Metagenomic Analysis Of Functional Bacteria And Their Phosphorus-removing Function Of Activated Sludge In Enhanced Biological Phosphorus Removal

The enhanced biological phosphorus removal(EBPR)is widely used in wastewater treatment plant because of its phosphorus removal efficiency.Unfortunately,the effect of phosphorus removal in EBPR system is not stable.It's due to many factors,such as environment,microbial community structure and functional bacteria of PAOs and GAOs.The polyphosphate metabolism functional genes and their gene metabolic expression also affect the phosphorus removal.However,the phosphorus-removing microorganisms,the relationship between functional bacteria and their effects on phosphorus removal,and the functional genes and their expression in EBPR are not known yet.In this paper,the bacterial community structure variation of an A/O-SBR system was studied by the high-throughput technology of 16 S rRNA sequencing during start-up to stable operation stage.The refined bacterial structure of A/O-SBR was approached by metagenomic sequencing in stable operation.The functional bacteria abundance of PAOs and GAOs were studied.The relationship of functional bacteria and their functional genes was studied as well.The conclusions are as following:(1)It took only 7 days that the A/O-SBR became stable,and the phosphate removal rate of A/O-SBR rose quickly,from 17.78% to 99%.23 days later,the A/O-SBR system has stable and efficient phosphorus removal ability.With 16 S rRNA sequencing and metagenomic sequencing analysis,it showed that Proteobacteria was the dominatedbacteria in the A/O-SBR,and the abundance of Proteobacteria in stable operation stage was distinctly higher than it in start-up phase.Candidatus Accumulibacter spp.was the dominant phosphorus accumulating bacteria in EBPR.Candidatus Accumulibacter phosphatis clade IIA str.UW-1,Dechloromonas aromatica,and Pseudomonas spp.were the main phosphorus accumulating bacteria in the system,with abundances of 18.93%,3.85% and 5.10%,respectively.Candidatus Accumulibacter phosphatis clade IIA str.UW-1 was the dominant bacteria of the system.It was considered that the high-efficiency phosphorus removal rate of A/O-SBR was significantly related to the higher Candidatus Accumulibacter in stable operation phase.(2)It showed that there were both PAOs and GAOs in the high-efficiency phosphorus removal A/O-SBR system,but the GAOs were fewer.With the phosphorus removal rate increasing,the amount of the total PAOs increased too,from 4.13% in start-up phase to 9.76% in stable phase,while the amount of the total GAOs decreased,from 0.37% in start-up phase to 0.24% in stable phase.However,the GAOs in the system had no effect not only to the PAOs growth but also to the phosphorus removal of the system.(3)In all of the PAOs,Candidatus Accumulibacter had the largest amount of functional genes which were related to phosphorus removal.It indicated that Candidatus Accumulibacter was the key bacteria in phosphorus removal in the A/O-SBR system,and polyphosphate kinase was the key gene in the system.It's also known that the polyphosphate kinase in Candidatus Accumulibacter was the largest amount of all functional genes.It showed that there was a close relationship between the phosphorus removal efficiency of the A/O-SBR system and the polyphosphate kinase gene of the Candidatus Accumulibacter.(4)In the high-efficiency phosphorus removal A/O-SBR system,the main metabolisms containd polyphosphate synthesis and disintegrate,PHA synthesis and disintegrate metabolism,phosphate transport and phosphate uptake.Polyphosphate synthesis was the main metabolism in the system.