Biochar-mediated DNRA pathway of anammox bacteria under varying COD/N ratios. (1st April 2022)

• Record Type: Journal Article
• Authors: Wang, Weigang; Wang, Tong; Liu, Qinghua; Wang, Han; Xue, Hao; Zhang, Zhuoran; Wang, Yayi
• Is Part Of: Water research. Volume 212(2022)
• Publication Date: 2022-04-01
• Subjects: Anammox -- Biochar -- DNRA -- Metagenomics sequencing -- Nitrogen removal; Water -- Pollution -- Research -- Periodicals; 363.7394
• DOI: 10.1016/j.watres.2022.118100
• Languages: English
• ISSNs: 0043-1354

Abstract

Highlights: Biochar stimulated DNRA and enhanced the NRE of anammox system at low COD/N (0.1–0.5). Ca. Jettenia caeni was the main bacteria responsible for DNRA metabolism. The improved ETC by biochar was the reason for the improved anammox SAA and NRE. Biochar increased the anammox-related ( hzs ) and complete DNRA-related genes abundance. Abstract: Coupling dissimilatory nitrate reduction to ammonium (DNRA) pathway with anammox process has a prominent advantage in enhancement of nitrogen removal. However, the anammox bacteria driven-DNRA is difficult to proceed at normal autotrophic circumstance. Herein, for the first time, biochar (prepared by bamboo) was used as a mediator to stimulate the DNRA pathway of anammox bacteria under varying chemical oxygen demand (COD) to nitrogen (COD/N) ratios (0.1–0.7), and the underlying stimulation mechanism was elucidated by metagenomics sequencing analysis. Results showed that biochar addition (10 g/L) stimulated DNRA pathway of anammox bacteria at low COD/N ratios (0.1–0.5), thus enhancing the nitrogen removal efficiency (NRE) of the anammox system by 7.2%–16.4% and 0.9%–3.0%, respectively, compared to that of tests without sodium acetate and biochar ( p <0.05). This enhancement was attributed to the improved extracellular electron accepting capacity of anammox biomass by biochar. The easily obtained electrons (from sodium acetate) further increased the relative abundances of anammox-related ( hzs ) and complete DNRA-related ( nap AB and nrf AH) genes ( p <0.05), which catalyze electron-consuming reactions. The stimulated anammox pathway and DNRA pathway further increased the specific anammox activity and the relative abundance of anammox bacteria (especially Ca. Jettenia) by 15.5%–23.0% and 11.3%–82.6% compared with that without biochar, respectively. Metagenomics sequencing also revealed that anammox bacteria, Ca. Jettenia caeni, was the main bacteria for DNRA metabolism in this system. Our findings reveal that biochar could selectively stimulate DNRA pathway of anammox bacteria affiliated by a low amount of carbon, which provides a novel strategy to improve the nitrogen removal of anammox-based processes. Graphical abstract: Image, graphical abstract .