Abstract: When surface flow passes through vegetative filter strips (VFS), the stems and branches of plant will convert the kinetic energy of water flow into turbulent flow energy, change the hydraulic characteristics of the surface flow, and then affect the migration of colloidal particles. The aim of this research is to explore the effect of surface slope flow with different hydraulic characteristics on the migration and removal mechanism of colloid in VFS, and furthermore to provide a theoretical basis for the design of VFS in removing colloidal pollutants. The migration process of colloids in VFS with different Reynolds numbers was observed via indoor experiment, and a numerical model of simulating the colloid migration was constructed by coupling the water balance equation and the colloid migration equation. Results manifested that, as the Reynolds number increased, the flow state complicated, the regularity attenuated, and the colloidal deposition and adsorption process strengthened. Given the same hydraulic characteristics, the particle of colloid in unfavorable adsorption state expanded and the surface potential decreased along the way, which weakened the diffusion capacity and deposition adsorption capacity. However, as the Reynolds number increased, the removal efficiency of colloids by VFS declined due to the increase in flow velocity under soil saturation and the decrease of the diffusion process of colloids into the soil.

Key words: colloidal, vegetative filter strips, saturated underlying surface, hydraulic characteristics, Reynolds number, deposition adsorption efficiency coefficient