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Effect of Initial Sludge Loading Rate on the Formation of Ethanol Type Fermentation for Hydrogen Production in a Continuous Stirred‐Tank Reactor

Ethanol type fermentation has attracted an increasing interest because of its high hydrogen yield. A continuous stirred‐tank reactor (CSTR) was introduced and the effect of sludge loading rate (SLR) on formation of ethanol type fermentation for hydrogen production was investigated in this research. It was found that the initial SLR influenced the formation process of ethanol type fermentation remarkably. When the CSTR was started up with an initial SLR of 0.63 kg chemical oxygen demand (COD)/kg mixed liquor volatile suspend solid (MLVSS)/d (COD: COD, MLVSS: mixed liquor volatile suspended solids), ethanol type fermentation was recognized within 16 days that was 7 and 14 days prior than the earlier SLR of 0.75 and 1.47 kg COD/kg MLVSS/d, respectively. However, the highest hydrogen‐producing rate of the activated sludge came up to 0.102 m3/kg MLVSS/d when initial SLR of 1.47 kg COD/kg MLVSS/d. A succession of acidogenic fermentation types had occurred during the formation process of ethanol type fermentation, they were mixed acid fermentation, propionic acid type fermentation, butyric acid type fermentation and ethanol type fermentation in a sequence. Moreover, it was also found that ethanol type fermentation could occur within a pH range of 4.0–5.3, much wider than that have been reported previously. © 2012 American Institute of Chemical Engineers Environ Prog, 32: 1271–1279, 2013