Enhancing bioremediation of petroleum sludge-polluted soil: The impact of fungal-bacterial consortium's application strategy

Many microbial consortia have demonstrated superior capabilities in petrochemical sludge bioremediation. However, their vast potential remains underutilized due to the lack of application strategies. In this study, different fungal-bacterial consortia and inoculation strategies were evaluated in biopiles of oily-sludge-contaminated soil with a total petrochemical hydrocarbons (TPH) concentration of 124,000 mg/kg. Strategies using sequential inoculation, one dose administered at the beginning and another at day 30, of a consortium comprising either Bacillus sp. and Acremonium sp. (treatment 1) or Bacillus sp. and Phanerochaete sp. (treatment 3), resulted in higher removal efficiency compared to their corresponding batch inoculation treatments (i.e., treatments 2 & 4) with the same total inoculation dose over a period of two months. Notably, treatment 5, involving sequential inoculation of the consortium of Bacillus sp., Acremonium sp., and Phanerochaete sp., achieved an impressive 91.2 ± 1.6 % TPH removal efficiency, one of the highest reported levels for this level of contamination. Furthermore, sequential inoculation of the same consortium led to enhanced removal of hydrocarbon fractions compared to batch inoculations. The sequential inoculation approach also increased the microbial population and dehydrogenase activity in the soil more effectively than batch inoculation. These findings demonstrate that sequential inoculation allows microbial consortia to function more efficiently than batch inoculation in the bioremediation process. Consequently, the application of sequential inoculation with fungal-bacterial consortia holds potential for large-scale soil bioremediation, contributing to improved soil fertility and sustainability in an effective manner.