Biodegradation of Hydrocarbons Present in Soils Contaminated with Different Petroleum Products

The contamination of soil by petroleum hydrocarbons has resulted in an increased attention towards the development of sound and innovative technologies for its remediation. Biodegradation of hydrocarbons by natural populations of microorganisms is the most eco-friendly and economically viable method for the management of petroleum contaminated sites.

The present study uses the potential of indigenous microorganisms to remediate soil contaminated with different petroleum products. The significance of molecular composition of the hydrocarbons present in the contaminated matrix in deciding the biodegradation rate is illustrated in this work. Two sets of bioreactors were set up for the study, wherein each set had 16 bioreactors. Each bioreactor was filled with fresh soil and contaminated with four different substrates or petroleum products (i.e. kerosene, diesel, lubricating oil and waste oil). One set was maintained at optimum environmental conditions and the other set with no maintenance throughout the study period of 12 weeks and served as the control.

Maximum percentage of total petroleum hydrocarbon (TPH) removal of 85.76% with a degradation rate of 0.0232 d-1 was observed in bioreactor contaminated with diesel and maintained at optimum environmental conditions. Minimum percentage of TPH removal of 40.84% with a degradation rate of 0.0062 d-1 was observed in bioreactor contaminated with waste oil with no maintenance of environmental conditions. The degradation rate was low in control setup. Hence, it could be inferred that environmental conditions have influence on the degradation rate and residual concentrations of the contaminants. Higher degradation was observed in lighter fractions of petroleum when compared to heavier fractions in both the setups. This strengthens the fact that lighter hydrocarbons evaporate in normal conditions and are degraded rapidly, while very long chain alkanes are increasingly resistant to microbial degradation.