Modelling the recovery time from peak loads in a full-scale horizontal flow wetland in Sicily

The aim of this study was to simulate the water flow and reactive transport of pollutants in a horizontal flow (HF) wetland to better understand the recovery time of the treatment performance for peak load events. For the simulation, the processes-based model HYDRUS and its Wetland Module is used. The system under investigation is the first stage of the 9-years old hybrid treatment wetland of a large retail store, located in Catania, Italy. For the calibration of the hydraulic model, the data of a tracer test was used. The data set of the systems is available for a seven year period including organic matter and ammonia nitrogen. The data was split into a standard event representing low loading conditions and determined peak load events with high loadings. The results show that the response time of the model correlates with the hydraulic retention time from the tracer experiment and indicates that higher peak load concentrations at the inlet of the system lead to a longer recovery time of the wetland.