Controlling the internal carbon source conversion of DPAOs by delayed anaerobic to achieve denitrification and phosphorus removal.

This study evaluated the delay anaerobic process using an SBR reactor with simulated municipal wastewater as the influent substrate. After enrichment of PAOs, anaerobic/anoxic/aerobic operation was used to enrich DPAOs, and the internal carbon source utilization, nitrogen and phosphorus removal efficiency, and enrichment degree of DPAOs during the extension of anaerobic time were investigated. The results showed that the anaerobic time was extended from 50min to 70min and 90min, leading to an increase in the carbon source storage and utilization rate of DPAOs. The improvement of delayed anaerobic conditions resulted in an increase in the enrichment of DPAOs. The average removal rates of COD and TP during anaerobic time of 90min were 91.54% and 94.6%, respectively. DPAOs/PAOs and DPAOs contribution to internal carbon sources reached 69.4% and 60.1%, respectively. After extending the anaerobic time to 110min and 130min, the storage of internal carbon sources in DPAOs and the phosphorus removal efficiency of the system decreased. The average removal rate of TP during anaerobic time of 130min, DPAOs/PAOs and DPAOs contribution to internal carbon sources decreased to 84.6%, 50.2% and 36.4%, respectively. During the delayed anaerobic operation, the change in LB-EPS content was relatively small, and the change in internal carbon source storage had a significant impact on TB-EPS. Analysis of microbial community structure showed that the dominant phyla in the system are Bacteroidetes, Proteobacteria and Chloroflexi. DPAOs represented by Dechloromonas and Candidatus_Accumulibacter during anaerobic treatment for 90min were the dominant microorganisms in the system (relative abundance increased from 1.44% and 2.12% of inoculated sludge to 15.58% and 5.86%). When anaerobic time was extended for 130min, the abundance of DPAOs decreased, while DGAOs represented by Candidatus_Competibacter significantly increased (relative abundance increased from 3.29% in anaerobic time of 90min to 16.16%), leading to a decrease in phosphorus removal performance of the system. © 2024 Chinese Society for Environmental Sciences. All rights reserved.