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Abstract: A full factorial design was conducted to investigate the combined effects of temperatures and initial pH on fermentative hydrogen production by mixed cultures in batch tests. The experimental results showed that the modified Logistic model can be used to describe the progress of cumulative hydrogen production in the batch tests of this study. The modified Ratkowsky model can be used to describe the combined effects of the temperatures and initial pH on the substrate degradation efficiency, hydrogen yield and average hydrogen production rate. The temperatures and initial pH had interactive impact on fermentative hydrogen production. The maximum substrate degradation efficiency, the maximum hydrogen yield and the maximum average hydrogen production rate was predicted at the temperature of 37.8°C and the initial pH of 7.1, 37.4°C and 6.9, and 38.2°C and 7.2, respectively. In general, the optimal temperature for the fermentative hydrogen production was around 37.8°C and the optimal initial pH for the fermentative hydrogen production was around 7.1. [Copyright &y& Elsevier]

Abstract: The inhibitory effect of added ethanol, acetic acid, propionic acid and butyric acid on fermentative hydrogen production by mixed cultures was investigated in batch tests using glucose as substrate. The experimental results showed that, at 35°C and initial pH 7.0, during the fermentative hydrogen production, the substrate degradation efficiency, hydrogen production potential, hydrogen yield and hydrogen production rate all trended to decrease with increasing added ethanol, acetic acid, propionic acid and butyric acid concentration from 0 to 300mmol/L. The inhibitory effect of added ethanol on fermentative hydrogen production was smaller than those of added acetic acid, propionic acid and butyric acid. The modified Han–Levenspiel model could describe the inhibitory effects of added ethanol, acetic acid, propionic acid and butyric acid on fermentative hydrogen production rate in this study successfully. The modified Logistic model could describe the progress of cumulative hydrogen production. [Copyright &y& Elsevier]

The effect of ammonia concentration ranging from 0 to 10g N/L on fermentative hydrogen production by mixed cultures was investigated in batch tests using glucose as substrate at 35°C and initial pH 7.0. The experimental results showed that during the fermentative hydrogen production, the substrate degradation efficiency increased with increasing ammonia concentration from 0 to 0.01g N/L. The hydrogen production potential, hydrogen yield and average hydrogen production rate increased with increasing ammonia concentration from 0 to 0.1g N/L. The maximum hydrogen production potential of 291.4mL, maximum hydrogen yield of 298.8mL/g glucose and maximum average hydrogen production rate of 8.5mL/h were all obtained at the ammonia concentration of 0.1g N/L. [Copyright &y& Elsevier]