Remediation Approaches to Reduce Hydrocarbon Contamination in Petroleum-Polluted Soil

Abstract

Heavy metals pollution associated with oil spills has become a major concern worldwide. It is essential to break down these contaminants in the environment. In the environment, microbes have been used to detoxify and transform hazardous components. The process can function naturally or can be enhanced by adding nutrients, electron acceptors, or other factors. This study investigates some factors affecting hydrocarbon remediation technologies/approaches. Combinations of biological, chemical, and eco-toxicological techniques are used for this process while monitoring the efficacy of bacterial products and nutrient amendments to stimulate the biotransformation of contaminated soil. Different hydrocarbon removal levels were observed with bacterial augmentation (Beta proteobacterium and Rhodococcus ruber), exhibiting a total petroleum hydrocarbon (TPH) reduction of 61%, which was further improved to a 73% reduction using bacterial augmentation combined with nutrient amendment (nitrogen, potassium, and phosphorus). A heavy metal analysis of the polluted soils showed that the combination of nutrient and bacterial augmentation resulted in a significant reduction (p-value < 0.05) in lead, zinc, and barium. Toxicity testing also showed that a reduction of up to 50% was achieved using these remediation approaches.

Keywords: bioremediation; contaminated soil; heavy metals; microorganisms; oil spills; total petroleum hydrocarbon (TPH).

Figure 1

Changes in hydrocarbon degrader counts (CFU g⁻¹ soil) in contaminated soil samples with treatments. Bars represent the average of triplicate plate counts; error bars indicate the standard deviation of the triplicates. Abbreviations: CSS, control soil sample; P, phosphorus; NPK, nitrogen, phosphorous, and potassium; BAS: bio-augmentation soil.

Figure 2

Reduction in TPHs in contaminated soil samples with treatments. Bars represent the average of triplicate microcosms readings; error bars indicate the standard deviation of the triplicates. Abbreviations: Abbreviations: CSS, control soil sample; P, phosphorus; NPK, nitrogen, phosphorous, and potassium; BAS: bio-augmentation soil.

Figure 3

Representative GC chromatograms of TPHs extracted from petroleum-contaminated soil after 15 days of incubation, shown as percentages remaining compared to those at the initiation of the experiment (zero time). Bars represent the average of triplicate samples. Error bars indicate the standard deviation of the triplicates. Abbreviations: CSS, control soil sample; P, phosphorus; NPK, nitrogen, phosphorous, and potassium; BAS: bio-augmentation soil.

Figure 4

Representative GC chromatograms of TPHs extracted from petroleum-contaminated soil after 90 days of incubation shown as percentages remaining compared to those at the initiation of the experiment (zero time). Bars represent the means of triplicate samples. Error bars indicate the standard deviation of the triplicates. Abbreviations: CSS, control soil sample; P, phosphorus; NPK, nitrogen, phosphorous, and potassium; BAS: bio-augmentation soil.

Figure 5

Biotoxicity values (acute toxicity assay) during bioremediation treatment determined by V. fisheri bacteria.