Biohydrogen production from synthetic wastewater in anaerobic sequencing batch reactors

Abstract

Biohydrogen is fo interest because it can be produced from renewable resources, including wastes, under ambient conditions. In this study, anaerobic sequencing batch reactors (ASBR) were used to produce hydrogen from synthetic wastewater under mesophilic conditions. Glucose was used as a substrate for the carbon source. The anaerobic sludge taken from an anaerobic unit treating brewery wastewater was pretreated by boiling for 15 min before adding into the ASBR units as the seeding sludge. The ASBR units were opreated at different chemical oxygen demand (COD) loading rates, and the produced gas compoition and the concentration of the produced volatile fatty acids (VFA) were analyzed using a gas chromatograph (GC) with a thermal conductivity detector (TCD) and a GC with a flame ionization detector (FID), respectively. As the COD loading rate increased from 10 to 40 kg m-3d-1, the system pH decreased from 6.68 to 5.2 At the optimum COD loading rate of 30 kg m-3d-1, which corresponded to a hydraulic retention time (HRT) of 24 h, the produced gas was found to contain 38% H2 and 62% CO2, and the highest hydrogen yield was 1.16 mol-H2/mol-glucose consumed. However, the hydrogen yield reached the highest value of 1.46 mol H2/mol glucose consumed at COD loading rate of 40 kg m-3d-1 in the ASBR with pH control (pH = 5.5). At this COD loading rate, the produced gas was found to contain 43% H2 and 57% CO2