title: Complete Nutrient Removal Coupled to Nitrous Oxide Production as a Bioenergy Source by Denitrifying Polyphosphate-Accumulating Organisms.
abstract: Coupled aerobic-anoxic nitrous decomposition operation (CANDO) is a promising emerging bioprocess for wastewater treatment that enables direct energy recovery from nitrogen (N) in three steps: (1) ammonium oxidation to nitrite; (2) denitrification of nitrite to nitrous oxide (N2O); and (3) N2O conversion to N2with energy generation. However, CANDO does not currently target phosphorus (P) removal. Here, we demonstrate that denitrifying polyphosphate-accumulating organism (PAO) enrichment cultures are capable of catalyzing simultaneous biological N and P removal coupled to N2O generation in a second generation CANDO process, CANDO+P. Over 7 months (>300 cycles) of operation of a prototype lab-scale CANDO+P sequencing batch reactor treating synthetic municipal wastewater, we observed stable and near-complete N removal accompanied by sustained high-rate, high-yield N2O production with partial P removal. A substantial increase in abundance of the PAO Candidatus Accumulibacter phosphatis was observed, increasing from 5% of the total bacterial community in the inoculum to over 50% after 4 months. PAO enrichment was accompanied by a strong shift in the dominant Accumulibacter population from clade IIC to clade IA, based on qPCR monitoring of polyphosphate kinase 1 (ppk1) gene variants. Our work demonstrates the feasibility of combining high-rate, high-yield N2O production for bioenergy production with combined N and P removal from wastewater, and it further suggests a putative denitrifying PAO niche for Accumulibacter clade IA.
authors.forename: Han
authors.initials: H
authors.lastname: Gao
authors.affiliation: Department of Civil and Environmental Engineering, University of Illinoisat Urbana-Champaign , Urbana, Illinois 61801, United States.
authors.forename: Miaomiao
authors.initials: M
authors.lastname: Liu
authors.forename: James S
authors.initials: JS
authors.lastname: Griffin
authors.forename: Longcheng
authors.initials: L
authors.lastname: Xu
authors.forename: Da
authors.initials: D
authors.lastname: Xiang
authors.affiliation: Anaergia, Inc. , Carlsbad, California 92008, United States.
authors.forename: Yaniv D
authors.initials: YD
authors.lastname: Scherson
authors.affiliation: Department of Civil and Environmental Engineering, University of Illinoisat Urbana-Champaign , Urbana, Illinois 61801, United States.
authors.forename: Wen-Tso
authors.initials: WT
authors.lastname: Liu
authors.forename: George F
authors.identifier: 0000-0002-9100-1628
authors.initials: GF
authors.lastname: Wells
mesh_terms: D019149:Bioreactors / Q000382:microbiology*; D058440:Denitrification; D009573:Nitrites; D009609:Nitrous Oxide; D010758:Phosphorus; D011122:Polyphosphates
chemical_list: D009573:Nitrites; D011122:Polyphosphates; D010758:Phosphorus; D009609:Nitrous Oxide