| 1. |
- Blecken, Godecke-Tobias, et al.
(författare)
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Dataset on stormwater bioretention column studies: Impact of temperature, salt and a submerged zone on the removal of metals, nutrients and suspended solids
- 2022
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Annan publikationabstract
- This data set presents the full raw data from bioretention column studies conducted at Luleå University of Technology in 2010-2014. The pilot scale columns were watered with synthetic stormwater. Influent and effluent samples were collected and analysed for pollutants including total and dissolved metals, nutrients, pathogens and suspended sediment. Further, supporting parameters (e.g. pH, conductivity) are included. The data enables quantifying the impact of bioretention design factors (submerged zone) and ambient factors (salinity in stormwater inflow, temperature) on the removal of these pollutants by bioretention. All filters utilised the same general column design and filter material as well as stormwater preparation. This enables inter-comparability between the different studies. Synthetic stormwater inflow concentrations and bioretention effluent concentrations are presented in the data set. Further, metal concentrations in the filter material and plant tissue have been analysed. The data set enables further analyses of bioretention performance, comparison with similar work performed elsewhere and can be used in modelling of bioretention removal performance and processes. Scientific papers describing the data have been published (see Publications)
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| 2. |
- Søberg, Laila, et al.
(författare)
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A comparison of freshwater mussels and passive samplers as indicators of heavy metal pollution in aquatic systems
- 2013
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Konferensbidrag (refereegranskat)abstract
- 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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| 3. |
- Søberg, Laila, et al.
(författare)
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Bioaccumulation of heavy metals in two wet retention ponds
- 2016
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Ingår i: Urban Water Journal. - 1573-062X. ; 13:7, s. 697-709
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 4. |
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| 5. |
- Søberg, Laila C., et al.
(författare)
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Nitrogen removal in stormwater bioretention facilities: effect of drying, temperature and submerged zone
- 2021
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Ingår i: Ecological Engineering. - : Elsevier. - 0925-8574 .- 1872-6992. ; 169
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Tidskriftsartikel (refereegranskat)abstract
- Removal of ammonium‑nitrogen (NH4-N), nitrite/nitrate‑nitrogen (summarized as NOx—N) and total nitrogen (TN) was examined in pilot-scale bioretention columns with and without a submerged zone under varied temperature and length of antecedent dry periods. The experiment was divided into wet and dry periods and samples were collected to represent continuously wet conditions and conditions with antecedent dry periods. Removal percentages and main effects of the examined factors as well as the effect of their two-way interactions were evaluated. Generally, low temperature favored NOx-N and thus TN removal independent of bioretention column design. Interestingly, bioretention columns with a submerged zone achieved the highest nitrogen removal at low temperature (1.5 °C). For standard bioretention columns, outflow concentrations of NOx-N and TN increased with increasing length of antecedent dry period, whereas a submerged zone mitigated this effect.
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| 6. |
- Søberg, Laila C., et al.
(författare)
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Phosphorus and TSS Removal by Stormwater Bioretention : Effects of Temperature, Salt, and a Submerged Zone and Their Interactions
- 2020
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Ingår i: Water, Air and Soil Pollution. - : Springer. - 0049-6979 .- 1573-2932. ; 231:6
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Tidskriftsartikel (refereegranskat)abstract
- To prevent deterioration of receiving water bodies, phosphorus and total suspended solid (TSS) removal from stormwater is commonly targeted, e.g., by bioretention. However, their removal may vary due to ambient conditions and design features. In this study, the effect of a submerged zone with embedded carbon source (SZC), temperature, and (road) salt on phosphorus removal was investigated using a two-level full factorial design. A sand-based filter material was used. Overall, phosphorus and TSS removal percentages were high. Higher temperature (4.6 vs. 17.1 °C) caused higher outflow concentrations, thus lowering removal rates. The presence of salt deteriorated total phosphorus removal, whereas dissolved phosphorus removal was not affected. The impact of the SZC was statistically significant but not regarded to be of practical significance for P removal. In contrast, TSS removal was enhanced by a SZC. The results demonstrated that a relatively simple filter material could provide excellent P removal, avoiding the need for additives suggested in other studies.
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| 7. |
- Søberg, Laila C., et al.
(författare)
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The influence of temperature and salt on metal and sediment removal in stormwater biofilters
- 2014
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Ingår i: Water Science and Technology. - : IWA Publishing. - 0273-1223 .- 1996-9732. ; 69:11, s. 2295-2304
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 8. |
- Søberg, Laila, et al.
(författare)
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Dissolved metal adsorption capacities and fractionation in filter materials for use in stormwater bioretention facilities
- 2019
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Ingår i: Water Research X. - : Elsevier. - 2589-9147. ; 4
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 9. |
- Søberg, Laila, et al.
(författare)
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Do salt and low temperature impair metal treatment in stormwater bioretention cells with or without a submerged zone?
- 2017
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Ingår i: Science of the Total Environment. - : Elsevier. - 0048-9697 .- 1879-1026. ; 579, s. 1588-1599
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 10. |
- Søberg, Laila
(författare)
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Metal pathways in stormwater treatment systems
- 2014
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- 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.
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