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Roles of oxygen in methane oxidation coupled denitrification in membrane biofilm reactors

[Display omitted] •Two aeration modes were evaluated and compared in parallel.•Various oxygen conditions were assessed to determine their roles on denitrification.•The denitrification rate peaked at a DO concentration ranging from 1.5 to 2.0 mg/L.•The maximum yield of short-chain fatty acids (SCFAs)...

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Published in:Chemical engineering journal (Lausanne, Switzerland : 1996) Switzerland : 1996), 2024-08, Vol.493, p.152744, Article 152744
Main Authors: Tan, Jingyan, Chen, Chuan, Zhang, Chengcheng, Wang, Zihan, Wu, Jie-Ting, Xing, De-Feng, Ren, Nan-Qi, Wang, Aijie, Zhao, Lei
Format: Article
Language:English
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Summary:[Display omitted] •Two aeration modes were evaluated and compared in parallel.•Various oxygen conditions were assessed to determine their roles on denitrification.•The denitrification rate peaked at a DO concentration ranging from 1.5 to 2.0 mg/L.•The maximum yield of short-chain fatty acids (SCFAs) was measured at 664.5 mg/L.•Limited-oxygen facilitated methane-driven denitrification by generating SCFAs. With a focus on efficient and low-carbon wastewater treatment, methane driven denitrification has garnered significant attention. Membrane biofilm reactors (MBfRs) are commonly employed to enhance methane utilization. However, previous studies have identified the impact of unavoidable oxygen infiltration on reactor performances without specifying the critical oxygen threshold. In this study, two parallel CH4-MBfRs with different oxygen intakes were established for mutual control. Three different oxygen concentrations, namely 4.5 ± 0.4 mg/L, 1.7 ± 0.2 mg/L, and 0.1 ± 0.1 mg/L, were defined as Rich, Limited, and Poor-oxygen condition, respectively. Results revealed that the maximum denitrification rate in CH4-MBfRs occurred under Limited-oxygen condition (220 mg N/L/d), followed by Poor-oxygen (108.1 mg N/L/d) and Rich-oxygen (60.0 mg N/L/d) conditions. Notably, methane driven denitrification consistently resulted in short chain fatty acids (SCFAs) production. The maximum SCFAs accumulation of 664.5 mg/L was also observed under Limited-oxygen condition. Microbial community characterization showed that the biofilm was predominated by Pseudomonas, Paracoccus, Lentimicrobium, Arcanobacterium, and Proteiniphilum. Based on the known metabolism characteristics of these microorganisms, it was assumed that these denitrifiers and SCFAs producers contributed jointly to methane driven denitrification, potentially triggered by oxygen. The findings contribute to understanding the role of oxygen in methane oxidation-coupled denitrification.
ISSN:1385-8947
DOI:10.1016/j.cej.2024.152744