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Bioremediation of naphthalene-contaminated soils and watres
根據水相批次實驗結果顯示，以44 mL血清瓶為反應容器，naphthalene濃度在23 mg/L以下時，naphthalene分解菌均能將naphthalene降解至偵測極限以下，naphthalene濃度為26 mg/L時則有明顯之抑制現象，但相同濃度下呼吸儀之實驗結果則未有抑制現象產生。另根據McCarty計量公式所得之理論耗氧量與各組實驗最終耗氧量均十分接近，顯示氣泡式呼吸儀為測試生物呼吸效率之有效儀器。而未經馴化之酚分解菌、氯酚分解菌及BTEX分解菌亦可降解naphthalene至偵測極限以下，顯示其酵素對環狀結構相似之化合物亦具降解能力。若以漸次增加進流基質中naphthalene濃度之方式馴養酚分解菌，則可發現隨馴養時程之增加，酚分解菌適應與降解naphthalene之速率亦隨之增加。
土壤批次實驗結果顯示，以44 mL血清瓶為實驗容器時，當naphthalene濃度分別為50、100、300及576 μg/g-soil時，在經過144、192、288及350小時後，土壤中naphthalene之殘餘濃度分別為21、21、167及484 μg/g-soil，其去除率分別為58 ﹪、79 ﹪、43 ﹪及 16 ﹪。若增加初始微生物之添加量，則可發現降解速率有顯著之提高，但實驗終止時之naphthalene殘餘濃度則無明顯改變，顯示降解效率之趨緩可能為菌體活性喪失或氧氣量不足所致。若於上述實驗終止時於反應瓶內分別重複添加菌液、氧氣及同時添加菌液和氧氣，則發現同時添加菌液和氧氣之實驗組效果最佳。例如當naphthalene原始濃度為576 μg/g-soil時，經過350小時實驗時間後之殘餘濃度為484 μg/g-soil，在同時重複添加菌液和氧氣後，naphthalene殘餘濃度則大幅降為95 μg/g-soil，顯示復育過程中維持適當的供氧與添加適當的微生物量將可大幅提升復育效率。
若以呼吸儀測定土壤中naphthalene生物降解所需之耗氧量，則發現在初始菌數添加量相同下，含水率為300 ﹪及500 ﹪之實驗組，其實際耗氧量與理論耗氧量比值約為17.7與15.6左右。推測過高之耗氧量應為土壤中原有有機質耗氧所致，惟相關數據須進一步實驗證實並釐清土壤中naphthalene生物降解所需之耗氧量。
The objective of this study was to discuss the bioremedation of soils and waters naphthalene-contaminated. A respirometer was used to measure the oxygen demand required for the biodegradation of Naphthalene in soils and waters. The rate of degradation was also studied with the respirometer.
The biodegradation of naphthalene in waters was conducted with a series of batch reactors. The experimental results indicated that naphthalene could be degraded and removed by the acclimated microorganisms, if the initial naphthalene concentration was less than 23 mg/L. However, the inhibition effect was observed when the initial naphthalene concentration was higher than 26 mg/L. Although, the batch results showed the inhibition effect with the presence of high concentration of naphthalene, the results of respirometer study did not show any inhibition effect.
Respirometer is an effective equipment to measure the rate of respiration. The result gained from the respiration study was almost the same as that calculated from McCarty''s stoichiometry equation.
Experimental results indicated that the unacclimated phenol degraders, chlorophenol degraders and BTEX degraders also had the capability to degrade naphthalene. The capability was proportional to the degree of acclimation.
In the batch experiments for soil bioremediation, naphthalene was controlled at the concentrations of 50, 100, 300 and 576 μg/g-soil. The residual concentration of naphthalene in soil were 21, 21, 167 and 484 μg/g-soil after 144, 192, 288 and 350 hrs of operation respectively.
It is found that the rate of degradation increases with an increase in added microbes. However, the residual concentrations of naphthalene did not show any improvement with an increase in the cell concentrations because of the insufficient oxygen supply or the decay of microbe in the reactors. As such, if more microbes and oxygen were re-supplied, a better result in the removal efficiencies would be obtained. For example, naphthalene with concentration at 576 μg/g-soil could be reduced to 484 μg/g-soil after 350 hrs. If the extra microbes and oxygen were re-added simultaneously, the concentration of naphthalene could be reduced to 95 μg/g-soil. As such, sufficient oxygen supply and the presence of abundant microorganisms could enhance the efficiency of bioremediation.
A respirometer was used to detect the oxygen demand that required for the biodegradation of naphthalene. The results indicated that the actual oxygen demands differ from the theoretically oxygen demand by 17.7 and 15.6 times in the reactor with same microbial population but difference WHC at 300 % and 500 %, respectively. The high oxygen demand may be caused by the degradation of other organic matters in the soil. A further study would be necessary to measure the actual oxygen demand for the degradation of naphthalene in soil.
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