Kinetics of BTEX biodegradation coupled with Fe(III) reduction by indigenous microorganisms in simulated underground environment

Abstract

Pressure on widespread contamination of BTEX (benzene, toluene, ethylbenzene, and xylene) in sediments and groundwater requires better understanding of biogeochemical removal process of the pollutant. Oxidation of BTEX coupled with reduction of Fe(III) is one of the most efficient ways. BTEX degradation dynamics was investigated by observing BTEX oxidation rates at different concentrations (from 50 to 200 mg/L) at the presence of Fe(III) (from 106 to 212 mg/L). The dual-substrate Michaelis–Menten model was derived (Vmax=10.14 mg/L d, Km,Fe(III)=20.02 mg/L, Km,BTEX=128.75 mg/L). Experiment data agreed well with the model when the initial BTEX concentration was under 100 mg/L, which indicated that microorganisms in the system could keep balance. With the increasing of initial BTEX concentration, oxidation rates did not fit the model, indicating that high BTEX concentration would be toxic to the function microorganisms and would dampened the BTEX oxidation reaction. The dynamics of BTEX with different compositions (the B:T:E:X ratios) coupled to the dissimilatory Fe(III) reduction in contaminated underground environment was also modified. The proposal is to remedy contaminated groundwater by using Fe(III) in aquifer material instead of other substances, so that the operating conditions do not destruct ecological environment of groundwater. These findings provide important parameters for the remediation of BTEX in sediments and groundwater coupled with Fe(III) reduction.