| 1. |
- 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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| 2. |
- Johannesson, Karin, 1982-, et al.
(författare)
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Efficiency of a constructed wetland for retention of sediment associated phosphorus
- 2011
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Ingår i: Hydrobiologia. - Dordrecht : Springer. - 0018-8158 .- 1573-5117. ; 674:1, s. 179-190
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Tidskriftsartikel (refereegranskat)abstract
- A constructed wetland (2.1 ha; 2% of catchment area) in southeast Sweden, in a catchment with 35% arable land on clay soils, was investigated with respect to phosphorus (P) retention, focusing on particulate P (PP) and sediment accretion. The aims were to i) estimate P retention and identify the dominating retention processes; ii) investigate how well estimates of P retention based on inflow-outflow measurements compared with the amount of P accumulated in the sediment. In- and outflow of P was measured during four years with continuous flow measurements and flow proportional weekly composite samples. P in the accumulated sediment was estimated based on core samples and analyzed using sequential fractionation. Total P load during four years was 65 kg/ha and intensive sampling events detected 69% as PP. Based on inflow-outflow estimates the mean P retention was 2.8 kg/ha/yr, or 17%, but the amount of P accumulated in the inlet zone equated 78% of the TP load. This discrepancy showed the need to add studies of sediment accumulation to inflow-outflow estimates for an improved understanding of the P retention. The dominating P forms in the sediment were organic P (38%) and P associated with iron or aluminum (39%), i.e. potentially mobile forms. In areas colonized by Typha latifolia, the amount of P in the upper sediment layer (390 kg) was more than double the total P load of 136 kg. Cycling and release in those areas is a potential source of P that deserves further attention.
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| 3. |
- Johannesson, Karin M., 1982-, et al.
(författare)
-
Can spatial and temporal nutrient concentration variability be captured by catchment agro-geographical characteristics and water quality modelling?
- 2015
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- In water management, source areas need to be identified and seasonal variability of nutrient flows assessed to facilitate design of cost-efficient mitigation programs. This study aimed at investigating to what degree sub-catchment spatial and temporal nutrient concentration variability could be captured by their agro-geographical characteristics and water quality modelling.An agricultural catchment (160 km2) in Southeast Sweden was investigated with respect to source areas for phosphorus (P), nitrogen and particle losses. The specific aims were to 1) investigate the spatial variability of nutrient and particle concentrations and transport from different sub-catchments, 2) analyze if sub-catchment characteristics could explain differences in nutrient and particle concentration dynamics and overall nutrient losses, and 3) evaluate how well monitored temporal and spatial variability in nutrient concentrations could be simulated by a catchment model (HYPE). The purpose with the latter was to find recommendations for further model development and identify limitations for the use of catchment models in local water management.Water flow was measured in two stations during 2009-2011. Grab samples were collected in synoptic sampling campaigns covering 10 sampling points during periods that represented various water flow regimes. Water samples were analyzed for total P (TP), dissolved phosphate (PO4-P), nitrate (NO3-N) and suspended matter (SUSP). The HYPE model was setup with the same detailed agro-geographical data as used for the statistical analyses of spatial and temporal correlations. The results showed that the sub-catchment variability of all measured nutrient concentrations were correlated with agro-geographical characteristics. All fractions of P concentrations were strongly correlated with soil type, whereas NO3-N concentrations were more related to crop factors. With regard to temporal dynamics of monitored concentrations, links to seasonality and water flow were more significant for NO3-N than for TP. Concentrations generated from the water quality model (HYPE) did not capture the subcatchment or temporal variability indicated from monitoring, particularly not for P concentrations. Neither did the modelled correlation between agro-geographical factors and concentrations correspond to that found for monitored concentrations. Some suggestions for model improvement were identified. Although water quality models are useful for local water management when it comes to modelling the impact of e.g. measures or climate change, our results suggest that their value might still be more limited when assessing variability on the subcatchment scale.
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| 4. |
- Kynkäänniemi, P., et al.
(författare)
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Assessment of particle deposition and accumulation in newly constructed wetlands receiving agricultural runoff
- 2015
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- This study analysed variations in sediment deposition and accumulation to improve understanding of retention processes in small wetlands constructed on clay soils. Sediment deposition (in traps) and accumulation (on plates) was measured in four wetlands in east-central Sweden.Particle deposition generally exceeded (up to eight-fold) the total particle load to the wetlands, especially in the spring-summer period, suggesting that the settled particles in the traps were generated from internal processes. The particles probably originated from erosion of the bottom and sides of the wetlands, or from production of organic material which deposited in the traps.Particle resuspension was evident in all wetlands and considered an important process. Only 13-23% of the deposited material in the traps remained on the plates in the wetlands. Both particle deposition and accumulation was very low in one wetland receiving high hydraulic load (HL, 400 m yr-1), suggesting that such high-loaded wetlands are not efficient as particle sinks in clay soil areas. In the other wetlands, more than 80% of the total sediment accumulation occurred in the initial parts of the wetlands (which represented the first 20% of the total wetland area), indicating the importance of designing wetlands with an initial wetland section that is easy accessed for sediment removal as maintenance.The results from this study point to the importance of internal processes and resuspension for annual particle accumulation in constructed wetlands.
