Biomethane Production in an AnSBBR Treating Wastewater from Biohydrogen Process

Abstract

An anaerobic sequencing batch reactor containing immobilized biomass (AnSBBR) was used to produce biomethane by treating the effluent from another AnSBBR used to produce biohydrogen from glucose- (AR-EPHG) and sucrose-based (AR-EPHS) wastewater. In addition, biomethane was also produced from sucrose-based synthetic wastewater (AR-S) in a single AnSBBR to compare the performance of biomethane production in two steps (acidogenic and methanogenic) in relation to a one-step operation. The system was operated at 30 °C and at a fixed stirring rate of 300 rpm. For AR-EPHS treatment, concentrations were 1,000, 2,000, 3,000, and 4,000 mg chemical oxygen demand (COD) L−1 and cycle lengths were 6 and 8 h. The applied volumetric organic loads were 2.15, 4.74, 5.44, and 8.22 g COD L−1 day−1. For AR-EPHG treatment, concentration of 4,000 mg COD L−1 and 4-h cycle length (7.21 g COD L−1 day−1) were used. For AR-S treatment, concentration was 4,000 mg COD L−1 day−1 and cycle lengths were 8 (7.04 g COD L−1 day−1) and 12 h (4.76 g COD L−1 day−1). The condition of 8.22 g COD L−1 day−1 (AR-EPHS) showed the best performance with respect to the following parameters: applied volumetric organic load of 7.56 g COD L−1 day−1, yield between produced methane and removed organic material of 0.016 mol CH4 g COD−1, CH4 content in the produced biogas of 85 %, and molar methane productivity of 127.9 mol CH4 m−3 day−1. In addition, a kinetic study of the process confirmed the trend that, depending on the biodegradability characteristics of the wastewaters used, the two-step treatment (acidogenic for biohydrogen production and methanogenic for biomethane production) has potential advantages over the single-step process. © 2014, Springer Science+Business Media New York.