Fermentative H2 production in an upflow anaerobic sludge blanket reactor at various pH values

Fermentative H2 production in an upflow anaerobic sludge blanket reactor (UASB) at various pH values was investigated in this study. Experimental results show that the H2 partial pressure in biogas, H2 production rate and H2 yield were all pH-dependent, in the range of 0.25–0.52 atm, 42–145 ml-H2 l−1 h−1 and 0.47 to 1.61 mol-H2 mol-glucose−1, respectively. The maximum pH for the H2 partial pressure was observed at pH 7.50. However, the optimum H2 production rate and H2 yield were observed at pH 6.50–7.50. In this UASB reactor, acetate, propionate, butyrate, i-butyrate, valerate, caporate and ethanol were present in the effluent as main aqueous products, and the dominant fermentation was butyrate-type at various pHs. The metabolic pathways and thermodynamics of H2 production were also analyzed. Both H2 production performance and fermentation pathways in this H2-producing UASB reactor were significantly affected by the pH value.