HR: 16:15h
AN: NB44C-04    [Abstracts]
TI: Tracer experiment and flow modelling applied to Ekeby treatment wetland, Sweden.
AU: * Kjellin, J P
EM: johan.kjellin@bt.slu.se
AF: Dept. of Biometry and Engrg / SLU, Box 7032, Uppsala, S-750 07 Sweden
AU: Worman, A
EM: anders.worman@bt.slu.se
AF: Dept. of Biometry and Engrg / SLU, Box 7032, Uppsala, S-750 07 Sweden
AB: The use of treatment wetlands have come to play an important role in reducing nutrient content in wastewater and in run-off water from agricultural areas. It is of interest to optimize the nutrient removal efficiency. In order to do so hydrological and geochemical processes, and the coupling between them, must be known in greater detail than is currently the case. One way of investigating this matter is to perform tracer experiments and evaluate the results using computer simulations. In November 2002 a simultaneous tracer experiment was performed in a treatment wetland, using tritiated water, P-32 and N-15. The wetland is situated 120 km west of Stockholm in Sweden, and the basin where the experiment was performed has an area of 2,6 ha. The simultaneous use of conservative tracer and reactive tracers enables a fair evaluation of both hydraulic processes and biochemical reactions. In this presentation evaluation of the hydraulic matters will be in focus, the geochemical issues will be described in companion presentations. In order to evaluate the hydraulic behaviour and the fate of tritium through the wetland, a two-dimensional flow model was developed in a MATLAB environment. The model is able to deal with variations in shape, bottom topography and friction factors. It was used to simulate flow of inert particles through the wetland. Breakthrough curves of tritium and simulation results were studied and compared for different setups of friction parameters. The simulations show that bottom topography and shape of basin alone are not enough to explain the spreading of water residence times in the wetland. Distribution and density of vegetation, simulated as friction factors, are shown to be crucial when it comes to reproducing the residence time distribution from the experiment.
DE: 1719 Hydrology
DE: 1890 Wetlands
DE: 4842 Modeling
SC: North American Benthological Society [NB]
MN: 2005 Joint Assembly