| 1. |
- Bojcevska, Hristina, 1977-, et al.
(author)
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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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In: Ecological Engineering. - 0925-8574 .- 1872-6992. ; 29:1, s. 66-76
-
Journal article (peer-reviewed)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.
(author)
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Efficiency of a constructed wetland for retention of sediment associated phosphorus
- 2011
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In: Hydrobiologia. - Dordrecht : Springer. - 0018-8158 .- 1573-5117. ; 674:1, s. 179-190
-
Journal article (peer-reviewed)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.
(author)
-
Can spatial and temporal nutrient concentration variability be captured by catchment agro-geographical characteristics and water quality modelling?
- 2015
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Other publication (other academic/artistic)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.
(author)
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Assessment of particle deposition and accumulation in newly constructed wetlands receiving agricultural runoff
- 2015
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Other publication (other academic/artistic)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.
(author)
-
Selection of sustainable sanitation arrangements
- 2007
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In: Water Policy. - : IWA Publishing. - 1366-7017 .- 1996-9759. ; 9:3, s. 305-318
-
Journal article (peer-reviewed)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.
(author)
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National Large-Scale Wetland Creation in Agricultural Areas—Potential versus Realized Effects on Nutrient Transports
- 2016
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In: Water. - Basel : MDPI. - 2073-4441. ; 8:11
-
Journal article (peer-reviewed)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.
(author)
-
Free water surface wetlands for wastewater treatment in Sweden : Nitrogen and phosphorus removal
- 2005
-
In: Water Science and Technology. - 0273-1223 .- 1996-9732. ; 51:9, s. 39-46
-
Journal article (peer-reviewed)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.
(author)
-
Impact of loads, season, and plant species on the performance of a tropical constructed wetland polishing effluent from sugar factory stabilization ponds
- 2007
-
In: Ecological Engineering. - : Elsevier BV. - 0925-8574 .- 1872-6992. ; 29:1, s. 66-76
-
Journal article (peer-reviewed)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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| 11. |
- Diwan, Vishal, et al.
(author)
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Antibiotics and antibiotic-resistant bacteria in waters associated with a hospital in Ujjain, India
- 2010
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In: BMC Public Health. - : BioMed Central. - 1471-2458. ; 10:414
-
Journal article (peer-reviewed)abstract
- Background: Concerns have been raised about the public health implications of the presence of antibiotic residues in the aquatic environment and their effect on the development of bacterial resistance. While there is information on antibiotic residue levels in hospital effluent from some other countries, information on antibiotic residue levels in effluent from Indian hospitals is not available. Also, concurrent studies on antibiotic prescription quantity in a hospital and antibiotic residue levels and resistant bacteria in the effluent of the same hospital are few. Therefore, we quantified antibiotic residues in waters associated with a hospital in India and assessed their association, if any, with quantities of antibiotic prescribed in the hospital and the susceptibility of Escherichia coli found in the hospital effluent. Methods: This cross-sectional study was conducted in a teaching hospital outside the city of Ujjain in India. Seven antibiotics - amoxicillin, ceftriaxone, amikacin, ofloxacin, ciprofloxacin, norfloxacin and levofloxacin - were selected. Prescribed quantities were obtained from hospital records. The samples of the hospital associated water were analysed for the above mentioned antibiotics using well developed and validated liquid chromatography/tandem mass spectrometry technique after selectively isolating the analytes from the matrix using solid phase extraction. Escherichia coli isolates from these waters were tested for antibiotic susceptibility, by standard Kirby Bauer disc diffusion method using Clinical and Laboratory Standard Institute breakpoints. Results: Ciprofloxacin was the highest prescribed antibiotic in the hospital and its residue levels in the hospital wastewater were also the highest. In samples of the municipal water supply and the groundwater, no antibiotics were detected. There was a positive correlation between the quantity of antibiotics prescribed in the hospital and antibiotic residue levels in the hospital wastewater. Wastewater samples collected in the afternoon contained both a higher number and higher levels of antibiotics compared to samples collected in the morning hours. No amikacin was found in the wastewater, but E. coli isolates from all wastewater samples were resistant to amikacin. Although ciprofloxacin was the most prevalent antibiotic detected in the wastewater, E. coli was not resistant to it. Conclusions: Antibiotics are entering the aquatic environment of countries like India through hospital effluent. Indepth studies are needed to establish the correlation, if any, between the quantities of antibiotics prescribed in hospitals and the levels of antibiotic residues found in hospital effluent. Further, the effect of this on the development of bacterial resistance in the environment and its subsequent public health impact need thorough assessment.
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| 12. |
- Geranmayeh, Pia, et al.
