Effect of fermentation time/hydraulic retention time in a UASB reactor for hydrogen production using surface response methodology

The present work was to study the fermentation and the hydraulic retention times effect using surface response methodology for hydrogen production using a synthetic media as substrate. The reactor used 60 spheres with anaerobic biofilms developed in fiber ixtle for immobilization of anaerobic sludge and was operated at mesophilic temperatures and initial pH of 5.0. The inoculum used for biofilms was pretreated, the anaerobic sludge was heat (100 °C, 30 min), and after was subject to acid-basic procedures to selectively enrich the hydrogen producing mixed consortia. A factorial arrangement of 23 was carry out on MINITAB statistical program, the statistical analysis of the surface response methodology of the hydrogen production process after the development and growth of biofilms was carried out at 3 different hydraulic retention times (1,3 and 6 h), as well as three fermentation times, as response variables (40, 140 and 280 h). The analysis of variance given by the statistical program with respect to the two factors studied: hydraulic retention time and fermentation time showed that they are highly significant, but in the interaction between variables no significance was detected. A longer time of hydraulic retention (HRT = 6) as well as a longer fermentation time (280 h) the hydrogen production is favored obtaining a hydrogen production rate of 4.34 LH2/L/d, and no methane was detected. •Utilization of agroindustrial residue from agave lechuguilla tor (ixtle).•Use of ixtle as a natural support for the formation of biofilms.•Biofilms used for hydrogen production.•The study of the effect of the: HRT and fermentation time.