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Potential nitrification and denitrification on different surfaces in a constructed treatment wetland
Linköping University, Department of Physics, Chemistry and Biology, Ecology . Linköping University, The Institute of Technology.
Dep. of Ecology/Limnology, Lund Univ., Lund, Sweden.
Dep. of Zoology, Univ. of Coimbra, Coimbra, Portugal .
Dep. of Zoology, Univ. of Coimbra, Coimbra, Portugal .
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2004 (English)In: Journal of environmental quality, ISSN 0047-2425, Vol. 32, no 6, 2414-2420 p.Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
2004. Vol. 32, no 6, 2414-2420 p.
National Category
Natural Sciences
URN: urn:nbn:se:liu:diva-14076OAI: diva2:22576
Available from: 2006-10-09 Created: 2006-10-09 Last updated: 2009-05-22
In thesis
1. Nitrogen removal in treatment wetlands: Factors influencing spatial and temporal variations
Open this publication in new window or tab >>Nitrogen removal in treatment wetlands: Factors influencing spatial and temporal variations
2006 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

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 community

composition 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.

Place, publisher, year, edition, pages
Institutionen för fysik, kemi och biologi, 2006
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1041
Wetlands, denitrification, macrophytes, nitrogen, nitrification, model, treatment wetlands, potential denitrification
National Category
Biological Sciences
urn:nbn:se:liu:diva-7564 (URN)91-85523-12-7 (ISBN)
Public defence
2006-11-10, Planck, Fysikhuset, Campus Valla, Linköpings universitet, Linköping, 10:15 (English)
Available from: 2006-10-09 Created: 2006-10-09 Last updated: 2009-06-10

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