Microbial transport plays an essential role in microbial activities in the subsurface soil. In this research, transport of Echerichia coli, Pseudomonas fluorescens and Bacillus subtilis in silica sand under water unsaturated conditions was investigated using column experiments and a tworegion solute transport model was used to simulate the bacterial transport with an assumption that bacterial deposition occurred within the immobile region only. It was concluded from this research that bacterial retention in unsaturated porous media was determined by their interactions within the system, which could be predicted based on independently determined surface properties. Following this research, I further investigated the activities of Shewanella putrefaciens in reducing iron oxide in the iron rich soil of Northwest Florida with landfill leachate serving as the carbon source. In addition, adsorption of reduced ferrous iron on S. putrefaciens was characterized. Considering that organic compounds can be potentially served as energy source, I explored the feasibility of the usage of microbial fuel cell (MFC) technology for landfill leachate decomposition and power generation. Landfill leachate collected from landfills located in Northwest Florida was tested in a laboratory scale MFC to provide evidence that landfill leachate can be decomposed and electrons released from leachate decomposition in the anodic chamber can be transported and consumed in the cathodic chamber and consequently, electricity can be generated. Finally, I studied the interactions of bacteria with the porous media to explain microbial biofouling.

All the research work in this dissertation has been published in peer-reviewed technical papers, details of which are provided in Chapter 1.