(author)
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Phosphorus Retention in a Newly Constructed Wetland Receiving Agricultural Tile Drainage Water
- 2013
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In: Journal of Environmental Quality. - : Wiley. - 0047-2425 .- 1537-2537. ; 42, s. 596-605
-
Journal article (peer-reviewed)abstract
- One measure used in Sweden to mitigate eutrophication of waters is the construction of small wetlands (free water surface wetland for phosphorus retention [P wetlands]) to trap particulate phosphorus (PP) transported in ditches and streams. This study evaluated P retention dynamics in a newly constructed P wetland serving a 26-ha agricultural catchment with clay soil. Flow-proportional composite water samples were collected at the wetland inlet and outlet over 2 yr (2010-2011) and analyzed for total P (TP), dissolved P (DP), particulate P (PP), and total suspended solids (TSS). Both winters had unusually long periods of snow accumulation, and additional time-proportional water samples were frequently collected during snowmelt. Inflow TP and DP concentrations varied greatly (0.02-1.09 mg L-1) during the sampling period. During snowmelt in 2010, there was a daily oscillation in P concentration and water flow in line with air temperature variations. Outflow P concentrations were generally lower than inflow concentrations, with net P losses observed only in August and December 2010. On an annual basis, the wetland acted as a net P sink, with mean specific retention of 69 kg TP, 17 kg DP, and 30 t TSS ha(-1) yr(-1), corresponding to a reduction in losses of 0.22 kg TP ha(-1) yr(-1) from the agricultural catchment. Relative retention was high (36% TP, 9% DP, and 36% TSS), indicating that small constructed wetlands (0.3% of catchment area) can substantially reduce P loads from agricultural clay soils with moderately undulating topography.
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| 13. |
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| 14. |
- Kallner Bastviken, Sofia, et al.
(author)
-
Effects of vegetation and hydraulic load on seasonal nitrate removal in treatment wetlands
- 2009
-
In: Ecological Engineering. - Amsterdam : Elsevier. - 0925-8574 .- 1872-6992. ; 35:5, s. 946-952
-
Journal article (peer-reviewed)abstract
- Optimising nitrate removal and identifying critical factors for nitrate removal in wetlands is an important environmental task in the effort to achieve better surface water quality. In this study, eighteen free water surface wetlands with similar shape and size (22 m2 each) received groundwater with a high nitrate-N concentration (about 11 mg l−1). The effects of two hydraulic loads, 0.13 m d−1 and 0.39 m d−1, and three vegetation types – emergent, submersed and freely developing vegetation – on the nitrate-N removal were investigated through mass inflow and outflow measurements.No significant difference in nitrate removal between the different hydraulic loads could be detected. Significantly higher area-specific nitrate removal and first-order area-based rate coefficients were found in the basins with emergent vegetation, with no difference between the basins with submersed and freely developing vegetation. The nitrate-N removal increased as the wetlands matured and the vegetation grew denser, emphasizing the role of dense emergent vegetation for nitrate removal at high nitrate concentrations.
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| 15. |
- Kallner Bastviken, Sofia, 1973-
(author)
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Nitrogen removal in treatment wetlands : Factors influencing spatial and temporal variations
- 2006
-
Doctoral thesis (other academic/artistic)abstract
- Decreasing the nitrogen transport from land to surrounding seas is a major task throughout the world to limit eutrophication of the coastal areas. Several approaches are currently used, including the establishment of wetlands, to decrease the transport of nitrogen. Wetlands represent ecosystems where the nitrogen removal from water can be efficient given that they are appropriately designed. The aim of this thesis was to investigate and quantify the effect of critical factors that regulate the nitrogen removal in wetlands, and to develop better guidelines for wetland design. Studies were performed at different scales, from microcosms to full scale wetlands, and methods included modelling, mass balance calculations and process studies.A first order rate model was used to simulate the nitrogen transformations in two large wetlands treating wastewater containing both ammonium and nitrate nitrogen. It was found that the dynamics of the main itrogen transformation processes could not be satisfactorily described using this approach. Large wetlands containing vegetation are complex ecosystems, and the process rates vary in both time and space. The great diversity of microenvironments favours different nitrogen processes, and large differences in potential nitrification and denitrification rates were found between different surface structures within a wetland. The results from microcosms measurements showed that the highest potential for nitrification was on surfaces in the water column, while the denitrification capacity was highest in the sediment.For the sediment denitrification capacity, the plant communitycomposition was shown to be of major importance primarily by supplying litter serving as a carbon and energy source, and/or attachment surfaces, for denitrifying bacteria. Denitrification rates may be affected more than three fold by different types of litter and detritus in the sediments. Intact sediment cores from stands of the emergent plants Glyceria maxima and Typha latifolia had higher denitrification potential than sediment cores from stands of the submersed plant Potamogeton pectinatus. However, the quality of the organic material for the denitrifying bacteria was highest in G. maxima and P. pectinatus stands. All sediment cores from the wetland were limited by carbon, and the lower denitrification capacity of the submersed plant, P. pectinatus, was likely due to lower amounts of organic matter. However, in another wetland, intact cores from stands of the submersed plant Elodea canadensis had a higher denitrification capacity than the cores from stands of T. latifolia and Phragmites australis. This was possibly due to a larger biomass, and better quality, of the organic matter from that submersed specie, or to epiphytic biofilms on the living plants. Those microcosms studies showed that both the quality of the organic matter as a substrate for the microbial communities, and the amount of organic material produced were important for the denitrification capacity.In pilot scale wetlands, the composition of the plant community was also a more important factor for high nitrate removal than the differences in hydraulic loads (equivalent of 1 or 3 d retention time), despite the cold climate. The greatest removal was found in wetlands with emergent vegetation dominated by P. australis and G. maxima, rather than in wetlands with submersed vegetation. In brief, the results presented in this thesis emphasize the importance of dense emergent vegetation for high annual nitrate removal in treatment wetlands.
