Characterization of the microbial community in the anaerobic/oxic/anoxic process combined with sludge ozonation and phosphorus adsorption

Abstract

In this study, the microbial community in the anaerobic/oxic/anoxic (A/O/A) process combined with sludge ozonation and phosphorus recovery was characterized by using phosphorus uptake rate (PUR) analysis and PCR-cloning analysis. Despite effective phosphorus removal, PUR analysis indicated a lower activity of both polyphosphate-accumulating organisms (PAOs) and denitrifying PAOs (DNPAOs) than in other systems utilizing DNPAOs. This result suggested that endogenous denitrifying bacteria actively contributed to denitrification. The PCR-cloning analysis revealed that Bacteroidetes was most prominent in the process, followed by Betaproteobacteria and Alphaproteobacteria. For Bacteroidetes, most of the sequences obtained in this study were not closely related to isolates. On the other hand, for the Alphaproteobacteria, the genera Amaricoccus, Aminobacter, Hyphomicrobium, and Paracoccus, which have the ability both to accumulate poly-β-hydroxybutyrate (PHB) and to reduce nitrate to nitrite, were detected. For the Betaproteobacteria, which are major denitrifying bacteria in wastewater treatment systems, the genera Dechloromonas and Zoogloea, were identified. Organisms belonging to the family Comamonadaceae, some of which have been reported as being primary poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV)-degrading denitrifying bacteria, also existed in the system. Major PAOs/DNPAOs, Rhodocyclus-related PAOs and Actinobacterial PAOs, were not detected, suggesting that unknown PAOs/DNPAOs could have played an important role for phosphorus removal.