| Summary: | 碩士 === 逢甲大學 === 環境工程與科學所 === 92 === A series of assays were carried out using serum bottles with sucrose acclimated seed sludge to investigate the effects of heavy metals on fermentative hydrogen production. The heavy metal used were Cu2+, Zn2+ and Cr+6 , which had the concentrations ranged between 0~16 mg/l, 0~40 mg/l and 0~120 mg/l, respectively. Cu2+, Zn2+ and Cr+6 had the inhibition effects on hydrogen production which had C50 values of 6.5, 4.5 and 60 mg/l, respectively. However, hydrogen production was stimulated by Cu2+ and Cr+6 at 2 mg/l and 15 mg/l, respectively. With the increasing metal dosing, the variation of composition in liquid products had been observed. This indicated that the overall metabolic pathways were changed by metals addition. The relative inhibition on hydrogen production had an order of Zn>Cu>Cr. Comparing with the literature, fermentative hydrogen production was more sensitive to Cu2+ and Zn2+ but more tolerant to Cr+6 than methanogenesis process. The inhibition of Cu2+ and Zn2+ on specific hydrogen production rate fitted the model of competitive inhibition and had inhibition coefficients of 2.9 mg/l and 4.5 mg/l, respectively.
Another experiment was to investigate the effects of pH (pH=7.0, 6.7, 6.5, 6.0, 5.5) on fermentative hydrogen production using a continuously fed reactor under the condition of HRT 12hr, temp. 35℃ and sucrose 20 g-COD/l. The results showed that the optimum HP, HPR, SHPR was occurred at pH 6.7 with values of 2.39 mol H2/ mol sucrose, 304 mmol H2/l/day and 81.9 mmol H2/g-VSS/day, respectively. The worst Hydrogen productivity、Hydrogen production rate and Specific hydrogen production rate occurred at pH7.0 with values of 0.06 mol H2/ mol sucrose, 7 mmol H2/l / day, 1.5 mmole H2/g-VSS/day, respectively. The dominant microbial population shifted to nonhydrogen-producing bacteria based on raised concentrations of ethanol and VSS. On bioenergy production, the highest total value occurred at pH5.5; Energy production rate and Specific energy production rate values were 461 KJ/l/day and 206 KJ/g-VSS/day, respectively.
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