Urban Swimming - Sweden Water Research

Urban Swimming

The Swedish summer dream often revolves around sun, warmth, and swimming. Thus, a good swimming spot is crucial when planning holidays and leisure activities. But what is the actual quality of our bathing waters – and is it affected by our water treatment facilities? This is something the Urban Swimming project delves into.

Alarms about E. coli bacteria in the bathing water surface almost every summer, creating problems with water quality. The research project “Urban Swimming” was initiated in 2018 as a joint project between the city of Helsingborg, the city of Malmö, and Lund University to understand more about the connections between the quality of bathing water, why E. coli bacteria have been found at the beaches, and if they can be linked to rain and discharges from our sewage treatment plants.

Where do the bacteria come from?

During 2019 and 2020, researchers at Lund University tested sediments at the seabed around the Öresund plant’s outlet near Helsingborg’s coast to see if they contained any living Escherichia coli, commonly called E. coli bacteria. The answer was yes, the researchers found living E. coli bacteria in the sediment at the bottom of the sea, something that research has also shown previously.

The project now continues to understand if the bacteria can move from the sediment to the beaches and affect the water quality, or if the bacteria that cause unfit bathing water come from elsewhere. Water samples will be taken from swimming spots to see where the bacteria come from – and if our sewage treatment plants are part of the problem with unfit bathing water.

The first results from the project resulted in the report Marine sediments as a reservoir for fecal indicator bacteria associated with pollution of recreational waters, which came out in 2020. But the big question remains: where do the bacteria that affect the quality of bathing water come from? This is now what the project continues to investigate.

New technology tested, gives answers about bacteria in bathing water in 15 minutes

The research project Urban Swimming conducted a pilot project in Helsingborg during the summer of 2022. We tested combining two methods – flow cytometry and measurement of E. coli and enterococci. The combination of these two measuring methods can give answers on the levels of E. coli and enterococci in the bathing water in just 15 minutes, instead of taking three days to show results like the usual tests. Furthermore, the combination of two techniques could lead to predicting changes in the bacterial flora that indicate harmful bacteria are on the rise. The two techniques we are testing in combination are called ColiMinder and BactoSense.

– We are extremely pleased with this collaboration and have high hopes that the pilot project will eventually lead to us being able to warn our swimmers directly instead of three days later on the rare occasions when we get bad test results. Of course, we will also continue to follow the current regulations and take the usual water samples – this is just a bonus, says Elisabet Lindberg, beach manager in Helsingborg’s city.

– It will be very exciting to see the outcome when we test running the two measurement methods together. Both methods have been well-tested before, but to my knowledge, no one has used them in combination. We are breaking new ground here, says Therese Jephson, project leader at Sweden Water Research.

The measurement results are analyzed to provide quick answers on water quality and to lead to the development of smart algorithms that, in the long term, can be used to predict problems with water quality before they actually occur.

The pilot project this summer was made possible through the collaboration between specialists within Urban Swimming, the testbed Källby Water Workshop, and innovation funds from the city of Helsingborg.

About the project

The “Urban Swimming 2020” project is a joint project between Sweden Water Research, Lund University, the city of Helsingborg, the city of Malmö, NSVA, and VA SYD. Sweden Water Research is responsible for the administrative project management and Lund University for the scientific project management.

The total budget for the project is 6,030,000 SEK distributed over the period 2022-2025.

  • Comparing DNA sequences from sediment samples outside water treatment plants and water samples from beaches to investigate if sediment, with or without E. coli, is present in the water that reaches the beach.
  • Using DNA sequencing to describe the presence and diversity of cyanobacteria, the bacteria that produce toxins. How can these results be correlated with the results from routine tests to assess connections between the type of cyanobacteria and warnings related to algal toxins?
  • Investigating if the interpretation of flow cytometry data can be developed to predict bathing water quality in real-time.