| 1. |
- Blecken, Godecke-Tobias, et al.
(författare)
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Biofilter treatment of stormwater : temperature influence on the removal of nutrients
- 2007
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Ingår i: Techniques et stratégies durables pour la gestion des eaux urbaines par temps de pluie. - Villeurbanne : Graie. - 9782950933775
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Konferensbidrag (refereegranskat)abstract
- Nutrients can cause eutrophication of natural water bodies. Thus, urban stormwater which is an important nutrient source has to be treated in order to reduce its nutrient loads. Biofilters which use media, biofilms and plants, are a good treatment option regarding nutrients. This paper presents the results of a biofilter column study in cold temperatures (+2°C, +8°C, control at +20°C) which may cause special problems regarding the biofilter performance. It was shown that particle bound pollutants as TSS and a high fraction of phosphorus were reduced well without being negatively influenced by cold temperatures. Nitrogen, however, was not reduced; especially NOx was produced in the columns which can be explained with both insufficient denitrification and high leaching from the columns.
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| 2. |
- Blecken, Godecke-Tobias, et al.
(författare)
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Effect of retrofitting a saturated zone om the performance of biofiltration for heavy metal removal : preliminary results of a laboratory study
- 2010
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Ingår i: NOVATECH 2010. - Villeurbanne : Graie.
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Konferensbidrag (refereegranskat)abstract
- Stormwater biofilters are a stormwater treatment technology which has been becoming increasingly popular. Recently it has been shown that a submerged zone in the filter media improves the magnitude and consistency of nitrogen treatment. Furthermore, the submerged zone has even been shown to be beneficial for retention of heavy metals, particularly Cu. However, most existing biofilters do not include a saturated zone. Since it is relatively simple to retrofit a submerged zone by elevating the outflow, the effect of such a retrofitting on metal removal was investigated in this laboratory study using biofilter columns. It has been shown that a retrofitted submerged zone has a statistically significant but practically small effect on metal removal: Zn removal is slightly enhanced while the effect on Cu removal is inconsistent. Thus, retrofitting of a submerged zone is not recommended if metals are the main target pollutants. But if a submerged zone would have other benefits (e.g. for nitrogen removal or to protect the system from prolonged drying periods) it can be retrofitted without compromising metal removal.
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| 3. |
- Blecken, Godecke-Tobias, et al.
(författare)
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Heavy metal removal by stormwater biofilters : can it withstand alternative drying and wetting conditions?
- 2008
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Ingår i: Conference Proceedings : 11th International Conference on Urban Drainage. - Munich : Oldenbourg Industrieverlag.
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Konferensbidrag (refereegranskat)abstract
- Urban stormwater contains substantial loads of Cu, Pb and Zn, which are considered as key stormwater contaminants. Stormwater biofiltration is a promising option to treat these contaminants. Biofilters are exposed to an alternate cycle of drying and wetting, and the influence of this on pollutant removal performance is as-yet unknown. To investigate the effect of drying and subsequent rewetting on the retention of heavy metals by stormwater biofilters, a laboratory study has been conducted using three groups of biofilter columns, which were dosed with semi-synthetic stormwater according to three different drying and wetting regimes. Some biofilters were fitted with a submerged zone combined with a carbon source, at the bottom of the filter. Overall, the biofilters were very effective in heavy metal removal, provided that they received regular stormwater input. However, after drying extending to three or four weeks, removal of heavy metals decreased significantly. A statistically significant correlation between antecedent dry days and metal removal was shown. Furthermore, a clear effect of the submerged zone was found: after extended dry periods, biofilters with this feature performed significantly better than those without it. In particular, the removal of Cu was clearly increased both during wet and dry periods; for Pb the negative effect of drying was completely eliminated by introducing a submerged zone.
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| 4. |
- Blecken, Godecke-Tobias, et al.
