Microbial Community Structure During the Formation of Anaerobic Hydrogen Granular Sludge
| Autor: | Shu-Ting Wang, 王淑亭 |
|---|---|
| Rok vydání: | 2008 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 96 Among all the anaerobic fermentation hydrogen producing systems, anaerobic continuous stirred tank reactor (CSTR) was proved to have high producing efficiency. However, when it was operated under 4 hour hydraulic retention time (HRT), the system tended to undergo serious washing out of biomass as well as decreasing of the hydrogen production efficiency. This disadvantage can be solved by adding immobilized cell to promote the formation of granular sludge. It had been proven that this addition not only raises the biomass concentration and the organic loading rate but also enhances the hydrogen production yield up to 3.35 mole H2/mole sucrose at low HRT operation. Previous studies conducted by our lab have found that a EPS producing bacteria strain Streptococcus sp. could significantly participate in the formation of self-form granular. Therefore, the goal of this study is to explore the relationship between the production of EPS and granular structure as well as the changing of microorganism composition during the granular formation. Results from this study indicated that when the system was operated under 2 hr HRT, low concentration of EPS was produced and average size of the anaerobic granules was 0.66 mm. Hydrogen production rate and hydrogen production yield were 1.49 L/h/L and 2.24 mole H2/mole sucrose, respectively. The results also revealed that there was a high proportion of Streptococcus sp. (LGC354) existed in the system. When the system was operated at 1 hr HRT, significant production of EPS was observed and average particle size of the anaerobic granules was 1.48 mm in accompany with the a highest observed MLSS concentration (52,700 mg/L) and existence of many Clostridium sp. cell counts. Hydrogen production rate and hydrogen production yield were enhanced to 3.80 L/h/L and 2.97 mole H2/mole sucrose, respectively. When the system was operated under HRT=0.5 hr, we fined that the proportion of Clostridium sp. were higher than that of Streptococcus sp. and the granule structure at HRT 0.5 hr was not denser than that of HRT 1 hr. At this operation, the best hydrogen production rate and hydrogen production yield were 6.95 L/h/L and 5.03 mole H2/mole sucrose were found and the C. pasteurianum were the main Clostridium species in the granule sludge which average particle size was 2.26 mm. Also, from the microorganism community structure between the granule-phase and suspension-phase, the bacteria of Streptococcus lutetiensis only can be fined in the granule-phase. Based on the results collected in this study, it appeared that the size of the granular, hydrogen production rate, and hydrogen production yield all increased with a shortening of hydraulic retention time. We also fined that the production of EPS were helping bacteria to aggregate and promoting the formation of granular sludge. C. pasteurianum was the still the predominated hydrogen producing bacteria. Furthermore, the amount of EPS adhered at granule sludge were also influenced the structure of granule sludge, and then affected the hydrogen production efficiency. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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