Filtration of kaolinite particles in a saturated porous medium: hydrodynamic effects

A study was undertaken on physical clogging of a porous medium by injecting suspended particles (SP), ranging in diameter from 1.7 to 40 mu m, into a sand-filled column. Long-term tracer tests were carried out at various flow velocities. Retention of the SP is significantly influenced by the flow velocity. At low flow velocities, retention is confined to a limited length of porous medium, from the entrance of the column, leading to a substantial modification of the hydraulic characteristics of the porous medium. However, at high flow velocities, a much greater length of the porous medium is affected. Particle-size analyses indicate that the particle-size distribution (PSD) of recovered particles changes with time, while the PSD of retained particles changes with depth and time. At the beginning of the filtration process, larger particles were mainly retained at the column entrance. As the injection volume increases, the larger particles penetrate more deeply into the porous medium, and the size of particles observed in the effluent gradually increases. This study highlights the influence of flow velocity, duration of filtration, and the particles' polydispersity, on the hydraulic characteristics of the porous medium.