A comparative study on the process efficiencies and microbial community structures of six full-scale wet and semi-dry anaerobic digesters treating food wastes

The purpose of this study was to investigate the effect of different types of food wastes on the process efficiency and microbial community structures in full-scale anaerobic digesters and to identify parameters that affect these criteria. Six full-scale anaerobic digesters were investigated; three were operated under “wet” condition (total solids TS ≤ 10%), and three were run under “semi-dry” condition (10% ≤ TS ≤ 20%). Removal efficiency of volatile solids was much higher in the wet digesters (75.2 ± 3.8%) than in the semi-dry digesters (42.6 ± 5.5%). The bacterial and archaeal communities were distinctly characterized by families Porphyromonadaceae, Sphingobacteriaceae, Syntrophomonadaceae, and Methanobacteriaceae in the wet digesters; and of Clostridiaceae, Patulibacteraceae, Pseudonocardiaceae, Lachnospiraceae, Rikenellaceae, and Methanomicrobiaceae in the semi-dry digesters. The discriminant parameters identified were TS content of influent, concentration of total ammonia nitrogen and the ratio of soluble chemical oxygen demand (COD) to COD in the digester.