BIOENERGETICS AND BIOREMEDIATION OF CONTAMINATED SOIL

The microbial biodegradation of xenobiotic compounds in soil and groun d water is constrained by the laws of thermodynamics. Bioremediation i s being investigated in a rhizosphere environment in which higher plan ts provide carbon and energy to sustain the microbial population. Tolu ene, phenol, trichloroethylene and trichloroethane have been fed in se parate experiments to a pilot scale system with alfalfa growing in san dy soil containing less than 10% of silt. It is well known that microb ial populations are numerous in the root zone of healthy vegetation. R oot exudates can stimulate aerobic microbial biodegradation of compoun ds which by themselves support growth poorly or not at all. Polynuclea r aromatic compounds such as phenanthrene, anthracene, and pyrene, whi ch are not very soluble in water, and chlorinated aliphatic hydrocarbo ns such as trichloroethylene are examples of compounds that can be bio degraded in the rhizosphere when root exudates are present to enhance and sustain microbial activity. Solar driven transport processes such as water and solute movements due to evapotranspiration increase the l ikelihood that the contaminants will come into contact with the microo rganisms and be degraded. The thermodynamic and bioenergetic aspects o f transport and biodegradation in the rhizosphere are examined through a review of the literature and the analysis of experimental data coll ected in the pilot scale system.