Insight into the microbial community and its succession of a coupling anaerobic-aerobic biofilm on semi-suspended bio-carriers

•A coupling anaerobic-aerobic biofilm was established on semi-suspended bio-carriers.•The coupling biofilm created suitable multi-habitats for diverse microorganisms.•The coupling biofilm stimulated the simultaneous removal of organics and nutrients.•The microbial community on bio-carrier was dominated by functional microorganisms.

This work aims at establishing a coupling anaerobic-aerobic biofilm within a single bioreactor and revealing its microbial community and succession. By using a semi-suspended bio-carrier fabricated with 3D printing technique, an obvious DO gradient was gradually created within the biofilm, which demonstrated that a coupling anaerobic-aerobic biofilm was successfully established on the surface of bio-carriers. The results of metagenomic analysis revealed that the microbial community on the bio-carriers experienced a continuous succession in its structure and dominant species along with the operational time. The formed coupling biofilm created suitable micro multi-habitats for the co-existence of these microorganisms, including nitrifying and denitrifying bacteria, which were beneficial to the removing of organic pollutants and converting nutrients. Along with the succession, the microbial community was gradually dominated by several functional microorganisms. Overall, the results presented an approach to improve the microbial biodiversity by constructing a new structure and floating status of bio-carriers.