Alkaline pH shocks alter digester activity and community dynamics during long-term operation

• Published in: Journal of environmental chemical engineering Vol. 12; no. 5; p. 113557
• Main Authors: Chen, Boyang, Azman, Samet, Sweygers, Nick, Crauwels, Sam, Dewil, Raf, Appels, Lise
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.10.2024
• Subjects: Alkaline adaptation; Anaerobic digestion; Methane production; Microbial dynamics; Alkaline adaptation; Microbial dynamics; Methane production; Anaerobic digestion
• ISSN: 2213-3437
• DOI: 10.1016/j.jece.2024.113557

This study investigated the impact of applying a pH shock on the anaerobic digestion (AD) performance, via digestate activity batch assays and microbial community dynamics in long-term continuous AD experiments. Sudden pH increases to 9.5 were applied, and the duration of the perturbation increased after every application (from 1 to 7 days – and up to 14 days in the batch assays). The potential for alkaline adaptation in AD processes was demonstrated, since the microbial communities under scrutiny exhibited an increasingly shorter recovery period at increasing pH shock duration, i.e., from 75 days to 39 days, and methane production was not irreversibly inhibited. Microbial analysis revealed a dynamic response that evolves from acidogenic dominance (e.g., Parabacteroides, Sphaerochaeta) to a more balanced community with a greater presence of hydrolytic bacteria (Clostridium and Ruminococcus). The research highlighted the resilience of microbial communities to pH shocks and suggested that extending pH shock durations could further reduce recovery times and facilitate gradual alkaline adaptation. •Methane production remains stable around 250 mL/g VS despite undergoing pH shocks.•Methanogenesis recovery accelerated after subjection to multiple pH shocks.•Hydrolytic bacteria remained dominant after microbial recovery.•Microbiome shifted after pH shocks, indicating possible alkaline adaptation.