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|摘要:||本研究主要目的在利用批次實驗的方式，探討氫氣是否可在厭氧系統中做為微生物還原脫氯作用的電子供給者，以及討論如何提昇四氯乙烯還原脫氯作用之效率。實驗結果顯示微生物可以利用氫當成還原脫氯反應中之電子供給者。在單次添加氫氣的實驗方面，當氫氣濃度由0 ppmV增加至500 ppmV，四氯乙烯的最終去除效率也由22%增加至46%，而在半連續添加氫氣方面，當添加之氫氣濃度由0 ppmV增加至5000 ppmV，一階反應速率常數也由0.0213 (day-1)增加至0.1133 (day-1)。而在另一方面，無論是單次或是半連續式添加，共同添加氫及醋酸鈉對四氯乙烯的降解速率及降解率皆比單獨添加氫或醋酸鈉佳，例如：單次添加醋酸鈉600 mg/L與共同添加醋酸鈉600 mg/L及氫5000 ppmV，最終去除率由45%增加至72%，而一階反應速率常數也由0.0193 (day-1)增加至0.0381 (day-1)。而在添加方式方面，半連續添加方式，在氫及醋酸鈉的添加量上皆比單次添加要來的經濟，且在脫氯效率與速率方面也比單次添加要來的好。在不加任何基質及電子供給者的情況下，長達約70天的觀察中發現，四氯乙烯在脫氯速率方面雖較緩慢，但仍有降解之趨勢(65%去除率)，且可將四氯乙烯完全脫氯而到達較無毒性的乙烯。這顯示了微生物在還原能缺乏的情況下仍有脫氯的現象，另一方面也顯示了混合族群中可能包含了可直接進行脫氯作用的菌種存在系統中。|
The objective of this study was to discuss whether H2 could be used as the electron donor in the anaerobic system and how to promote the efficiency of reductive decholrination. The results showed that anaerobic cells could use H2 as the electron donor in the reductive decholrination reaction. When the concentration of H2 increased from 0 ppmV to 5000 ppmV, the initial first order reaction rate constants increased from 0.0213 (day-1) to 0.1133 (day-1). However, when H2 and sodium acetate (NaAc) were added simultaneously, the tetrachoroethylene (PCE) removal rate and transformation ratio were better than that H2 and NaAc were added individually. For example, when H2 at 5000 ppmV and NaAc at 600 mg/L were added simultaneously, the PCE final transformation ratio was 72% and the initial first order reaction rate constant was 0.381 (day-1). However, when NaAc at 600 mg/L was the only substrate, the final PCE transformation ratio and the initial first order reaction rate constant was 45% and 0.0193 (day-1), respectively. If H2 and NaAc were semi-continuous added into the reactor, the final transformation ratio and removal rate were relatively better compared to that H2 and NaAc were added once with the same total amount. If the substrate was absent for a long time (68.5 days), the removal rate became slower but the transformation ratio still could reach 65%. Moreover, PCE could also be transferred to ethylene (ETH) by anaerobic cells. Therefore, it indicated that anaerobic cells could dechlorinate PCE, if the system was absent of substrate. The results maybe suggest that there were another anaerobic cells which could directly dechlorinate PCE in this system.
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