Synergistic Influence of Bacterial Proliferation and EPS Secretion on Porous Media

Bio-clogging is critical to the efficiency of soil aquifer treatment. In this study, we utilized a percolation column device to investigate the dynamic evolution of biofilm and the corresponding responses changes of three typical hydraulic properties with the column within the percolation column. The results showed that the biofilm development exhibited five-stage growth morphology: bacterial stage, colony stage, biofilm with filamentous EPS stage, biofilm with mesh EPS stage, and dense biofilm stage. The hydraulic conductivity exhibited nonuniform decay across five stages: initial fluctuation period, swiftly declining period, accelerated declining period, gently decreasing period, and equilibrium stabilizing period. Both bacteria and EPS contribute to the attenuation of the infiltration properties. Due to its hydrophilic nature, EPS played a more prominent role in storing and dispersing water. As such, significant changes in water holding capacity and material transport mechanism occurred at EPS secretion onset. From 0-18 h, bacterial colonization slightly enhanced water retention, accompanied by a gradual rise in the hydraulic dispersion coefficient. After approximately 18 h, substantial EPS production markedly increased water-holding capacity and transformed the dominant transport mechanism from convection to dispersion.