This study was based on the pilot one-stage combined partial nitritation and ANAMMOX process (CPNA), using data mining and analysis of 16S rRNA high-throughput sequencing data of activated sludge in the process of sludge bulking and recovery, combined with PISCRUSt2. The function prediction analysis aimed to reveal the microbial community changes and the characteristics of nitrogen metabolism and carbon metabolism at different stages of sludge bulking and recovery of the one-stage CPNA process. The results of the study showed that the microbial α-diversity in the sludge bulking and recovery process first increased and then declined. The relative abundance of Nitrosomonas, Candidatus_Brocadia, and Thaurea decreased in the sludge-bulking stage from 12.36%, 11.86%, and 0.272% to 5.97%, 8.30%, and 0.061%, whereas the relative abundance of Candidatus Kuenenia remained stable. The relative abundance of Levilinea, Longilinea, and Turicibacter increased from 0.031%, 0.018%, and 0.009% to 0.055%, 0.025%, and 0.033%. The PICRUSt2 function prediction analysis results showed that there were a total of 47 functional enzyme genes involved in nitrogen metabolism, of which nitrification, denitrification, dissimilative nitrate reduction (DNRA), assimilation nitrate reduction (ANRA), and nitrogen fixation were relatively abundant. The degrees of each had changed. During the sludge-bulking stage, the relative abundance of the ammonia monooxygenase gene (pmoABC-amoABC) and the hydroxylamine dehydrogenase gene hao decreased, whereas the relative abundance of the nitrate-reducing gene increased at the initial stage and then showed a downward trend. Carbon metabolism analysis showed that sodium acetate had a promoting effect on the heterotrophic growth of the CPNA process, but the energy metabolism and glucose production of sodium acetate were not active.
Keywords: PICRUSt2; anaerobic ammonia oxidation (ANAMMOX); carbon metabolism; diversity; high-throughput sequencing; microbial community; nitrogen metabolism.