Effect of Nitrate Addition on Biorestoration of Fuel‐Contaminated Aquifer: Field Demonstration

Abstract

AbstractA spill of JP‐4 jet fuel at the U.S. Coast Guard Air Station in Traverse City, Michigan, contaminated a water‐table aquifer. An infiltration gallery (30 ft × 30 ft) was installed above a section of the aquifer containing 700 gal JP‐4. Purge wells recirculated three million gallons of ground water per week through the infiltration gallery at a rate designed to raise the water table above the contaminated interval. Ground water containing ambient concentrations of oxygen and nitrate was first recirculated for 40 days. Concentrations of benzene in monitoring wells beneath the infiltration gallery were reduced from 760 to <1μ/1. Concentrations of toluene, ethylbenzene, m,p‐xylene, and o‐xylene were reduced from 4500 to 17, 840 to 44, 2600 to 490, and 1400 to 260 μ/1, respectively. Average core concentrations of benzene, toluene, ethylbenzene, m,p‐xylene, and o‐xylene were reduced from 0.84 to 0.032, 33 to 0.13, 18 to 0.36, 58 to 7.4, and 26 to 3.2 mg/kg, respectively. Ground water amended with nitrate (10 mg/1 nitrate‐nitrogen) and nutrients was then recirculated for 76 days. Final core concentrations of benzene, toluene, ethylbenzene, m,p‐xylene, and o‐xylene were 0.017,0.036,0.019,0.059, and 0.27 mg/kg, respectively. Final aqueous concentrations were <1 μ/1 for benzene and toluene, 6 μ/1 for ethylbenzene, and 20 to 40 μ/1 for the xylene isomers, in good agreement with predicted values based on residual fuel content and partitioning theory. Although alkylbenzene concentrations have been substantially reduced, the test plot is still contaminated with the weatheredfuel. Based on stoichiometry, approximately 10 times more nitrate was consumed than could be accounted for by BTX degradation alone, indicating that other compounds were also degraded under denitrifying conditions.