| This research program was established to investigate bioremediation as an oil spill response technology from the fundamental science to field scale evaluations. Methods were developed to characterize the composition of petroleum and to evaluate its fate in the environment. The methods incorporate a series of analyses that progress from simple gross measurements of the bulk fluid to more sophisticated approaches discerning specific analytes. Once methods were developed, a wetland was selected from a spill-of-opportunity following the San Jacinto River oil spill in October 1994. To evaluate the site for the application of bioremediation, a site assessment was conducted which included: the petroleum contamination, nutrient concentrations, microbial populations, toxicity, and ecological surveys. It was concluded the site was amenable to this research and was subsequently used for two related studies. The first study evaluated the intrinsic bioremediation of the petroleum from the spill. Intrinsic bioremediation of the spilled petroleum was determined to be an important removal mechanism in this study. Elevated nutrient levels following the flood and the unconsolidated state of the recently deposited sediment, provided conditions conducive to petroleum biodegradation. It was determined that under the proper conditions, intrinsic bioremediation was an effective remedial option in this sensitive system where traditional remedial options can be severely damaging. The second study evaluated biostimulation with inorganic nutrients and an alternative electron acceptor. A controlled application of a weathered crude oil was uniformly applied and three treatments were evaluated to determine the most effective treatment. A no-action control, an inorganic nutrient treatment, and an inorganic nutrient plus nitrate as an alternative electron acceptor treatment were evaluated in replication. The results of this study indicated that the inorganic nutrient treatment was most effective in enhancing the biodegradation rate of the petroleum compared to the control. The nutrient plus nitrate treatment effectively enhanced the biodegradation rate of the saturate hydrocarbons, but did not enhance the degradation of the aromatic hydrocarbons. The inorganic nutrient treatment enhanced the biodegradation rates of the saturate and aromatic hydrocarbons. Further studies are in progress to optimize these treatments and to evaluate additional treatments in these systems and others. |
