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Evalutating the combination of the hydrogen reactor and the photohydrogen reactor
|關鍵字:||厭氧發酵產氫;anaerobic hydrogne fermentation;光合產氫;紫色不含硫光合作用細菌;photohydrogen production;purple nonsulfur bacteria;poly-β-hydroxybutyric acid (PHB)||出版社:||環境工程學系||摘要:||
本研究利用一個陶瓷薄膜系統，將厭氧產氫槽中的菌體與出流水分離，並將出流水供給光合產氫槽使用，達到實際串聯操作的目的。另外，由操作過程中所遭遇的問題，設計批次實驗，研究Rhodopseudomonas palustris WP3-5利用有機酸產氫效果不佳可能原因，並從中找尋串聯的操作策略。
The microorganisms with the ability of hydrogen production can be divided into anaerobic fermentation and photosynthetic microorganisms. Fermentative bacteria use organic compounds as electron donors in anaerobic condition, and produce volatile fatty acids (VFAs) and hydrogen. Photosynthetic bacteria, such as purple non-sulfur bacteria, can use VFAs to produce hydrogen with high production rate and are not inhibited by oxygen because of their metabolic characteristics. Moreover, they can use solar energy as energy source. Thus, the development of a system that combines fermentative bacteria and photosynthetic bacteria makes the combination of organic wastewater treatment and the energy recycle possible.
In order to combine the anaerobic hydrogen fermentation reactor and photohydrogen reactor and to decide the best operating strategies of these two reactors, this study tried to separate the useful byproducts such as VFAs from the outlet of anaerobic hydrogen fermentation reactor with a ceramic membrane system, and these separated organic acids could be the substrate of photohydrogen reactor. In this study, some batch experiments to investigate the metabolic characteristics of Rhodopseudomonas palustris WP3-5 were designed and tried to find out the reason of the low efficiency of the photohydrogen reactor.
The results of the continuous flow tests of anaerobic fermentation reactor showed that the best inlet proportion of glucose:peptone for H2 production was 3:1. However, when the substrate proportion of the inlet of fermentation reactor adjusted to 4:1, the hydrogen production rate (HPR) of the tri-cylinder photohydrogen reactor was highest, and the HPR of three photohydrogen reactors were 64.1、323.6、269.7 mL-H2/L-reactor/day, respectively. From the result mentionrd above, the inlet composition of fermentation reactor deeply affected the efficiency of H2 production and the influent water qualityof photohydrogen reactor.
It was observed that the pH of photohydrogen reactor affected the hydrogen production significently. From the result of the pH test, it showed that pH influenced the regulation of hydrogen production and the accumulation of poly-β-hydroxybutyric acid (PHB) of Rhodopseudomonas palustris WP3-5. Besides, from other result of batch experiments, the change of temperature and nitrogen source would also be the factors which affected the hydrogen production and PHB content of WP3-5. The results could be concluded that the PHB synthesis and hydrogen production were competitive, and these two different pathways seemed to be controlled by the same regulation mechanisms and environmental factors.
The experiments of connecting an anaerobic hydrogen fermentation reactor and a serial photohydrogen reactor showed that when the dilution of anaerobic hydrogen fermentation reactor outlet increased from 2.5-fold to 5-fold, the HPR of photohrogen reactor increased, and the HPR of three reactors were 269.2、345.6、256.7 (mL-H2/L-reactor/day), respectively. Although hydrogen production efficiency of the series system was high, the system could not maintain stably for a long time. The reason may be that there were still some microorganisms remained after membrane filtration, and then they flowed into the photohydrogen reactor to compete with WP3-5. However, if a UV-sterilizer was placed between the fermentation reactor and photohydrogen reactor, the system could be operate stably for more than two weeks.
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