Efficacy of intervention strategies for bioremediation of crude oil in polluted soil microcosm

Abstract

Crude oil, though not manmade but largely manipulated by man to provide different oil-based products has become a major source of environmental pollution. This menace on land do contribute to the retardation of vegetation growth and human health hazards, while in water it may be toxic to aquatic animals. The search for the solution to ameliorate the seemingly unending pollution and its side effects necessitated the evaluation on the effect of bioaugmentation, biostimulation and natural attenuation of crude oil pollution in soil microcosms. The bacterial species selected for this study ( Bacillus thuringensis strain LG32 and Burkolderia pseudomallei strain A81) were preliminarily identified using the conventional biochemical tests and further identification was carried out using the API kit. The results of the study carried out over a period of five weeks indicated that there was a marked reduction in the available phosphorous and potassium in the bioaugmented and biostimulated soils compared with that of the control. The mean values for total viable counts (TVC) of population of hydrocarbon  utilizing bacteria (HUB) was higher in the bioaugmented soil ranged (LG32=6.0-7.5log10cfu g -1 ; A81=5.5- 7.5log10cfug -1 ; LG32+A81=6.0-7.5log10cfug -1 ) compared with that of the control (6.0-6.2log10cfug -1 ). When  bioaugmentation was combined with biostimulation, the soil had higher counts of HUB (6.0-9.0log10cfug -1 ) and HUF (3.5-6.5log10cfug -1 ) compared to bioaugmentation without stimulation (HUB: 6.0-7.5; HUF: 3.5-5.5). The GC result indicated that by day 35, 96.92% of the aliphatic and aromatic components have been degraded in the augmented soil, higher than the natural attenuation control. Key words : Biodegradation, Biostimulation, Bioaugmentation, Microcosm, Attenuation, Metabolize.