Comparative analysis of the bacterial diversity in a lab-scale moving bed biofilm reactor (MBBR) applied to treat urban wastewater under different operational conditions

► Carrier FR is the major operational parameter on the biofilm formation in a lab-scale MBBR. ► HRT and carrier type not influence statistically on the bacterial diversity of the biofilm. ► Carrier FR is the critical parameter in the start-up of MBBR-based WWTP.