THERMOPHILIC BIOMETHANE PRODUCTION BY VINASSE IN AN AnSBBR: START-UP STRATEGY AND PERFORMANCE OPTIMIZATION

Abstract Thermophilic anaerobic digestion treatment of industrial wastewater generated at high temperatures can be used as an alternative for environmental pollution control and bioenergy production. Therefore, this study investigated thermophilic anaerobic reactors containing immobilized biomass (AnSBBR) to treat vinasse for methane production, in batch and fed-batch mode, in a three-step approach. In Step I (batch), the biomass was properly adapted to the thermophilic condition (55 °C) with a feed containing vinasse plus molasses as a co-substrate. In Step II (batch), the applied volumetric organic load (AVOL) was increased and resulted in a methane molar productivity of 304 molCH4.m-3.d-1 at an AVOL of 25.9 gCOD.L-1.d-1 and a yield of methane per removed organic matter near 331 NmL-CH4.gCOD-1. In Step III, a fed-batch strategy was employed at an AVOL of 25.1 gCOD.L-1.d-1 and achieved an optimum methane productivity of 352 molCH4.m-3.d-1 with COD and carbohydrate removal efficiencies of approximately 80 % and 90%, respectively. A kinetic model fitted to the experimental data allowed better understanding of the anaerobic metabolic reactions. Finally, the results obtained demonstrated that a thermophilic AnSBBR is an efficient technological alternative for methane production through vinasse digestion.