Urban Swimming
The Swedish summer dream often involves sun, warmth, and swimming. Therefore, a good swimming spot is important when planning holidays and leisure activities. But what about the quality of our bathing waters, and is it affected by our water treatment facilities? The project Urban Swimming is looking into this matter.
Alerts about coliform bacteria in bathing waters appear almost every summer, causing problems with water quality. The research project “Urban Baths” started in 2018 as a joint initiative between the cities of Helsingborg and Malmö and Lund University to understand more about the connections between bathing water quality and the presence of coliform bacteria on the beaches. In 2020, Sweden Water Research joined the project along with two of its owner companies, VA SYD and NSVA. Since 2020, Sweden Water Research has been the project leader for this collaboration.
In 2019 and 2020, researchers from Lund University tested the sediment on the seabed around the Öresund Treatment Plant’s outlet along the coast of Helsingborg to see if it contained any live Escherichia coli, commonly known as E. coli bacteria. The answer was yes; the researchers found live E. coli bacteria in the sediment on the seabed.
Where do the bacteria come from?
But the big question remains: where do the bacteria that affect bathing water quality come from? Are there connections to sewage treatment facilities? The questions are many, and the answers are complex.
The project is now progressing, and water samples will be taken from swimming areas to determine where the bacteria come from – and if our sewage treatment facilities are part of the problem with poor bathing water quality.
New technology provides answers in 15 minutes
During the summers of 2022 and 2023, Urban Baths conducted data collections on beaches in Helsingborg and Malmö. The data collection involved testing a combination of two methods – flow cytometry and measurement of E. coli and enterococci. The two techniques being tested in combination are called ColiMinder and BactoSense. By combining these two measurement methods, results on the levels of E. coli and enterococci in the bathing water can be obtained in just 15 minutes, instead of waiting three days as with traditional tests. The combination of the two techniques can also make it possible to predict changes in the bacterial flora that indicate harmful bacteria are on the rise.
We are extremely pleased with this collaboration and have high hopes that the pilot project will eventually allow us to warn our bathers immediately instead of three days later on the rare occasions when we get poor test results. Of course, we will continue to follow the current regulations and take the usual water samples – this is just a bonus, says Elisabet Lindberg, beach manager in the city of Helsingborg.
Machine learning predicts poor bathing water quality
The research uses machine learning and modeling to study abiotic factors such as rainfall, wind direction, and temperature.
The measurement results are analyzed not only to provide quick answers on water quality but also to develop smart algorithms that can eventually be used to predict problems with water quality before they actually occur.
We have come a long way, and there is great interest in the work we are doing. Bathing water quality is complex, with many factors at play, which is why the collaboration between the cities, research, and our water companies is very important, says Carina Svensson, project manager at Sweden Water Research.
What’s next?
In the spring of 2024, preparatory work is underway to conduct data collection in Helsingborg again this summer, including everything from installing ColiMinder and BactoSense to staffing. The data collected will then be analyzed and used in machine learning and modeling to, together with data from previous summers, enhance the development of smart algorithms.
We continue to analyze and compare DNA sequences from sediment samples outside sewage treatment facilities and water samples from beaches to investigate whether sediment, with or without E. coli, is present in the water reaching the beach.
Furthermore, work continues with machine learning, interpretation of flow cytometry data, and other tools to explore the possibilities of predicting bathing water quality results in real-time.
About the project
The Urban Baths project is a joint initiative between Sweden Water Research, Lund University, the City of Helsingborg, the City of Malmö, NSVA, and VA SYD. Sweden Water Research handles the administrative project management, while Lund University is responsible for the scientific project management.
Two doctoral students are associated with the project: Isabel Erb, who focuses on machine learning and modeling, and Ellinor Frank, who investigates the source of poor bathing water quality using DNA sequencing of the bacterial community in seawater and sediment.
The first results from the project have resulted in the report “Marine sediments as a reservoir for fecal indicator bacteria associated with pollution of recreational waters,” which was published in 2020.