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| 16. |
- Kallner Bastviken, Sofia, et al.
(author)
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Potential denitrification in wetland sediments with different plant species detritus
- 2005
-
In: Ecological Engineering: the Journal of Ecotechnology. - : Elsevier BV. - 1872-6992. ; 25:2, s. 183-190
-
Journal article (peer-reviewed)abstract
- The effect of detritus originating from different plant species on denitrifying capacity was investigated in a Swedish wastewater treatment wetland. Intact sediment cores containing sediment with a detritus layer were collected from wetland basins dominated by Typha latifolia, Phragmites australis, or Elodea canadensis in November 2000 and potential denitrification was measured using the acetylene-inhibition method. The cores from stands of E. canadensis showed more than three times higher denitrification capacity than the cores of the other plants. Bacterial abundance per unit dry weight was both highest and lowest in the detritus of R australis, whereas the C/N ratio was lower in the cores of E. canadensis. This suggests that the submerged plant provided more organic material of high quality to support heterotrophic organisms. It is also possible that the surfaces of E. canadensis offered more or more suitable surfaces for bacterial growth and thereby increased the bacterial population. It is apparent that denitrifying bacteria were more favored by E. canadensis detritus than by detritus from the emergent plant species at the time of sampling. Since the turnover of plant detritus varies considerably among species, the seasonal variation in denitrification capacity is likely to be quite different for different plants.
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| 17. |
- Kallner Bastviken, Sofia, et al.
(author)
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Potential nitrification and denitrification on different surfaces in a constructed treatment wetland
- 2004
-
In: Journal of environmental quality. - 0047-2425. ; 32:6, s. 2414-2420
-
Journal article (peer-reviewed)abstract
- Improved understanding of the importance of different surfaces in supporting attached nitrifying and denitrifying bacteria is essential if we are to optimize the N removal capacity of treatment wetlands. The aim of this study was therefore to examine the nitrifying and denitrifying capacity of different surfaces in a constructed treatment wetland and to assess the relative importance of these surfaces for overall N removal in the wetland. Intact sediment cores, old pine and spruce twigs, shoots of Eurasian watermilfoil (Myriophyllum spicatum L.), and filamentous macro-algae were collected in July and November 1999 in two basins of the wetland system. One of the basins had been constructed on land that contained lots of wood debris, particularly twigs of coniferous trees. Potential nitrification was measured using the isotope-dilution technique, and potential denitrification was determined using the acetylene-inhibition technique in laboratory microcosm incubations. Nitrification rates were highest on the twigs. These rates were three and 100 times higher than in the sediment and on Eurasian watermilfoil, respectively. Potential denitrification rates were highest in the sediment. These rates were three times higher than on the twigs and 40 times higher than on Eurasian watermilfoil. The distribution of denitrifying bacteria was most likely due to the availability of organic material, with higher denitrification rates in the sediment than on surfaces in the water column. Our results indicate that denitrification, and particularly nitrification, in treatment wetlands could be significantly increased by addition of surfaces such as twigs.
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| 18. |
- Kallner Bastviken, Sofia, et al.