(författare)
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Impact of a submerged zone and a carbon source on heavy metal removal in stormwater biofilters
- 2009
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Ingår i: Ecological Engineering. - : Elsevier BV. - 0925-8574 .- 1872-6992. ; 35:5, s. 769-778
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Tidskriftsartikel (refereegranskat)abstract
- Biofilters are an effective treatment option for the substantial heavy metal loads in urban stormwater. However, to increase their nitrogen treatment efficacy, the introduction of a submerged (anoxic) zone (SZ) and a cellulose based carbon source (C) has been recommended because it has been shown to enhance denitrification and thereby increase overall nitrogen removal. To examine the impact of this design modification on heavy metal treatment, a laboratory study using biofilter mesocosms with different levels of SZ and with or without added C was conducted. The results show that SZ and C have a significant impact on metal treatment. In particular, the removal of Cu was improved significantly. The presence of SZ and C allows outflow Cu concentrations to meet Swedish and Australian water quality guidelines, which are not met with a standard biofilter without SZ or C. Although Zn and Pb removal was enhanced slightly by the presence of a SZ, this improvement is of less practical importance, since Zn and Pb removal is already very high (>95%) in standard biofilters. The best metal treatment was achieved with 450 and 600 mm SZ. Based on these results, the incorporation of SZ with C in stormwater biofilters is recommended.
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| 5. |
- Blecken, Godecke-Tobias, et al.
(författare)
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Influence of intermittent wetting and drying conditions on heavy metal removal by stormwater biofilters
- 2009
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Ingår i: Water Research. - : Elsevier BV. - 0043-1354 .- 1879-2448. ; 43:18, s. 4590-4598
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Tidskriftsartikel (refereegranskat)abstract
- Biofiltration is a technology to treat urban stormwater runoff which conveys pollutants, including heavy metals. However, the variability of metals removal performance in biofiltration systems is as yet unknown.A laboratory study has been conducted with vegetated biofilter mesocosms, partly fitted with a submerged zone at the bottom of the filter combined with a carbon source. The biofilters were dosed with stormwater according to three different dry/wet schemes, to investigate the effect of intermittent wetting and drying conditions on metal removal.Provided that the biofilters received regular stormwater input, metal removal exceeded 95%. The highest metal accumulation occurs in the top layer of the filter media.However, after antecedent drying before a storm event exceeding three to four weeks the filters performed significantly worse, although metal removal still remained relatively high. Introducing a submerged zone into the filter improved the performance significantly after extended dry periods. In particular, copper removal in filters equipped with a submerged zone was increased by around 12% (α = 0.05) both during wet and dry periods and for lead the negative effect of drying could completely be eliminated, with consistently low outflow concentrations even after long drying periods.
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| 6. |
- Blecken, Godecke-Tobias, et al.
(författare)
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Laboratory studies on metal treatment efficiency of stormwater biofilters
- 2010
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Stormwater biofilters are a reliable technology to remove metals from stormwater. A solid carbon source in the filter (combined with a submerged zone) enhances especially Cu removal further; the already high Pb and Zn removal is slightly enhanced. However, the submerged zone helps to minimize (Cu, Zn) or eliminate (Pb) the negative effects which prolonged drying has on the removal rates. Thus, the introduction of a submerged zone is only recommended if nitrogen treatment is targeted (Zinger et al. 2007) or if drying is expected. Temperature differences might have a little influence on especially Cu treatment. However, this influence is not of practical importance indicating that biofilters can successfully be implemented throughout the whole seasonal cycle. A high proportion of metals are retained at the top of the filter which is important for biofilter design and maintenance planning. A filter less than the currently recommended 800 to 900 mm might be sufficient for reliable metal treatment. Furthermore, scraping of the top layer could delay replacing of the whole filter media
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| 7. |
- Blecken, Godecke-Tobias, et al.
(författare)
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Laboratory study on stormwater biofiltration : nutrient and sediment removal in cold temperatures
- 2010
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Ingår i: Journal of Hydrology. - : Elsevier BV. - 0022-1694 .- 1879-2707. ; 394:3-4, s. 507-514
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Tidskriftsartikel (refereegranskat)abstract
- Stormwater biofilters have the ability to remove nutrients from stormwater. Reliable pollutant removal during the cold season is particularly important due to the comparably high contamination levels. However, the removal performance might be negatively affected by low temperatures. A biofilter column study was conducted in thermostat-controlled climate rooms (at 2, 7 and 20 °C) to investigate the effect of low temperatures on nutrient removal. Phosphorus and suspended solids removal were significantly correlated and consistently very high (typically in excess of 90 and 95%, respectively, at all temperatures). This is important for the successful implementation of biofilters in cold climates since phosphorus is commonly of principal concern, often being the limiting factor for eutrophication in freshwater ecosystems. Unfortunately, nitrogen removal was poor and leaching was shown, which increased with temperature. The increasing nitrate-nitrogen production rates with temperature were well described by the Arrhenius relationship with temperature coefficients Q10 in the range which is typically used to describe temperature effects on nitrification. Thus, temperature effects have to be considered when nitrogen removal is targeted and the biofilter might be exposed to cold temperatures.
