| 1. |
- Al-Rubaei, Ahmed, et al.
(författare)
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Long-term hydraulic and treatment performance of a 19-year old constructed stormwater wetland : Finally maturated or in need of maintenance?
- 2016
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Ingår i: Ecological Engineering. - : Elsevier BV. - 0925-8574 .- 1872-6992. ; 95, s. 73-82
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Tidskriftsartikel (refereegranskat)abstract
- Constructed stormwater wetlands (CSWs) are a commonly used measure for stormwater retention and quality treatment. However, although questions have been raised about the long-term performance of CSWs, only a few studies have targeted this issue and none have evaluated the performance of CSWs more than approximately 5–10 years old. Further, most studies have not examined the development of the long-term performance of CSWs but delivered a snapshot at a certain point of time. The present study investigated the performance of a 19-year-old CSW in Växjö, Sweden, treating stormwater from a 320-ha urban catchment. Besides removal of sediment from the CSW’s forebay, no other maintenance had been conducted. However, regular inspections had been performed. The results of the present sampling campaign were compared to two existing datasets collected at the same CSW after three years of operation in 1997 and nine years of operation in 2003. The CSW was found to provide efficient peak flow reduction and, depending on the event characteristics, also volume reduction. It still treated stormwater effectively: removal of Cd, Cu, Pb, Zn, TSS and TP event mean concentrations were between 89 and 96%, whereas mean concentrations of TN were reduced by 59%. The load removal efficiencies were even higher. Comparative analysis of the three monitoring periods based on the load removal efficiency revealed that the CSW, despite the lack of maintenance, performed more efficiently and stably for most pollutants compared to when newly constructed. This underlines the importance of the establishment and maturation of constructed wetland systems. Overall, the results showed that CSWs are resilient systems, which if designed well and regularly inspected to prevent major issues, can work efficiently for at least two decades.
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| 2. |
- Angelstam, Per, et al.
(författare)
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Tall herb sites as a guide for planning, maintenance and engineering of riparian continuous forest cover
- 2017
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Ingår i: Ecological Engineering. - : Elsevier BV. - 0925-8574 .- 1872-6992. ; 103 Part B, s. 470-477
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Tidskriftsartikel (refereegranskat)abstract
- Continuous cover riparian forests host significant plant and animal species richness, a range of habitats, and natural processes of importance for both terrestrial and aquatic ecosystems. Riparian forest is thus a green infrastructure for biodiversity conservation. However, a long history of landscape alteration now calls for maintenance and restoration by ecological engineering. This study evaluates management guidelines advocating constant vs. variable width of riparian forest protected zones in managed landscapes. In naturally dynamic forests, stands with gap-phase dynamic along streams often provide a network of habitats with a high degree of continuity in tree canopy cover and dead wood for biodiversity conservation and delivery of ecosystem services including water purification. Based on the observation that tall herb sites indicate a potential for temporally continuous forest cover, we tested three null hypotheses. Tall herb sites ( 1) are equally common in the riparian zone and in the surrounding forest landscape; ( 2) have the same width on both sides of a stream; and ( 3) their widths are independent of the width of the adjacent stream. We described the ground vegetation in transects along and perpendicular to streams, and in the surrounding landscape, in six 3rd stream order catchment located in Sweden, Lithuania and the Komi Republic of Russia. The results showed that tall herb sites were 21-27 times more common along streams compared to in the rest of the landscape, the width of tall herb sites varied considerably along streams, and it was independent of the width of the adjacent stream. This study suggests that rather than fixed-width guidelines for riparian set-asides, to support cost-efficient maintenance of riparian forest, local site conditions should be used as guide for planning, maintenance and engineering of riparian ecotones. Because tall herb forest sites were historically cleared for agricultural purposes, the potential natural amount of riparian forest is severely underestimated. (C) 2016 Elsevier B.V. All rights reserved.
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| 3. |
- Arheimer, B., et al.
