Bacterial biofilm and extracellular polymeric substances in the moving bed biofilm reactor for wastewater treatment: A review

Among the several biofilm-based bioreactors, moving bed biofilm reactors (MBBR) have been extensively used for wastewater treatment due to low operational costs, technical feasibility, and stability. Biofilm forming strains, e.g., Stenotrophomonas maltophila DQ01, achieved 94.21% simultaneous nitrification and denitrification (SND) and 94.43% removal of total nitrogen (TN) at a cycle time of 7 h, and a biofilm consortium consisting of Chryseobacteriumsp. andRhodobactersp. achieved 86.8% removal of total organic carbon (TOC) at hydraulic retention time (HRT) of 24 h using lab-scale MBBR. Modifications in the surface properties of the biocarrier materials achieved 99.5 ± 1.1% chemical oxygen demand (COD) and 93.6 ± 2.3% NH₄⁺-N removal, significantly higher than the conventional commercial carrier. This review article summarizes the application of MBBR technology for wastewater treatment. The importance of bacterial biofilm and extracellular polymeric substances (EPS), anammox-n-DAMO coupled processes, and carrier surface modifications in MBBR technology have also been discussed.