title: Non-denitrifying polyphosphate accumulating organisms obviate requirement for anaerobic condition.
abstract: Enhanced biological phosphorus removal (EBPR) is a widely used process in wastewater treatment that requires anaerobic/aerobic or anaerobic/anoxic cycling. Surprisingly, phosphorus (P) release was observed in the presence of nitrate in the anoxic compartment of the activated sludge tank in a full-scale treatment plant with the Modified Ludzack Ettinger configuration. We therefore studied the potential of this full-scale activated sludge community to perform EBPR under anoxic/aerobic cycling. The polyphosphate accumulating organism (PAO) Candidatus Accumulibacter represented 3.3% of total bacteria based on 16S rRNA gene amplicon sequencing, and metagenome analysis suggested it was likely to be dominated by Clade IIC. Using acetate as the carbon source in batch experiments, active denitrifying organisms (DPAOs) were estimated to comprise 39-44% of the total PAO population in the sludge, with the remaining 56-61% unable to utilize nitrate. When propionate was provided as the organic carbon source, 95% of the PAO population was unable to denitrify. EBPR occurred under defined anoxic/aerobic conditions, despite the presence of DPAOs, when synthetic wastewater was supplemented with either acetate or propionate or when primary effluent was supplied. In addition, the P release and subsequent uptake rates under anoxic/aerobic conditions were comparable to those observed under anaerobic/aerobic conditions. In contrast, a significant reduction in P release rate was observed when acetate was provided under oxic conditions. We postulate that non-DPAOs that recognize the anoxic condition as pseudo-anaerobic were the key players in anoxic/aerobic EBPR.
authors.affiliation: Singapore Centre for Environmental Life Sciences Engineering, Nanyang Technological University, Singapore 637551, Singapore.
authors.forename: A Anisa
authors.initials: AA
authors.lastname: Cokro
authors.affiliation: Singapore Centre for Environmental Life Sciences Engineering, Nanyang Technological University, Singapore 637551, Singapore. Electronic address: yylaw@ntu.edu.sg.
authors.forename: Yingyu
authors.initials: Y
authors.lastname: Law
authors.affiliation: Singapore Centre for Environmental Life Sciences Engineering, National University of Singapore, Singapore 119077, Singapore.
authors.forename: Rohan B H
authors.initials: RBH
authors.lastname: Williams
authors.affiliation: Public Utilities Board, 40 Scotts Road, Environment Building, Singapore 228231, Singapore.
authors.forename: Yeshi
authors.initials: Y
authors.lastname: Cao
authors.affiliation: Singapore Centre for Environmental Life Sciences Engineering, Nanyang Technological University, Singapore 637551, Singapore; Centre for Microbial Communities, Department of Chemistry and Bioscience, Aalborg University, DK-9220, Aalborg, Denmark.
authors.forename: Per H
authors.initials: PH
authors.lastname: Nielsen
authors.affiliation: Singapore Centre for Environmental Life Sciences Engineering, Nanyang Technological University, Singapore 637551, Singapore; School of Civil and Environmental Engineering, Nanyang Technological University, Singapore. Electronic address: swuertz@ntu.edu.sg.
authors.forename: Stefan
authors.initials: S
authors.lastname: Wuertz
mesh_terms: D019149:Bioreactors / Q000382:microbiology; D058440:Denitrification; D010758:Phosphorus; D011122:Polyphosphates; D012336:RNA, Ribosomal, 16S; D012722:Sewage / Q000382:microbiology
chemical_list: D011122:Polyphosphates; D012336:RNA, Ribosomal, 16S; D012722:Sewage; D010758:Phosphorus
keywords: Accumulibacter; Acetate; EBPR; Non-DPAOs; Phosphorus; Propionate