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| 8. |
- Blecken, Godecke-Tobias, et al.
(författare)
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The influence of temperature on nutrient treatment efficiency in stormwater biofilter systems
- 2007
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Ingår i: Water Science and Technology. - : IWA Publishing. - 0273-1223 .- 1996-9732. ; 56:10, s. 83-91
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Tidskriftsartikel (refereegranskat)abstract
- Nutrients can cause eutrophication of natural water bodies. Thus, urban stormwater which is an important nutrient source in urbanised areas has to be treated in order to reduce its nutrient loads. Biofilters which use soil filter media, biofilms and plants, are a good treatment option for nutrients. This paper presents the results of a biofilter column study in cold temperatures (+2 °C, +8 °C, control at +20 °C) which may cause special problems regarding biofilter performance. It was shown that particle-bound pollutants as TSS and a high fraction of phosphorus were reduced well without being negatively influenced by cold temperatures. Nitrogen, however, was not reduced; especially NOx was produced in the columns. This behaviour can be explained with both insufficient denitrification and high leaching from the columns
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| 9. |
- Löwe, Roland, et al.
(författare)
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Simulating flood risk under non-stationary climate and urban development conditions : Experimental setup for multiple hazards and a variety of scenarios
- 2018
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Ingår i: Environmental Modelling & Software. - : Elsevier. - 1364-8152 .- 1873-6726. ; 102, s. 155-171
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Tidskriftsartikel (refereegranskat)abstract
- A framework for assessing economic flood damage for a large number of climate and urban development scenarios with limited computational effort is presented. Response surfaces are applied to characterize flood damage based on physical variables describing climate-driven hazards and changing vulnerability resulting from urban growth. The framework is embedded in an experimental setup where flood damage obtained from combined hydraulic-urban development simulations is approximated using kriging-metamodels. Space-filling, sequential and stratified sequential sampling strategies are tested. Reliable approximations of economic damage are obtained in a theoretical case study involving pluvial and coastal hazards, and the stratified sequential sampling strategy is most robust to irregular surface shapes. The setup is currently limited to considering only planned urban development patterns and flood adaptation options implemented over short time horizons. However, the number of simulations is reduced by up to one order of magnitude compared to scenario-based methods, highlighting the potential of the approach.
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| 10. |
- McCarthy, David T., et al.
(författare)
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Assessment of sampling strategies for estimation of site mean concentrations of stormwater pollutants
- 2018
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Ingår i: Water Research. - : Elsevier. - 0043-1354 .- 1879-2448. ; 129, s. 297-304
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Tidskriftsartikel (refereegranskat)abstract
- The estimation of stormwater pollutant concentrations is a primary requirement of integrated urban water management. In order to determine effective sampling strategies for estimating pollutant concentrations, data from extensive field measurements at seven different catchments was used. At all sites, 1-min resolution continuous flow measurements, as well as flow-weighted samples, were taken and analysed for total suspend solids (TSS), total nitrogen (TN) and Escherichia coli (E. coli). For each of these parameters, the data was used to calculate the Event Mean Concentrations (EMCs) for each event. The measured Site Mean Concentrations (SMCs) were taken as the volume-weighted average of these EMCs for each parameter, at each site. 17 different sampling strategies, including random and fixed strategies were tested to estimate SMCs, which were compared with the measured SMCs. The ratios of estimated/measured SMCs were further analysed to determine the most effective sampling strategies. Results indicate that the random sampling strategies were the most promising method in reproducing SMCs for TSS and TN, while some fixed sampling strategies were better for estimating the SMC of E. coli. The differences in taking one, two or three random samples were small (up to 20% for TSS, and 10% for TN and E. coli), indicating that there is little benefit in investing in collection of more than one sample per event if attempting to estimate the SMC through monitoring of multiple events. It was estimated that an average of 27 events across the studied catchments are needed for characterising SMCs of TSS with a 90% confidence interval (CI) width of 1.0, followed by E.coli (average 12 events) and TN (average 11 events). The coefficient of variation of pollutant concentrations was linearly and significantly correlated to the 90% confidence interval ratio of the estimated/measured SMCs (R2 = 0.49; P < 0.01) as well as the number of events required to achieve certain accuracy, and hence could be a promising surrogate for determining the sampling frequency needed to accurately estimate SMCs of pollutants
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