New insight on nitrogen and phosphorus removal of moving bed biofilm reactor driven by ferromanganese binary oxide: Performances and mechanisms.

The moving bed biofilm reactor with different iron-manganese ratios was developed to treat the simulated domestic wastewater with a low carbon-to-nitrogen ratio. The result showed that NH4+-N and NO3--N of 96 ± 2 % and 55 ± 5 %, 97 ± 1 % and 34 ± 6 %, and 40 ± 5 % and 75 ± 4 % were removed in phases II-IV, and phosphorus removal included adsorption of biological iron and manganese oxides and biological removal. Ferromanganese binary oxide stimulated the extracellular polymeric substances secretion, and dissolved organic matter accelerated the iron-manganese redox cycling. Furthermore, fate of manganese and iron was explored, indicating that location of iron-manganese redox cycling was mainly outside the cells. Specific mechanism of iron-manganese redox cycling driven nitrogen and phosphorus removal was clarified including biofilm community. In conclusion, iron-manganese redox cycling reduced the reactive oxygen species level, and Proteobacteria and Planctomycetota were the dominant genera for nutrient, Fe(II), and Mn(II) removal. This study provides a novel method for efficient removal of nutrients.