A comparative study for petroleum removal capacities of the bacterial consortia entrapped in sodium alginate, sodium alginate/poly(vinyl alcohol), and bushnell haas agar

The purpose of this study was to identify and compare the degradation efficiencies of free and entrapped bacterial consortia (Staphylococcus capitis CP053957.1 and Achromobacter marplatensis MT078618.1) to different polymers such as Sodium Alginate (SA), Sodium Alginate/Poly (Vinyl Alcohol) (SA/PVA), and Bushnell Haas Agar (BHA). In addition to SA and SA/PVA, which are cost-effective, non-toxic and have different functional groups, BHA, which is frequently encountered in laboratory-scale studies but has not been used as an entrapment material until now. Based on these, the polymers with different surface morphologies and chemical compositions were analyzed by SEM and FT-IR. While the petroleum removal efficiency was higher with the entrapped bacterial consortia than with the free one, BHA-entrapped bacterial consortium enhanced the petroleum removal more than SA and SA/PVA. Accordingly, the degradation rate of bacterial consortia entrapped with BHA was 2.039 day⁻¹, SA/PVA was 1.560, SA was 0.993, the half-life period of BHA-entrapped bacterial consortia is quite low (t_1/2 = 0.339) compared with SA (t_1/2 = 0.444) and SA/PVA (t_1/2 = 0.697). The effects of the four main factors such as: amount of BHA (0.5, 1, 1.5, 2, 2.5, 3 g), disc size (4, 5, 6, 7, 8 mm), inoculum concentration (1, 2.5, 5, 7.5, 10 mL), and incubation period on petroleum removal were also investigated. The maximum petroleum removal (94.5%) was obtained at ≥ 2.5 mL of bacterial consortium entrapped in 2 g BHA with a 7 mm disc size at 168 h and the results were also confirmed by statistical analysis. Although a decrease was observed during the reuse of bacterial consortium entrapped in BHA, the petroleum removal was still above 50% at 10th cycle. Based on GC-MS analysis, the removal capacity of BHA-entrapped consortium was over 90% for short-chain n-alkanes and 80% for medium-chain n-alkanes. Overall, the obtained data are expected to provide a potential guideline in cleaning up the large-scale oil pollution in the future. Since there has been no similar study investigating petroleum removal with the bacterial consortia entrapped with BHA, this novel entrapment material can potentially be used in the treatment of petroleum pollution in advanced remediation studies.