Oxygenation of the Root Zone and TCE Remediation: A Plant Model of Rhizosphere Dynamics; Master's thesis

摘要

This study analyzes rhizosphere conditions that enhance the effective aerobic degradation of TCE in wetland bioremediation systems. A plant model was built using Stella 9.0 modeling software and uses numerical integration evaluation; it addresses movement of oxygen through plant vascular and aerenchymal systems, and into the rhizosphere where oxygen and other substrates influence bacteria. Methanotrophs and heterotrophs are assumed to be influential bacteria groups. Variations of humidity-induced-convection, methane, soil carbon, and copper concentrations are evaluated. Varying concentrations and hydraulic loadings of TCE are assessed with respect to TCE consumption rate and TCE treatment efficiency. Soil conditions most directly affected TCE consumption, and hydraulic conditions most directly influenced treatment efficiencies. The research identified low carbon, low copper, high oxygen, and high methane concentrations as most conducive conditions for remediation. Variations in soil carbon had the highest impact on consumption rates; minimizing organic carbon concentrations of the influent may enhance remediation rates. It is recommended to first optimize soil conditions in a wetland treatment system, and then adjust hydraulic loading to achieve optimal treatment efficiencies. The model developed can be used to determine likely remediation rates and to then optimize efficiency by adjusting flow rates for a wetland bioremediation system.