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| 5. |
- Mara, D., et al.
(författare)
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Selection of sustainable sanitation arrangements
- 2007
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Ingår i: Water Policy. - : IWA Publishing. - 1366-7017 .- 1996-9759. ; 9:3, s. 305-318
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Tidskriftsartikel (refereegranskat)abstract
- To meet the Millennium Development Goal for sanitation around 440,000 people will have to be provided with adequate sanitation every day during 2001-2015, and the corresponding figure to meet the WHO/UNICEF target of "sanitation for all" by 2025 is around 480,000 people per day during 2001-2025. The provision of sanitation services to such huge numbers necessitates action on an unprecedented scale. This is made even more difficult by the general lack of knowledge on the part of professionals and the intended beneficiaries about which sanitation arrangement is the most appropriate under which circumstances. A sanitation selection algorithm, which considers all the available sanitation arrangements, including ecological sanitation and low-cost sewerage, and which is firmly based on the principles of sustainable sanitation, is developed as a guide to identify the most appropriate arrangement in any given situation, especially in poor and very poor rural and periurban areas in developing countries. © IWA Publishing 2007.
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| 6. |
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| 7. |
- Weisner, Stefan, 1954-, et al.
(författare)
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National Large-Scale Wetland Creation in Agricultural Areas—Potential versus Realized Effects on Nutrient Transports
- 2016
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Ingår i: Water. - Basel : MDPI. - 2073-4441. ; 8:11
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Tidskriftsartikel (refereegranskat)abstract
- During 2007–2013, the Swedish Board of Agriculture granted support within a national program to about 1000 wetlands, corresponding to a 5300-hectare wetland area, with the dual goal to remove nutrients from water and to improve biodiversity in agricultural landscapes. The aim of the present study was to compare the effects on nutrient transports that are realized within the national program to what could be obtained with the same area of wetlands if location and design of wetlands were optimized. In single, highly nutrient-loaded wetlands, a removal of around 1000 kg nitrogen and 100 kg phosphorus per hectare wetland area and year was estimated from monitoring data. Statistical models were developed to estimate the overall nutrient removal effects of wetlands created within the national program. Depending on model, the effect of the national program as a whole was estimated to between 27 and 38 kg nitrogen and between 2.7 and 4.5 kg phosphorus per hectare created wetland area and year. Comparison of what is achieved in individual wetlands to what was achieved in the national program indicates that nutrient removal effects could be increased substantially in future wetland programs by emphasising location and design of wetlands.
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| 8. |
- Andersson, J., et al.
(författare)
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Free water surface wetlands for wastewater treatment in Sweden : Nitrogen and phosphorus removal
- 2005
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Ingår i: Water Science and Technology. - 0273-1223 .- 1996-9732. ; 51:9, s. 39-46
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Tidskriftsartikel (refereegranskat)abstract
- In South Sweden, free water surface wetlands have been built to treat wastewater from municipal wastewater treatment plants. Commonly, nitrogen removal has been the prime aim, though a significant removal of tot-P and BOD7 has been observed. In this study, performance data for 3-8 years from four large (20-28 ha) FWS wetlands have been evaluated. Two of them receive effluent from WWTP with only mechanical and chemical treatment. At the other two, the wastewater has also been treated biologically resulting in lower concentrations of BOD7 and NH4+-N. The wetlands performed satisfactorily and removed 0.7-1.5 ton N ha-1 yr-1 as an average for the time period investigated, with loads between 1.7 and 6.3 ton N ha-1 yr-1. Treatment capacity depended on the pre-treatment of the water, as reflected in the k20-values for N removal (first order area based mode). In the wetlands with no biological pre-treatment, the k20-values were 0.61 and 1.1 m month-1, whereas for the other two they were 1.7 and 2.5 m month-1. P removal varied between 10 and 41 kg ha-1 yr-1, and was related to differences in loads, P speciation and to the internal cycling of P in the wetlands. © IWA Publishing 2005.
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| 9. |
- Bojcevska, Hristina, 1977-, et al.
(författare)
-
Impact of loads, season, and plant species on the performance of a tropical constructed wetland polishing effluent from sugar factory stabilization ponds
- 2007
-
Ingår i: Ecological Engineering. - : Elsevier BV. - 0925-8574 .- 1872-6992. ; 29:1, s. 66-76
-
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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| 10. |
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