Adhesion and Deadhesion of Ureolytic Bacteria on Sand under Variable Pore Fluid Chemistry

It is essential to understand the phenomena of adhesion, deadhesion, and transport of microorganisms in porous media to scale up bioengineering processes. In this study, the adhesion and deadhesion of two ureolytic microorganisms were investigated in loose sand using a set of flow-through column experiments by varying the pore fluid chemistry. An increase in the ionic strength altered the surface-charge properties of the microbes and the selected geomaterial, which in turn reduced the energy barrier, leading to significant adhesion of microbes on the sand surface. After microbial adhesion, permeation of a lower-ionic-strength solution exhibited considerable bacterial deadhesion from the sand column, indicating the reversible nature of the interaction between bacteria and the sand surface. The physicochemical adhesion and deadhesion mechanisms are elucidated in terms of extended Derjaguin-Landau-Verwey-Overbeek theory. The variation of the energy barrier between the microbe and sand, the appearance of primary and secondary energy minima attributed to the change in pore fluid chemistry, and its influence on microbial adhesion and deadhesion on to the sand were also studied.