Continuous operation of hydrogen bio-production reactor with ethanol-type fermentation

The natural response of a continuous stirred tank reactor (CSTR) for hydrogen bio-production using molasses wastewater as substrate was investigated. Emphasis was placed on assessing the operational controlling strategy on the stable operation of CSTR with high efficiency. It was found that at an initial biomass of 15 g/L, an equilibrial microbial community in the ethanol-type fermentation and efficient stable operation of CSTR could be established with following conditions: temperature of 35°C ± 1°C, COD organic loading rate (OLR) of 40 kg/(m³·d), hydraulic retention time (HRT) of 4 h, pH value of 4.6-4.9 and oxidation reduction potential (ORP) of -450--470 mV. Following that, hydrogen production in the reactor was relatively stable. The observed maximal hydrogen bio-production rate was 7.63 m³/(m³·d). The content of hydrogen in the biogas was about 40%-58%. COD removal rate was between 22%-26%. The total content of ethanol and acetic acid in the fermentative end products was above 80%.