Biohydrogen Production and Value-Added Product Recovery from Co-Digestion of Cassava Wastewater and Glycerol in an Anaerobic Fluidized Bed Reactor

Abstract

This study aimed at evaluating H2 production and value-added products during the co-digestion process of cassava processing wastewater (CW) and glycerol (50% CW and 50% glycerol on a COD basis) in an anaerobic fluidized bed reactor (AFBR) under mesophilic conditions (30 ± 1 °C), at a hydraulic retention time (HRT) of 4 h, and an organic loading rate (OLR) ranging from 6 to 75 g chemical oxygen demand (COD).L− 1.d− 1. The acidogenic reactor exhibited optimal performance at OLR 45 gCOD.L− 1.d− 1, with a H2 yield (HY) corresponding to 1.13 mmol H2.g− 1COD and H2 production rate (HPR) of 1.21 L H2.L− 1.d− 1, as well as the production of ethanol and propionic acid. By means of the 16 S rRNA sequencing, a similar microbial profile was observed between different OLRs (45 gCOD.L− 1.d− 1 and 75 gCOD.L− 1.d− 1), effectively enriching H2-producing bacteria from the seed sludge, and a high relative abundance of Lactobacillus was identified in both conditions. The butyric acid (HBu) and acetic acid (HAc) production pathways, highly related to H2 production, were possibly favored, especially due to the activity of the inferred enzyme acetate CoA-transferase and short-chain acyl-CoA dehydrogenase for HBu generation and pyruvate synthase, acetaldehyde dehydrogenase and acetate-CoA ligase in the generation of HAc.Graphic Abstract