| Summary: | 碩士 === 國立高雄第一科技大學 === 環境與安全衛生工程所 === 91 === Biomass is abundant in natural environment. It can be converted to energy in various forms via microbial activities. Among these bioenergy, hydrogen has drawn great attention for the future development due to its high heat value and free of green house gases after burning. In the anaerobic digestion process that is the major scheme for biohydrogen evolution, hydrogen is an intermediate product during the microbial metabolism. Many environmental factors such as temperature, pH, HRT, S0/X0, … etc. affect the metabolic pathways toward the production of hydrogen, acids or alcohols. However, most of the previous studies focused on the relationship between production and different factors, the adoption of shock from these factors to boost the production was seldom investigated. Therefore, the purpose of this study was to create shocks by sludge withdrawn, withdraw interval, and substrate filling to activate hydrogentrophic bacteria and achieve a higher conversion efficiency..
Concentrated brewery wastewater from a nearby plant was collected as the substrate. The experiment demonstrated in both batch and continuous systems. The serum vials with 125 and 250 ml in volume were employed as the batch reactors. A completely stirred reactor with a 4-L effective volume was set-up for the continuous study. The brewery wastewater with COD concentration of 100g/L was prepared and served as the influent and continuously fed to the reactor at a 8-hr HRT that was the optimal condition by the previous study. The batch test was a pre-test whose outcomes were applied to the operation of the continuous system. There were 3 individual runs in the batch system to examine the relationship among substrate/seeding (S0/X0), sludge withdrawn, and withdraw interval. Based on the results of the batch study, the continuous test was designed with 13 individual runs to investigate the optimal condition on sludge withdrawn/substrate refill, sludge withdraw interval, and w/o seeding addition in influent.
In the batch tests, the result indicated that the maximum potential of hydrogen production of 22∼24 mlH2/g VSS added was achieved at S0/X0 =3∼5 g COD/g VSS. Hydrogen production almost doubled as the sludge withdrawn in the range of 35﹪∼55﹪. Meanwhile, the study demonstrated that the reasonable time for sludge withdrawn should be at the hydrogen production reached steady state. In the continuous tests that was based on the optimal conditions from the batch study, the results indicated that the hydrogen production had a highest 41% increase when the sludge withdrawn reached 50%. The way of sludge refilling after withdrawn also affected the hydrogen production. It showed that refill-up at once had an 18% increase than refill gradually. As a comparison, the mixture of substrate and seeding material for refilling was also examined. However, it showed a 67% lower hydrogen production rate than refilling with pure substrate. As to the withdraw interval, the shorter the interval, the higher hydrogen production rate could be achieved. It showed that the interval at 1HRT had 48% higher than that at 6HRT. Both the batch and the continuous study demonstrated that shocks introduced by sludge withdrawn stimulated the hydrogen production. The optimal rate could be achieved as sludge withdrawn at 50%, withdraw interval at 1HRT, refill-up at once after withdrawing, and refill with substrate only.
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