Search

Pseudomonas sp. ZHL02, removing nitrogen via ammonia nitrogen (NH 4 +) → hydroxylamine (HN 2 OH) → nitrite (NO 2 −) → nitrate (NO 3 −) → NO 2 − → nitric oxide (NO) → nitrous oxide (N 2 O) pathway was employed for getting in-depth information on the heterotrophic nitrification-aerobic denitrification (HNAD) pathway from carbon oxidation, nitrogen conversion, electron transport process, enzyme activity, as well as gene expression while sodium succinate, sodium citrate, and sodium acetate were utilized as the carbon sources. The nitrogen balance analysis results demonstrated that ZHL02 mainly removed NH 4 +-N through assimilation. The carbon source metabolism resulted in the discrepancies in electron transport chain and nitrogen removal between different HNAD bacteria. Moreover, the prokaryotic strand-specific transcriptome method showed that, amo and hao were absent in ZHL02, and unknown genes may be involved in ZHL02 during the HNAD process. As a fascinating process for removing nitrogen, the HNAD process is still puzzling, and the relationship between carbon metabolism and nitrogen metabolism among different HNAD pathways should be studied further. [Display omitted] • Pseudomonas sp. ZHL02 mainly removed NH 3 through assimilation in the HNAD process. • Carbon metabolism was crucial for nitrogen removal of Pseudomonas sp. ZHL02. • Pseudomonas sp. ZHL02 via NH 4 +.→ HN 2 OH → NO 2 − → NO 3 − → NO 2 − → NO → N 2 O pathway conduct HNAD process. [ABSTRACT FROM AUTHOR]

[Display omitted] • An efficient MBBR was operated for simultaneous removal of N, P, and COD. • Nitrogen balance was evaluated throughout the MBBR operation phase. • EPS, ETSA, and enzyme activity were used to evaluate biofilm performance. • Proteobacteria and Gammaproteobacteria were identified as the dominant PAO. • A new synchronous N and P removal pathway was proposed at various C/N ratios. The long-term moving bed biofilm reactor (MBBR) with carrier-attached biofilm was successfully operated for simultaneous removal of nitrogen, phosphorus, and COD at various C/N ratios. Results indicated that 99.60%, 63.58%, 78.94%, and 59.64% of NH 4 +-N, NO 3 –-N, TN, and TP were removed at C/N ratio, hydraulic retention time (HRT), and carrier film amount of 5, 40 h, and 1.2 mg·g−1. Nitrogen balance analysis showed that more than 89% of nitrogen (C/N = 20, 15, 10, 5) was converted to gas products. Extracellular polymeric substances (EPS), electron transport system activity (ETSA), and enzyme activity of biofilm were evaluated. Protein (PN)/polysaccharose (PS) values and ETSA decreased with the decrease of C/N ratios. Metagenomics sequencing further revealed that the prominent phyla for nitrogen and phosphorus removal were identified including Proteobacteria , Acidobacteria , Nitrospirae , and Chloroflexi. Proteobacteria and Gammaproteobacteria were identified as the dominant denitrifying phosphate accumulating organisms (PAO) at the phylum and class level, respectively. [ABSTRACT FROM AUTHOR]