Biohydrogen production in anaerobic reactors from wastewater: understanding the role of the fixed-bed and its influence on the acidogenic microbiota

Author(s)

Matheus Neves de Araujo

• Document type: Master's Dissertation
• Press: São Carlos.
• Institution: Universidade de São Paulo (USP). Escola de Engenharia de São Carlos (EESC/SBD)
• Defense date: 2022-01-12

Examining board members

Marcelo Zaiat; Guilherme Peixoto; Valeria Reginatto Spiller

• Advisor: Marcelo Zaiat

Abstract

The search for alternative sources of fuels aiming to replace non-renewable energy matrices is a highly relevant topic extensively addressed in recent scientific research. The biological production of hydrogen (biohydrogen-bioH2) from wastewater from fermentative processes is considered a promising strategy to substitute fossil matrices in the coming decades, besides being a renewable energy carrier capable of mitigating global warming. Despite the widely reported capacity of fermentative processes for hydrogen production from organic waste in scientific literature, there are still gaps concerning the dynamics of biomass growth and retention in fixed-film reactors, which are key factors for the success or failure of the process. Recent studies have revealed gaps related to the bed purpose in fixed-film reactors and its influence on biohydrogen (bioH2) evolution via dark fermentation, given the pivotal role of the basal portion (i.e., feeding chamber) in converting fresh substrate and establishing bioH2 precursor metabolic pathways, which is opposed to that observed in the bed zone. This study aimed to assess the influence of different cell immobilization arrangements (as well as its absence) on biomass retention and washout and their effects on bioH2 evolution and metabolic profiles of an anaerobic tubular reactor (AnTR, which does not include support material), an anaerobic structured-bed reactor (AnSTBR, which includes support material laid out in an orderly pattern) and an anaerobic packed-bed reactor (AnPBR, which considers support material laid out in a disorderly pattern) operated under equivalent operating conditions in the feeding chamber. Higher bioH2 evolution was achieved in the AnSTBR (743.25 mL-H2 L-1 d-1) compared to the AnPBR (662.04 mL-H2 L-1 d-1) and AnTR (586.22 mL-H2 L-1 d-1). For the former, a massive carbohydrateuptake occurred in the feeding chamber and at the beginning of the bed zone, both comprising an intense metabolic activity versus the upper regions. Conversely, this pattern was restricted to the AnPBR feeding chamber, while an alternative source of lactic activity occurred in the bed zone. Overall, the presence of media in the bed zone proved to be imperative to ensure suitable biomass retention in quanti-qualitative terms in opposition to no-bed, influencing biomass distribution, specific substrate conversion, bioH2 evolution and metabolic pathways. (AU)

• FAPESP's process: 19/11012-6 - Biohydrogen production from wastewaters in anaerobic structured bed reactor: understanding the role of the fixed bed and its influence on the acidogenic microbial community
• Grantee: Matheus Neves de Araujo
• Support Opportunities: Scholarships in Brazil - Master