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Performance of perchloroethylene dechlorination by bioaugmentation in upflow anaerobic sludge bed reactors
本研究之主要目的在建立real-time PCR應用於UASB系統中微生物的絕對定量分析；並進行批次實驗（微生物添加試驗），探討添加不同比例的微生物（已馴化顆粒性污泥與Dehalococcoides ethenogenes strain 195）對四氯乙烯降解的影響；最後以連續流實驗（生物強化試驗），探討生物強化前後，對UASB反應槽處理四氯乙烯的效應。
研究結果顯示，real-time PCR的R2皆為0.99以上及PCR產物的Tm值無其他干擾物質，對於Eubacteria與Dehalococcoides ethenogenes是一種良好的絕對定量分析法。添加已馴化顆粒性污泥於未馴化顆粒性污泥文中，四氯乙烯的去除率由8%增加為34%，且添加0.1 g-VS的菌量，可提高41%的四氯乙烯降解速率；在添加strain 195於已馴化與未馴化顆粒性污泥後，四氯乙烯的去除率分別由57%與8%，增加為100%，且每加0.1 g-VS的純菌，分別可提高24%與335%的四氯乙烯降解速率。已馴化顆粒性污泥與純菌的添加比例增加，四氯乙烯的去除率亦隨之提高，中間產物的回收率卻降低。推測上述菌群對四氯乙烯的降解機制：未馴化顆粒性污泥為共代謝作用，已馴化顆粒性污泥為共代謝與鹵化呼吸作用，而純菌為鹵化呼吸作用。UASB連續流在未生物強化階段對四氯乙烯的生物去除率為77 ± 4%，在已生物強化階段對四氯乙烯的生物去除率為89 ± 2%，生物去除率增加約12%，此結果顯示可藉由生物強化作用來增加UASB處理四氯乙烯的效率。實驗期間以real-time PCR監測菌量變化，發現UASB系統於生物強化後，Dehalococcoides ethenogenes strain 195數量約3 ± 0.6 × 105 copies/g-granular sludge，經計算可知，每一複製數（copies）的strain 195可增加四氯乙烯的生物降解率（nmole/day）為2 × 10-4 nmole/day-copies。
The objectives of this study were to establish a quantitative method of real-time PCR for quantifying biomass amount in UASB reactors and to investigate the effects of bioaugmentation (with acclimated granular sludge and Dehalococcoides ethenogenes strain 195) on PCE degradation in batch tests and continuous UASB studies.
The results showed that real-time PCR was a good method for quantification of Eubacteria and Dehalococcoides ethenogenes because the R2 values were up to 0.99 and Tm values were no interferences. When unacclimated granular sludge was augmented with acclimated granular sludge, PCE removal increased from 8% to 34%. An addition amount of 0.1 g-VS increased PCE biodegradation rate up to 41%. When strain 195 was augmented to unacclimated and acclimated granular sludges, PCE removals increased from 57% and 8%, respectively, both to 100%. An addition amount of 0.1 g-VS increased PCE biodegradation rates of 24% and 335%, respectively. It was observed that the increased efficiencies were coupled with decreased product recoveries, indicating that chlorinated ethylenes, apart from those not detected, might have been assimilated into biomass. It is therefore suggested that the possible mechanisms of PCE degradation by unacclimated granular sludge, acclimated granular sludge, and pure culture were cometabolism, both cometabolism and halorespiration, and halorespiration, respectively. For the continuous UASB runs, the bioaugmentation enhanced PCE biological removal from 77 4 to 89 2%. Quantification by real-time PCR showed that the concentration of Dehalococcoides ethenogenes strain 195 in the UASB was about 3 0.6 105 copies/g-granular sludge after bioaugmentation. Each copy of strain 195 was responsible for increasing PCE biological removal rate (nmole/day) at 2 10-4 nmole/day-copies.
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