Orage: design-support model of vertical flow CSO-CWs

In France, CSO-CWs are variably saturated vertical flow constructed wetlands with throttled outflow. These systems treat TSS, COD and NH4-N and mitigate flow peaks. The received flows and concentrations are stochastic; as such, design optimization requires a dynamic approach. Processbased models would be difficult to handle and therefore, a new design support tool called Orage was developed. Orage is based on a simplified core model and has an iterative shell for optimization as well as a user interface. It interpolates the optimal dimensions and the simplest recommendable material site-specifically, using a low number of inputs and inflow data series. The core model simulates hydraulics and the removal of TSS, COD and NH4-N and has to be reliable to base predictions on its output. First results with the core show a good fitting to a single load and a load series with closed material balance. The sensitivity analysis confirmed model robustness and warned that different parameters are important for a good performance in the case of the two operation modes.