Morphological Changes and Dynamic Equilibrium Analysis of Phosphorus in Mobile Bed Biofilm Reactor

The influence of C/P change on the occurrence form and content of phosphorus in the municipal wastewater treatment system by MBBR was studied, and the dynamic equilibrium process of phosphorus in the reactor was analyzed, in order to reveal the biological treatment mechanism of phosphorus in MBBR. The results show that when C/P changes from 36 to 109, the removal effect of chemical oxygen demand (COD) is small, and the removal rates of ammonia nitrogen (NH4±N) and total phosphorus (TP) show an increasing trend. The highest removal rates of COD, NH4±N, and TP are 93.1%, 51.1%, and 72.4%, respectively. The content of phosphorus in the biofilm was higher than that in the suspended sludge, and the content of phosphorus in the attached biofilm and exfoliated biofilm was higher under higher C/P conditions. In the biofilm, the content of inorganic phosphorus was significantly higher than that of organic phosphorus, which accounted for 75.43%–92.67% of TP, and non-apatite inorganic phosphorus accounted for 44.93%–65.69% of TP. The content of phosphorus in the attached biofilm was significantly higher than that in the exfoliated biofilm, and the phosphorus in the system was in a state of dynamic balance, and the amount of phosphorus treated was equal to the content of phosphorus in the discharged biofilm. These results can provide a theoretical basis for efficient phosphorus treatment and stable phosphorus removal.