Visualisation study on Pseudomonas migulae AN-1 transport in saturated porous media

Influence of granular size and groundwater flow rate on transport of Pseudomonas migulae AN-1 in saturated porous media was non-invasively and visually investigated with a novel imaging technique based on our previously established green fluorescent protein-tagging approach. AN-1 was transported faster than water was. The finer the media were, the greater the enhancement of bacterial velocity was. Mass recovery (MR) increased, while deposition rate coefficient (K_c) decreased, with increasing granular size. Similar and linear trends of MR and K_c, respectively, were quantitatively observed with increasing water flow rate. The images revealed that the initial shape of bacterial plume after injection was a narrow strip along the injection well and an ellipsoid in the lower part of the injection well in medium and coarse sand, respectively. Bacterial plume migrated horizontally in medium sand, but shifted slightly downward in coarse sand. Under similar conditions, the fluorescent area carrying AN-1 in medium sand was larger than that carrying AN-1 in coarse sand during the same period. The visualisation method of this study captured both the movement of free-state and retained bacteria that adhered to sediments. A continuous biological zone composed of planktonic and retained AN-1 was observed. These findings are significant for actual bioremediation.