The impact of the varying nutrient concentrations on the enhanced biological phosphorus removal performance and functional phosphorus-accumulating and denitrifying genes in an anaerobic-aerobic-anoxic sequencing batch reactor

The denitrifying phosphorus-accumulating organisms (DPAOs) were extensively focused in the past years due to their high efficiencies in simultaneous removal of phosphorus (P) and nitrogen (N) in wastewater treatment. However, it is not clear how this group of bacteria evolve along with the operation process of a specific wastewater treatment system. Here, it is firstly investigated that the effects of simultaneous variations in chemical oxygen demand (COD), P, and N concentrations on enhanced biological phosphorus removal and phosphorus accumulating (PAOs) and DPAOs in an anaerobic-aerobic-anoxic SBR. The results showed that P and N removal ratios were 83.10 +/- 6.72% and 64.21 +/- 7.10%, 90.38 +/- 3.63% and 84.52 +/- 4.91%, 78.82 +/- 8.78% and 78.71 +/- 3.98% corresponding to the SBR operation process of phases I, II and III respectively. The potential PAOs and DPAOs (such as genera Thauera and Dechloromonas) were clearly enriched at different operation phases, especially at phase II. Q-PCR and correlation analysis indicated that phosphorus accumulating-related ppkl genes and denitrifying-related genes coexisted in the SBR and their contents varied with influent COD, P, and N concentrations. Moreover, ppkl genes Glade IIC/IIF and denitrifying-related genes nirK were highly correlated in the SBR. Therefore, simultaneous variations in nutrient concentrations significantly affected the abundance and distribution of functional bacteria and genes related to P and N removal. The results are valuable in N and P removal of practical wastewater treatment engineering (C) 2020 Elsevier B.V. All rights reserved.