(author)
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Seasonal denitrification potential in wetland sediments with organic matter from different plant species
- 2007
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In: Water, Air and Soil Pollution. - : Springer Science and Business Media LLC. - 0049-6979 .- 1573-2932. ; 183:1-4, s. 25-35
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Journal article (peer-reviewed)abstract
- Vegetation both physically and biochemically influences denitrification in wetlands. Litter from various plant species supplies various amounts and qualities of organic carbon to denitrifying bacteria, and may thus affect denitrification capacity. We explore whether there is seasonal variation in the denitrification potential in stands of Glyceria maxima, Phragmites australis, Typha latifolia, and Potamogeton pectinatus (the stands differed in terms of which species was predominant). Experiments and measurements investigated whether denitrification potential was related to organic matter and its availability to denitrifying bacteria, suitability for bacterial growth, and amount in the wetland. Availability of organic material, as measured in the slurries, was highest in the G. maxima and P. pectinatus samples, with the highest availability in May and August. However, when the samples were closer to wetland conditions, i.e., intact sediment cores containing litter and organic sediment, the denitrifying capacity was highest in the cores from G. maxima stands, but lowest in P. pectinatus cores. In addition, the denitrification potential of the intact cores was highest in November. Differences in denitrification capacity between the slurries and intact sediment cores, considering the organic material of the plant species and the seasonal pattern, were attributed to differences in the amount of plant litter generated.
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| 19. |
- Kyambadde, Joseph, 1970-
(author)
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Optimizing processes for biological nitrogen removal in Nakivubo wetland, Uganda
- 2005
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Doctoral thesis (other academic/artistic)abstract
- The ability of Nakivubo wetland (which has performed tertiary water treatment for Kampala city for the past 40 years) to respond to pollution and to protect the water quality of Inner Murchison Bay of Lake Victoria was investigated. The aim of this study was to assess the capacity of Nakivubo wetland to remove nitrogen from the wastewater after its recent encroachment and modification, in order to optimize biological nitrogen removal processes using constructed wetland technology. Field studies were performed to assess the hydraulic loading, stability and water quality of this wetland. The distribution and activity of ammonium-oxidizing bacteria (AOB) in Nakivubo channel and wetland were also investigated, and the significance of the different matrices in biological nitrogen transformations within the two systems elucidated. Studies to optimize nutrient removal processes were carried out at pilot scale level both in container experiments and in the field using substrate-free constructed wetlands (CWs) planted with Cyperus papyrus and Miscanthidium violaceum which were adapted to the local ecological conditions. Results showed that Nakivubo wetland performs tertiary treatment for a large volume of wastewater from Kampala city, which is characterised by large quantities of nutrients, organic matter and to a lesser extent metals. Mass pollutant loads showed that wastewater effluent from a sewage treatment plant constituted a larger proportion of nitrogen and phosphorus and biochemical oxygen demand (BOD) discharged into the wetland. The upper section of Nakivubo wetland exhibited high removal efficiencies for BOD, whereas little or no ammonium-nitrogen and metals except Lead were removed by wetland. Studies further showed that nitrifying bacteria existed in the wetland but their activity was limited by oxygen depletion due to the high BOD in the wastewater and heterotrophic bacteria from the sewage treatment plant. Distributional studies indicated the presence of more AOB in surface sediments than the water column of the lower section of Nakivubo channel, an indication that nitrifiers settled with particulate matter prior to discharge into the wetland, and thus did not represent seeding of the wetland. The significant reductions in concentrations of BOD compared to ammonium and total nitrogen in the channel and wetland wastewater confirmed this finding. Whereas suspended nitrifiers upstream of Nakivubo channel equally influenced total nitrogen balance as those in surface sediments, epiphytic nitrification was more important than that of sediment/peat compartments in the wetland, and thus highlighted the detrimental impacts of wetland modification on the water quality Inner Murchison Bay and Lake Victoria as a whole. Performance assessment of pilot-scale container experiments and field-based CWs indicated highly promising treatment efficiencies, notably in papyrus-based treatments. Plant biomass productivity, nutrient storage, and overall system treatment performance were higher in papyrusbased constructed wetlands, and resulted in effluent that met national discharge limits. Thus, papyrus-based CWs were found to be operationally efficient in removing pollutants from domestic wastewater.
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| 20. |
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| 21. |
- Lind, Linus, et al.
