| 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. |
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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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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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| 7. |
- Muthanna, Tone Merete, et al.
(författare)
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Snowmelt pollutant removal in bioretention areas
- 2007
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Ingår i: Water Research. - : Elsevier BV. - 0043-1354 .- 1879-2448. ; 41:18, s. 4061-4072
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Tidskriftsartikel (refereegranskat)abstract
- Snow accumulating in urban areas and alongside roads can accumulate high pollutant loads and the subsequent snowmelt can produce high pollutant loads in receiving waters. This paper examines the treatment of roadside snowmelt in bioretention with respect to pollutant removal, pollutant pathways, and major sinks. Bioretention was used to treat snowmelt from three types of urban roads in Trondheim, Norway: residential, medium, and roads with high-density traffic. Metal retention in bioretention boxes had a mass reduction in zinc, copper, lead, and cadmium in the range of 89-99%, and a decrease in outflow concentrations in the range 81-99%. Cadmium was only measured in the water samples, while the other three metals were traced through the system to identify the main sinks. The top mulch layer was the largest sink for the retained metals, with up to 74% of the zinc retained in this mulch layer. The plant metal uptakes were only 2-8% of the total metal retention; however, the plants still play an important role with respect to root zone development and regeneration, which fosters infiltration and reduces the outflow load. Dissolved pollutants in snowmelt tend to be removed with the first flush of meltwater, creating an enrichment ratio with respect to the average pollutant concentrations in the snow. The effect of this enrichment ratio was examined through the bioretention system, and found to be less predominant than that typically reported for untreated snowmelt. The enrichment factors were in the range of 0.65-1.51 for the studied metals.
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| 8. |
- Zinger, Yaron, et al.
(författare)
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Optimisation of the nitrogen retention capacity of stormwater biofiltration systems
- 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
- Excess nitrogen in stormwater is a principal cause for eutrophication of many water bodies in the world. Biofilters, which used a vegetated soil media, have been shown to reduce nitrogen concentrations in stormwater, although there is substantial scope to improve their current nitrogen removal performance. This paper explores the nitrogen transformations in biofilters and optimised theirs design to maximise removal. To achieve this, 20 columns were constructed to test a range of submerged anoxic zone (SAZ) depths, to maximise denitrification. The effect of adding a carbon source to act as an electron donor supplement in the filter media was also tested. Nitrate removal of up to 99% was achieved, with removal by columns with added carbon significantly greater, with a mean removal of greater than 90%, whilst the non-carbon columns showed an average 50% nitrate removal. Depth profiles revealed that mineralization is the limiting step of nitrogen removal in the biofilter columns. The results will contribute to guidelines for optimal biofilter design.
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