Modeling and Optimization of Aerobic Biodegradation Conditions of Gasoline and Diesel by a Bacterial Consortium

Crude oil and its by-products are sources of environmental pollution. Their elimination by biological processes is part of the bioremediation of ecosystems. This study aims at developing models of aerobic biodegradation of gasoline and diesel and specifying the factors allowing the optimization of this biological process. The response surface methodology (RSM) was used with a centered 4-factors composite plan. The factors selected were the bacterial consortium concentration (x1), temperature (x2), dissolved oxygen (x3) and the quantity of nutrients (x4). The response measured was the rate of aerobic biodegradation. The experimental design consisted of 27 trials carried out in 10 days of incubation. The two second-order mathematical models obtained, for the rate of degradation of gasoline and diesel, were validated using different parameters. These are the values of the coefficient of determination R2 (95.88 %, 95.32 %) close to 100 %, the low average values of the residues (1.70 and 1.72) and the polarized factors between 0. 91 and 1.19 which indicate a strong correlation between the values of the percentage of measured biodegradation and those predicted by the models. The concentration of the bacterial consortium and the temperature in their linear (x1 and x2) and interactive (x1 x2) forms have a significant positive effect on the rate of biodegradation of gasoline and diesel (P?????0.05). The aerobic biodegradation of gasoline is optimized at 80 % and that of diesel at 70 % when the bacterial concentration is 108 CFU/ml, the temperature is 30????C and the dissolved oxygen content is between 150 and 200 mg/l.