Variations in Lipid Accumulation and Methanogenic Predominance in Full-Scale Anerobic Digestors Treating Food Waste Leachate

Purpose Food waste leachate (FWL) is a byproduct of the recycling process of food wastes. Three anaerobic digestion (AD) reactors A, B and C that had identical dimensions and < 3% load differences were treating FWL. The start-up of the reactors took place more than 6 years ago. Reactor C exhibited non-optimal pH and lipid accumulation. The research was required to identify the cause and troubleshoot AD reactors. Methods Samples were collected from three AD reactors and an acidogenic reactor in April and December. The samples were analyzed based on Standard Methods for the Examination of Water and Wastewater and 16 s rRNA sequencing. Results In April, the three reactors exhibited no fatal process instability. In December, Reactor A and C had lipid content higher than 13 g/L. Meanwhile, B had less than 1 g/L Reactor A had lipid precipitation. Reactor A showed a higher relative abundance of Tepidimicrobium than reactor C. Dominant methanogen of reactors A and B was Methanoculleus , but C had Methanospirillum as a majority. The pH difference led to lipid saponification in reactor A only. Conclusion The process disturbance was caused by lipid accumulation. The reactors exhibited a gap in lipid granule formation and process stability. Graphical Abstract