Long-term microbial community dynamics in full-scale dry and wet anaerobic digesters for food waste

This study investigated the long-term microbial community dynamics (nearly 200 d) in four full-scale dry anaerobic digestion (DAD) reactors and two wet anaerobic digestion (WAD) reactors for treating food waste. Compared with WAD, DAD demonstrated significantly higher operational instability under elevated concentrations of volatile fatty acids (VFAs, 8000–15000 mg/L) and total ammonia nitrogen (TAN, 5000–7500 mg/L), particularly during recovery phases following prolonged feeding interruption. 16S rRNA sequencing analysis revealed distinct microbial community structures between the two systems. In DAD, syntrophic acetate oxidation bacteria (SAOB) dominated by the genera Halocella and DTU014 was significantly enriched, whereas the bacterial community in WAD was primarily characterized by Defluviitoga. Both systems exhibited hydrogenotrophic methanogenesis (HM) as the dominant pathway, with Methanoculleus being the prevalent archaeal genus in both configurations. Notably, Methanobrevibacter was exclusively detected in DAD. Furthermore, increasing VFA concentrations triggered a structural reorganization of microbial communities in DAD. The relative abundances of Halocella and DTU014 decreased markedly under high-VFA stress, whereas Methanobrevibacter abundance was positively correlated with VFA accumulation. These findings highlight system-specific microbial resilience mechanisms and provide critical insights into VFA-driven community dynamics in anaerobic digestion systems. The results have practical implications for optimizing process stability and methane recovery efficiency in DAD, particularly under high organic loading or feedstock variability conditions.

Graphical abstract