PAHs biodegradation in soil washing effluent by native mixed bacteria embedded in polyvinyl alcohol-sodium alginate-nano alumina gel beads

In this study, the biodegradation of polycyclic aromatic hydrocarbons (PAHs) in soil washing solution containing Tween 80 was conducted using native mixed bacteria (Pseudomonas sp. Z1, Sphingobacterium sp. Z2, and Klebsiella sp. K) embedded in polyvinyl alcohol-sodium alginate-nano alumina (PVA-SA-ALNPs) gel beads. The optimal dosage of immobilized beads and embedded biomass for the biodegradation of phenanthrene (PHE), fluoranthene (FLU), and pyrene (PYR) were 10 % (v/v) and 20 % (v/v), respectively. SEM analysis showed that the porous structure of the immobilized beads was a cross-linked network with abundant pores that provided many potential adhesion sites for microorganisms. The beads with the immobilized mixed bacteria maintained a high activity during batch experiments and could even be reused for 3 cycles (90 d). Compared with the beads containing individual immobilized strain, the immobilized mixed bacteria showed a more efficient biodegradation of PHE (91.67 %), FLU (88.6 %), and PYR (88.5 %) in synthetic soil washing effluent within 30 d. The first-order kinetic model suitably described the degradation process of the three target PAHs. By adding Tween 80 to the synthetic eluent, the degradation of PHE, FLU, and PYR increased by 16.39 %, 22.25 %, and 21.29 %, respectively, indicating that Tween 80 promoted PAHs biodegradation, even though it was also rapidly degraded during the reaction cycle. These findings suggest that the developed mixed bacteria embedded in PVA-SA-ALNPs gel beads has great potential for PAHs remediation.