Comparative Study of the Treatment Performance and Microbial Diversity of an Innovative Upflow Microaerobic Sludge Bed Bioreactor and an Aerobic Control System

The treatment performance and microbial diversity of two parallel single-stage activated sludge bioreactors were investigated and compared. An innovative upflow microaerobic sludge bed (UMSB) bioreactor and an aerobic control system (ACS) were operated at dissolved oxygen levels of 0.5–0.9 and 2.5–4 mg/L, respectively. Under similar conditions, at a hydraulic retention time of 25 h, an organic loading rate of 1.4±0.1 kg COD/m3·d, and an influent total phosphate (TP) of 43±4 mg/L, the chemical oxygen demand (COD) removal efficiencies of the UMSB and the ACS were 94%±1% and 95%±1%, respectively, and no significant difference in performance was noted between the two systems (p=0.498). It was, however, noted that TP removal efficiency of the UMSB (57%±5%) was significantly higher compared with ACS (34%±6%) (p=0.00). Phylogenetic analysis indicated that bacteria in the UMSB and ACS were highly diverse and obviously different. It is likely that facultative anaerobes, microaerophiles, and aerobes were able to coexist in the UMSB. This suggests the possibility of constructing microecosystems that integrate anaerobic and aerobic niches in one reactor. In this study, we demonstrate that under oxygen-limited conditions, it is possible to construct a single-stage activated sludge bioreactor for removing organic substances and phosphorous simultaneously. These findings have important consequences for recognizing and supplementing the enhanced biological phosphorus removal process and for developing new energy-saving treatment technologies.