EPA Grant Number: R827015-01-0
Title: Anaerobic Intrinsic Bioremediation of Whole Gasoline
Investigators: Joseph Suflita
Institution: University of Oklahoma
EPA Project Officer: Bala Krishnan
Project Period: February 1, 1999 to January 31, 2000 (N/C Ext. to
February 28, 2001)
Project Amount: $130,036
Research Category: Intrinsic bioremediation/natural attenuation
As according to the project's work plan, the terminal electron-accepting conditions of a large set of anaerobic incubations constructed of materials from the gas condensate-contaminated site at Ft. Lupton have been monitored. Separate sets of incubations held under nitrate-reducing, sulfate-reducing, and methanogenic conditions have been continuously monitored for over 250 days. These results are shown in the three graphs below.
Under methanogenic conditions, it appears that the endogenous methane production has finally subsided after approximately 230 days. Methane production in the gasoline-amended incubations paralleled the unamended controls. However, in a concurrent pilot experiment, the addition of Alaska North Slope (ANS) weathered crude oil has stimulated methanogenesis above both the unamended and gasoline-amended microcosms. Under sulfate-reducing conditions, a similar trend is seen. It appears that the rate of sulfate reduction has declined considerably in the unamended controls after 210 days. Gasoline-amended bottles generally paralleled the control bottles. The ANS amendment also stimulated sulfate reduction by the Ft. Lupton microbiota. Under nitrate-reducing conditions, there has been little electron acceptor consumption either in the unamended or the gasoline-amended incubations. Quite surprisingly, however, nitrate reduction was greatly stimulated by the amendment of ANS oil. Concomitant with the nitrate reduction, we have observed the accumulation of sulfate, suggesting the oxidation of reduced sulfur species such as sulfide or sulfur.
Incubations up to the 180 day timepoint have been sent to Exxon for detailed analysis of the whole gasoline. At this we have preliminary results from this analysis. As expected, there is little evidence for hydrocarbon degradation under nitrate-reducing conditions. Significant biodegradation has occurred under both methanogenic and sulfate-reducing conditions.
Separate experiments with single hydrocarbon compounds as substrate are progressing well. Transfers of original enrichments are beginning to demonstrate hydrocarbon degradative activity with notable results for both hexane under sulfate-reducing conditions and undecane under methanogenic conditions