Biodegradation of soluble aromatic compounds of jet fuel under anaerobic conditions: laboratory batch experiments

Laboratory batch experiments were performed with contaminated aquifer sedim ents and four soluble aromatic components of jet fuel to assess their biode gradation under anaerobic conditions. The biodegradation of four aromatic c ompounds, toluene, o-xylene, 1,2,4-trimethylbenzene (TMB), and naphthalene, separately or together, was investigated under strictly anaerobic conditio ns in the dark for a period of 160 days. Of the aromatic compounds, toluene and o-xylene were degraded both as a single substrate and in a mixture wit h the other aromatic compounds, while TMB was not biodegraded as a single s ubstrate, but was biodegraded in the presence of the other aromatic hydroca rbons. Substrate interaction is thus significant in the biodegradation of T MB. Biodegradation of naphthalene was not observed, either as a single subs trate or in a mixture of other aromatic hydrocarbons. Although redox condit ions were dominated by iron reduction, a clear relation between degradation and sulfate reduction was observed. Methanogenesis took place during the l ater stages of incubation. However, the large background of Fe(II) masked t he increase of Fe(II) concentration due to iron reduction. Thus, although m icrobial reduction of Fe(III) is an important process, the evidence is not conclusive. Our results have shown that a better understanding of the degra dation of complex mixtures of hydrocarbons under anaerobic conditions is im portant in the application of natural attenuation as a remedial method for soil and groundwater contamination.