Comparative Kinetic Study of Different Bioremediation Processes for Soil Contaminated with Petroleum Hydrocarbons

Bioremediation of hydrocarbon polluted soil can be achieved by natural attenuation, biostimulation and/or bioaugmentation processes. In this study the three technologies were evaluated to treat hydrocarbons polluted soil of total petroleum hydrocarbon (TPH) content of 42,000mg/kg semipilot scale cells, over an incubation period of 120 days at room temperature (25-30°C), moisture content of 45% and pH around neutrality. Bioaugmentation with bacterial consortium Pseudomonas aeruginosa I.1.1.6 and Brevibacterium casei I.2.1.7 showed the highest degradation potential (76%), followed by biostimulation process with biodegradation efficiency of (62%) and then come the natural attenuation (48%). Kinetic modeling was performed to estimate the rates of TPH biodegradation in the studied systems. Three different error functions (root mean square, sum of the absolute errors and average relative error) were employed in this study to evaluate the goodness of fit of the model equation to the obtained experimental data. This showed that the degradation was found to follow first order model. The highest rate constant (0.012 day-1) was observed in cell augmented with bacterial consortium I.1.1.6 and I.2.1.7, followed by biostimulation cell (0.008 day-1). The lowest rate constant was observed in natural attenuation cell (0.005 day-1). Accumulative evaluation of CO2 was good qualitative indicator of biodegradation activity in each cell. The CO2 formations in bioaugmented cells were relatively higher than those in natural attenuation and biostimulation cells.