Ahfir Nasre-Dine, Hammadi Ahmed, Alem Abdellah, Wang HuaQing, Le Bras Gilbert, Ouahbi Tariq
Normandie University, UNIHAVRE, UMR 6294 CNRS, LOMC, 76600 Le Havre, France.
Normandie University, UNIHAVRE, UMR 6294 CNRS, LOMC, 76600 Le Havre, France.
J Environ Sci (China). 2017 Mar;53:161-172. doi: 10.1016/j.jes.2016.01.032. Epub 2016 Jun 5.
The effects of porous media grain size distribution on the transport and deposition of polydisperse suspended particles under different flow velocities were investigated. Selected Kaolinite particles (2-30μm) and Fluorescein (dissolved tracer) were injected in the porous media by step input injection technique. Three sands filled columns were used: Fine sand, Coarse sand, and a third sand (Mixture) obtained by mixing the two last sands in equal weight proportion. The porous media performance on the particle removal was evaluated by analysing particles breakthrough curves, hydro-dispersive parameters determined using the analytical solution of convection-dispersion equation with a first order deposition kinetics, particles deposition profiles, and particle-size distribution of the recovered and the deposited particles. The deposition kinetics and the longitudinal hydrodynamic dispersion coefficients are controlled by the porous media grain size distribution. Mixture sand is more dispersive than Fine and Coarse sands. More the uniformity coefficient of the porous medium is large, higher is the filtration efficiency. At low velocities, porous media capture all sizes of suspended particles injected with larger ones mainly captured at the entrance. A high flow velocity carries the particles deeper into the porous media, producing more gradual changes in the deposition profile. The median diameter of the deposited particles at different depth increases with flow velocity. The large grain size distribution leads to build narrow pores enhancing the deposition of the particles by straining.
研究了多孔介质粒度分布在不同流速下对多分散悬浮颗粒输运和沉积的影响。通过逐步输入注入技术将选定的高岭土颗粒（2 - 30μm）和荧光素（溶解示踪剂）注入多孔介质中。使用了三根填砂柱：细砂、粗砂以及通过将后两种砂按等重量比例混合得到的第三种砂（混合物）。通过分析颗粒突破曲线、使用具有一阶沉积动力学的对流 - 扩散方程解析解确定的水动力弥散参数、颗粒沉积剖面以及回收颗粒和沉积颗粒的粒度分布，来评估多孔介质对颗粒的去除性能。沉积动力学和纵向水动力弥散系数受多孔介质粒度分布控制。混合砂比细砂和粗砂更具弥散性。多孔介质的均匀系数越大，过滤效率越高。在低流速下，多孔介质捕获所有注入的悬浮颗粒尺寸，较大颗粒主要在入口处被捕获。高流速会使颗粒深入多孔介质，导致沉积剖面变化更平缓。不同深度处沉积颗粒的中值直径随流速增加。大粒度分布导致形成狭窄孔隙，通过筛分作用增强颗粒的沉积。
