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Controlling factors for water residence time and flow patterns in Ekeby treatment wetland, Sweden
Swedish University of Agricultural Science.
Swedish University of Agricultural Science.
Swedish University of Agricultural Science.
Swedish University of Agricultural Science.
2007 (English)In: Advances in Water Resources, ISSN 0309-1708, E-ISSN 1872-9657, Vol. 30, no 4, 838-850 p.Article in journal (Refereed) Published
Abstract [en]

Treatment wetlands play an important role in reducing nutrient content and heavy metals in wastewater and run-off water. The treatment efficiency strongly depends on flow pattern and residence times of the water. Here, we study the impact of different factors on water flow patterns based on a tracer experiment with tritiated water in a 2.6 ha constructed wetland pond. A 2D flow and inert transport model was used to evaluate the relative importance of bottom topography, vegetation distribution, water exchange with stagnant zones and dispersion.

Results from computer simulations and independent measurements of friction losses as well as wetland geometry showed that variations in bottom topography, formed by several deep zones, decreased the variance in water residence times to a minor extent. Heterogeneity in vegetation, on the other hand, significantly contributed to the spread in water residence times and explained the multiple peaks observed in the breakthrough curves. Analyses showed that in the Ekeby treatment wetland, basin shape explained about 10% of the variance in the observed residence times, whereas vegetation explained about 60-80%. To explain all variance secondary factors were needed, such as dispersion and water exchange with stagnant zones. These were shown to contribute to the spread of residence times and primarily to the long tail of the observed breakthrough curves.

Place, publisher, year, edition, pages
2007. Vol. 30, no 4, 838-850 p.
Keyword [en]
Constructed wetland, Flow resistance, Hydraulic model, Residence time, Tracer experiment, Vegetation
National Category
Oceanography, Hydrology, Water Resources
Identifiers
URN: urn:nbn:se:kth:diva-7081DOI: 10.1016/j.advwatres.2006.07.002ISI: 000245259400009OAI: oai:DiVA.org:kth-7081DiVA: diva2:11987
Note
QC 20100906Available from: 2007-05-14 Created: 2007-05-14 Last updated: 2017-12-14Bibliographically approved
In thesis
1. Coupled Hydrological and Microbiological Processes Controlling Denitrification in Constructed Wetlands
Open this publication in new window or tab >>Coupled Hydrological and Microbiological Processes Controlling Denitrification in Constructed Wetlands
2007 (English)Licentiate thesis, comprehensive summary (Other scientific)
Abstract [en]

Treatment wetlands play an important role in reducing nitrogen content in wastewater and agricultural run-off water. The main removal process is denitrification and the removal efficiency depends on the hydrological and microbiological features of the wetland, especially in terms of water residence times and denitrification rates. The aim of this thesis was to increase the understanding of the coupled hydrological and microbiological processes regulating the denitrification capacity. This was done by applying a broad spectrum of analyses methods, including tracer experiment, water flow modeling, denitrification rate measurements, and analyses of the microbial community structures. The tracer experiment and flow modeling revealed that the wetland design, especially the vegetation, largely can affect the water residence time distributions in wetlands. In the investigated wetland, vegetation dominated the water flow, explaining 60-80% of the variance in water residence times, whereas basin shape only explained about 10% of the variance, but also mixing phenomena significantly affected the residence times and could considerably delay solutes. Measured potential denitrification rates in the wetland exhibited significant spatial variations, and the variations were best described by concentration of nitrogen in sediments and water residence time. Analyses of the denitrifying bacteria populations indicated that a few key populations dominated and that the community diversity increased with decreasing nutrient levels and increasing water residence times. Moreover, it was found that denitrification rates in terms of Menten and first order kinetics can be evaluated by fitting a mathematical expression, considering denitrification and other nitrogen transforming processes to measured product formation in nitrate limited experiments.

Place, publisher, year, edition, pages
Stockholm: KTH, 2007. x, 20 p.
Series
Trita-LWR. LIC, ISSN 1650-8629 ; 2038
Keyword
Constructed wetland, Residence time, water flow modeling, denitrification rate, Tracer experiment, denitrifying bacteria community structure
National Category
Oceanography, Hydrology, Water Resources
Identifiers
urn:nbn:se:kth:diva-4370 (URN)978-91-7178-663-0 (ISBN)
Presentation
2007-05-25, V2, Teknikringen 76, Teknikringen 76, KTH, Stockholm, 13:15
Opponent
Supervisors
Note
QC 20101110Available from: 2007-05-14 Created: 2007-05-14 Last updated: 2010-11-10Bibliographically approved

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