Fluid Velocity, Particle Penetration, and Permeability Reduction in Clogging Porous Media

Colloids depositing in porous media cause significant permeability reduction, which is relevant in groundwater remediation, aquifer storage and hydroseismicity. It is well known that permeability depends on soil chemistry, which influences deposit morphology. However, the effect of hydrodynamics on deposit morphology has received less attention; efforts to describe this relationship in constant-flow column experiments have been confounded by the fact that higher fluid velocity causes deeper particle penetration and consequentially less clogging near the filter inlet. This poster describes an attempt to quantify the influence of fluid velocity on particle penetration and deposit morphology based on O'Melia and Ali's filter clogging model. Previous applications of this model have accounted for non-uniform deposition along the flow direction by considering segments in series. We propose an alternative approach by assuming that (1) O'Melia and Ali's clogging model is locally valid, and (2) the distribution of particles along the flow direction is exponential, as predicted by the classical filtration theory for clean beds. Integrating a differential head loss equation along the flow direction results in an expression for head loss at any point along the column that depends on two empirical factors: one that describes the characteristic distance of particle penetration, and one that describes the deposit morphology. The approach was applied to published data from three sources, representing a total of 29 filtration experiments, in which head loss was measured separately in the top section of the column. The imposed approach velocity in these experiments ranged from 6 to 480 m/d. Results confirm that increasing fluid velocity results in deeper particle penetration. However, the increasing penetration depth only partially explains the increasing permeability observed for a given mass of deposited particles, suggesting that deposit morphology also plays an important role.