For the simulation of vertical flow constructed wetlands (VFCWs), the multicomponent reactive transport module CW2D implemented in the HYDRUS software is used. This biokinetic model describes the biochemical transformation and degradation process in subsurface flow CWs, including aerobic and anoxic processes. The data used for this simulation study was measured during a pilot scale experiment at the University of Natural Resources and Life Sciences, Vienna (BOKU University), monitoring three parallel operated, not planted, two-stage VF constructed filters for the treatment of domestic wastewater. Only data from the first stage of each system were used for this simulation study. The setup of each of the first stage systems were as follows, sand-impounded drainage layer, zeolite-impounded drainage layer and zeolite-free drainage layer. The measurements addressed the hydraulic flow, influent and effluent concentrations and the Freundlich adsorption isotherms for NH4-N and NO3-N for both filter materials. This data is used to perform a simulation study based on these three systems to underline the conclusions made based on the measured data, (i) higher NH4-N removal within the zeolite systems based on its high adsorption capacity and (ii) higher denitrification rate within the impounded systems compared to the free drainage system. The model parameters in CW2D were calibrated within the sand - impounded system. One parameter, the maximum nitrification rate was changed in the fitting process and the COD fractions (readily, slowly and inert organic matter) were determined. These settings were used for the other two systems and the adsorption isotherm for zeolite and NH4-N was implemented, using a two-site chemical non-equilibrium model. In the last step, the lysis rate of heterotrophic bacteria had to be adjusted within the zeolitefree drainage system to fit the high measured COD effluent. An overall good fit for the three systems could be achieved using the CW2D module.