| Bacterial deposition and survival in porous media is a crucial phenomenon in various environmental processes including bioremediation, water treatment, and pathogen contamination. The fate of bacteria in porous media may be greatly influenced by cell interactions with surface-attached biofilms and cell surface extracellular polymeric substances (EPS). In the nature environment, biofilms form on surfaces in virtually all aquatic ecosystems that can support microbial growth, such as soil, rocks, plants, and sediment, and are prevalent in filter media in water treatment plants. The objective of this dissertation is to elucidate the role of biofilm and biofilm EPS on cell initial adhesion, survival and detachment in porous media.;Experiments were performed in glass beads packed columns with and without biofilm coating to examine the dependence of bacterial colonization, survival and detachment on variables such as cell surface EPS composition, biofilm EPS mass production, biofilm thickness, solution ionic strength, bacteria surface charge, and substrate hydrophobicity.;Experimental results indicate that EPS on bacterial surfaces or substratum surfaces are involved in different stages of bacterial initial attachment. Without biofilm coating, non-monotonic deviation from filtration theory was observed for bacteria encapsulated by EPS, and can be attributed to bacteria re-entrainment, and the steric interactions between bacterial surface extracellular polymers and glass beads. Bacteria deposition behavior in the biofilm mediated column differs significantly from that observed in the clean column media. It was concluded that with thin biofilm accumulation, polymer interaction between the biofilm surface EPS and bacteria plays an important role in controlling bacterial adhesion while porous media physical and hydrodynamic changes as a result of biofilm growth may become significant when biofilm accumulates to a certain thickness. Additionally, the growth of bacteria in the biofilm matrix was detected in this study. Injected bacteria could become an integral part of biofilm, and biofilm sloughing was the phenomenon most likely influencing the fate of newly injected bacteria over the course of the experimental period and the down stream water qualities. |
