Significance of electrophoretic mobility distribution to bacterial transport in granular porous media

A method is developed to obtain the electrophoretic mobility distribution of colloidal particles by microelectrophoresis. The results demonstrate that for small particles (< 1 mum), the experimental mobility distribution must be deconvoluted to remove the effect of the random Brownian motion so that the electrophoretic mobility distribution can be obtained. For bacteria-sized particles (on the order of 1 mum or larger), the random Brownian motion is not significant, and the experimental mobility distribution represents the electrophoretic mobility distribution. The significance of the electrophoretic mobility distribution to bacterial transport is demonstrated through comparison between experimental and theoretical values of collision efficiency. Using the extended Derjaguin-Landau-Verwey-Overbeek (DLVO) theory, the electrophoretic mobility distribution of bacteria is transformed to the distribution of collision efficiencies. For strain Comamonas sp. DA001, the predicted collision efficiency values span orders of magnitude, indicating that variation of surface charge density in a monoclonal bacterial population is a cause for the orders of magnitude variation of experimentally determined collision efficiencies. However, despite the fact that the predicted and experimental alpha distributions overlap, the match is not adequate. This inadequacy is ascribed to inability to probe heterogeneity of bacterial surface hydrophobicity, and the inability of the DLVO theory to quantitatively model particle deposition. (C) 2002 Elsevier Science B.V. All rights reserved.