Metagenomic analysis revealed the mechanism of extracellular polymeric substances on enhanced nitrogen removal in coupled MABR systems with low C/N ratio containing salinity

• Published in: Journal of environmental chemical engineering 2023-04, Vol.11 (2), p.109599, Article 109599
• Main Authors: Sun, Zhiye, Li, Yi, Yue, Jianwei, Song, Zhongzhong, Li, Ming, Wang, Ning, Liu, Jun, Guo, Hong, Li, Baoan
• Format: Article
• Language: English
• Subjects: EPS; Functional genes; MABR; Microbial community; Nitrogen removal
• ISSN: 2213-3437
• DOI: 10.1016/j.jece.2023.109599

A combined membrane-aerated biofilm reactor (MABR) was conducted to treat various C/N ratios with saline wastewater. The influence of C/N on nitrogen removal property, extracellular polymeric substances (EPS) features, bacterial community and relevant functional genes were investigated. Fourier-transform infrared spectrum (FTIR), three-dimensional exaction and emission matrix (3D-EEM) fluorescence spectra and metagenomics analysis were conducted to study the mechanism of EPS for enhanced nitrogen removal at low C/N ratio. The results showed that TN removal rate of the whole MABR system were 73.21%, 69.51% and 67.04%, respectively, with the C/N ratio of 6, 4.5 and 3. MABR-2 biofilms secreted more EPS under low C/N and high-salinity conditions to maintain intracellular and extracellular osmotic pressure balance and to participate in cellular metabolic processes. Meanwhile, under the stimulation of low C/N, MABR-2 system with low influent loading was in a “starvation state”, thus EPS could be utilized by the biofilm of MABR-2 system as carbon source to enhance nitrogen removal. Besides, metagenomics analysis showed that aerobic denitrification and dissimilatory nitrite reduction to ammonia (DNRA) were dominant nitrogen removal pathways in MABR-2 system at low C/N ratio. EPS might participate in related metabolic processes in the electron donors and energy production processes as well as the electron transfer pathways in denitrification system. This work provided a feasible practical application scheme for the enhanced TN removal of low C/N ratio containing salinity. •The coupled MABR system was employed to improve TN removal from various C/N ratio with saline wastewater.•The effect of C/N ratio on nitrogen removal performance, EPS characteristics, bacterial composition were evaluated.•Aerobic denitrification and DNRA were main nitrogen metabolic pathways at low C/N ratio.•EPS might involve in electron donor production, energy supply and electron transfer pathways.