Colloid deposition in porous media and an evaluation of bed-media cleaning techniques

This paper discusses deposition rates of carboxyl latex spheres (0.245 μm) in packed beds examined in the presence of repulsive electrostatic interaction forces. Quartz grains and glass beads (275 μm), were selected for comparison as bed media on the basis of their similar zeta potentials. Observed attachment efficiencies (α) were compared with values predicted from models based on DLVO theory at varying pH and ionic strength. Attachment efficiencies in quartz and glass media were similar only once aggressive cleaning measures for both surfaces were employed. Observed values of α were also much closer to theoretical predictions with this treatment than without it, although they are still generally under-estimated. Values of α as small as 3.4 x 10-4 have been measured at low ionic strengths by using columns up to 4 meters in length. The results suggest that greater colloid mobility can be attributed to electrostatic repulsion than has been previously demonstrated