Particle Shape Effect On Colloid Retention and Release in Saturated Porous Media.

Abstract Natural soil colloids and microorganisms often have non-spherical shapes. However, theories and models, e.g. the classical filtration theory, have usually been developed for spherical particles. The objective of this study was to evaluate the effect of particle shape on colloid retention and release in saturated porous media. Non-spherical colloids were prepared by stretching spherical sulfate latex colloids (diameter = 1 μm) to an aspect ratio of 2.2 following a modified procedure. The spherical particles were treated in the same manner but without stretching in order to maintain consistent surface properties with the stretched particles. Filtration experiments using columns filled with glass beads were conducted with the stretched particles as well as the spherical ones (as controls). Results showed that no difference on the retention and transport of the two tested colloids was observed. They suggested that the reported higher filtration rates of rod-shaped bacteria previously in the literature might be caused by bacterial heterogeneous surface property but not by bacterial shape.