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An anaerobic/aerobic sequencing batch reactor was used to test enhanced biological phosphorus removal (EBPR) in wastewater. In the present study, after 6 weeks of operation, the phosphorous and TOC removal efficiency reached to 97.8 and 97.5%, respectively. Our results suggest that phosphate-accumulating organisms (PAOs) play a key role in the phosphorus removal in the EBPR system. Qualitative and quantitative measurements indicate the appear and changing trend of characteristic particles in activated sludge, which further illustrates the metabolic activity and mechanism of PAOs. Fluorescence in situ hybridization (FISH) images showed that PAOs gradually became the predominant bacteria in the EBPR system, aligning with the results of phosphorus removal rate. PCR-DGGE profile demonstrated that with the operation of EBPR process, the composition of microorganisms became more and more abundant in the EBPR system over time. Further sequencing analysis indicated that these microbial populations belonged to α-Proteobacteria, β-Proteobacteria, γ-proteobacteria, Rhodococcus sp. and Pseudomonas sp.

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