NUMERICAL SIMULATION OF A FINE-GRAINED DENITRIFICATION LAYER FOR REMOVING SEPTIC SYSTEM NITRATE FROM SHALLOW GROUNDWATER

Presentation of governing equation for variably saturated groundwater flow in a 3D non-deforming porous medium. Macroscopic equations governing aqueous advective - dispersive and air-phase diffuse transport in a variably saturated porous medium sandy aquifer are described. Are discussed numerical solution, simulation scenario, modelling domain for the site plume simulations and simulated nitrate plume without denitrification layer with drains spaced at various distances. Presentation of values of the van Genuchten parameters used for the experimental site. Profiles of water saturation with a de-nitrification layer. Simulation plumes for a horizontal de-nitrification layer for : ammonium, nitrate , dissolved carbon, dissolved oxygen, DOC, dissolved molecular nitrogen and pH. Profiles of pH an HCO3 and water saturation are done for deep table case with de-nitrification layer. Discussion on the effect of drain spacing.