Mass transport phenomena which affect the supply or mixing of contaminants, oxidants and microorganisms needed for biodegradation and the enhanced bioremediation of contaminated soil and plumes will be examined. Bench-scale physical aquifer model experiments will be used to establish mathematical relationships between hydrodynamic dispersion and plume geometry, source strength and oxidant amendment supply in heterogeneous systems. Plumes will be created in the model aquifers using reactive tracers and analysed with state-of-the art methods. The mathematical relationships developed in the lab studies will be a valuable tool to estimate contaminant plume length under natural conditions and assess the value of amendments (e.g. oxidant delivery) or procedures (e.g. hydraulic manipulation) used to enhance biodegradation. These relationships will be tested at field scale using data from well-characterised sites, for validation and to identify monitoring requirements. A separate study will explore the development of soil microbial fuel cells to enhance soil and groundwater bioremediation. Electrodes inserted in soil can increase oxidant delivery to support anaerobic biodegradation of organic compounds. The electron transfer created by in situ microbial degradation reactions can be coupled to reduction of oxygen in the atmosphere and generates an electrical current as an energy source to sustain the process for bioremediation. Using lab-based model soil systems containing different organic compounds, the research will deduce the fundamental electron transfer mechanisms, the efficiency of treatment for specific contaminants and develop design criteria to optimise treatment performance for a range of conditions. The output from these studies will be a quantitative basis to predict mass transport limitations in heterogeneous media and predict the technology performance, and new techniques which can enhance biodegradation processes in situ.