To address the challenges faced during the breakdown of crude oil waste sludge (COWS), this study developed an active bacterial formula (ABF) to enhance the breakdown of COWS. The formula used was a bacteria consortium (BC) with the desired characteristics immobilised on corncob powder (CCP). A mixture of soil-COWS (SSM) (w/w) was treated with ABF (w/w) in a laboratory trial for 90 days. The treated SSM was analysed for residual concentrations of hydrocarbon components of the COWS by solvent extraction and GC/MS. To elucidate the bacterial community composition, Illumina/MiSeq was used. Immobilised bacteria cells (IBC) on corncob powder (CCP) were confirmed and effectively shown by scanning electron microscopy (SEM) images. The formula on SSM caused a shift in microbial composition, ascribed to nutrients and carbon sources (CS) used in the treatment and other features such as symbiosis and competition to use the diverse carbon sources. The four phyla Proteobacteria, Actinobacteria, Firmicutes, and Bacteroidetes identified were dominant and affiliated to 90 genera including Rhodococcus, Bacillus, Gordonia, Dietzia, Ochrobactrum, Clostridium, Pseudomonas, and Microbacterium at a high relative abundance of >1.0 to >10. Parameters such as bacterial diversity (BD) and composition, relative abundance (RA), and PAH-residual concentration were used to assess the effectiveness of ABF. The results obtained suggest that ABF alleviated issues of survival of degrading bacteria and nutrient deficiency, as some PAH were thoroughly degraded (100 %) and others almost wholly degraded (95 %) in 90 days in all the treatments, unlike the 10 months in preceding studies.
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