (22:45 pm)

 

We have the results for today's measurements, started at 12:50pm. The water shows a significant improvement compared to yesterday: the planktonic count dropped to 704 E.coli/100 mL, which is below the Worldf Triathlon safety limit of 1000. However, the comprehensive E.coli count remains above the limit, at 1563 E.coli/100 mL, proving that E.coli-rich sediment and fecal particles are still present in the water column.

 

As we are writing this, it is raining in Paris. We hope that water quality will have sufficient time to improve by Monday morning. Our next sets of samples will be collected tomorrow, at multiple times throughout the day, at the Olympic Triathlon venue. Will keep you posted with what we learn !

 

August 3, 2024 (8:00 am)
 

We have just posted the data from our August 2 samples at Alexandre III bridge. We measured a planktonic E.coli count of 3431 E.coli/100 mL, and a comprehensive E.coli count of 11100 E.coli/100 mL. These values are very high, indicating substantial sewage pollution, and the river is likely to stay polluted for a few days. Not clear yet what that means for the Mixed Relay Triathlon event scheduled for 8am on Monday, August 5.

 

What is also notable is that the E.coli concentrations in the Seine and Marne rivers just upstream of Paris (measured upstream of their confluence at Alfortville), while showing high pollution, were significantly lower than what was measured at Alexandre III, indicating that the likely source of pollution was within the City: Seine Alfortville (1356 E.coli/100 mL planktonic, 5082 comprehensive count), Marne Alfortville (2488 E.coli/100 mL  planktonic, 5968 comprehensive count).

 
What can we currently say ?

The observed pattern seem to confirm major sewage pollution originating within the City walls, which should normally have been retained by the Austertlitz sewage capture infrastructure. The 12mm rainfall on August 1st, which came on the back of multiple rainy days, likely overcame the capacity of the basin again, leading to its overflow. While we have no confirmation from the authorities that this is indeed the case, this is what the available data indicate.

 

We are currently seeing a trend similar to that observed prior to the regular triathlon, where heavy rain during the opening ceremony created a resilient sewage pollution pattern that lasted for days, leading to the postponement of the men's triathlon. Currently, the data suggests that the observed pollution combines upstream components and sewage overflow from within Paris.

 

The data will need to be monitored very tightly, and the decision about opening the Mixed Relay Triathlon event on Monday will likely not be easy.

 

 

 

 

 

 

Olympic Men's and Women's Triathlon (July 31, 2024)

 

 

 

ALERT LAB Olympic Alex III

August 1, 2024
 

A short update to report that the MPN laboratory results obtained using the EPA-approved IDEXX Colilert Quantitray method, provided this morning a laboratory value of 435 MPN E.coli/100 mL for the sample collected at 11:40am. The ALERT LAB planktonic concentration measured on this sample came in at 641 E.coli/100 mL, with the MPN and ALERT measurements had overlapping confidence intervals.

The additional 11:40am measurement was added to the table below. This new datapoint does not change much the geometric means (planktonic: 660 E.coli/100 mL, comprehensive: 2261 E.coli/100 mL), nor does it change the interpretation of the data, provided below.

 

July 31, 2024
 

The Triathlon finally took place today, with both women's and men's competitions happening on the same morning ! We sampled throughout the event, as you may by now expect from Fluidion, just upstream of the Alexandre III bridge where the competition was held ! Samples were collected and analyzed using multiple ALERT Lab instruments onsite, at the following times:

 

 

- 8:05am - just after the start of the women's swimming leg

- 11:30am - just after the end of the men's swimming leg

- 12:50pm - just after Alex Yee won the Gold

An additional sample was brought to the lab for laboratory MPN analysis using EPA-approved methods, and for a control ALERT measurements of planktonic and comprehensive concentrations. Those results were only available on August 1st, see update above.

 

The detailed results are shown in the table below. Overall, the planktonic counts for all three samples were below the Triathlon thershold of 1000 E.coli/100 mL, with a geometric mean at 666 E.coli/100 mL, whereas the comprehensive counts provided a geometric count of 2203 E.coli/100 mL. The tendency was decreasing for the planktonic E.coli levels throughout the competition, but on the contrary, the comprehensive E.coli counts showed the opposite tendency, increasing from 1518 in the morning to 3538 E.coli/100 mL in the earlly afternoon. The comprehensive count for every sample was significantly higher than the 1000 threshold, with a geometric mean measured at 2203 E.coli/100 mL. This is more than a factor of 2 higher than the triathlon limit for acceptable water quality.