(author)
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Nitrate removal capacity and nitrous oxide production in soil profiles of nitrogen loaded riparian wetlands inferred by laboratory microcosms
- 2013
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In: Soil Biology and Biochemistry. - : Elsevier. - 0038-0717 .- 1879-3428. ; 60, s. 156-164
-
Journal article (peer-reviewed)abstract
- Riparian wetlands located in agricultural catchments may often receive a high nitrate (NO3−) load because of the leaching of nutrients derived from upland farming activities. Nitrate can be removed in wetland soils by denitrification which is the reduction of NO3− to the gaseous forms nitrous oxide (N2O) and dinitrogen (N2). However, the release of N2O is detrimental to the environment because N2O is a potent greenhouse gas. Therefore, this study aimed at investigating the factors controlling the production of N2O and at evaluating the risk for N2O emissions from riparian wetland soils. In a laboratory setup, we simulated an upward flow of NO3− enriched groundwater through intact soil cores collected from four wetlands with contrasting soil characteristics. The results showed a rapid reduction of the NO3− fluxes, supporting the effectiveness of wetlands for removal of N. However, during the reduction of NO3− transient accumulation of N2O was observed, but the N2O concentration decreased with declining NO3− availability. In this study, the NO3− load was revealed as the only significant factor controlling both NO3− reduction and N2O production. Our results confirm the capacity of wetlands to remove large amounts of N, but it also showed that substantial emission of N2O might occur if the reduction of NO3− is not complete, a matter to be considered when diverting N rich waters toward wetlands.
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| 22. |
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| 23. |
- Okoth Raburu, Phillip, et al.
(author)
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Use of macroinvertebrate assemblages for assessing performance of stabilization ponds treating effluents from sugarcane and molasses processing
- 2017
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In: Environmental Monitoring & Assessment. - : SPRINGER. - 0167-6369 .- 1573-2959. ; 189:2
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Journal article (peer-reviewed)abstract
- Wastewater discharge from sugarcane processing is a significant pollutant of tropical aquatic ecosystems. For most developing countries, monitoring of the level of pollutants is done mostly through chemical analysis, but this does not reflect potential impacts on aquatic assemblages. In addition, laboratory facilities for accurate concentration measurements are often not available for regular monitoring programs. In this study, we investigated the use of benthic macroinvertebrates for biological monitoring in western Kenya. Benthic macroinvertebrates were sampled in stabilization ponds treating wastewater from sugarcane- and molassesbased processing plants to assess their composition and abundance in relation to different concentrations of chemical variables. Optimum concentrations and tolerance values were identified for various taxa, and a biotic index was developed that combined tolerance values (ranked between 0 and 10) for the various macroinvertebrate taxa. A succession in composition and distribution of macroinvertebrate taxa was observed from the inlet to the outlet of the pond systems. Diptera dominated in the first ponds that had high concentrations of chemical oxygen demand (COD), biological oxygen demand (BOD5), and nutrients, while intolerant Ephemeroptera, Plecoptera, and Trichoptera (EPT) appeared as the concentrations dropped in subsequent ponds. The effluent quality was classified as "good","fair," and "poor," corresponding with biotic index value ranges 0-3.50, 3.51-6.50, and 6.51-10, respectively. During validation, the index grouped sites with respect to levels of measured environmental variables. The study revealed that the developed biotic index would help in monitoring the quality of sugarcane processing and molasses effluents before release into recipient aquatic ecosystems, replacing the need for costly chemical analyses.
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| 24. |
- Sharpley, Andrew N., et al.
(author)
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Future agriculture with minimized phosphorus losses to waters: Research needs and direction
- 2015
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In: Ambio. - : Springer Verlag (Germany). - 0044-7447 .- 1654-7209. ; 44, s. S163-S179
-
Journal article (peer-reviewed)abstract
- The series of papers in this issue of AMBIO represent technical presentations made at the 7th International Phosphorus Workshop (IPW7), held in September, 2013 in Uppsala, Sweden. At that meeting, the 150 delegates were involved in round table discussions on major, predetermined themes facing the management of agricultural phosphorus (P) for optimum production goals with minimal water quality impairment. The six themes were (1) P management in a changing world; (2) transport pathways of P from soil to water; (3) monitoring, modeling, and communication; (4) importance of manure and agricultural production systems for P management; (5) identification of appropriate mitigation measures for reduction of P loss; and (6) implementation of mitigation strategies to reduce P loss. This paper details the major challenges and research needs that were identified for each theme and identifies a future roadmap for catchment management that cost-effectively minimizes P loss from agricultural activities.
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| 25. |
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| 26. |
- Sundberg, Carina, 1963-, et al.
