Contributions of MOF-808 to methane production from anaerobic digestion of waste activated sludge

Haoyu Liu; Ying Xu; Hui Geng; Yongdong Chen; Xiaohu Dai

doi:10.1016/j.watres.2022.118653

Contributions of MOF-808 to methane production from anaerobic digestion of waste activated sludge

Water Res. 2022 Jul 15:220:118653. doi: 10.1016/j.watres.2022.118653. Epub 2022 May 24.

Authors

Haoyu Liu¹, Ying Xu², Hui Geng¹, Yongdong Chen¹, Xiaohu Dai³

Affiliations

¹ State Key Laboratory of Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Tongji University, Shanghai 200092, China.
² State Key Laboratory of Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Tongji University, Shanghai 200092, China. Electronic address: xuying73@yeah.net.
³ State Key Laboratory of Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Tongji University, Shanghai 200092, China; Shanghai Institute of Pollution Control and Ecological Security, Shanghai 200092, China. Electronic address: daixiaohu@tongji.edu.cn.

PMID: 35635911
DOI: 10.1016/j.watres.2022.118653

Abstract

The bioconversion of waste activated sludge (WAS) into methane is usually limited by the poor hydrolysis of sludge and/or poor syntrophic methanogenesis during anaerobic digestion (AD). In this study, the underlying mechanism of MOF-808 enhancing hydrolysis and syntrophic methanogenesis during AD process of WAS was investigated. Experimentally, with the effects of MOF-808 (150 mg MOF-808/g Volatile Solid (VS)), the methane production and the proportion of methane in biogas increased by approximately 26.7% and 15.6%, respectively, and the lag phase of methanogenesis decreased by 50.8%, which indicate that MOF-808 enhanced the generation efficiency of methane. The changes in activities of main hydrolytic enzymes with and without MOF-808 (150 mg MOF-808/g VS) during AD process revealed that MOF-808 improved the enzymatic hydrolysis of sludge, and the abiotic hydrolysis of sludge extracellular organic substances by MOF-808 shows that the maximum proportion and the initial increasing rate of low-molecular weight fractions increased by 60% and 583.7%, respectively, indicating that MOF-808 can greatly enhance the hydrolysis degree and rate of sludge via abiotic effect. These demonstrate that MOF-808 enhanced both biological and abiotic hydrolysis of sludge during AD. In addition, changes in the concentrations of acetate kinase and volatile fatty acids (VFAs) with and without MOF-808 (150 mg MOF-808/g VS) during AD process showed that MOF-808 accelerated the bioconversion of VFAs to methane, suggesting MOF-808 has a positive effect on syntrophic metabolism for methanogenesis. Moreover, further analyses of the microbial community structure of sludge samples with and without MOF-808 (150 mg MOF-808/g VS) showed that MOF-808 enriched hydrogen-producing bacteria and mixotrophic methanogens (i.e. Methanosarcina), and changed the methanogenic pathway via accelerating proton transfer between syntrophic anaerobes, especially improving the reduction of CO₂ to methane, and resulting in highly efficient syntrophic methanogenesis. These findings, however, may provide an important reference for enhancing AD efficiency of WAS based on MOF-like materials.

Keywords: Anaerobic digestion; Biodegradation; Metal-organic frameworks; Methane production; Proton transfer; Sewage sludge.

MeSH terms

Anaerobiosis
Bacteria, Anaerobic / metabolism
Bioreactors*
Fatty Acids, Volatile
Methane / metabolism
Sewage* / chemistry
Waste Disposal, Fluid / methods

Substances

Fatty Acids, Volatile
Sewage
Methane