Hydraulic Operating Conditions and Particle Concentration Effects on Physical Clogging of a Porous Medium

The effects of the hydraulic operating conditions and the concentration of suspended particles (SP) in pore fluid on the filtration and physical clogging of a porous medium were investigated. Polydisperse kaolinite SP was injected into a sand-filled column under two different operating conditions: constant flow rate and constant head. The retention rate was observed to be greater under the condition of constant head than under the condition of constant flow rate, mainly for the high concentrations. Under constant head, the porous medium were clogged more rapidly; the pore velocities decreased with time and the permeability reduction occurred in fewer pore volumes injected than under constant flow rate. Under the same hydraulic condition, an increase of the concentration leads to a more rapid reduction in permeability. Regardless of the hydraulic operating conditions, particle-size analysis shows an increase with time of the median diameter of the particle-size distribution of the recovered particles. At the beginning of the filtration process, larger particles are mainly retained in the column. As the injection volume increases, the larger particles are better transported and the size of particles observed in the effluent gradually increases. It appears that the median diameter of the recovered SP increases more rapidly with time under constant flow rate.