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

This study provides a framework for a new approach addressed to performing constructed wetlands modeling 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 provide a detailed representation of water flow through CFD as well as solid phase consideration by using DEM. The advantages of this approach over conventional porous media are highlighted, and details to perform computational fluid dynamics and discrete element method (CFD-DEM) modeling of a subsurface flow constructed wetland (CW) are presented. Validation of the CFD-DEM model was performed on two CWs case studies, and the results were compared to the classical Darcy-Forchheimer porous media model. Statistical and hydraulic performance indexes were used to evaluate the efficacy of models. The results indicated that CFD-DEM approach outperformed the classical model based on the aforementioned metrics and considering the similarity with experimental results. The application of CFD-DEM coupling for CWs showed to be an interesting approach as it enables to perform more complex analyses of the hydrodynamics of CWs, becoming a valuable tool for future research and system optimization.