The effect of pH on the hydrogen production from the noodle manufacturing wastewater by anaerobic microflora was investigated using batch experiments with pH control at 35°C. Soluble carbohydrate was the main organic substance in the noodle manufacturing wastewater. The pH was changed from 4.0 to 8.5. The hydrogen yield was significantly influenced by pH. At pH of 5.2, the maximum hydrogen yield was 1.47 mol H2/mol hexose (0.12gCOD H2/g COD hexose) and 12% of COD was converted into hydrogen gas. At pH of 4.5, the hydrogen yield drastically decreased. At pH of 4.0, no hydrogen production was observed and lactate was predominantly produced, suggesting that hydrogenase was inhibited by the low pH. On the other hand, the hydrogen yield gradually decreased with increasing pH from 6.0 to 8.5. The concentrations of acetate and butyrate were changed by pH. In particular, the hydrogen production was accompanied with the butyrate production between pH 4.5 and 8.5. The results indicate that pH is a key factor affecting hydrogen gas recovery from the noodle manufacturing wastewater.
