[Succession and PICRUSt2-based Predicted Functional Analysis of Microbial Communities During the Sludge Bulking Occurrence and Restoration in One-stage Combined Partial Nitritation and ANAMMOX Process].

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.

[Nitrite Regulation During Start-up of Combined Partial Nitritation and ANAMMOX Process].

Two types of full-scale reactors(SBR, 116.6 m3, activated sludge process; SBBR, 64.8 m3, activated sludge and biofilm process) were inoculated with activated sludge from a swine wastewater treatment plant. The effect of NO2--N concentration on ANAMMOX was investigated in the reactors during the start-up of the combined partial nitritation and ANAMMOX(CPNA) process by controlling the dissolved oxygen(DO), aeration mode, and NaNO2 dosing. The results showed that the SBBR was more suitable for rapid start-up of partial nitritation under the same operation conditions. Despite NO2--N inhibition(100-129 mg·L-1, 7 days), the ANAMMOX process was successfully started by the SBR on day 39, and the total nitrogen removal rate and efficiency(TNRR and TNRE) were 0.069 kg·(m3·d) -1 and 23.3%, respectively. However, 17 days of NO2--N inhibition(129-286 mg·L-1) had an unrecoverable effect on ANAMMOX activity in the SBBR. By adding NaNO2, the SBR successfully started the CPNA process on day 77. The TNRR, TNRE, and activity of ANAMMOX from day 51 to 77 increased rapidly from 0.070 to 0.336 kg·(m3·d) -1, 16.0% to 52.2%, and 0.012 to 0.307 kg·(kg·d) -1, respectively. The gene copy concentration of AOB and ANAMMOX bacteria in the SBR increased from the original 8.06×106 and 4.42×104 copies·mL-1 to 1.02×109 and 1.77×107 copies·mL-1, respectively, which indicated that the rapid enrichment of AOB and ANAMMOX bacteria in the SBR was achieved mainly by controlling DO, aeration mode, and NaNO2 dosing. Reasonable nitrite regulation is the key for the start of the CPNA process.