(författare)
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Modelling nitrogen removal in potential wetlands at the catchment scale
- 2002
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Ingår i: Ecological Engineering. - 0925-8574 .- 1872-6992. ; 19:1, s. 63-80
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Tidskriftsartikel (refereegranskat)abstract
- The reduction of nitrogen fluxes from land to sea is an important task in areas with estuarine or marine eutrophication. Wetland creation has been proposed as one method to reduce nitrogen from streams draining agricultural areas. In this study, a scenario of nitrogen removal in created wetlands was evaluated by mathematical modelling of nitrogen fluxes in a catchment (224 km2) in southern Sweden. The scenario was based on topographically realistic siting of 40 potential wetlands with a total area of 0.92 km2 (0.4% of the catchment area). Nitrogen removal in the wetlands was described with a simple and robust first-order model, which was modified and evaluated against data from eight monitored surface-flow wetlands. However, the modifications gave no substantial support for changing the basic model. For catchment-scale modelling this wetland model was incorporated into a dynamic process-based catchment model (HBV-N). The catchment was then divided to several coupled subbasins, so that the wetland influence on nitrogen load could be estimated separately for each potential wetland. The modelling showed that the 40 potential wetlands would reduce the nitrogen transport to the coast with approximately 6%. Specific removal rates ranged between 57 and 466 kg ha-1 yr-1 for the different wetlands, depending on residence time (size and hydraulic loading) and nitrogen concentration in inflow. Due to temperature dependence and seasonal variation in water discharge, significant decrease in nitrogen concentrations mainly occurred during summer periods with low loading. The study illustrates that catchment modelling is a useful method for analysing wetland creation plans, and that wetland creation must cover fairly large areas and be combined with other measures in order to achieve substantial reduction of nitrogen fluxes to coastal waters. Further monitoring of existing wetlands will improve the removal expression and decrease uncertainty. For instance, at present it could not be deducted whether wetlands with low average residence times (< 2 days) have net removal or net resuspension on an annual basis. © 2002 Elsevier Science B.V. All rights reserved.
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| 4. |
- Axelsson, Petter, et al.
(författare)
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Lessons learned from 25 years of operational large-scale restoration: The Sow-A-Seed project, Sabah, Borneo
- 2024
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Ingår i: Ecological Engineering. - 0925-8574 .- 1872-6992. ; 206
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Tidskriftsartikel (refereegranskat)abstract
- While restoration projects globally scale-up to meet the growing demand to restore degraded ecosystems, data on the long-term benefits of restoration are still rare. Here, we describe the lessons learned from the Sow-A-Seed project in Sabah, Borneo: a long-term and large-scale restoration project launched in 1998 with the aim to rehabilitate 18,500 ha of tropical rainforest degraded by logging and forest fires. The project was built from the ground-up, including establishment of essential infrastructure and knowledge creation via trial-and-error. Three restoration techniques were used depending on the level of degradation; 1) Assisted Natural Regeneration (weeding, climber cutting and selective girdling) to promote natural regeneration of late-successional species in the least disturbed forests, and; 2) Enrichment Planting in gap-clusters in moderately disturbed forests, and; 3) Enrichment Planting in rows (i.e, line-planting) throughout heavily degraded forests with no- or few late successional tree species in the overstory. The project includes successful propagation of 92 native tree species including dipterocarps and fruit trees, and planting of over 5 million trees during the last 25 years. Long-term monitoring shows that the mortality rate of planted seedlings is -15% per year up to 3 years, but decreases to -2% between years 3-10 and 10-20. One of the largest trees, a Shorea leprosula planted in 1998, is now 74 cm in DBH and some planted trees have reached reproductive age and are contributing to natural regeneration. A range of wildlife including orangutans, elephants, hornbills and all five wildcat species in Sabah have been documented in the area. In 2015, the area was classified as a Class 1 protected forest, the highest level of conservation status in Malaysia, and removed from commercial forestry. We highlight that there is much knowledge to be gained by research dove-tailing with operational activities, and we encourage that the lessons learned from operational restoration are shared among practitioners and restoration ecologists. We present 8 key lessons learned from the Sow-a-Seed project.
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| 5. |
- Bergsten, Urban
(författare)
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Restoration of reindeer lichen pasture after forest fire in northern Sweden: seven years of results.
