Operation and hydrogen production characteristics in different types of reactors

CSTR reactor (suspended growth) and EGSB reactor (attached growth) were used to study the influence of biohydrogen production process through different types of reactors. Anaerobic activated sludge was used as inocula and molasses wastewater was selected as substrate. Keeping temperature at 35°C, the hydrogen production rate (HPR), pH value, liquid end products and biomass were examined to study the operation characteristics of the two reactors with the organic loading rate (OLR) adjusted firstly by increasing the COD concentration and then by shortening the hydraulic retention time (HRT). The results showed that HPR increased gradually with the increase of OLR. The optimal OLRs for CSTR reactor and EGSB reactor were 25-35 kg/(m³·d) and 70-80 kg/(m³·d) with the maximum HPR of 6.21 L/(L·h) and 18.0 L/(L·h), respectively. When in stable running periods, EGSB reactor maintained a high biomass concentration of 27.6 gVSS/L, while that was 7.8 gVSS/L for CSTR reactor. It is indicated that high biomass concentration effectively contributes to the high HPR and high stable running of hydrogen producing reactor. Both of CSTR reactor and EGSB reactor form ethanol-type fermentation, which suggests that fermentation type is not influenced by reactor types. Moreover, EGSB reactor presents more tolerance to low pH compared with CSTR reactor.