Production of bio‐hydrogen by mesophilic anaerobic fermentation in an acid‐phase sequencing batch reactor

Abstract

The pH and hydraulic retention time (HRT) of an anaerobic sequencing batch reactor (ASBR) were varied to optimize the conversion of carbohydrate-rich synthetic wastewater into bio-hydrogen. A full factorial design using evolutionary operation (EVOP) was used to determine the effect of the factors and to find the optimum condition of each factor required for high hydrogen production rate. Experimental results from 20 runs indicate that a maximum hydrogen production rate of 4,460-5,540 mL/L/day under the volumetric organic loading rate (VOLR) of 75 g-COD/L/day obtained at an observed design point of HRT = 8 h and pH = 5.7. The hydrogen production rate was strongly dependent on the HRT, and the effect was statistically significant (P < 0.05). However, no significant effect (P > 0.05) was found for the pH on the hydrogen production rate. When the ASBR conditions were set for a maximum hydrogen production rate, the hydrogen production yield and specific hydrogen production rate were 60-74 mL/g-COD and 330-360 mL/g-VSS/day, respectively. The hydrogen composition was 43-51%, and no methanogenesis was observed. Acetate, propionate, butyrate, valerate, caproate, and ethanol were major liquid intermediate metabolites during runs of this ASBR. The dominant fermentative types were butyrate-acetate or ethanol-acetate, representing the typical anaerobic pathway of Clostridium species. This hydrogen-producing ASBR had a higher hydrogen production rate, compared with that produced using continuous-flow stirred tank reactors (CSTRs). This study suggests that the hydrogen-producing ASBR is a promising bio-system for prolonged and stable hydrogen production.

Microbial diversity and genomics in aid of bioenergy

“…Incidentally, in another study, H 2 -producing anaerobic sequencing batch reactor (ASBR) had a higher H 2 production rate, compared with that produced using CSTRs. This study suggested that the H 2 -producing ASBR is a promising bio-system for prolonged and stable H 2 production particularly if enriched H2-producing bacterial populations are achieved [22].…”

Hydrogen Production by Anaerobic Fermentation - General Aspects and Possibility of Using Brazilian Agro-Industrial Wastes

“…91 Outros tipos de reatores também têm sido utilizados, tais como o reator anaeróbio de fluxo ascendente e manta de lodo (upflow anaerobic sludge blanket -UASB), o biorreator de leito empacotado, o reator de leito fixo, o biorreator de leito fixo e fluxo ascendente, o reator batelada anaeróbio em série e o reator de leito fluidizado anaeróbio, entre outros. [92][93][94][95][96][97] Em alguns estudos de produção de H 2 , verificou-se que o processo em batelada apresenta maiores rendimentos de H 2 quando comparado ao modo contínuo. Isto pode ser atribuído ao microambiente substancialmente diferente no reator em batelada quando comparado aos reatores contínuos.…”

Biohydrogen production byClostridium beijerinckii

“…When this occurs, a compromise must be made. In this system, out of the two response variables, P s and R s , the rate is of more interest since continuous biogas systems operate more optimally at low to mid-range hydraulic retention times [20,21] meaning that maximum conversion is hardly ever achieved. For this reason, more effort should be devoted to maximizing the rate of hydrogen production with partial sacrifice to the conversion efficiency.…”