AccScience Publishing / AJWEP / Online First / DOI: 10.36922/AJWEP026100062
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ORIGINAL RESEARCH ARTICLE

Methanol as an ecological regulator enhancing anaerobic degradation of nitrogenous heterocyclic compounds: Insights into community structure and metabolic function

Yimin Fan1 ,  Zhuxuhui Huang2 ,  Jingxin Shi2*
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1 Department of Municipal Engineering, School of Civil Engineering and Architecture, Taizhou University, Taizhou, Zhejiang, China
2 Jiangsu Key Laboratory of Atmospheric Environment Monitoring and Pollution Control, Jiangsu Collaborative Innovation Center of Atmospheric Environment and Equipment Technology, School of Environmental Science and Engineering, Nanjing University of Information Science and Technology, Nanjing, Jiangsu, China
AJWEP, 026100062 https://doi.org/10.36922/AJWEP026100062
Received: 6 March 2026 | Revised: 19 March 2026 | Accepted: 19 March 2026 | Published online: 4 May 2026
© 2026 by the Author(s). This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution 4.0 International License ( https://creativecommons.org/licenses/by/4.0/ )
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Abstract

Coal gasification wastewater contains a large amount of refractory nitrogenous heterocyclic compounds (NHCs), which are toxic and difficult to biodegrade. These substances are poorly removed by traditional biological treatment processes, such as anaerobic treatment. Therefore, the anaerobic degradation of NHCs, such as quinoline and indole, presents a significant challenge. This study investigated the efficacy and mechanism of methanol as a co-metabolic substrate for enhancing this process. Two anaerobic reactors—R1 as a control and R2 containing methanol—were operated to treat synthetic wastewater containing quinoline and indole. The results demonstrated that methanol supplementation significantly improved the degradation efficiency of both compounds. Mechanistic studies revealed that methanol fundamentally modified the system’s ecology—it altered the physicochemical properties of anaerobic granular sludge by increasing the protein-to-polysaccharide ratio in extracellular polymeric substances, thereby enhancing microbial cohesion. Furthermore, methanol induced a targeted microbial community succession, notably enriching key specialist degraders such as Levilinea and Longilinea while suppressing generalist competitors. Functional gene prediction analysis indicated a comprehensive activation of metabolic pathways, energy production, and cellular processes. For the archaeal community, methanol increased diversity and facilitated a shift toward a multi-pathway methanogenic pattern, enriching methylotrophic methanogens (Methanomassiliicoccus) alongside acetoclastic pathways. This study highlights that methanol acts as a comprehensive ecological modulator, enhancing NHCs degradation by optimizing the sludge matrix, restructuring the microbial community for efficient metabolic division of labor, and activating overall metabolic potential, thereby providing a robust strategy for the treatment of industrial wastewater containing refractory organics.

Graphical abstract
Keywords
Anaerobic degradation
Co-metabolism
Quinoline
Indole
Methanol
Microbial community
Funding
This study was supported by the Taizhou Science and Technology Project (Grant No. 24sfa01).
Conflict of interest
The authors declare they have no competing interests.
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Asian Journal of Water, Environment and Pollution, Electronic ISSN: 1875-8568 Print ISSN: 0972-9860, Published by AccScience Publishing
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