Establishment and differential performance of hyperthermophilic microbial community during anaerobic self-degradation of waste activated sludge

• Published in: Environmental research 2020-12, Vol.191, p.110035-110035, Article 110035
• Main Authors: Wu, Li-Jie, Li, Xiao-Xiao, Qin, Zhi-Feng, Yang, Fan, Zhou, Quan, Ren, Rui-Peng, Lyu, Yong-Kang
• Format: Article
• Language: English
• Subjects: Acclimation; Anaerobic digestion; Anaerobiosis; Archaea - genetics; Bioreactors; Hyperthermophilic; Methane; Microbial community; Microbiota; RNA, Ribosomal, 16S - genetics; Sewage; Temperature; Waste activated sludge (WAS)
• ISSN: 0013-9351; 1096-0953
• DOI: 10.1016/j.envres.2020.110035

Hyperthermophilic anaerobic digestion, especially at 70 °C, has drawn wide attention. In order to acquire the inoculum and digestion characteristics, batch acclimation and continuous operation experiments were conducted under hyperthermophilic (70 °C), thermophilic (55 °C) and mesophilic (35 °C) conditions, respectively. Archaea at each temperature was successfully enriched from the sole-source waste activated sludge (WAS). Hyperthermophilic digestion achieved higher archaea diversity, close to the Shannon index 2.23 for the thermophilic digestion, but the population were not improved, at a 16S rRNA genes 5.99 × 105 copies mL−1. Hydrogenotrophic methanogens, Methanospirillum and Methanothermobacter, dominated in the hyperthermophilic digester, accounting for 27.15%, while the primary phylum Firmicutes was promoted to 36.31%, with the proteolytic genus Coprothermobacter in Firmicutes at 19.50%. Refractory organic fractions were converted more with a higher digestion temperature, which was demonstrated by the fact that the COD/VS increased to 5.8, 5.2 and 4.2 at 70 °C, 55 °C and 35 °C, respectively, at the end of batch acclimation. In addition, the most solubilization for the dominant fraction protein in the WAS occurred at 70 °C as well. Similar hydrolysis ratio, over 10%, and specific hydrolysis rate, around 0.025 g COD (g VSS·d)−1, were achieved at 70 °C and 55 °C. The higher hydrolysis for hyperthermophilic digestion even resulted in a higher methane yield than that for the mesophilic digestion. Nevertheless, contrary to higher hydrolysis, methanogenesis limited hyperthermophilic digestion in WAS degradation, with an ultimate methane yield 71.2 mL g−1 VSadded, despite an almost complete VFA conversion through the continuous operation. [Display omitted] •Waste activated sludge was acclimated and degraded in a hyperthermophilic digester.•Digestion at 70 °C achieved an ultimate methane yield 71.2 mL g−1 VSadded.•Volatile fatty acids, especially propionic acid, easily accumulated at 70 °C.•Methanogenesis step limited the complete digestion at 70 °C more than hydrolysis.•Genera Methanospirillum and Methanothermobacter dominated in the 70 °C digester.