The performance characteristics of anaerobic baffled reactor (ABR) fermentation system

An anaerobic baffled reactor (ABR) with an effective volume of 28.7 L was adopted, and the hydrogen production efficiency was investigated with diluted molasses as the substrate. Using a mixture of aerobic and anaerobic activated sludge, the ABR was start-up with a hydraulic retention time (HRT) of 24 h and 35°C. When the influent chemical oxygen demand (COD) concentration was gradually increased from 500 mg/L to 6000 mg/L after a 63-day operation, the ABR kept a steady state. The increase of influent COD concentration, from 6000 mg/L to 8000 mg/L stage by stage, had the remarkable changes on the fermentative system. The ethanol-type fermentation was formed in the first three compartments, while butyric acid-type fermentation in the 4th compartment. In the steady stage at the influent COD of 8000 mg/L, the biogas (H₂) yield was found 61.54 L/d (12.85 L/d) while specific H₂ production rate of the activated sludge was 48 L/kgMLVSS·d. Although the ABR system accumulated hydrogen-producing acetogen, due to the hydrogen-consuming bacteria (methanogen and homoacetogenic bacteria), the hydrogen production efficiency was badly inhibited.