 
Note:

The laboratory MPN count will be available in the morning. We also sent samples for DNA analysis of various bacterial and viral human markers. We will be reporting on that when the results come in.

 
What do these results really mean ?

The water quality was in an unknown, and potentially unsafe, zone prior to and throughout the Triathlon competition. The planktonic E.coli count (free floating bacteria) was just below the acceptable threshold, yet particles of fecal and/or sedimentary origin, containing large quantities of E.coli and potentially other pathogens, were present in the water, raising the E.coli comprehensive count to significantly above the "acceptable quality" threshold.

 

This suggests that the official results significantly underestimate the real E.coli count, and the actual risk for the athletes is not managed and remains an unknown. We can nevertheless confidently say that the risk is substantially higher than what the laboratory counts suggest. We hope that none of the Triathlon competitors will become ill following the exposure to the Seine water in this intermediary and possibly unsafe state. Congratulations go to them for an amazing competition, despite the uncertainty around water quality which must have been highly disruptive!

 

 

 

 


July 30, 2024 (11:30pm CET)

New measurements have just come in, confirming our earlier data:

- Planktonic E.coli count: 868 E.coli/100 mL, consistent with the previous sample.

- Comprehensive E.coli count: 2870 E.coli/100 mL.

 

Geometric means for today are 867 E.coli/100 mL (planktonic) and 3444 (comprehensove). The laboratory MPN number will be available later tonight and is expected to be slightly higher than the planktonic count.

 

We're in a complex situation: the comprehensive E.coli count suggests a significant health risk, while the planktonic count, which measures free-floating bacteria and small aggregates (<5µm), is below the Triathlon's 1000 E.coli/100 mL acceptable threshold.

 

It's important to note that the comprehensive count includes all E.coli bacteria, even those attached to fecal or sediment particles, which are not detected by standard methods. Today, the Seine has a significant presence of particle-bound E.coli, and the associated health risk is uncertain as it isn't accounted for in current epidemiological studies.

 

Stay informed as we continue to monitor the situation closely.


July 30, 2024 (7:15pm CET)

Our first water quality results from this morning (7:20am) are in and were quality checked. The planktonic (free-floating) E.coli count is at 867 E.coli/100 mL, which is just under the Triathlon threshold of 1000. However, the comprehensive count, which includes bacteria attached to fecal or sediment particles, remains high at 4132 E.coli/100 mL, similar to yesterday's results.

We have additional samples currently being analyzed, and we will share these results on our Open Data Initiative website later tonight. The laboratory MPN count will be available early morning tomorrow.

From a risk perspective, we're in a gray zone. While the planktonic count is below the Triathlon limit, the large concentrations of E.coli aggregated on particles (which cannot be detected by the standard laboratory methods but can be measured with Fluidion ALERT technology) result in a total count that is nearly four times over the limit.

We will update our reporting as new data comes in tonight. Stay tuned!

 

July 30, 2024 (8:00am CET)

As expected given the data we reported yesterday, the men's Triathlon event was postponed to tomorrow. We congratulate the organizing committee for the courageous decision to put the competitors' health upfront, in an environment where there is a lot of pressure to proceed. Our teams will be sampling multiple times today, so again we will be the first to report reliable water quality data for the 2024 Olympics. Watch this website often!

 

We are hopeful that the sunshine and lower river discharge will result in a drastic improvement in Seine water quality, but as always, in (our) data we trust !

 
July 29, 2024

We were the first to report on poor water quality in the Seine on Monday, July 29, 2024, less than a day prior to the Olympic Men's Triathlon was scheduled to begin. The Fluidion team performed two independent measurements in the late morning (11:54 AM) and early afternoon (12:36 PM) at the Olympic Triathlon venue (Pont Alexandre III). Both sets of results have been thoroughly quality-checked and are validated.

