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Pollutants in biofilters and long-term function in cold climates

Published: 10 June 2022

In the autumn of 2022, Robert Furén will present his licentiate thesis within DRIZZLE - center for stormwater management with the title “Storm water bioretention: Pollutant occurrence and accumulation in filter material and forebay” at Luleå University of Technology. The results highlight the importance of planned systematic maintenance and well considered design to achieve good function over time

In modern cities, pollutants accumulate and mix with precipitation. In combination with the rapid urban runoff, this leads to major challenges regarding storm water quality and quantity control measures. Bioretention cells are popular and a commonly applied technique since this low impact development practice for stormwater treatment in urban areas and its performance is considered an efficient treatment of various pollutants. Often, they are installed as part of our urban stormwater system where both quality and esthetical aspects are of importance.

Robert's research concentrates on studies of bioretention facilities for stormwater treatment in urban areas with special focus on accumulation of pollutants and treatment capacity over time. When it comes to bioretention facilities, the filter material is of great importance because of its high impact on the stormwater treatment efficiency. Also, the treatment facilities’ site-specific design in terms of placement of inlets and forebays is important for the long-term function. A major field study of biofilters was carried out in autumn 2019 in the United States, the results having been analyzed and assessed in 2020 and 2021 and will be published in 2022.


The results from the study show that the concentrations and occurrence of metals (Cd, Cr, Cu, Ni, Pb and Zn) and four groups of organic pollutants (PAHs, PCBs, phthalates and alkylphenols) are higher in the surface layers and near the inlets. The results also show that metals are relatively mobile in filter materials. Therefore, there is a potential risk of leaching over time or when handling the filter material or sediments from stormwater facilities that have been in operation for a longer time. Overall, the results provide a picture of how different substances bind and accumulate in biofilters, but also of the risks that are built in over time. 

In doing so, the results contribute to increased understanding and a better assessment of the facilities’ design and maintenance which facilitates better functioning and reduced risk of spreading pollutants in connection with operation and maintenance measures or future replacement of the filter material. 

Robert Furén

Robert Furén, Industrial Ph.D student

Organisation: Urban Water Engineering, Architecture and Water, Department of Civil, Environmental and Natural Resources Engineering