Biodegradation rates of separated diesel components

Abstract

AbstractThree hydrocarbon classes (n‐alkanes, branched and cyclic alkanes, and aromatics) were separated from diesel fuel and used as hydrocarbon treatments during a 35‐d batch culture experiment in which biodegradation rates of the individual classes were quantified and compared with the biodegradation rate of a treatment consisting of a composite of the three fractions. Triplicate batch cultures of each hydrocarbon treatment were sampled on experimental days 0, 3, 7, 15, and 35. The microbial inoculum used in this study was a crude oil‐degrading culture isolated from a contaminated soil. As the experiment proceeded, microbial populations were estimated by total heterotrophic plate counts. Hydrocarbon concentrations were quantified by GC with flame ionization detection, and specific compound identification was confirmed by GC‐MS. The composite treatment was separated into aliphatic and aromatic fractions before hydrocarbon analysis. After 35 d, the relative biodegradation for each hydrocarbon class was as follows: n‐alkanes > aliphatic fraction of composite solution > aromatics > branched and cyclic alkanes > aromatic fraction of composite solution. In the composite treatment, biodegradation of both aromatic and aliphatic fractions was observed during the 35‐d study period and thus did not follow a clear pattern of sequential degradation. However, the biodegradation rate for the aromatic fraction was significantly slower than the aliphatic fraction.