Unfortunately, the data reveal that water quality in the Seine has not improved since Sunday. The counts of planktonic (free-floating) E.coli bacteria measured today were 1356 and 2176 E.coli/100 mL (geometric mean: 1718), whereas the comprehensive counts (including E.coli clumped onto fecal particles or sediment) were 5082 and 3538 E.coli/100 mL, respectively (geometric mean: 4240). The laboratory MPN count is expected to fall between these values, and will be available very soon.

All measured values exceed the World Triathlon's quality limit of 1000 E.coli/100 mL. While there was a slim chance that water quality might have improved by the morning, based on the data and our eight years of Seine river sampling experience, the likelihood of meeting the required standards by 8am today was relatively low.

Hopefully, sunny weather will improve things in the coming days!

 

 

 

Olympic opening ceremony (July 26, 2024)

 

 

FLUIDION ALERT LAB One Alexandre III sml 

On July 26, 2024, the Fluidion sampling team conducted water sampling throughout the day, beginning in the morning and continuing through the Opening Ceremony of the 2024 Olympics. Samples were collected at the Alexandre III Bridge Olympic venue and immediately analyzed using ALERT Lab instruments. This event showcased the incredible value of ALERT portable instruments, which enable automated onsite water quality measurements, with accurate results available online within a few hours. It also allowed our team to enjoy the breathtaking show on the Seine River, a spectacular performance that captivated the entire city. Congratulations to the 2024 Olympics organizers for an extraordinary accomplishment!

 
What did the data reveal?
Weather context:

Following light showers the previous night, the weather was mild during the day until the ceremony began. Then, heavy rain started and persisted until after midnight with minor pauses, resulting in the second heaviest daily rainfall recorded in Paris since our 2024 monitoring began (early April).

 
Planktonic E.coli count
Morning measurements:

On the morning of July 26, planktonic E.coli concentrations (free-floating individual bacteria) were near the World Triathlon threshold of 1000 E.coli/100mL, with measurements of 980 at 9:24 AM and 1019 at noon.

During the opening ceremony:

The E.coli concentration significantly decreased to as low as 39 E.coli/100 mL during the Opening Ceremony, likely due to the initial dilutive effect of the rainfall. The effects of E.coli pollution will likely become evident several hours later.


Comprehensive E.coli count

The comprehensive count includes E.coli clumped together (aggregated) onto fecal particles and sediment. Unlike planktonic E.coli, these levels remained consistently above the World Triathlon threshold of 1000 E.coli/100 mL throughout the day. This consistency is likely due to sediment resuspension caused by increased current and boating activity during the ceremony.

 
Conclusion

While planktonic E.coli levels (free-floating individual bacteria) dropped well below the World Triathlon limits during the 2024 Olympic opening ceremony, comprehensive E.coli counts (which include bacteria aggregated onto fecal or sediment particles) stayed high, and were consistently above the 1000 threshold. Here we are witnessing complex water science at work, with a subtle interplay between rainwater dilution and sediment resuspension. This dataset underscores the importance of timely, onsite data collection and the complexity of managing risk in urban environments. Fluidion ALERT technology illuminates areas where traditional culture-based laboratory methods fall short, generating new water science and providing profound insights into water safety.

 

Molecular DNA analyses

 

 

 

We also conduct molecular analyses of our samples to measure the quantity of E.coli DNA and detect the presence of HF-183 bacteroides, a human-associated sewage marker. These measurements are presented both as planktonic and comprehensive counts, showing trends similar to our culture-based ALERT measurements.

 

The molecular data confirms that the observed pollution is linked to human sewage, ruling out sources like agriculture or animal excrements (dogs, birds). Additionally, it reveals significant quantities of aggregate-bound human sewage components (clumped together on larger particles) rather than in free or planktonic form.

 

Traditional laboratory methods often overlook these aggregated bacteria, failing to capture the associated health risks in official assessments. In contrast, Fluidion ALERT technology and molecular methods offer comprehensive techniques that are sensitive to these aggregated bacteria, providing a more accurate picture of water quality and public health risks.

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Laboratory MPN vs. Planktonic vs. Comprehensive E.coli counts

 

 

 

On this page, we are comparing different methods for measuring E.coli: the laboratory most probable number (MPN) count, the planktonic count, and the comprehensive count. So, what is the difference?