- 2017
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Ingår i: Ecological Engineering. - : Elsevier BV. - 0925-8574 .- 1872-6992. ; 108, s. 143-151
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Tidskriftsartikel (refereegranskat)abstract
- Fire suppression since the 19th century has modified the functioning of boreal forest ecosystems in northern Sweden. In the long run, it induces changes in understory vegetation that result, especially on mesic sites, in feather mosses and Ericaceous dwarf shrubs outcompeting ground lichens, thus decreasing winter pastures for reindeer husbandry. In 2008, a field experiment was established in which, two years after a large forest fire, reindeer lichen (Cladonia spp.) was transplanted across various plots. The general objective was to accelerate the recovery of lichen-rich reindeer pastures, and test the ability of lichen thalli to establish on burnt surfaces following different post-fire treatments (tree harvest and standing trees retained), in different transplantation seasons (summer and winter) and at different doses (0.45 L m(-2) and 2.25 L m(-2)). The abundance and level of occupancy of viable and established lichen fragments was determined in 0.25 m(2) quadrats in 2010, 2013 and 2015. There was a continuous increase in lichen establishment over time, and seven years after transplantation, established lichen occupied, on average, 55% and 83% of the 0.25 m(2) quadrats treated with the lower and higher doses, respectively. Nine years after fire, no lichen had colonized the control, i.e. the burnt surface outside the experimental area. At the site with standing trees retained, lichen had already formed a well-established mat with a significantly higher lichen occupancy and abundance than in the open, clear-cut sites, where lichen agglomerated in proto-mats. Lichen transplanted in late-summer exhibited higher abundance and occupancy than that transplanted in late-winter. On average, the difference in lichen occupancy and abundance between different doses after seven years was of lower magnitude than between the doses of lichen transplanted initially. The experiment reveals useful results for the restoration of reindeer pastures and for specifying fire management regimes adapted to both forestry and reindeer husbandry. (C) 2017 Published by Elsevier B.V.
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| 6. |
- 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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| 7. |
- Bodin, Hristina, 1977-, et al.
(författare)
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Effects of biopellets composed of microalgae and fungi on pharmaceuticals present at environmentally relevant levels in water
- 2016
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Ingår i: Ecological Engineering. - : Elsevier. - 0925-8574 .- 1872-6992. ; 91, s. 169-172
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Tidskriftsartikel (refereegranskat)abstract
- Removal of seven pharmaceuticals (acetaminophen, carbamazepine, diclofenac, metoprolol, naproxen, ranitidine and sulfamethoxazole) from water was investigated using three different microbial treatments with: (1) the microalga Chlorella vulgaris, (2) the fungus Aspergillus niger and (3) biopellets composed of both microorganisms. The three-day experiment was performed under laboratory conditions and pharmaceuticals were spiked at the environmentally relevant concentration of 10 mu g L-1. The biopellets and fungal treatments resulted in significantly lower ranitidine concentration compared with the initial value. Also, treatment with biopellets resulted in significantly lower final ranitidine concentrations compared to those found after control and microalgal treatments. Low removal rates were obtained for other substances, possibly because the amount of microbial biomass used was 16-500-fold lower than that normally used in activated sludge processes in wastewater treatments plants. Thus, the pharmaceutical removal potential, elimination potential and performance of biopellets should be further investigated at higher biomass concentrations. (C) 2016 Published by Elsevier B.V.
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| 8. |
- Bodin, Hristina, et al.
(författare)
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Effects of biopellets composed of microalgae and fungi on pharmaceuticals present at environmentally relevant levels in water
- 2016
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Ingår i: Ecological EngineeringThe Journal of Ecotechnology. - : Elsevier BV. - 0925-8574 .- 1872-6992. ; 91, s. 169-172
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Tidskriftsartikel (refereegranskat)abstract
- Removal of seven pharmaceuticals (acetaminophen, carbamazepine, diclofenac, metoprolol, naproxen, ranitidine and sulfamethoxazole) from water was investigated using three different microbial treatments with: (1) the microalga Chlorella vulgaris, (2) the fungus Aspergillus niger and (3) biopellets composed of both microorganisms. The three-day experiment was performed under laboratory conditions and pharmaceuticals were spiked at the environmentally relevant concentration of 10 mu g L-1. The biopellets and fungal treatments resulted in significantly lower ranitidine concentration compared with the initial value. Also, treatment with biopellets resulted in significantly lower final ranitidine concentrations compared to those found after control and microalgal treatments. Low removal rates were obtained for other substances, possibly because the amount of microbial biomass used was 16-500-fold lower than that normally used in activated sludge processes in wastewater treatments plants. Thus, the pharmaceutical removal potential, elimination potential and performance of biopellets should be further investigated at higher biomass concentrations. (C) 2016 Published by Elsevier B.V.
