Modification of Heterotrophic Plate Counts for Assessing the Bioremediation Potential of Petroleum-Contaminated Soils

Abstract

Bioremediation is becoming an accepted treatment option for the remediation of petroleum-contaminated sites. Instrumental in implementing bioremediation is the characterization of bacteria capable of degrading the contaminants of interest. A wide variety of techniques have been reported in the literature but they often involve volatile solvents or petroleum mixtures as substrates and thus are difficult to use. Standard heterotrophic plate counts are often required by environmental regulations to be included as part of contaminated site investigations and assessments. Standard heterotrophic plate count techniques were found in this study to be unable to detect changes in population sizes in contaminated and uncontaminated soils. A more specific assay using benzoate, a metabolite of many BTEX compounds, was also used. This technique was capable of detecting differences in population size between contaminated and uncontaminated soils and benzoate is thus a better substrate to use when characterizing petroleum-contaminated soils. Furthermore, the data (population size vs. contaminant concentration) fit a hyperbolic model well. Such a model could be used to monitor population size with respect to contaminant concentration as well as population size outside the contaminant plume to further assess the progress of bioremediation at a contaminated site.