Succession of fungal communities and fungal-bacterial interactions in biofilm samples within a multistage bio-contact oxidation reactor during the treatment of low-COD and high-salinity produced water

The multistage bio-contact oxidation reactor (MBCOR) has been extensively applicated in the oily wastewater treatment. Nonetheless, the underlying mechanisms, especially the fungal community information during the bioremediation of low-COD and high-salinity oilfield produced water is still poorly understood. In this study, the fungal community succession, and fungi-bacteria interactions of a MBCOR were investigated. The result of Illumina high-throughput sequencing showed that the chemical oxygen demand was the main variable in influencing the community structure within the first tank. Besides, the linear discriminant analysis effect size analysis disclosed the feature fungal taxa at different stages, revealing that the fungal community shift was driven by its functional needs. Additionally, network analysis revealed that fungal and bacterial communities were highly interconnected and possessed cooperative relationships. Furthermore, the equilibrium of fungal-bacterial communities was primarily influenced by species richness and diversity. This study provides a deeper insight into the role of fungi within MBCOR in treating oily wastewater.