Calibration of a simulation tool for subsurface flow constructed wetlands for wastewater treatment

This paper deals with the calibration of the multi-component reactive transport model CW2D ( C onstructed W etland 2D ) for subsurface flow constructed wetlands for wastewater treatment. CW2D is able to describe the transformation and elimination processes of organic matter, nitrogen, and phosphorus. Simulation results are shown for an indoor pilot-scale constructed wetland. A good calibration of the flow model was possible for the pilot-scale constructed wetland and therefore the results of the reactive transport simulations with CW2D fit the measured data well. A sensitivity analysis shows the most influential parameters of CW2D. The parameters of the model that describe the properties of the unsaturated zone turn out to be the most influential parameters. Besides hydralic parameters the oxygen re-aeration rate, and yield coefficients and lysis rates of the micro-organisms are the most important parameters. The result of the sensitivity analysis also supports the statement that good results with CW2D can only be achieved when a calibration of the flow model is possible.