Microbial Bioremediation of Petroleum-contaminated Coastal Soils in Rivers State, Nigeria

Abstract

Petroleum contamination of coastal soils poses significant environmental concerns due to the persistence and ecological toxicity of petroleum hydrocarbons. This study evaluated the potential of indigenous microorganisms for the bioremediation of petroleum-contaminated coastal soils in Rivers State, Nigeria. Soil samples were collected from four petroleum-impacted locations and analysed for physicochemical characteristics, total petroleum hydrocarbons (TPH), and hydrocarbon-degrading microorganisms. Representative bacterial and fungal isolates were characterised using cultural, morphological and biochemical techniques. Laboratory-scale bioremediation was subsequently conducted using individual microbial isolates, bacterial and fungal consortia, and a bacterial–fungal consortium over 28 days. TPH concentrations, microbial populations and soil pH were monitored at predetermined intervals. Initial TPH concentrations ranged from 3,918 ± 127 to 5,126 ± 159 mg/kg, while hydrocarbon-degrading bacteria and fungi were detected at all sampling stations. TPH concentrations progressively decreased in the inoculated treatments throughout the experimental period. After 28 days, the bacterial–fungal consortium produced the greatest TPH reduction, from 4,516 ± 135 to 1,328 ± 48 mg/kg, corresponding to 70.59 ± 2.01% removal. Bacterial and fungal consortia achieved 60.99 ± 1.89% and 58.07 ± 1.82% removal, respectively, whereas the uninoculated control achieved only 15.61 ± 1.14% removal. The bacterial–fungal consortium also supported the highest hydrocarbon-degrading microbial population. One-way ANOVA indicated significant differences among treatments (p < 0.001). The findings demonstrate that microbial consortia, particularly combined bacterial–fungal cultures, have considerable potential for enhancing the remediation of petroleum-contaminated coastal soils.