Journal of Microbial & Biochemical Technology

Abstract

Biodegradation of Bitumen in Soil and Its Enhancement by Inorganic Fertilizer and Oxygen Release Compound: Experimental Analysis and Kinetic Modelling

Samuel E Agarry and Kigho M Oghenejoboh

The objective of this work was to investigate and evaluate the effect of inorganic nutrient (NPK fertilizer), hydrogen peroxide and their combinations on the kinetics of bitumen degradation by autochthonous microorganisms in the soil. The study was carried out by artificially contaminating an un-impacted tropical soil with 40 g/kg of bitumen in plastic bins and amended with various amount of NPK fertilizer (1.63 g, 2.10 g and 2.56 g), hydrogen peroxide (0.5 g and 1.0 g) and combinations of NPK fertilizer and hydrogen peroxide (2.13 g, 2.60 g and 3.06 g), respectively. The bioremediation was carried out for 21 days. Results showed that inorganic NPK fertilizer, hydrogen peroxide and their combinations stimulated microbial growth and enhanced bitumen biodegradation. The bacterial count and percentage total petroleum hydrocarbon degradation relatively increased with increase in the amount of inorganic nutrient and oxygen release compound used in this study. More than 50% of the hydrocarbons were degraded within each remediation period. The combined addition of inorganic NPK fertilizer and hydrogen peroxide provided the highest percentage biodegradation (>60%). Under abiotic conditions, no total petroleum hydrocarbon removal was observed while a maximum of 10.8% total petroleum hydrocarbons removal was obtained in unamended soil (natural attenuation) experiment. A first-order kinetic model successfully described the bitumen biodegradation. The model revealed that bitumen contaminated-soil microcosms amended with inorganic nutrient and oxygen release compound had higher biodegradation rate constants, as well as lower half-life times, than unamended soil (natural attenuation) remediation system. The biodegradation rate constant was higher with lower half life time as the amount of inorganic nutrient and oxygen release compound in soil increased.