(author)
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Ammonia oxidation and the corresponding bacterial communities in two overland flow areas treating landfill leachate or wastewater
- 2011
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In: Overland Flow and Surface Runoff. - : Nova Science Publishers, Inc.. - 9781611228687 ; , s. 346-
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Book chapter (peer-reviewed)abstract
- A high diversity of ammonium oxidising bacteria (AOB) has been observed in overland flow areas (OFA) treating ammonia-rich landfill leachate. The current section aimed to explore if treatment OFAs in general supports more diverse AOB communities than conventional treatment systems, or if it is a result of effluent composition. The potential ammonium oxidation and the AOB community composition were studied during three seasons in an OFA where one part received wastewater and the other landfill leachate. The AOB communities were investigated using group-specific PCR primers targeting the 16S rRNA gene, and analysed by DGGE and nucleotide sequencing. The potential ammonia oxidation, studied by short-time slurry incubation, was higher in the landfill OFA than in the wastewater area and highest in the litter layer. Higher activity correlated with the appearance of Nitrosomonas sp. belonging to cluster 7. Both overland flow areas supported a more diverse AOB community than in common wastewater treatment plants. Fifteen different AOB sequences were detected, but only three were observed in both OFAs, pointing to the impact of the effluent quality and/or the hydraulic load. The wastewater OFA, which received a higher load of effluents with 5-10 times lower ammonia concentrations, was dominated by AOB populations that are usually found in less favourable conditions.
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| 27. |
- Sundberg, Carina, 1963-, et al.
(author)
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Development of the community structure and activity of ammoniaoxidising bacteria in overland flow systems used to treat landfill leachates
- 2009
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In: Journal of Applied Microbiology. - 1364-5072 .- 1365-2672.
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Journal article (other academic/artistic)abstract
- Ammonium in landfill leachates can be nitrified in overland flow areas (OFA). We studied OFAs to investigate if changes occur in the ammonium oxidizing community as the ecosystem develops, and the influence of different operating conditions. Samples were collected from the macrophyte litter layers, the rhizospheres and the sediments in their associated settling ponds in May, August, and November during four years. Potential ammonia oxidation (PAO) was investigated by a short-term slurry incubation method. The composition of the ammonia-oxidising bacteria (AOB) communities was investigated by PCR, using a group-specific primer pair, followed by denaturing gradient gel electrophoresis and subsequent sequencing. A shift from a Nitrosomonas community to a mixture of Nitrosomonas and Nitrosospira was and a gradual increase in PAO was observed, but only in the litter layer in the youngest OFA. Both OFAs had diverse AOB communities belonging to six different clusters. Nitrosomonas clusters predominated in the OFA with higher PAO, whereas Nitrosospira clusters were more common in the OFA with lower PAO. There was a seasonal increase of AOB populations in the OFA that was not in use during winter, and a more stable composition of the AOB community and the PAO in the OFA with year-round application. Keywords: Ammonia-oxidising bacterial community; Landfill leachates; Nitrification; Overland flow; 16S rDNA; Denaturing gradient gel electrophoresis.
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| 28. |
- Sundberg, Carina, 1963-
(author)
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Nitrifyers in constructed wetlands treating landfill leachates
- 2008
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Doctoral thesis (other academic/artistic)abstract
- Landfill leachate is produced many years after a landfill site closes. Hence, treatment by “natural methods”, as e.g. constructed wetlands, with low management requirements is attractive. Constructed wetlands usually provide both shallow and deep areas with aerobic and anaerobic zones, which is suitable for nitrification followed by denitrification of the ammonium-rich leachates. Full-scale treatment systems are influenced by climatic variables that affect the microbial community. Also, the operational strategy can have a considerable impact on both activity and composition of the microorganisms. Many studies have measured inflow/outflow water quality in treatment systems. Such “black box” studies describe the treatment efficiency but add little to an increased understanding of theorganisms performing the treatment or the spatial distribution of their activities and treatment processes.In this thesis we investigated seasonal and annual changes in potential nitrification and denitrification, and in the corresponding bacterial communities in constructed wetlands treating landfill leachates. Variations in the potential activity in full-scale systems were investigated over several years, using short-term incubation. The composition of the bacterial communities was investigated using a group-specific PCR primer pair targeting the 16S rRNA genes or a primer pair targeting the funtional gene nosZ. The PCR products were analysed by denaturing gradient gelelectrophoresis and subsequent nucleotide sequencing and phylogentic analysis.A stable ammonia-oxidising bacterial (AOB) community composition and potential ammonia-oxidation (PAO) were detected in the system with a year-round operation. On the other hand, changes in the AOB community composition which followed the operational schedule were detected in the overland flow area (OFA) running seasonally. Furthermore, the influence of operational strategy was indicated by a low PAO in the wastewater overland flow area and compact constructed wetland receiving high hydraulic loads, indicating the value of aeration. Higher PAO was detected in the OFAs where the hydraulic load followed literature guidelines.All systems supported diverse AOB communities, represented by several Nitrosomonas and Nitrosospira populations. The number of different populations detected in these wetlands was much higher than reported in municipal wastewater treatment plants, and differed from those in a parallel OFA treating municipal wastewater. Furthermore, the large variation in both potential activity and sequences detected in replicate samples suggests that such systems are spatially heterogenic.
