Improvement of Bacterial Activity for the Depollution of Contaminated Soil by Diesel Oil

Some human activities cause soil and groundwater pollution. Physical and chemical processes are used to eliminate or reduce this contamination. However, these techniques are very expensive and can be very invasive to ecosystems. Bioremediation is a remediation process that uses bacteria's metabolic capacity to degrade organic pollutants. Certain parameters, however, have a significant impact on the development of the bacteria, namely the level of oxygen and the nutrient content, particularly nitrogen and phosphorus (N and P). In this study, the effect of these two parameters on bacterial reproduction and decontamination power on soil polluted by diesel oil at 10 g/kg was investigated. Bubble column bioreactors have been used; each bioreactor was filled with polluted soil. The experiments were carried out in two configurations, A and B, to characterize separately the biodegradation rate generated solely by bacterial activity and the removal rate generated by aeration. In the first case, bio-stimulation was used to increase the bacterial flora, while in the second, the bacterial flora was neutralized by using HgCl2. The contaminated soil was amended using NH4Cl, and KH2PO4, salts according to C/N/P molar ratios of 100/10/1, 100/5/1, 100/25/1, 10/10/3, and 100/10/0.33. The results showed a significant relationship between airflow rate, C/N/P molar ratio, and diesel oil removal on the one hand, and biomass growth on the other. After 26 days, the removal rates were 58, 70, 79, 78, and 97% for 0.25, 0.5, 1, 1.5, and 2 L/min, respectively, for a C/N/P molar ratio of 100/10/1. Furthermore, after 12 days, the best biodegradation rate was 36% with an airflow rate of 1 L/min and a C/N/P molar ratio of 100/10/1. It would be interesting to continue this research to determine the best conditions for increasing the rate of biodegradation.