Bioaugmentation and biostimulation for enhanced TPH^d biodegradation in diesel-contaminated soil

Contamination with petroleum hydrocarbon compounds in soil and groundwater draws attention regarding environmental and healthy issues, resulting in an increased interest in developing innovative and sound technologies for its remediation. Bioremediation of petroleum hydrocarbons has been proposed as an effective, economic, and environmentally-friendly technology, although the presence of contaminantdegrading bacteria and bioavailability of hydrophobic organic compounds (HOCs) to microorganisms could be limiting factors during the biodegradation process. This study investigated the potential application of bioaugmentation and biosurfactants (rhamnolipid) for enhanced biodegradation of diesel-contaminated soil with a series of bench-scale experiments. Measurements of soil total petroleum hydrocarbon-diesel (TPH_d) indicated that all eight tested biopiles provided enhanced biodegradation abilities, with respect to both diesel removal efficiency and biodegradation rate, in soil samples contaminated with diesel at a concentration of 20,000 mg-TPH_d/kg soil. Molecular methods, including microarray hybridization, terminal restriction fragment length polymorphism (T-RFLP), and denaturing gradient gel electrophoresis (DGGE), were applied to monitor the microbial population dynamics of augmented diesel-degrading bacteria in tested biopiles. The results of microbial community analyses confirmed the application of bioaugmentation in biopiles conducted in this study would be a beneficial measure to increase the microbial diversity of diesel-degrading bacteria and the diesel biodegradation rate.