Bioremediation of Diesel Fuel Contaminated Soil: Comparison of Individual Compounds to Complex Mixtures

Bioremediation is a cost effective means of remediating soils contaminated with petroleum hydrocarbons. Various factors affect the efficiency of the process, including environmental conditions, microbial population present and composition of the hydrocarbon spill. To evaluate the impact of mixture composition on individual compound and overall degradation, biodegradation experiments were conducted in sealed, 1-liter bioreactor/respirometer vessels containing soil spiked with hydrocarbon compounds in isolation and in mixtures. The influence of bacteria and fungi on the degradation process was also monitored. The degradation behavior of the various compounds was monitored using the fraction of contaminant remaining and first-order degradation coefficients based on hydrocarbon loss.

The results showed that the degradation trend of a compound changed when present in a simple mixture or when degraded in isolation. The presence of the compounds as either an aliphatic or aromatic mixture did not change the degradation trend. The presence of a mixture also affected the amount of degradation with some compounds degrading to a greater extent when in isolation. Overall, the majority of degradation occurred in the first 10 d, suggesting that the first-order model may not be an appropriate model for degradation periods longer than 10 d when nutrient limited. It was also found that fungal metabolism is important for the degradation of hydrocarbons, particularly for branched species such as pristane as the decay rate increased one order of magnitude when bacteria were inhibited.

Keywords:

• Petroleum hydrocarbons
• diesel fuel
• complex mixtures
• bioremediation
• decay rates
• microbial species

Acknowledgements

The authors wish to acknowledge the support of the NSERC of Canada in the form of a postgraduate scholarship and a Discovery Grant and the support from Bell Canada. In addition, the advice of Dr. Hung Lee, Professor, Environmental Biology, University of Guelph, is greatly appreciated.

Notes

^aIncludes 60 d reactor.

^bMaximum duration 30 d.

NED*—not enough data as only 14 d and 30 d runs completed.