Bacteria transport and adhesion experiments under water-saturated and partially saturated conditions were examined over a wide range of ionic strength, from 1 to 100 mM KCl, CaCl2, and MgCl2, and at water contents of 0. 15 and 0.22 in sand columns packed with three different sands, baked, sterilized, and raw sands in order to investigate the effects of ionic strength, water content, and porous media type on the microbial adhesion in soil aquifer treatment (SAT). Well-characterized Escherichia coli JM 109 were used as model bacterial cells in this study. Column study results showed that bacterial deposition rates increased with increasing ionic strength and decreasing water content, and were higher in raw sand columns than those in other sand columns. The Derjaguin-Landau-Verwey-Overbeek (DLVO) theory was applied to experimental results in order to consider the interaction energies between the bacterial cells and collector grains; results revealed that a considerable amount of bacterial cells was weakly deposited onto the solid surfaces in secondary minimum.