Assessment of the microbial potential for nitrate-enhanced bioremediation of a JP-4 fuel-contaminated aquifer

A site that was contaminated with JP-4 jet fuel was characterized microbiologically to assess the feasibility of nitrate-enhanced bioremediation. The results of microcosm studies indicated that the mean pseudo zero-order rate constants for alkylbenzene biodegradation and NO3--N removal were 1.2 and 2.4 mg L-1 per day, respectively. Several alkylbenzenes were removed to a greater extent in samples contaminated with residual JP-4 than in unexposed samples and samples downgradient of the spill; benzene was recalcitrant in all samples. Numbers of total heterotrophs, JP-4-degraders, oligotrophs, total denitrifiers, denitrifiers growing in the presence of JP-4, estimates of cell number by analysis of phospholipid fatty acids, direct counts and aerobic and anaerobic protozoa were determined; however, numbers of microorganisms were not reliable predictors of alkylbenzene biodegradation activity. The presence of aerobic and anaerobic protozoa suggests that protozoa may be active under a variety of different electron acceptor conditions. The results of the characterization study indicated that the site was amenable to nitrate-enhanced bioremediation.