암발효와 광발효미생물의 복합 및 상분리 반응조를 이용한 유기성폐기물의 수소생산 Hydrogen production from organic wastes by co-culture or two phase system of dark and photo fermentative microorganisms원문보기
Among various techniques for hydrogen production, biological fermentation method is considered to be the most feasible one due to many advantages, but has some drawbacks to be solved in the near future. To overcome these drawbacks, a co-culture system of dark- and photo-fermentation bacteria was emp...
Among various techniques for hydrogen production, biological fermentation method is considered to be the most feasible one due to many advantages, but has some drawbacks to be solved in the near future. To overcome these drawbacks, a co-culture system of dark- and photo-fermentation bacteria was employed in this study. In a pure-culture system of dark-fermentation bacterium, Clostridium butyricum, pH 6.25 was found to be optimal in producing hydrogen from glucose. On the other hand, pH 7.0 was the optimum condition for a pure-culture of photo-fermentation bacterium, Rhodobacter sphaeroides. In consideration of its hindrance effect on methanogenic activity, the pH of the co-culture system was eventually set at 6.25 in this study. In the co-culture system, hydrogen could be steadily produced without any lag-phase but there was a distinguishable inflection point resulted from dynamic production and consumption of VFAs by the fermentation bacteria. Among volatile fatty acids produced in the co-culture system, lactic acid was firstly consumed completely, while acetic acid was most attractive to the cell growth of R. sphaeroides but not less efficient in producing hydrogen. Finally, the potentiality of the co-culture system for continuous hydrogen production was assessed in a fed-batch mode of operation. A repeated fed batch co-culture of Chlostridium butyricum and Rhodobacter sphaeroides using a single and dual reactor after batch tests was tested for the hydrogen production. There were two separated reactor in which the optimal pH of each medium was set for the enhanced hydrogen-producing condition of C. butyricum and R. sphaeroides, while those microorganisms were re-circulated inside the dual reactor. In case of dual reactor system, hydrogen yield and production rate were 1.16 mol H2 /mol-glucose and 26.2 ml H2/L/h, respectively. Those values were higher than in the system using just a single reactor. And dual systems are proved for sustainable hydrogen production by the a repeated fed batch operation with 0.44 mol-H2 mol/ glucose hydrogen yield and 25.2 ml-H2/L/h hydrogen production rate, daily. A two phase fermentation system of mixed organic acids, food-wastes and sewage primary sewage sludge was operated by a repeated fed type without injection of additives such as nutrients and micro elements for the secondary photo fermentation. The total hydrogen yield by the two phase fermentative system was 0.06 L H2 /g COD while the value of dark fermentation was only 0.02 L H2 /g COD. The hydrogen yield was increased due to the consumption of by-products from the first dark fermented wastes by R. sphaeroides.
Among various techniques for hydrogen production, biological fermentation method is considered to be the most feasible one due to many advantages, but has some drawbacks to be solved in the near future. To overcome these drawbacks, a co-culture system of dark- and photo-fermentation bacteria was employed in this study. In a pure-culture system of dark-fermentation bacterium, Clostridium butyricum, pH 6.25 was found to be optimal in producing hydrogen from glucose. On the other hand, pH 7.0 was the optimum condition for a pure-culture of photo-fermentation bacterium, Rhodobacter sphaeroides. In consideration of its hindrance effect on methanogenic activity, the pH of the co-culture system was eventually set at 6.25 in this study. In the co-culture system, hydrogen could be steadily produced without any lag-phase but there was a distinguishable inflection point resulted from dynamic production and consumption of VFAs by the fermentation bacteria. Among volatile fatty acids produced in the co-culture system, lactic acid was firstly consumed completely, while acetic acid was most attractive to the cell growth of R. sphaeroides but not less efficient in producing hydrogen. Finally, the potentiality of the co-culture system for continuous hydrogen production was assessed in a fed-batch mode of operation. A repeated fed batch co-culture of Chlostridium butyricum and Rhodobacter sphaeroides using a single and dual reactor after batch tests was tested for the hydrogen production. There were two separated reactor in which the optimal pH of each medium was set for the enhanced hydrogen-producing condition of C. butyricum and R. sphaeroides, while those microorganisms were re-circulated inside the dual reactor. In case of dual reactor system, hydrogen yield and production rate were 1.16 mol H2 /mol-glucose and 26.2 ml H2/L/h, respectively. Those values were higher than in the system using just a single reactor. And dual systems are proved for sustainable hydrogen production by the a repeated fed batch operation with 0.44 mol-H2 mol/ glucose hydrogen yield and 25.2 ml-H2/L/h hydrogen production rate, daily. A two phase fermentation system of mixed organic acids, food-wastes and sewage primary sewage sludge was operated by a repeated fed type without injection of additives such as nutrients and micro elements for the secondary photo fermentation. The total hydrogen yield by the two phase fermentative system was 0.06 L H2 /g COD while the value of dark fermentation was only 0.02 L H2 /g COD. The hydrogen yield was increased due to the consumption of by-products from the first dark fermented wastes by R. sphaeroides.
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