4 Conclusions

This study aimed to investigate the effectiveness of biofilm reactors inoculated with azo dye degrading Shewanella and using different carrier materials (biochar, moving bed biofilm reactor (MBBR), and polypropylene carrier (PPC)) for the decolorization of Reactive Black 5 (RB5). The results showed that all three carriers exhibited good RB5 decolorization performance, with varying degrees of efficiency. Although the effluent from the biochar reactor and the two polymer carrier reactors showed some similarity in UV-Vis and FTIR results, LC-MS analysis revealed significant differences in the degradation pathways of RB5, indicating the role of carrier materials and microbial communities in the process.
The MBBR carrier had a rough surface with a large number of microbial aggregates clustered at the protruding tooth-like positions, which intertwined with each other and were not easily detached, resulting in good stability of MBBR operation. Furthermore, the sequencing results showed that the carrier material had a significant impact on the microbial structure in the reactor. The differences in the microbial community structure were relatively small between the MBBR and PPC carriers compared to the almond shell biochar carrier. The highly efficient degrading microbial communities on the biochar carrier were markedly different from those on the MBBR and PPC polymer carrier reactors, with Shewanella being the dominant functional bacteria in the MBBR and PPC polymer carrier reactors.
Overall, this study demonstrated that the physicochemical properties of the carrier materials had a significant impact on the microbial community in the reactor, which in turn influenced the degradation efficiency of RB5. The findings provide valuable insights into the optimization of biofilm reactors for the treatment of dye-containing wastewater.