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| 29. |
- Sundberg, Carina, 1963-, et al.
(author)
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Overland flow systems for treatment of landfill leachates : Potential nitrification and structure of the ammonia-oxidising bacterial community during a growing season
- 2007
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In: Soil Biology and Biochemistry. - : Elesevire. - 0038-0717 .- 1879-3428. ; 39:1, s. 127-138
-
Journal article (peer-reviewed)abstract
- Overland flow systems are useful for treating landfill leachates, because they provide favourable conditions for nitrification and they are easy to maintain. However, little is known about the microbial communities in such systems or the nitrification capacity of those microorganisms. In this study, seasonal variations in potential nitrification and in community composition of nitrifying bacteria were investigated in two overland flow areas receiving leachate from landfills at Korslöt and Hagby, Sweden. Samples were collected in the settling ponds sediment and at two depths in the overland flow areas (the macrophyte litter layer and the rhizosphere) in May, August and November 2003. A short-term incubation method was used to measure potential oxidation of ammonia and nitrite (designated PAO and PNO). The ammonia-oxidising bacterial (AOB) community was investigated using a 16S rRNA gene approach that included PCR amplification and analysis of PCR products by denaturing gradient gel electrophoresis (DGGE), followed by nucleotide sequencing and phylogenetic analysis. PAO was determined in the range 5–2700 (NO2−+NO3−)-N g−1 dw d−1 and PNO in the range 60–2000 μg NO2−-N g−1 dw d−1. At Korslöt, PAO and PNO showed similar temporal variation in the different ecosystems, whereas no such relationship was noticed at Hagby. Considering both sites, there was no obvious change in the composition of the AOB community over the growing season. However, the composition did differ between the ecosystems: Nitrosomonas-like sequences were more common in the ponds, and in the litter layers they were found as often as Nitrosospira-like sequences, whereas Nitrosospira-like sequences were more common in the rhizospheres. Altogether, we found nine different AOB sequences, five Nitrosomonas-like and four Nitrosospira-like, which belonged to clusters 0, 2, 3b, 6a, 6b and 7. There was no apparent relationship between the number of AOB populations and the PAO in different soil layers and sediments.
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| 30. |
- Sundberg, Carina, et al.
(author)
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Potential nitrification and denitrification and the corresponding composition of the bacterial communities in a compact constructed wetland treating landfill leachates
- 2007
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In: Water Science and Technology. - : IWA Publishing. - 0273-1223 .- 1996-9732. ; 56:3, s. 159-166
-
Journal article (peer-reviewed)abstract
- Constructed wetlands can be used to decrease the high ammonium concentrations in landfill leachates. We investigated nitrification/denitrification activity and the corresponding bacterial communities in landfill leachate that was treated in a compact constructed wetland, Tveta Recycling Facility, Sweden. Samples were collected at three depths in a filter bed and the sediment from a connected open pond in July, September and November 2004. Potential ammonia oxidation was measured by short-term incubation method and potential denitrification by the acetylene inhibition technique. The ammonia-oxidising and the denitrifying bacterial communities were investigated using group-specific PCR primers targeting 16S rRNA genes and the functional gene nosZ, respectively. PCR products were analysed by denaturing gradient gel electrophoresis and nucleotide sequencing. The same degree of nitrification activity was observed in the pond sediment and at all levels in the filter bed, whereas the denitrification activity decreased with filter bed depth. Denitrification rates were higher in the open pond, even though the denitrifying bacterial community was more diverse in the filter bed. The ammonia-oxidising community was also more varied in the filter bed. In the filter bed and the open pond, there was no obvious relationship between the nitrification/denitrification activities and the composition of the corresponding bacterial communities.
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| 31. |
- Sundblad-Tonderski, Karin, 1958-
(author)
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Recycling of wastewater nutrients in a wetland filter
- 1988
-
Doctoral thesis (other academic/artistic)abstract
- This thesis demonstrates the possibility of using wastewater nutrients for plant biomass production and concomitantly achieving year-round wastewater treatment. As part of a joint research project, the emphasis in this thesis is on nutrient recycling capacity relative to treatment efficiency.An artificial wetland system was studied in experimental field lysimeters. Wastewater was infiltrated into soil planted with reed sweetgrass (Glyceria maxima). In natural stands of this grass, harvesting two or three times per year had a negative impact on biomass yields. This was attributed to a reduced amount of carbohydrates stored in the rhizomes, resulting in the formation of thinner shoots in harvested stands. In contrast to this, high biomass yields were obtained with two harvests per year in the wetland filter.Crop removal of nitrogen and phosphorus amounted to a maximum of 55% and 28% of the amount applied during a growing season. Year-round wastewater application would decrease the relative removal because no plant uptake occurrs during the winter months. However, applied nutrients are also transferred to the soil, thus contributing to the nutrient recycling capacity of the system. This may determine the longevity of a wet! and filter as a method of wastewater treatment, since the soil is gradually saturated with phosphorus. Another factor of importance for the long-term limitations is the observed decrease in soil permeability.Treatment efficiency of phosphorus and BOD7 met the required limits for wastewater emissions in Sweden. An average 60% removal of nitrogen was achieved, which is significantly more than in a conventional tertiary treatment plant. The costs for reaching this treatment level were estimated to be lower for a wet land filter than for the existing treatment systems for urban areas up to 1000 inhabitants. The feasibility for this conceptual change of better resource management with regard to present Swedish wastewater treatment strategy is discussed.