 

The best way to explain this is to use an analogy. Imagine that instead of a river carrying E.coli, we are dealing with a road in a big city, and we need to determine how many people are on the road. We ask three police officers, let's call them L, P, and C, to figure out how to count these people.

 

L takes a helicopter and hovers above a big intersection, seeing something like the picture below. L will count all the pedestrians accurately but has no way of knowing how many people are inside each car or bus. So, L counts each car and bus as one (the driver, let's say).

 

P proceeds differently by installing barriers on each road, so cars and buses cannot proceed, and only pedestrians and perhaps small scooters can get through. P then counts all the pedestrians and scooters.

 

Finally, C goes out into the middle of the intersection, counts every pedestrian, and also stops every single vehicle to count the number of people inside.

 

Which police officer got it right ? It is clear that C provides the correct count. L and P will provide similar counts, which are significantly lower than those provided by C, particularly if there are many cars and buses carrying multiple people each.

 

Now, let's translate this metaphor to our context. The people we need to count are the E.coli bacteria,  the cars are small bacterial aggregates carrying 1-5 bacteria, and the buses are large aggregates carrying up to 50 bacteria. The police officers are the different methods: L stands for Laboratory MPN,  P stands for the Planktonic, and C for Comprehensive Here's the revised explanation:

 

Which method got it right? It is clear that the Coprehensive method provides the correct count. The Laboratory MPN and Planktonic methods will provide similar counts, which are significantly lower than those provided by the Comprehensive method, particularly if there are many small and large aggregates carrying multiple E.coli each.

 

 

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Science explained

 

 

 

Our article "Addressing Underestimation of Waterborne Disease Risks Due to Fecal Indicator Bacteria Bound in Aggregates" was recently uploaded as a bioRxiv preprint due to the urgency and importance of its findings, highlights significant limitations in traditional methods for detecting fecal indicator bacteria (FIB), such as E. coli, which fail to account for bacteria bound in aggregates, leading to substantially underestimated waterborne disease risks. ALERT technology, developed by Fluidion, is an automated rapid method for measuring both planktonic (free-floating) and comprehensive (including aggregate-bound bacteria) E.coli counts. In certain waters, the comprehensive measurement can provide much higher bacterial counts than traditional methods. The study underscores the need to update global water safety regulatory frameworks to include more accurate testing methods and automation, enhancing water quality monitoring and public health protection, and enabling monitoring in resource-limited or remote locations, which do not have access to laboratory services.

 

Key points:

 

Limitations of Traditional Methods: 

The study highlights significant limitations in traditional culture-based methods for detecting fecal indicator bacteria (FIB), such as E. coli. These methods fail to account for bacteria bound in aggregates, leading to substantial underestimation of waterborne disease risks. This underestimation can severely skew public health risk assessments and highlights the limitations of the current regulatory frameworks to protect water users in waters containing fecal or sediment particles, such as urban rivers subject to combined sewer overflows.

 

ALERT Methodology: 

The research uses ALERT as a new technology for automated rapid method for comprehensive quantification of culturable bacteria. ALERT can measure both planktonic (free-floating) and comprehensive bacteria (which are bound in aggregates, such as on fecal or sediment particles), providing more accurate risk assessments. This method revealed that aggregate-bound bacteria are present in much higher quantities than detected by traditional methods, creating a major and currently non-monitored risk. This risk is particularly highlighted in the water of the Seine river in Paris, venue for the 2024 Olympic Triathlon and Marathon swimming events.

 

Implications for Water Safety: 

The study's findings underscore the need for updating global water safety regulatory frameworks to include methods that can accurately measure comprehensive E.coli counts, including aggreagate-bound bacteria. Incorporating such comprehensive methods can improve water quality monitoring, particularly in recreational and agricultural water uses, but also for drinking water assessment in remote locations without managed distribution networks. ALERT can better protect public health by providing more accurate risk assessments.

 

 

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Methodology

 

 

 

Samples were collected near the Alexandre III bridge (GPS coordinates: 48.863248, 2.314508) using standard grab sampling techniques, and then either processed onsite or transported to the laboratory in a cooler with ice. In the laboratory, samples were processed immediately.

