Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/4979
標題: 氫對地下水中四氯乙烯厭氧生物分解之研究
作者: 陳碩修
關鍵字: 氫氣;地下水;還原脫氯
出版社: 環境工程學系
摘要: 
摘要
本研究主要目的之一,是希望以人為直接添加氫氣的方式,觀察是否能直接促使還原脫氯的反應加快而達到完全脫氯的目標,並探討氫氣在整個脫氯過程中所扮演的角色及最適添加濃度為何,第二個目標是希望瞭解菌量在整個四氯乙烯地下水生物復育過程中所具有的效應,並藉此一實驗所的之結果,提供未來在整治地下水中氯化有機物污染時之參考。
由實驗的結果顯示,無其他基質(AcNa = 0 mg/L)的狀況下,單次添加高濃度氫氣,對於生物性脫氯反應並無明顯促進的現象。而在有其他基質(AcNa = 600 mg/L)存在的狀況下,當氫氣添加濃度由0 ppm增加至60 ppm時,初始反應速率也由1.73 nmol/day增加至3.34 nmol/day,氫氣濃度由60 ppm增加至500 ppm時初始反應速率反而由3.34 nmol/day再降回2.25 nmol/day。而且實驗中發現以人為直接添氫氣的方式,氫氣會快速被微生物所利用,但主要的代謝途徑可能經由CO2+4H2→CH4+2H2O形成甲烷,而非脫氯反應。
就菌量及代謝速率之間的關係中發現菌量濃度由3.5 mg-MLVSS/L增加至350 mg-MLVSS/L時,四氯乙烯擬一階速率常數也隨著由0.0165 day-1增加至0.0463 day-1,四氯乙烯初始降解率也由1.03 nmol/day增加至3.40 nmol/day,此外就菌量、四氯乙烯總代謝量及基質三者間的交互關係,可發現主要基質添加量相同的條件下,菌量數濃度由3.5 mg-MLVSS/L增加至350-MLVSS/L時,四氯乙烯在35天內的總代謝量卻由74.9 nmol/bottle降至23.26 nmol/bottle,每毫克的醋酸鈉能降解的四氯乙烯也由0.0272 nmol/bottle降至0.0031 nmol/bottle。可發雖然在高濃度菌量時,四氯乙烯會具有較高的代謝速率,但四氯乙烯的總代謝量,卻明顯的較低濃度菌量為低,而且高濃菌量時醋酸鈉利用效益,也明顯較低濃度菌量為低。
就醋酸鈉添加濃度對四氯乙烯四氯乙烯的初始降解速率而言,當醋酸鈉濃度由0 mg/L增加至250 mg/L時,四氯乙烯的初始代謝速率由0 nmol/day增加至6.52 nmol/day,但當醋酸鈉濃度高至500 mg/L後,發現初始代謝速率不增反降。就醋酸鈉添加濃度對四氯乙烯的總代謝量而言,發現當醋酸鈉濃度由0 mg/L增加至500 mg/L時,四氯乙烯的總代謝量由7.55 nmol/bottle增加至32.17 nmol/bottle。

ABSTRACT
The objective of this study is to discuss whether the direct addition of hydrogen could enhance the reductive dechlorination of PCE. The effects of the concentrations of biomass and AcNa in reductive dechlorination of PCE were also studied.
The experimental results showed that PCE was no apparent to degrade by direct hydrogen addition without the presence of substrate (AcNa = 0 mg/L). However PCE was apparent by degraded in reactor contain both hydrogen and substrate ( AcNa = 600 mg/L). When the concentration of hydrogen increased from 0 ppm to 60 ppm in the presence of AcNa, the initial PCE removal rate increased from 1.73 nmol/day to 3.34 nmol/day. But the concentration of hydrogen increased from 60 ppm to 500 ppm, the initial PCE removal rate decreased from 3.34 nmol/day to 2.25 nmol/day. The major pathway for hydrogen in the reactor was to form CH4, but not to be used for reductive dechlorination.
The results of biomass study showed that the concentration of biomass increased from 3.5 mg-MLVSS/L to 350 mg-MLVSS/bottle, the initial first order reaction rate constant for PCE removal increased from 0.017 day-1 to 0.046 day-1, the initial PCE removal rate increased from 1.03 nmol/day to 3.4 nmol/day. On the other hand, with the same amount of substrate added, the total amount of degraded PCE decreased from 74.9 nmol/bottle to 23.26 nmol/bottle when the biomass conc. increased from 3.5 mg-MLVSS/L to 350 mg-MLVSS/bottle respectively. The ratio of total amount of PCE degraded to the total of AcNa consumed decreased form 0.0272 nmol/bottle to 0.0031 nmol/bottle. Although higher biomass had high initial PCE removal rate, but the total amount of PCE removal rate decreased.
The results of the effect of AcNa conc. study showed that an in increase in AcNa concentrations increased the initial PCE removal rate, but when concentration of AcNa reached to 500 mg/L, the initial removal rate PCE decreased. When the concentrations of AcNa increased from 0 mg/L to 500 mg/L, the total amount of PCE removed increased from 7.55 nmol/bottle to 32.17 nmol/bottle.
URI: http://hdl.handle.net/11455/4979
Appears in Collections:環境工程學系所

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