Bioremediation of Three Brazilian Soils Contaminated with Used Lubricating Oil

Objectives: This study aimed at bioremediation potentials of organic pollutants, in particular, used lubricating oil contaminated soils, using commercial microbial nutrient. Other objectives were the evaluation of kinetic model to determine the rate of biodegradation of petroleum hydrocarbon in soil and to subsequently determine the half-life of the oil degradation.
Materials and Methods: The patterns of biodegradation of used motor oil were studied for a period of 90 days under laboratory condition. The model soil (300 g) was contaminated with 1.5 % (w/w) of used motor oil at room temperature in the laboratory using microcosm of 1 L. The microcosm was used to simulate the comparative effect of used lubricating oil addition and bioremediation using a commercially available hydrocarbon degrading microbial consortium - Amnite P1300 as bioaugmentation (T1), nutrients amendments - (NH4)2SO4 and K2HPO4 (NPK) as biostimulation (T2), unammended soil - natural attenuation as (T3) and the control soil treated with sodium azide (NaN3) as (T4).
Results: Treatment effects were evaluated on microbial community using three soil types (S1, S2 and S3). Hydrocarbon-utilizing bacterial counts were obtained in the amended soils under treatments T1, T2, and T3 ranging from 3.47 × 106 to 3.27×108 cfu/g compared to T4 throughout the 90 days of study. Soils amended with Amnite p1300 showed highest reduction in total petroleum hydrocarbon with net loss of 36.17 % throughout the period of experiment compared to other treatments. The changes (decline and recovery) in population of microbial community are a useful and sensitive way of monitoring the impact and recovery of used motor oil-contaminated soils.
Conclusion: The results suggest that different soils have different inherent microbial potential to degrade hydrocarbons of soils contaminated with used lubricating oil.