 

Rapid microbiology ALERT data were obtained using Fluidion® ALERT LAB portable E. coli analyzers. Samples were analyzed as-received (to measure the comprehensive E.coli concentration) but also after 5µm filtration (to measure the planktonic E.coli concentration). 95% confidence intervals (CI) were obtained from peer-reviewed published scientific literature.

 

Laboratory most probable number (MPN) measurements were performed using the EPA-approved IDEXX Colilert-18 Quantitray-2000, following standardized protocols. Samples were measured as-received and also with a dilution of 1:100, to extend the measurement range of the MPN method. Dilutions were performed using sterilized glassware and autoclave-sterilized de-ionized water. The MPN laboratory measurement values and 95% CI were obtained from the IDEXX Quanti-Tray®/2000 MPN Table (per 100 mL) with 95% Confidence Limits.

 

Historical rainfall data in Paris (measured at the Montsouris station) were obtained from: https://prevision-meteo.ch/climat/mensuel/paris-montsouris. Historical Seine River discharge data (measured at the Austerlitz bridge in Paris) were obtained from: https://www.hydro.eaufrance.fr/stationhydro/F700000103/fiche

 

Open data availability

 

 

 

All data available here belong to Fluidion and are protected by copyright. Any use of the data must provide a clear reference to this website and include the following text: "Data provided courtesy of the Fluidion Open Data Initiative". Whenever multiple measurements were performed on a single day, their geometric mean is shown. The data presented on this page are available for download in various plain text and open source formats, shown below. Fluidion assumes no responsibility for any specific usage or any decisions made that are based on these data. Any use of the data is under the sole responsibility of the end-user.

 

Data formats:

- Plain text PDF

- Comma-separated values (CSV)

- Tab-separated values (TSV)

 

Disclaimer and Copyright Notice

 

 

 

It has come to our attention that some major news outlets have infringed on our copyright and falsely attributed our data to other sources. It is regrettable that journalistic standards, much like those in science, are not always upheld. Due to these issues, we have decided to move our copyright notice to the top of the page, where it was previously located at the bottom.

 

To clarify: Fluidion is an entirely independent organization, with no affiliations with the City of Paris or the 2024 Olympics committee. We stand by our Open Data Initiative, rigorous scientific practices, and ethical standards. The data we provide are our property, shared transparently as part of our Open Data Initiative. These data are protected by copyright and require proper attribution as specified below.

 

The water quality data presented on this page are collected and reported by Fluidion as a best-efforts attempt to offer accurate, timely, and accessible information about the Seine River quality leading up to and during the Olympic events. The data come from samples collected by Fluidion personnel and trained citizen scientists under Fluidion’s supervision. Samples are taken from the Seine at the Alexandre III bridge in Paris, the site of the 2024 Olympic events.

 

These data are quality-controlled by Fluidion scientists, which may result in delays in data availability. Any errors found in the data are unintentional, and corrections are made immediately upon detection. The information and data provided are intended solely for scientific purposes. Fluidion assumes no responsibility for specific uses of these data, which are at the sole risk of the end-user.

 

All data presented on this page belong to Fluidion and are protected by copyright. Any use of the data must provide a clear reference to this website and include the following text: "Data provided courtesy of the Fluidion Open Data Initiative".

 

 

Related Products

Several Fluidion products are well-adapted for Recreational Water applications, by providing rapid microbiological risk information from instruments with extraordinary ease-of-use, that are fully-automated and perform automatic remote data transmission and archival. Below is a selection of recommended products:

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ALERT One

The ALERT One is an compact portable analyzer for measuring bacterial contamination (E.coli, total coliforms, fecal coliforms) in a single sample of drinking or surface water. It works autonomously in any field location, powered from a universal USB-C port.

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ALERT Lab

The ALERT Lab is a portable, IoT-connected and remote-controlled analyzer for the measurement of E.coli and other bacteria. It provides rapid, on-site bacterial enumeration for source water and environmental monitoring in labs or field locations.

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ALERT System V2

The ALERT System V2 is an autonomous in-situ analyzer for detecting E.coli and coliforms. IoT-connected and remotely controllable, it provides accurate, real-time water quality data and alerts, simplifying monitoring operations in any aquatic environment.

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