Coupled Hydrological and Microbiological Processes Controlling Denitrification in Constructed Wetlands
2007 (English)Licentiate thesis, comprehensive summary (Other scientific)
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.
Trita-LWR. LIC, ISSN 1650-8629 ; 2038
Constructed wetland, Residence time, water flow modeling, denitrification rate, Tracer experiment, denitrifying bacteria community structure
Oceanography, Hydrology, Water Resources
IdentifiersURN: urn:nbn:se:kth:diva-4370ISBN: 978-91-7178-663-0OAI: oai:DiVA.org:kth-4370DiVA: diva2:11989
2007-05-25, V2, Teknikringen 76, Teknikringen 76, KTH, Stockholm, 13:15
Klöve, Björn, Professor
Wörman, AndersHallin, SaraUlén, Barbro
QC 201011102007-05-142007-05-142010-11-10Bibliographically approved
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