Proposal of a new approach to perform advanced flow modeling for subsurface flow treatment wetlands.

This study describes a new approach to model treatment wetlands (TW) by using computational fluid dynamics (CFD) coupled with the discrete element method (DEM). This methodology is based on the adoption of open-source software to perform advanced hydraulic simulations that enable a detailed representation of water flow through CFD as well as solid phase consideration by using DEM. The main features of this approach are highlighted and details on how to perform CFD-DEM modeling of a horizontal flow treatment wetland (HFTW) are described. Validation of the CFD-DEM model was performed on two TW case studies. The results were compared to the Darcy-Forchheimer porous media model. Statistical and hydraulic performance indexes were used to evaluate the efficacy of models. Provided that no calibration was done, the results indicated that for these case studies the CFD-DEM approach outperformed the Darcy-Forchheimer model based on the aforementioned metrics and considering the similarity with experimental results. The application of CFD-DEM coupling for TW proved to be an interesting approach as it enables more complex analysis of the hydrodynamics of TWs, becoming a valuable tool for future research and system optimization.