Enhanced anaerobic phenol degradation: Critical roles of glucose and hydrochar on microbial traits

Phenolic wastewater poses a significant environmental threat due to its toxicity and persistence. This study examined the effects of hydrochar and easily degradable organic wastewater (using glucose as a model compound) on enhancing anaerobic digestion. Their combined application reduced degradation time from 90 days (control) to 30-78 days. Optimal glucose concentrations (1-2 g/L) minimized the lag phase, while higher concentrations (4 g/L) hindered degradation due to acid inhibition. Hydrochar mitigated this by promoting volatile fatty acid conversion. It also enriched key functional microorganisms, stimulated functional gene expression, and strengthened synergistic interactions between phenol-degrading bacteria associated with direct interspecies electron transfer, such as Syntrophomonas, Anaerocella, and Syntrophus, and other microbial groups. This study highlights the potential of hydrochar combined with easily degradable organic wastewater as a green and effective strategy for enhancing phenol degradation.