Ethanol fermentation of tapioca wastewater in anaerobic baffled reactor: Performance evaluation and microbial...

Anaerobic treatment of tapioca wastewater has a long processing time. This study aims to evaluate ethanol fermentation as an effective treatment of tapioca wastewater. Simulated tapioca wastewater with an average chemical oxygen demand (COD) of 6900 mg L^-1 was treated in a four-column anaerobic baffled reactor for 300 d. Ethanol production was achieved, however it was inconsistent. Ethanol cycles lasted 10-15 d, with a maximum yield of 51.0 ± 2.2 mg COD L^-1. With each decline in ethanol production, glycerol formation increased, peaking at 10.3 ± 1.7 mg COD L^-1. COD removal efficiency reached 93 %, resulted from biomass formation and sedimentation. Microbial analysis revealed that, during ethanol production, Clostridium sensu stricto 11 and Ethanoligenens were the predominant bacteria, whereas Sordariomycetes, Debaryomycetaceae, and Pichia dominated the fungal community. Meanwhile, Helotiales was prevalent during glycerol formation. Understanding the dynamics of microbial shifts could be key to optimizing ethanol fermentation in future processes.