Bacteriological and physicochemical analysis of a crude oil-polluted soil undergoing laboratory-scale bioremediation

Abstract

The bacteriological and physicochemical quality of crude oil-polluted soil undergoing laboratory-scale bioremediation was evaluated. Soil samples were collected from an abandoned oil field in the Gio community, Ogoni land, Nigeria. Four different bioremediations experimental setups comprised of the polluted soil only (A), polluted soil with bacterial consortium (B), polluted soil with NPK fertilizer (C) and polluted soil with cow dung (D) were employed in the degradation of crude oil-derived hydrocarbons present in the soil and monitored for 40 days. During treatment, there was an increase in total culturable heterotrophic bacterial count (TCHBC) and total culturable hydrocarbon utilising bacterial count (TCHUBC), especially in the test treatment (B) which experienced about 22.2% increase in TCHUBC. The total petroleum hydrocarbon (TPH) concentration reduced over treatment time by 33.8, 62.3, 61.49, and 40.25% respectively, for Samples A, B, C and D. Overall, pH reduced from highly acidic tending towards neutral pH. There was also an overall reduction in the percentage of moisture and phosphate concentration. There was an initial increase in nitrate concentration at day 20 for all samples but a decline in concentration at day 40. There was a 71% reduction in TOC in Sample A, 83% reduction in Sample B, and 79 and 24% reduction in samples C and D. This study has demonstrated the effectiveness of each treatment approach in the degradation of hydrocarbons, especially the use of indigenous bacterial consortium from polluted soil. The role of bacterial consortium in bioremediation proves their ability to clean hydrocarbon-impacted systems for environmental restoration.