Abstract
Distillation wastewater from a continuous ethanol fermentation process using the acid hydrolysate of wood biomass was fed into a methane fermentation reactor and treated anaerobically. The maximum TOC volumetric loading rate was only 1.0 g/l/d without aeration, but improved to 3.0 g/l/d with micro-aeration to suppress H2S buildup. By supplying air equivalent to 9.0 vol% of the evolved biogas into the top of the fixed-bed reactor, H2S concentration decreased to less than 50 ppmv (ml/m3) and the efficiency of SO42– removal was more than 99.5%. The methane concentration in the biogas was maintained around 45% when micro-aeration was used. The effluent from the simultaneous methane fermentation and sulfur removal process was then subjected to biological denitrification-nitrification treatment by recirculating the effluent from the nitrification reactor. As a result, NH4+－N was reduced to less than 5.0 mg/l without the addition of electron donors such as methanol.
