Effects of creosote compounds on the aerobic bio-degradation of benzene.

The inhibitory effect of creosote compounds on the aerobic degradation of benzene was studied in microcosm experiments. A total removal of benzene was observed after twelve days of incubation in microcosms where no inhibition was observed. Thiophene and benzothiophene, two heterocyclic aromatic compounds containing sulfur (S-compounds), had a significant inhibitory effect on the degradation of benzene, but also an inhibitory effect of benzofuran (an O-compound) and 1-methylpyrrole (a N-compound) could be observed, although the effect was weaker. The NSO-compounds also had an inhibitory effect on the degradation of p-xylene, o-xylene, and naphthalene, while they only had a weak influence on the degradation of 1-methylnaphthalene, o-cresol and 2,4-dimethylphenol. The phenolic compounds seemed to have a weak stimulating effect on the degradation of benzene whereas the monoaromatic hydrocarbons and the naphthalenes had no significant influence on the benzene degradation. The inhibitory effect of the NSO-compounds on the aerobic degradation of benzene could be identified as three different phenomena. The lag phase increased, the degradation rate decreased, and a residual concentration of benzene was observed in microcosms when NSO-compounds were present. The results show that NSO-compounds can have a potential inhibitory effect on the degradation of many creosote compounds, and that inhibitory effects in mixtures can be important for the degradation of different compounds.