The treatment performance of two parallel continuous single stage activated sludge bioreactor: an aerobic bioreactor (ABR) operated at dissolved oxygen (DO) levels of 3-4 mg/L, and an innovative micro-aerobic bioreactor (MABR) operated at DO levels of 0.4-0.8 mg/L and the microbial diversity of MABR was investigated and compared. Under the similar conditions, at a hydraulic time (HRT) of 25 h, an organic loading rate (OLR) of 3.4±0.1 kg COD /m3·d, the influent total phosphate (TP) was 44±2 mg/L. The COD removal efficiencies of the MABR and the ABR were 93±3 and 90±3%, respectively, and no significant difference in performance was noted between the two systems (P=0.087>0.05). It was, however, noted that TP removal efficiency of the MABR (62±4%) was significantly higher than that of ABR (43±2%) (P=0.00). Phylogenetic analysis indicated that bacteria in the MABR was highly diverse. It is likely that facultative anaerobes, microaerophile and aerobes were able to coexist in the MABR. These findings might be helpful in developing an economic treatment system, which can be a better alternative for treatment of many pollutants requiring aerobic/anaerobic sequential treatment.
Key words: Biodiversity, micro-aerobic bioreactor, phosphorous removal, phylogenetic analysis.
DO, dissolved oxygen; MABR, micro-aerobic bioreactor; ABR, aerobic bioreactor; OLR, organic loading rate; COD, chemistry oxygen demand; TN, total nitrogen; TP, total phosphate; PAOs, polyphosphate accumulating organisms; GAOs, glycogen accumulating organisms; EBPR, enhanced biological phosphorus removal; Inf., influent; Eff., effluent; Rem., removal rate.
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