Model-based prediction of bathing water quality in a lake polluted by fecal coliform bacteria from combined sewer overflows

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Abstract

In the European Union, recreational water quality is regulated by the bathing water directive, which requires authorities to regularly take water samples to identify fecal bacterial pollution, which can compromise the bathing water quality at designated recreational bathing water areas. Using a case study from Lake Knudsøin Denmark, this paper shows that the bathing water quality occasionally is compromised by overflows from combined sewer systems. Due to the randomness in the frequency of overflow occurrences, the entailing decrease in bathing water quality is not normally detected by the regulatory sampling campaigns. By dedicated sampling campaigns conducted in this project in the proximity of outlets and recreational bathing areas and by hydrodynamical transport modeling, it is shown that the transport patterns of pollutants are crucially and rapidly dependent on dynamic conditions. The occasional short-term pollution by fecal bacteria and consequent decrease in bathing water quality are, therefore, challenging to capture (both spatially and temporally) by regular water sampling. Rather than increasing the frequency of water sampling, an online model-based warning system for fecal bacteria contamination in bathing areas is proposed. This warning system framework includes: (1) dynamical modeling of combined sewer overflow based on rainfall over a catchment area, (2) a hydrodynamical model that simulates current fields in multiple vertical layers based on wind forcing and water fluxes, and (3) a particle dispersion model which provides an estimate of pollutant concentrations. The output from the model has shown potential to issue bathing prohibition if there is a risk of fecal bacteria concentrations below the criteria for good bathing water quality.

OriginalsprogEngelsk
Artikelnummer119483
TidsskriftJournal of Environmental Management
Vol/bind349
ISSN0301-4797
DOI
StatusUdgivet - 1 jan. 2024

Bibliografisk note

Funding Information:
The authors would like to acknowledge the partners in the project Safe Recreational Lake Waters II for their contributions to project management, water sampling, analysis, and ideas: Rikke Markfoged (Danish Technological Institute), Stig Jonassen (Skanderborg Forsyning), and Sara Elsborg Starcke (Niras). Furthermore, the authors would like to acknowledge the Danish Environmental Protection Agency (Danish EPA) for funding under the MUDP program (The Danish Eco-Innovation Program, https://ecoinnovation.dk/english/ ).

Funding Information:
The authors would like to acknowledge the partners in the project Safe Recreational Lake Waters II for their contributions to project management, water sampling, analysis, and ideas: Rikke Markfoged (Danish Technological Institute), Stig Jonassen (Skanderborg Forsyning), and Sara Elsborg Starcke (Niras). Furthermore, the authors would like to acknowledge the Danish Environmental Protection Agency (Danish EPA) for funding under the MUDP program (The Danish Eco-Innovation Program, https://ecoinnovation.dk/english/). The authors acknowledge the students at Aalborg University who have used this project as a case for their master's theses (Steffen Skaarup and Pernille Wahlberg in 2019, Janni Mosekær Nielsen and Claus Fastrup in 2020, and Tobias Sandegaard Aarsnes and Mikkel Ledet Nielsen in 2022) and bachelor thesis (Lise Ditte Nielsen in 2022). Finally, the authors acknowledge the use of temperature data provided by Maria Temponeras from Skoleskibet Ry (Temponeras, 2019).

Publisher Copyright:
© 2023 The Author(s)

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