Ammonium and organic carbon co-removal under feammox-coupled-with-heterotrophy condition as an efficient approach for nitrogen treatment

• Published in: Scientific reports Vol. 11; no. 1; pp. 784 - 11
• Main Authors: Le, Chung Phuong, Nguyen, Hai Thi, Nguyen, Toi Duy, Nguyen, Quyen Huynh Minh, Pham, Hai The, Dinh, Hang Thuy
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 12.01.2021; Nature Publishing Group; Nature Portfolio
• Subjects: 631/326; 704/172; Ammonium; Chemical oxygen demand; Fluorescence in situ hybridization; Heterotrophs; Heterotrophy; Humanities and Social Sciences; Iron; multidisciplinary; Nitrification; Nitrogen; Nitrogen dioxide; Nitrogen removal; Oligonucleotides; Organic carbon; Oxidation; Oxygen demand; Redox potential; Retention time; rRNA 16S; Science; Science (multidisciplinary)
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-020-80057-y

Nitrification is the rate limiting step in the nitrogen removal processes since nitrifiers have high oxygen demand, but poorly compete with aerobic heterotrophs. In a laboratory-scaled system, we investigated a process of ammonium oxidation under ferric-iron reducing condition (feammox) in the presence of organic carbon using influents with high NH 4 + and COD contents, and ferrihydrite as the only electron acceptor. Batch incubations testing influents with different NH 4 + and COD concentrations revealed that the [COD]/[NH 4 + ] ratio of 1.4 and the influent redox potential ranging from − 20 to + 20 mV led to the highest removal efficiencies, i.e. 98.3% for NH 4 + and 58.8% for COD. N 2 was detected as the only product of NH 4 + conversion, whereas NO 2 − and NO 3 − were not detected. While operating continuously with influent having a [COD]/[NH 4 + ] ratio of 1.4, the system efficiently removed NH 4 + (> 91%) and COD (> 54%) within 6 day retention time. Fluorescence in situ hybridization analyses using Cy3-labeled 16S rRNA oligonucleotide probes revealed that gamma-proteobacteria dominated in the microbial community attaching to the matrix bed of the system. The iron-reduction dependent NH 4 + and COD co-removal with a thorough conversion of NH 4 + to N 2 demonstrated in this study would be a novel approach for nitrogen treatment.