Understanding of biofilm formation inhibition in moving bed biofilm reactors treating wastewater of highly nontoxic organic matter

The current understanding of biofilm formation inhibition in moving bed biofilm reactors (MBBRs) treating wastewater of highly nontoxic organic matter (NOM) is limited. Three MBBRs were employed to treat wastewater at different organic matter loading rates (OMLR), and biofilm growth was investigated. The biomass on the carrier surface in the two MBBRs at high OMLR was found to be 43 % and 53 % lower than the MBBR at lower OMLR respectively, indicating that excess NOM supplements inhibit biofilm formation. Analysis results regarding biofilm characteristics suggest that excess NOM supplements can contribute to microbial growth by increasing environmental acidification, destroying biofilm structure and decreasing O2 availability, and microbial shedding by enhancing biofilm surface hydrophilicity and electrostatic repulsion. These findings contribute to a better understanding of how excess organic matter in wastewater inhibits biofilm formation in MBBRs, and the practical solutions, potential long-term impacts of highly NOM and the combined effects of other stressors needs to be explored further in the future. [Display omitted] •Inhibitory effect of highly NOM on biofilm growth was observed in MBBRs.•Mechanisms of inhibiting biofilm formation by excess NOM were investigated.•Highly NOM could decrease O2 availability in biofilm.•Highly NOM could increase biofilm surface hydrophobicity and electrostatic repulsion.