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  • 1.
    Søberg, Laila
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Bioretention for stormwater quality treatment: Effects of design features and ambient conditions2019Doctoral thesis, comprehensive summary (Other academic)
  • 2.
    Søberg, Laila
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Winston, Ryan
    Departments of Food, Agricultural, and Biological Engineering and Civil, Environmental, and Geodetic Engineering, Ohio State University, 590 Woody Hayes Drive, Columbus, OH, United States of America.
    Viklander, Maria
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Blecken, Godecke-Tobias
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Dissolved metal adsorption capacities and fractionation in filter materials for use in stormwater bioretention facilities2019In: Water Research X, ISSN 2589-9147, Vol. 4, article id 100032Article in journal (Refereed)
    Abstract [en]

    The dissolved metal adsorption and association was determined for ten different filter materials recommended and/or implemented in bioretention facilities. Batch adsorption and batch kinetic experiments were performed at lab-scale using both single and multi-metal solutions. Metal strengths and association were determined by sequential extraction analysis. All materials adsorbed metals and 90% of adsorption occurred within 1 h. However, as metal solutions became more complex, adsorption behavior changed. Generally, filter materials classified as sand with a naturally high pH, relatively low organic matter (OM) content and large specific surface area seem to be good choices for removing dissolved metals. Additionally, a chalk additive might improve metal adsorption whereas biochar did not significantly improve metal retention and may be an unwanted (due to degradation over time) extra source of OM. Regardless of filter material, metals primarily adsorbed to the exchangeable form which indicates that metal adsorption might not be permanent, but rather substantially reversible in some cases. More research is needed to assess whether dissolved metals adsorbed in filter materials of bioretention systems pose a delayed threat instead of an immediate threat. Finally, the authors strongly recommend filter materials intended for stormwater bioretention facilities to be tested prior to implementation.

  • 3.
    Søberg, Laila
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Viklander, Maria
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Blecken, Godecke-Tobias
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Hedström, Annelie
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Reduction of Escherichia coliEnterococcus faecalisand Pseudomonas aeruginosa in stormwater bioretention: Effect of drying, temperature and submerged zone2019In: Journal of Hydrology X, ISSN 2589-9155, Vol. 3, article id 100025Article in journal (Refereed)
    Abstract [en]

    The impact of drying and temperature on the reduction of Escherichia coliEnterococcus faecalis and Pseudomonas aeruginosa in stormwater bioretention systems with and without a submerged zone was assessed using 16 pilot-scale bioretention columns under controlled laboratory conditions. The experimental design enabled analysis of possible interactions between the factors. First outflow and event-based samples were collected. Outflow concentrations were independent of inflow concentrations and hence controlled by internal processes. Overall TSS removal was high but sensitive to bacterial synthesis. Event-based samples had significantly higher bacteria concentrations than first outflow samples, suggesting that remaining/surviving bacteria in the bioretention cells have little effect on initial peak outflow concentrations. The effect of temperature varied between bacterial species and sample types. Long dry periods seemed beneficial for bacteria reduction, but outflow bacteria concentrations peaked during the second watering after long dry periods. Submerged zones significantly reduced bacteria outflow concentrations. However, sudden temperature increases caused bioretention cells with a submerged zone to produce significantly higher bacteria outflow concentrations than before the temperature increase, which was not the case for standard cells. Bioretention cells with submerged zones may thus be poor choices for reducing bacterial concentrations in stormwater runoff in areas experiencing winter conditions. Finally, our results suggest that adsorption (e.g. further enhanced by biofilm formation) is the major mechanism governing bacteria reduction in bioretention systems.

  • 4.
    Søberg, Laila
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Viklander, Maria
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Blecken, Godecke-Tobias
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Do salt and low temperature impair metal treatment in stormwater bioretention cells with or without a submerged zone?2017In: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026, Vol. 579, p. 1588-1599Article in journal (Refereed)
    Abstract [en]

    Although seasonal temperature changes and (road) salt in winter and/or coastal stormwater runoff might interfere with the metal treatment performance of stormwater bioretention cells, no previous study has evaluated the effect of these factors and their interactions under controlled conditions. In this 18 week long study 24 well established pilot-scale bioretention columns were employed to evaluate the individual and combined effect(s) of low/high temperature, salt and presence of a submerged zone with an embedded carbon source on metal removal using a three factor, two-level full factorial experimental design. In most instances, the three factors significantly influenced the metal outflow concentrations and thus the treatment performance; the effect of temperature depended on the metal in question, salt had an overall negative effect and the submerged zone with carbon source had an overall positive effect. Despite these statistically significant effects, the discharge water quality was generally markedly improved. However, leaching of dissolved Cu and Pb did occur, mainly from bioretention cells dosed with salt-containing stormwater. The highest concentrations of metals were captured in the top layer of the filter material and were not significantly affected by the three factors studied. Overall, the results confirmed that bioretention provides a functioning stormwater treatment option in areas experiencing winter conditions (road salt, low temperatures) or coastal regions (salt-laden stormwater). However, validation of these results in the field is recommended, especially focusing on dissolved metal removal, which may be critically affected under certain conditions.

