Effectiveness of NPK Fertilizer-Saw Dust Amendment on Biodegradation of Crude Oil in Polluted Soil

Abstract

Soil pollution by crude oil causes nitrogen imbalance and impedes the flow of air and nutrient. Biostimulation improves this
nutrient and aeration and enhances the rate of biodegradation of the pollutants. This study was undertaken to use biostimulation
to strategically biodegrade crude oil in polluted soil. Optimization of NPK fertilizer (61:15:15) and sawdust enhances optimum growth of hydrocarbon-degrading microorganisms with a resultant restoration of the soil. Nine treatment cells (A, B, C, D, E, F,
G, H, I) and control (J) were subjected to various treatment combinations according to the experimental design. The resulting
residual concentrations of total petroleum hydrocarbon (TPH) and polycyclic aromatic hydrocarbon (PAH) are indicators of the
soil restoration. Moreover, the degradation efficiency for TPH ranged between 98.14% and 99.05% and the biodegradation kinetics rate between -0.0419 and -0.0479 per day while microbial kinetics growth rate varied between 0.1840 and 0.1931 per day in a 105 day bioremediation time. However, the percentage utilization of nitrogen and phosphorus were between 85.1%, 81.5% to 92.3%, 92.8% respectively. Interaction between the process independent variables provided both nutrient and favorable medium suitable for microbial activities for optimum treatment. Sawdust combined with NPK fertilizer is therefore effective for treating and restoring a hydrocarbon polluted soil.