The aim of this study was to characterize the changes of the microbial community in WWTPs based on hybrid-MBBR process in the Yangtze River Delta in a low temperature season, and to obtain the regularity of the microbial distribution. High-throughput sequencing of Illumina miSeq was conducted to analyze the microbial community structure of activated sludge and suspended carrier biofilm in the aerobic area of five WWTPs. The results showed that the number of microbial species in the suspended carrier biofilm was lower than that of the activated sludge in the same plant, and the species distribution was more uneven. The addition of a suspended carrier can improve the microbial diversity of the system, while the influent and operation mode have a certain selectivity to the microbial community composition of the system. The bacteria with high relative abundance in each plant primarily included Nitrospira, Mycobacterium, Defluvicoccus, Hyphomacrobium, and Macrocharacters,etc. The addition of suspended carriers significantly enhanced the enrichment of Nitrospira. The amount of nitrifying bacteria in the suspended carrier accounted for 86.12%-95.36% of that of the whole system. A certain relative abundance of denitrifying bacteria was detected in the suspended carrier in the aerobic area of each plant. Combined with the results of the measurement of water quality along the process and the lab-scale experiment, it was confirmed that significant SND occurred on the suspended carrier biofilm in the aerobic area, which enhanced the TN removal of the system.
Keywords: Yangtze River Delta; integrated biofilm and activated sludge(hybrid-MBBR); microbial diversity; moving bed biofilm reactor(MBBR); simultaneous nitrification and denitrification(SND).