  • 5.
    Søberg, Laila
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Vollertsen, Jes
    Department of Civil Engineering, Aalborg University.
    Blecken, Godecke-Tobias
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Nielsen, Asbjørn Haaning
    Department of Civil Engineering, Aalborg University.
    Viklander, Maria
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Bioaccumulation of heavy metals in two wet retention ponds2016In: Urban Water Journal, ISSN 1573-062X, Vol. 13, no 7, p. 697-709Article in journal (Refereed)
    Abstract [en]

    Metal accumulation in stormwater ponds may contaminate the inhabiting fauna, thus jeopardizing their ecosystem services function. We evaluated bioaccumulation of metals in natural fauna and caged mussel indicator organisms in two wet retention ponds. Mussel cages were distributed throughout the ponds to detect bioaccumulation gradients and obtain a time-integrated measure of metal bioavailability. We further investigated if sediment metal concentrations correlate with those in the fauna and mussels. Metal concentrations in the fauna tended to be higher in the ponds than in a reference lake, but statistical significance was only shown for Cu. Positive correlations were found for some metals in fauna and sediment. Sediment metal concentrations in one pond decreased from inlet to outlet while no gradients were observed in the mussels in either pond. These findings indicate that metal accumulation in the examined ponds currently does not pose a threat to their habitat function.

  • 6.
    Søberg, Laila
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Metal pathways in stormwater treatment systems2014Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Heavy metals in urban stormwater runoff affect the ecological status of receiving surface waters. To avoid this, various stormwater treatment systems have been developed and implemented during the last 50 years. One of themost common and continuously popular systems is wet stormwater ponds. Another and relatively new type of system is stormwater biofilters. In wet stormwater ponds the function and design with respect to both waterquantity and water quality has been comprehensively addressed in scientific studies. Concerns today are more related to the fact that they serve as aquatic and wildlife habitats thereby posing a possible ecological risk. Incontrast, for stormwater biofilters, a knowledge gap regarding function and factors affecting their performance still exists.Understanding metal pathways in these two systems can support development of future stormwater management by identifying ways to improve the treatment of stormwater discharges and minimize risks of metals spreadingfrom treatment facilities to the natural environment. Thus, in this thesis metal pathways in wet stormwater ponds and stormwater biofilters were investigated in laboratory studies and field experiments to evaluate metal accu-mulation in different compartments of the two systems. For wet stormwater ponds the primary issue addressed in focus was their risk of affecting the wider environment whereas for stormwater biofilters was about their capaci-ty to improve stormwater runoff discharge. The study was performed by sampling resident fauna in wet stormwater ponds to evaluate bioaccumulation and biomagnification in wet stormwater ponds; sediment was sampled to estimate pollutant loads they receive; and mussel biomarkers were used to assess bioaccumulation over time in them. In addition, a laboratory study wasconducted to assess the reliability of mussels as biomarkers. To assess metal removal pathways and efficiency in stormwater biofilters, heavy metal concentrations were measured in the influent and effluent, as well as in thefilter material and the roots and shoots of stormwater biofilter vegetation.Mussel biomarkers were not confirmed to be a reliable method to assess the ecological state of wet stormwater ponds since they did not reflect the overall bioaccumulation in them. However, the use of resident fauna seemspromising for this purpose since the metal pollution load received by the wet stormwater ponds was reflected in the resident fauna. The results of this study indicated that despite being continuously loaded with heavy metalswet stormwater ponds have the ability to provide high biodiversity and thus ecosystem services without critically contaminating the resident fauna. However, with time wet stormwater ponds will likely end up constituting anecological risk to the surrounding environment.The investigated stormwater biofilters showed an overall efficient metal removal. The retained metals were trapped in the top layer of the filter material and in the roots and shoots of the biofilter vegetation. However, saltwas found to have a negative effect on stormwater biofilter performance inducing leaching of dissolved Cu and Pb and impeding plant metal uptake. Temperature variation did not generally affect metal removal but low tem-peratures caused a higher plant metal uptake than high temperatures. The presence of a submerged zone had a positive effect on stormwater biofilters, improving the overall metal removal from stormwater and plant metaluptake as well as plant health. By drawing parallels between the two studied systems, wet stormwater ponds will most likely be negativelyaffected by wintry conditions, constituting a risk for receiving waters at the same time as they are more likely to pose an ecological risk to the wider environment than stormwater biofilters. Use of stormwater biofilters wherepossible is therefore recommended, to improve future urban stormwater management.

