title: Mesophilic and thermophilic alkaline fermentation of waste activated sludge for hydrogen production: Focusing on homoacetogenesis.
abstract: The present study compared the mesophilic and thermophilic alkaline fermentation of waste activated sludge (WAS) for hydrogen production with focus on homoacetogenesis, which mediated the consumption of H2 and CO2 for acetate production. Batch experiments showed that hydrogen yield of WAS increased from 19.2 mL H2/gVSS at 37 °C and pH 10-80.1 mL H2/gVSS at 55 °C and pH 10. However, the production of volatile fatty acids (mainly acetate) was higher at 37 °C and pH 10 by comparison with 55 °C and pH 10. Hydrogen consumption due to homoacetogenesis was observed at 37 °C and pH 10 but not 55 °C and pH 10. Higher expression levels of genes relating with homoacetogenesis and lower expression levels of genes relating with hydrogen production were found at 37 °C and pH 10 compared to 55 °C and pH 10. The continuous experiment demonstrated the steady-state hydrogen yield of WAS was comparable to that obtained from batch experiments at 55 °C and pH 10, and homoacetogenesis was still inhibited. However, the steady-state hydrogen yield of WAS (6.5 mL H2/gVSS) was much lower than that (19.2 mL H2/gVSS) obtained from batch experiments at 37 °C and pH 10 due to the gradual enrichment of homoacetogens as demonstrated by qPCR analysis. The high-throughput sequencing analysis of 16S rRNA genes showed that the abundance of genus Clostridium, containing several homoacetogens, was 5 times higher at 37 °C and pH 10 than 55 °C and pH 10.
authors.affiliation: Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention (LAP(3)), Department of Environmental Science and Engineering, Fudan University, 200433, Shanghai, China.
authors.forename: Jingjing
authors.initials: J
authors.lastname: Wan
authors.affiliation: Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention (LAP(3)), Department of Environmental Science and Engineering, Fudan University, 200433, Shanghai, China.
authors.forename: Yuhang
authors.initials: Y
authors.lastname: Jing
authors.affiliation: Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention (LAP(3)), Department of Environmental Science and Engineering, Fudan University, 200433, Shanghai, China.
authors.forename: Shicheng
authors.initials: S
authors.lastname: Zhang
authors.affiliation: Department of Environmental Engineering, Technical University of Denmark, DK-2800, Kgs Lyngby, Denmark.
authors.forename: Irini
authors.initials: I
authors.lastname: Angelidaki
authors.affiliation: Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention (LAP(3)), Department of Environmental Science and Engineering, Fudan University, 200433, Shanghai, China. Electronic address: gangl@fudan.edu.cn.
authors.forename: Gang
authors.initials: G
authors.lastname: Luo
mesh_terms: D019149:Bioreactors; D005285:Fermentation; D006859:Hydrogen / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D012336:RNA, Ribosomal, 16S / Q000378:metabolism; D012722:Sewage
chemical_list: D012336:RNA, Ribosomal, 16S; D012722:Sewage; D006859:Hydrogen
keywords: Alkaline fermentation; Fermentative hydrogen production; Homoacetoogenesis; Mesophilic; Thermophilic; Waste activated sludge