Restoration of acidified dry anaerobic digestion of food waste: Bioaugmentation of butyric acid-resistant microbes

Acidification is a key technical problem in the dry anaerobic digestion system. The effect of bioaugmentation of butyric-resistant microorganisms (BRM) on an unstable acidified anaerobic digestion (AD) system was studied in this work. BRM were enriched in an AD system fed with butyric acid for 36 days. The slurry containing BRM was collected from the fermenter peak on the 24th day when methane production reached the peak, and transferred to an acidified fermenter fed with food waste. After the bioaugmentation, the acidified system was restored obviously. The concentration of butyrate decreased from 16.57 g/L to 5.06 g/L in the acidified system and the methane production increased by 52.2 mL/g-VS in the bioaugmentation treatment, compared to the fermenter without bioaugmentation. Syntrophomonas (Firmicutes) and Proteiniphilum (Bacteroidetes) were enriched in BRM, which contributed to maintain the interspecies electron transfer relationship with Methanosaeta. Therefore, bioaugmentation of BRM restored the integrity of microorganisms in AD and relieved pressure of VFA accumulation. This study provided an experimental and theoretical foundation for the management of acidification in dry AD of food waste.