Methane production by treatment of xylose-based wastewater in AnSBBR: The effect of influent concentration and feeding time

Abstract

Brazil is the main producer of ethanol from sugar cane and interest in the production of second generation ethanol has increased over the years in order to boost productivity in relation to the planted area. Vinasse is the main residue of this industry and its use for methane generation is animportant option for process optimization. Vinasse production from second generation ethanol has a considerable amount of xylose, which is a pentose derived from the hydrolysis of hemicellulose from sugarcane bagasse and yeast does not assimilate it. Therefore, this study investigated the application of an AnSBBR (anaerobic sequencing batch biofilm reactor) of 3.0 L treating 1.0 L per cycle with recirculation of the liquid phase operated at 30°C in batch (cycle time of 8 h and feed time of 10 min) and fed-batch (cycle time of 8 h and feed time of 4 h) mode in the treatment of xylose based wastewater with the main objective of producing methane. The influence of organic matter concentration in the influent (1000-5000 mgCOD.L-1 in batch mode) and feeding mode (batch and fed-batch mode with concentration in the influent of 5000 mgCOD.L1) were assessed (discharge time of 10 min in both). In all assays, the anaerobic system achieved stability regarding pH, bicarbonate alkalinity and total volatile acids. The best performance indicators were achieved in the assay operated in batch mode with an influent concentration of 5000 mgCOD.L-1: there was 50% and 100% of COD and carbohydrates removal, respectively, reaching a volumetric molar productivity of 23.2 molCH4.m-3.d-1 and molar yield of 6.0 molCH4.kgCOD-1. The kinetic model proposed described a simplified metabolite mechanism in which acetic and propionic acids are the main intermediate compounds and it was effective in fitting the experimental data in all assays. © 2017 by Nova Science Publishers, Inc. All rights reserved.