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| 32. |
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| 33. |
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| 34. |
- Thoren, A.-K., et al.
(author)
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Temporal export of nitrogen from a constructed wetland : Influence of hydrology and senescing submerged plants
- 2004
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In: Ecological Engineering. - : Elsevier BV. - 0925-8574 .- 1872-6992. ; 23:4-5, s. 233-249
-
Journal article (peer-reviewed)abstract
- Nitrogen export was measured during monthly monitoring in an 18-ha constructed wetland in southeast Sweden 1998-2001. To investigate the influence of increased water flow on wetland nitrogen export, we performed intensive sampling (eight samples per day) of total-N, urea-N, NH4+-N, NO3--N in January-March 2001. Investigations of wetland plant distribution 1997-2001 and submerged plant biomass were combined with investigations of plant nitrogen content 1998-2001, to test the hypothesis that nitrogen export was linked to wetland plant decomposition. Nitrogen was exported from the wetland (3.3 kg N ha-1 d-1), during the end of the intensive sampling period (19 February-12 March), coinciding with increased water flow (from 0.2 to 0.6 m3 s-1). Plant cover expanded rapidly and nitrogen assimilated in the submerged plant community was estimated to be 39 kg ha-1 in July 2001. After senescence in April the following year, plant biomass was reduced by 75%. We concluded that a significant part (40%) of this wetland nitrogen export might be associated with the release of organic and inorganic nitrogen from the senesced submerged plant community. Moreover, we hypothesize that nitrogen removal in wetlands in cold temperate climate may be limited by temporal nitrogen export induced by high water flow velocity when wetland plants are decomposing. © 2004 Elsevier B.V. All rights reserved.
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| 35. |
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| 36. |
- Van Cleemput, O, et al.
(author)
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Denitrification in Wetlands
- 2007. - 1
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In: Biology of the nitrogen cycle. - Amsterdam : Elsevier. - 9780444531087 ; , s. 359-367
-
Book chapter (other academic/artistic)abstract
- All organisms require nitrogen to live and grow. The movement of nitrogen between the atmosphere, biosphere, and geosphere in different forms is described by the nitrogen cycle. This book is an activity of the COST 856 Action on Denitrification. It covers all aspects of the N-cycle: chemistry, biology (enzymology, molecular biology), physics, applied aspects (greenhouse effect, N-pollution problems, practices in farming, in waste-water treatment, and more). In this book, leading editors offer the latest research available on dentrification (reduction of nitrates or nitrites commonly by bacteria- as in soil). * Provides details on denitrification and its general role in the environment* Offers latest research in N-Cycle and its reactions* Discusses impacts on various environments: agriculture, wetlands, plants, waste-water treatment and more* The only book available in the field since the last 20 years* Contains 27 chapters written by internationally highly recognized experts in the field* Covers all modern aspects, emphasizes molecular biology and ecology* Written in an easily understandable way
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| 37. |
- Vymazal, J, et al.
(author)
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Constructed wetlands for wastewater treatment
- 2006
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In: Wetlands and Natural Resource Management. Ecological Studies. - Berlin : Springer Verlag. - 3540331867 ; , s. 69-96
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Book chapter (other academic/artistic)abstract
- Together with its companion, Volume 191 Wetlands: Functioning, Biodiversity Conservation and Restoration, this book provides a broad and well-integrated overview of recent major scientific results in wetland science and their applications in natural resource management issues.After an introduction to the field, a group of internationally known experts summarizes the state of the art on an array of topics, divided into four sections:-The Role of Wetlands for Integrated Water Resources Management: Putting Theory into Practice-Wetland Science for Environmental Management-Wetland Biogeochemistry-Wetlands and Climate Change Worldwide The volume will be useful to wetland scientists and natural resource managers, as well as environmental policy makers at all levels.
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