Modeling nutrient cycles of surface water constructed wetlands—developments and applications of a system dynamic model
Date Issued
2009
Date
2009
Author(s)
Wang, Yung-Chieh
Abstract
Constructed wetlands are applied as one of the best management practices to alleviate the impact of non-point source pollutions in watershed managing policies. To improve the design and implementation of wetlands, computer modeling provides an ability to make comparisons among alternative designs and managing strategies, thus allowing a wetland to be optimally utilized achieving its intended purpose. In this study, the approach of system dynamics is adopted to develop a simulation model for surface water constructed wetlands, and to provide appropriate values for the parameters of constructed wetland management. Following studies on wetland modeling, a dynamic model of surface water constructed wetlands was integrated by the system dynamic software STELLA, and then applied to two cases located in southern and northern Taiwan, respectively. As the model had been calibrated and validated using data from the tow study cases, sensitivity analysis was applied to find the major parameters that affected the simulation output. The results of calibration and validation indicate that many of the parameter values were the same as those reported in the literature with a few parameters calibrated deviating from the literature values including the maximum growth rate of autotrophs, DO yield coefficients of microbes, denitrification rate at 20C°in both cases. Furthermore, simulating results of the two cases show high statistical correlations, examined by linear regression and Pearson’s correlation (P < 0.05), between the simulated and measured outflow values, which indicate that the model not only can reproduce the seasonal trends of DO, BOD5, TN, TSS, and TP concentrations, but also simulate the variations of DO, BOD5, TSS, and TP. Sensitivity analysis reveals that the parameters of microorganisms, maximum growth rates and DO yield coefficients of autotrophic and heterotrophic bacteria, yield coefficient and TOC half saturation constant of heterotrophs, the N content in microbial biomass, and the denitrification rate at 20C°are included to be sensitive factors that affect DO, BOD5, and TN; while sediment diameter is the key influence on TP and TSS. In future studies, further investigations of environmental microorganisms and aquatic macrophytes are expected to improve the accuracy of the model and provide references for constructed wetland management and design.
Subjects
System dynamics
Constructed wetland
Water quality
Nutrient cycle
Simulation model
SDGs
Type
thesis
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