Abstract
Bioremediation can be considered as an effective strategy for managing the contaminants from the petroleum hydrocarbons. This paper assesses the bioremediation utility of Bacillus circulans C1 in cleanup of crude oil-contaminated soils surrounding Thi-Qar oil refinery in the laboratory (seasoning region) as well as in field experiments. The initial TPH levels in the soil sample used in the laboratory was 15,000 mg/kg and the soil tested in the field was 18,000 mg/kg. Soil samples treated with Bacillus circulans C1 in the laboratory environment had a first order degradation constant of TPH of 0.798 with a degradation period of 30 days; thus having a reduction of 70% compared to control samples with an overall reduction of only 10%. The subject field test also yielded similar results in a reduction of TPH levels from the plots treated for 60 days, 70 % of the TPH level was reduced in treated sample plots while, 10 % of the total TPH level in the control sample plots. The examinations of soil chemistry showed that the values of PH close to 8 of alkaline reaction, nitrogen increase and the stability of the micronutrient concentrations were crucial for the stimulation of bacterial processes and hydrocarbon leaching. These observations confirm the effectiveness of Bacillus circulans C1 as a strong biological solution to eliminate pollution of water and soil. According to the findings, Bacillus circulans C1 can be regarded as an efficient and eco-friendly method of dealing with contaminated soil and oil spillage, and this work confirms its capability of reducing the levels of the hydrocarbons to a significant level hence making it feasible to apply on a large scale. Performing more studies to fine-tune bioremediation and analyze connections with other microorganisms is advisable.