  • 7.
    Søberg, Laila
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Blecken, Godecke-Tobias
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Viklander, Maria
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Hedström, Annelie
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Metal uptake in three different plant species used for cold climate biofilter systems2014Conference paper (Refereed)
    Abstract [en]

    Stormwater biofilters have been developed without consideration of their cold climate design and performance. Vegetation has been shown to play an important role in biofilter effectiveness. Due to the effect of winter conditions on plants (no/reduced growth, high salinity from road salt), winter-related factors affecting biofilter vegetation, and especially the selection of vegetation for cold climate biofilter systems, need further investigation. The impacts of temperature, salt and the presence of a submerged zone on Cd, Cu, Pb and Zn uptake in three native wet/drought tolerant plant types, Juncus conglomeratus, Phalaris arundinacea and Carex panacea, were thus examined in 24 biofilter mesocosms under controlled laboratory conditions. The shoots of all three plant species accumulated higher metal concentrations than the roots. Generally, a higher metal uptake was observed under cold conditions. No significant difference in metal uptake was found between different biofilter combinations, indicating that these three plant species were not particularly affected by different temperatures and/or the presence/absence of salt and a submerged zone. The results of this study indicate the potential to use the investigated plant species for targeted cold climate biofilter design.

  • 8.
    Søberg, Laila
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Blecken, Godecke-Tobias
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Viklander, Maria
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    The influence of temperature and salt on metal and sediment removal in stormwater biofilters2014In: Water Science and Technology, ISSN 0273-1223, E-ISSN 1996-9732, Vol. 69, no 11, p. 2295-2304Article in journal (Refereed)
    Abstract [en]

    Stormwater biofilters are used to treat stormwater runoff. In countries with cold winter climates, biofilters are subject to low temperatures which, in some cases, are combined with potentially high salt concentrations from road de-icing, potentially affecting the biofilter’s performance. Since stormwater biofilters have been developed without consideration of their critical winter use, a laboratory study was carried out to evaluate the performance of stormwater biofilters subjected to low and high temperatures, with and without salt. Both factors and their interaction had a significant effect on outflow concentrations and removal percentages. Salt had a negative impact on outflow concentrations, causing lower removal percentages for (especially dissolved) metals, this impact being most pronounced for Cu and Pb. The unrealistic combination of salt with high temperature seemed to further amplify the negative impacts of salt despite the fact that temperature alone did not cause significant differences in outflow concentrations and removal percentages. Still, biofilters showed the ability to treat stormwater efficiently under the simulated winter conditions; outflow concentrations for total metals as a minimum met the class 4 threshold value defined in the Swedish freshwater quality guidelines, while inflow concentrations clearly exceeded the threshold value for class 5. The relatively coarse filter material (which is recommended to facilitate infiltration during winter) did not seem to exacerbate biofilter performance.

  • 9.
    Søberg, Laila
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Vollertsen, Jes
    Section of Water and Soil, Department of Civil Engineering, Aalborg University.
    Nielsen, Asbjørn Haaning
    Section of Water and Soil, Department of Civil Engineering, Aalborg University.
    Blecken, Godecke-Tobias
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Viklander, Maria
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    A comparison of freshwater mussels and passive samplers as indicators of heavy metal pollution in aquatic systems2013Conference paper (Refereed)
    Abstract [en]

    The utility of passive sampling as a tool for determining the ecological state of wet retention ponds was investigated as an alternative to the analysis of living organisms. The accumulation of heavy metals over time in mussels and passive samplers exposed to artificial stormwater was examined under controlled conditions in order to determine whether either system was capable of functioning as a reliable source of data on aquatic pollution. The laboratory results indicated that mussels are useful in this context. However, passive samplers will require further development to be useful since there was no strong correlation between the heavy metal concentrations observed in the mussels and those in the passive samplers.

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