Effects of temperature and organic loading rate on the performance and microbial community of anaerobic co-digestion of waste activated sludge and food waste

• Co-digestion of WAS and FW was investigated at different temperatures and OLRs.
• The CH4 yield and VS removal efficiency were decreased as OLR gradually increased.
• The thermophilic system had the highest endurable OLR of 7 g VS L−1 d−1.
• The mesophilic system showed the best stability at low OLR (< 5 g VS L−1 d−1).
• The microbial community was more affected by temperature than the OLR.

Anaerobic co-digestion of waste activated sludge and food waste was investigated semi-continuously using continuously stirred tank reactors. Results showed that the performance of co-digestion system was distinctly influenced by temperature and organic loading rate (OLR) in terms of gas production rate (GPR), methane yield, volatile solids (VS) removal efficiency and the system stability. The highest GPR at 55 °C was 1.6 and 1.3 times higher than that at 35 and 45 °C with the OLR of 1 g VS L−1 d−1, and the corresponding average CH4 yields were 0.40, 0.26 and 0.30 L CH4 g−1 VSadded, respectively. The thermophilic system exhibited the best load bearing capacity at extremely high OLR of 7 g VS L−1 d−1, while the mesophilic system showed the best process stability at low OLRs (< 5 g VS L−1 d−1). Temperature had a more remarkable effect on the richness and diversity of microbial populations than the OLR.