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批次反應瓶(125 mL)添加241 nmol四氯乙烯，顆粒污泥對四氯乙烯之降解，以丙酸及丁酸組的效果最佳，此二基質被轉化成醋酸及氫氣的速率比較慢，可使系統維持在低基質濃度的環境下，增加脫氯菌的競爭優勢，而得到較好的四氯乙烯降解率(約43%)，理論上，乳酸被轉化成醋酸及氫氣的速率較乙醇高，但由於部份的乳酸被轉化成可於系統中存在較久的丙酸，而得到比乙醇(20 %)更好的四氯乙烯降率(35 %)。醋酸鈉、甲醇及乙醇的效果最差，絕大部分被用於甲烷化，其中甲醇及乙醇無法造成四氯乙烯的完全脫氯，四氯乙烯只被降解至三氯乙烯而無進一步的持續降解。氫氣在本研究中的效果則不明顯，低濃度組(500~5,000 ppmv)，在無其他主要基質下，氫氣幾乎無促進效果；在有其他其基質存時會有些微的促進作用，其所造成的四氯乙烯降解率分別為:醋酸鈉組的6 %及丙酸組的3 %。高濃度組(10,000~40,000 ppmv)，於無其他基質下，氫氣可造成8 %的四氯乙烯降解率，不過當氫氣濃度超過20,000 ppmv時，反而促進甲烷化；以丙酸為主要基質時，氫氣可促使15 %的四氯乙烯降解，當所添加的濃度高於20,000 ppmv時，亦無明顯差別。
連續流實驗將UASB操作在不同水力停留時間下(1天及4天且於相同的有機負荷下)，當水力停留時間由1天延長至4天時，四氯乙烯平均的生物降解率由10515 nmole/day提高到21261 nmole/day，生物去除率也由38 %提高到76 %，因此在較長的的水力停留時間下，微生物與四氯乙烯的接觸時間較久，可使較多的四氯乙烯被降解。
The objective of this sdudy is to discuss the effect of PCE degradation by operating the upflow anaerobic sludge bed reactor at different hydraulic retention time (HRT) and batch test with different substrates (hydrogen, acetate, propionate, butyrate, lactate, methanol, or ethanol).
In the study of the effect of different substrates, it was found the addition of propionate or butyrate enhanced the PCE (241 nmole/bottle) biodegradation (about 43 %). Lactate was the next (about 35 %), following by acetate , methanol and ethanol. Propionate and butyrate degraded slowly and only under a low hydrogen partial pressure, thus providing a slow and steady release of low levels of H2 and acetate, dechlorination may be favored over competing with methanogenesis. In lactate-fed bottles, propionate was produced during lactate fermentation and made PCE dechlorination continuous after lactate was depleted. However, most of acetate, methanol and ethanol were degraded rapidly and produced significant methane, but not supported dechlorination. Among them, methanol and ethanol did not support complete dechlorination and PCE was just degraded to TCE. The hydrogen effect in this study was not distinct. In the test of low hydrogen concentrations (500~5,000 ppmv), the experimental results showed that PCE was no apparent to degrade by direct hydrogen addition without the presence of other substrate. However, PCE was somewhat apparent to degrade in bottles contained both not only hydrogen and acetate, but hydrogen and propionate. The PCE removal rate due to hydrogen was 6 % and 3 %, respectively. In the test of high hydrogen concentrations (10,000~40,000 ppmv), high hydrogen concentrations supported somewhat better dechlorination than the lower ones. The PCE removal rate due to hydrogen was 8 % in bottles contain hydrogen (reached 20,000 ppmv) and 15 % in those contain both hydrogen (reached 20,000 ppmv) and propionate (10 mM). Despite the presence or the absence of other substrate, hydrogen could not promote dechlorination, but methanogenesis when the additional concentrations of hydrogen reached 20,000 ppmv.
In the continuous flow column sdudy, the UASB was operated at different HRT of 1 day and 4 day conditions, but at the same organic loading rate. The best degradation (21264 nmole-PCE/day) was observed at a HRT of 4 days due to the longer contact time between sludges and PCE. When the HRT was increased from 1 day to 4 days, the PCE removal rate was enhanced from 38 % to 76 %.
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