Overlooked pathways of endogenous simultaneous nitrification and denitrification in anaerobic/aerobic/anoxic sequencing batch reactors with organic supplementation. (15th February 2023)

• Record Type: Journal Article
• Authors: Shi, Shuohui; He, Xuejie; He, Lei; Fan, Xing; Shu, Bin; Zhou, Jian; He, Qiang
• Is Part Of: Water research. Volume 230(2023)
• Publication Date: 2023-02-15
• Subjects: Anaerobic/aerobic/anoxic (A/O/A) -- Intracellular carbon -- Simultaneous nitrification and denitrification (SND) -- Heterotrophic nitrification -- Nitrogen removal pathway; A/O/A Anaerobic/aerobic/anoxic -- AOA Ammonium-oxidizing Archaea -- AOB Ammonium-oxidizing Bacteria -- ANOVA One-way Analysis of Variance -- C/N Carbon/nitrogen -- COD Chemical Oxygen Demand -- DO Dissolved Oxygen -- DGAOs Denitrifying Glycogen Accumulating Organisms -- ESND Endogenous Simultaneous Nitrification and Denitrification -- GAOs Glycogen Accumulating Organisms -- HNB Heterotrophic Nitrifying Bacteria -- HNAD Heterotrophic Nitrification and Aerobic Denitrification -- KEGG Kyoto Encyclopedia of Genes and Genomes -- MLSS Mixed Liquor Suspended Solids -- MLVSS Mixed Liquor Volatile Suspended Solids -- NADH Nicotinamide Adenine Dinucleotide -- OHOs Ordinary Heterotrophic Organisms -- OXPHOS Oxidative Phosphorylation -- PAOs Phosphate Accumulating Organisms -- PHAs Polyhydroxyalkanoates; Water -- Pollution -- Research -- Periodicals; 363.7394
• DOI: 10.1016/j.watres.2022.119493
• Languages: English
• ISSNs: 0043-1354

Abstract

Highlights: Organic supplementation promoted nitrification and denitrification in the A/O/A-SBR. Endogenous heterotrophic nitrification dominated in the enhanced nitrification. Batch tests verified endogenous heterotrophic nitrification driven by PHAs. Novel SND pathway based on endogenous nitrification/denitrification was unraveled. CN12 was optimal for endogenous simultaneous nitrification and denitrification. Abstract: The anaerobic/aerobic/anoxic (A/O/A) process is a promising biotechnology to intensify denitrification in low carbon/nitrogen (C/N) wastewater treatment, but the neglected typical rate-limiting step—nitrification—would hinder its wider application. Heterotrophic nitrification driven by intracellular carbon (PHAs) could enhance nitrification and achieve endogenous simultaneous nitrification and denitrification (ESND) in the A/O/A process, but its feasibility remains unexamined. Here we established four A/O/A-SBRs at different C/N ratios (3, 7.5, 12, and 16.5) to address the above-mentioned knowledge gaps. The results showed that organic supplementation promoted both nitrification and denitrification (performance and relevant enzymatic activities) until organic overdose (C/ N = 16.5) exacerbated niche competitions from other non-functional heterotrophs. qPCR and batch tests indicated that high C/N ratios inhibited autotrophic nitrifiers, and heterotrophic nitrifiers (HNB) dominated in the enhanced nitrification. Given the high HNB contribution (43.7%) and low COD variation (< 10 mg L − 1 ) in the SND (76.4%) of CN12, we proposed a potential SND pathway based on heterotrophic nitrification and denitrification driven by PHAs and verified it with batch tests. Microbial and functional analyses suggested that CN12 favored the intracellular carbon transformation and harbored the minimum autotrophic nitrifiers, supporting the dominance of ESND in the enhanced SND. Our findings expand the understanding of the relationships between intracellular carbon transformation and SND and provide a novel nitrogen removal pathway for the practical application of the A/O/A process. Graphical abstract: Image, graphical abstract