Flow hydrodynamics condition has a significant impact on the fate and transport of colloid-pollutant in vegetation filter strips, and is critical to the control of nonpoint source pollution.ABSTRACT: Flow hydrodynamic condition impacts the deposition process on vegetation and removal of colloid and colloid-associated contaminants in saturated vegetative filter strips (VFSs) under rainfall. A 9.6-m-long flume was constructed to investigate the retention of colloids through VFSs, with saturated soil and simulated rainfall. Colloidal filtration theory was applied to calculate the colloid deposition rate coefficient (k d ) on vegetation surface. The result showed that removal efficiencies (η) of the single-stem decreased, but colloid k d on the flume scale vegetation increased with increased Reynolds number (Re). Flume experiment found that the colloid retention rate in VFSs decreased as the Re increased. Since deposition on vegetation surface and diffusion into saturated soil are two main removal mechanisms, the discrepancy between k d and retention rate suggests that colloid diffusion into the soil was the dominant process of colloid removal in saturate VFSs. The research deepens the understanding of colloid transport mechanism in VFSs, and provides theoretical basis for the design of VFSs.

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