Electric Field Effects on Bacterial Deposition and Transport in Porous Media

Bacterial deposition and transport are key to microbial ecology and biotechnological applications. We therefore tested whether electrokinetic forces (electroosmotic shear force ( F_EOF), electrophoretic drag force ( F_EP)) acting on bacteria may be used to control bacterial deposition during transport in laboratory percolation columns exposed to external direct current (DC) electric fields. For different bacteria, yet similar experimental conditions we observed that DC fields either enhanced or reduced bacterial deposition efficiencies (α) relative to DC-free controls. By calculating the DLVO force of colloidal interactions, F_EOF, F_EP, and the hydraulic shear forces acting on single cells at a collector surface we found that DC-induced changes of α correlated to | F_EOF| to | F_EP| ratios: If | F_EOF| > | F_EP|, α was clearly increased and if | F_EOF| < | F_EP| α was clearly decreased. Our findings allow for better prediction of the forces acting on a bacterium at collector surface and, hence, the electrokinetic control of microbial deposition in natural and manmade ecosystems.