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| 9. |
- Bodin, Hristina, et al.
(författare)
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Tracer behaviour and analysis of hydraulics in experimental free watersurface wetlands
- 2012
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Ingår i: Ecological Engineering. - Amsterdam : Elsevier BV. - 0925-8574 .- 1872-6992. ; 49, s. 201-211
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Tidskriftsartikel (refereegranskat)abstract
- Effects of inlet design and vegetation type on tracer dynamics and hydraulic performance were investigated using lithium chloride in 18 experimental free water surface wetlands. The wetlands received similar water flow but had different vegetation types: 6 emergent vegetation wetlands (EVWs), 6 submerged vegetation wetlands (SVWs) and 6 free development wetlands (FDWs). Two types of inlet designs were applied: half of each wetland vegetation type had a barrier near the inlet to help distribute incoming tracer solution, while the rest had no barrier. Residence time distribution (RTD) functions were calculated from tracer data using two techniques: method of moments and a novel Gauss modelling approach. RTD functions were used to quantify hydraulic parameters: active wetland volume (e-value), water dispersion (N-value) and hydraulic efficiency (λ-value).For wetlands without barrier, significantly lower tracer mass recoveries were found from EVWs compared to FDWs and SVWs, signifying a risk of tracer methodological problems in small densely vegetated wetlands. These problems were minimized in wetlands with an inflow construction promoting distribution of incoming tracer solution.Compared to the method of moments, Gauss modelling seemed to produce more reliable λ-values but less reliable N-values. Data for precise hydraulic quantification were lost by Gauss modelling, as indicated by overall lower variance in these data sets and lower mass recoveries. However, Gauss modelling may minimize uncertainties associated with lithium immobilization/mobilization. Parameters were significantly affected by the RTD data analysis method, showing that the choice of method could affect evaluation of wetland hydraulics.The experimental wetlands in this study exhibited relatively high e-values and low N-values. This was probably caused by the small size of the wetlands and low water flow velocities, emphasizing that hydraulic parameter values obtained in small experimental wetlands may not be applicable to hydraulics in larger wetlands.The method of moments revealed lower e-values from EVWs compared to SVWs and FDWs. It was indicated that lower e-values were mainly caused by vegetation volumes. This highlighted a need for regular maintenance to secure efficient treatment volume in wetlands with dense vegetation.
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| 10. |
- Bojcevska, Hristina, 1977-, et al.
(författare)
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Impact of loads, season, and plant species on the performance of a tropical constructed wetland polishing effluent from sugar factory stabilization ponds
- 2007
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Ingår i: Ecological Engineering. - 0925-8574 .- 1872-6992. ; 29:1, s. 66-76
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Tidskriftsartikel (refereegranskat)abstract
- The effects of wastewater loading rates and two macrophyte species on treatment of sugar factory stabilization pond effluent were investigated in a pilot-scale free water surface constructed wetland (FWS CW) system in western Kenya. For 12 months, four CWs were operated at a hydraulic loading rate of 75 mm day−1 and four at 225 mm day−1. Half the CWs were planted with Cyperus papyrus and half with Echinochloa pyramidalis. Water samples were taken at the inlets and outlets and analyzed for TP, TDP, NH4-N, and TSS. Mass removal rates of the selected water quality parameters were compared during three periods designated the short rain (period 1), dry (period 2), and long rain (period 3) seasons. There was a significant linear relationship between the mass removal rate of TP, NH4-N, and TSS and the mass load, and season had a significant effect on the mass removal rate of TSS, NH4-N, and TDP. Mass loading rates for TDP were about 78% of those for TP, whereas TDP comprised 78–99% of TP mass outflow rates, indicating a release of dissolved P within the CWs. The only significant difference between the two macrophyte species was associated with mass removal of NH4-N, with more efficient removal in CWs planted with C. papyrus than those with E. pyramidalis. TP mass removal rates were 50–80% higher when a mean water loss for CWs 6–8 during periods 1 and 2 was assumed to represent evapotranspiration for all CWs in period 3 instead of pan evaporation data. This illustrated the importance of accurate estimations of evapotranspiration for pollutant mass removal rates in CWs in tropical climates.
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