Biohydrogen production from food waste and waste activated sludge in codigestion: influence of organic loading rate and changes in microbial community

BACKGROUND Food waste (FW) and waste activated sludge (WAS) are complementary substrates that improve H-2 production by dark fermentation. However, there is little experience in the process performance in the long-term operation of reactors co-processing FW-WAS. This study aims to determine the optimal FW-WAS ratio in batch H-2 production and then feed this FW-WAS ratio to an anaerobic sequencing batch reactor (SBR) to evaluate the influence of three organic loading rates (OLR) - 15, 22 and 45 g volatile solids (VS) L-1 d(-1) - on H-2 performance and microbial composition. RESULTS Batch tests showed that the FW-WAS ratio of 90-10 increased 22% of the H-2 production compared to the individual FW. In the SBR operation, the OLR significantly influenced H-2 performance, reaching the highest productivity of 733 +/- 282 mL H-2 L-1 d(-1) at an OLR of 22 g VS L-1 d(-1). The cooperative lactic acid cross-feeding between Olsenella and Megasphaera resulted in the highest H-2 productivity at an OLR of 22 g VS L-1 d(-1). OLR promoted the prevalence of different taxa of hydrolytic bacteria, where Enterococcus and Veillonella were positively correlated, with the highest substrate hydrolysis of 50% at an OLR of 15 g VS L-1 d(-1). Prevotella, a genus with a wide spectrum of hydrolytic enzymes, was predominant in the SBR operation regardless of the OLR. CONCLUSION The SBR operation at OLR of 22 g VS L-1 d(-1) improved H-2 production by applying a 90-10 FW-WAS ratio. The change in OLR promoted different taxa of hydrolytic species in the SBR; however, Prevotella spp. prevailed at the three OLRs. (c) 2022 The Authors. Journal of Chemical Technology and Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry (SCI).