You are here:
CONTROLLED FIELD STUDY ON THE USE OF NITRATE AND OXYGEN FOR BIOREMEDIATION OF A GASOLINE SOURCE ZONE
Citation:
Barbaro, J. R. AND J. F. Barker. CONTROLLED FIELD STUDY ON THE USE OF NITRATE AND OXYGEN FOR BIOREMEDIATION OF A GASOLINE SOURCE ZONE. BIOREMEDIATION JOURNAL 4(4):259-270, (2000).
Description:
Controlled releases of unleaded gasoline were used to evaluate the biotransformation of the soluble aromatic hydrocarbons (benzene, toluene, ethylbenzene, xylene isomers, trimethylbenzene isomers, and naphthalene) within a source zone using nitrate and oxygen as electron acceptors. Experiments were performed within two 2m X 2m X 3.5m deep sheet-piling cells. A gasoline-contaminated zone was created below the water table in each treatment cell. Groundwater amended with electron acceptors was then flushed continuously through the cells for 174 d. One cell received approximately 100 mg/L nitrate and "microaerophilic" (i.e., 2 mg/L or less) dissolved oxygen (DO), a second cell received microaerophilic DO only. Electron-acceptor utilization and hydrocarbon-metabolite formation were observed in both cells, suggesting that some microbial activity had been induced in response to flushing. However, nitrate utilization was slow relative to the cell residence time, and aromatic-hydrocarbon mass losses in response to microaerophilic DO addition were not apparent under these in situ conditions. Concentration trends in both cells suggested that there was relatively little biotransformation of the aromatic hydrocarbons over the 2-m flow path monitored in this experiment. Extraction-well concentration trends, for example, were consistent with abiotic gasoline dissolution. The results from the nitrate-amended cell suggest that a large denitrifying population capable of aromatic hydrocarbon biotransformation failed to develop within the gasoline source zone over a 14-month period of nitrate exposure. This study reinforces the need for detailed aquifer-specific testing prior to selecting bioremediation for full-scale cleanup, particularly for recent hydrocarbon spills.