Factors influencing the biodegradation of benzene, toluene, ethylbenzene, m-xylene (BTEX), naphthalene, and phenanthrene in subsurface environments

Contamination of soil and groundwater with mono and polycyclic aromatic hydrocarbons is a major environmental threat to the environment. Many studies and full-scale remediation efforts have demonstrated that in situ bioremediation can be effective in mitigating this contamination. Several factors influencing the efficacy of in situ bioremediation were evaluated in this work, including: (1) the effect of mixed oxygen/nitrate electron acceptor conditions on the biodegradation of a mixture of BTEX and naphthalene; (2) the effect of sorption/desorption on the bioavailability of naphthalene and phenanthrene; and (3) the influence of contaminant exposure time on the bioavailability of naphthalene and phenanthrene.; In batch laboratory experiments only toluene was degraded under denitrifying conditions while all of the substrates were degraded under microaerophilic and aerobic conditions. Toluene was degraded using nitrate as a terminal electron acceptor in the presence of microaerophilic oxygen concentrations. Experimental results demonstrated that mixed microaerophilic/nitrate reducing conditions were more favorable for biodegradation than anaerobic denitrifying conditions.; Additional batch laboratory experiments were conducted to evaluate and quantify the effects of sorption/desorption processes and mass transfer on the biodegradation of naphthalene and phenanthrene under conditions where aquifer solids have been exposed to long-term contamination. Batch mineralization studies revealed that the extent and rate of mineralization of PAHs was a function of aging time for Borden sand and Bozeman sediments. Slower mineralization rates were observed in the presence of Borden sand and Bozeman sediments as aging time increased. Abiotic batch studies revealed that the equilibrium partition coefficient increased with mixing time for Borden sand and Bozeman sediments indicating that true equilibrium was not reached in the time frame of typical sorption equilibrium studies (7–30 days). Desorption rate studies with these geosorbents also revealed that desorption rates decreased as the aging time was increased.; This research includes abiotic and biotic model parameters derived under conditions that more closely mimic observed conditions in the environment which will lead to more accurate predictions of the time and resources needed to bioremediate contaminated aquifers as well as provide a more accurate assessment of risk.