| 摘要: | 由於生活型態改變，國人處於室內環境中之時間比率高達80~90%，經由室內空氣接觸生物性危害之機會也隨之增加。本研究之目的為使用非熱介電質放電(Dielectric Barrier Discharge, DBD)系統產生之高濃度臭氧及結合觸媒分解臭氧尾氣來淨化室內生物氣膠，以瞭解不同操作條件對臭氧殺菌效力之影響、觸媒分解臭氧效力、釐清DBD電漿中臭氧殺菌之貢獻及評估臭氧殺菌結合觸媒系統應用於淨化室內空氣中生物性危害之可行性。
本研究第一階段之實驗室腔體(chamber)臭氧殺菌實驗是利用卡里遜霧化器產生濃度為106CFU/m3以上之四種不同生物氣膠(大腸桿菌、枯草桿菌內孢子、酵母菌、青黴菌孢子)，並量測不同臭氧濃度(0~175ppm)、相對溼度(30~70%)以及暴露時間(1~10秒)下，臭氧對生物氣膠之殺菌效力。殺菌後之尾氣臭氧以活性碳及氧化鋁為載體之二氧化錳觸媒進行處理並量測觸媒分解臭氧效率。第二階段實驗為參考第一階段得到較佳之臭氧殺菌操作條件(臭氧濃度150ppm，暴露時間10秒)，應用於實際小型辦公室場所之室內生物氣膠控制，並探討不同空氣交換率(ACH=0.45/hr及3.89/hr)下，高濃度臭氧對室內總細菌及總真菌生物氣膠之殺菌效力。
研究結果顯示，於相對溼度70%及暴露時間10秒條件下，對大腸桿菌、酵母菌及青黴菌孢子三種生物氣膠欲達90%以上殺菌效力所需之臭氧濃度分別為50ppm、100ppm及150ppm；然而在此相同相對濕度及暴露時間下，175ppm臭氧濃度仍無法對枯草桿菌內孢子生物氣膠產生殺菌效力。活性碳以及氧化鋁載體之二氧化錳觸媒在氣時空速(GHSV)為1.03×104h-1下，可將175ppm之尾氣臭氧濃度分解至無法量測之範圍。
臭氧對生物氣膠之殺菌效力為大腸桿菌>酵母菌>青黴菌孢子>枯草桿菌內孢子，提升相對溼度及延長暴露時間皆有助於提升臭氧對前三種生物氣膠殺菌效力，但無助於增加枯草桿菌內孢子生物氣膠殺菌效力。綜合研究結果並與文獻比對後發現，非熱DBD電漿殺菌機制中，臭氧對耐受性較低之細胞型態菌種殺菌貢獻較高，但對耐受性較高之孢子型態菌種則較無殺菌貢獻。小型辦公室經臭氧結合觸媒連續處理2小時後，室內空氣中之總細菌及總真菌數量皆衰減至50 CFU/m3以下，同時尾氣未偵測到殘留之臭氧氣體。換氣率對辦公室之臭氧殺菌效力並無產生重大影響且使用臭氧殺菌結合觸媒系統之年費用低經濟負擔。
綜合研究結果，臭氧對三種形態生物氣膠(兩種細胞形態及一種孢子型態)皆具有90%以上之高殺菌效力，而實場小型辦公室經臭氧連續處理也指出對生物氣膠具有良好殺菌效果，加上觸媒能完全分解尾氣臭氧，顯示臭
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氧殺菌結合觸媒系統不但具有高殺菌效能、成本低且能避免室內人員直接暴露臭氧，初步評估臭氧結合觸媒是一可行應用於控制室內生物性危害及改善室內空氣品質的方法。
Most people spend eighty to ninety percent of their time in indoor envi-ronment due to lifestyle changes in Taiwan. The probabilities to expose to bio-hazards threat through indoor air are increasing. The objective of this study was to disinfect indoor bioaerosols by using the hybrid system of high concentration ozone generated by non-thermal dielectric barrier discharge (DBD) system, and ozone decomposition by catalyst. There were many research results had been explored in this study including the influence of various experimental conditions on germicidal effects of ozone, the decomposed abilities of ozone by catalysts, the contributions of ozone toward disinfection in DBD plasma system, and the feasibility of purified indoor biohazards by the hybrid system of ozone and cat-alyst.
The first part of experiment was the bioaerosol disinfection in laboratory chamber. Four kinds of bioaerosols (E. coli, B. subtilis, C. famata and P. citri-num) with concentrations of 106CFU/m3 were generated by Collison three-jet nebulizer. The germicidal effects to bioaerosols of ozone were measured at ozone concentration of 0~175ppm, relative humidity of 30~70%, and exposed time of 1~10sec. The decomposed efficiency of ozone in tail gas after disinfec-tion, MnO2/AuO and MnO2/AC as catalysts, was detected by ozone monitor. The second part of experiment related to evaluating the controlled efficiency of total bacterial and fungal bioaerosols which were applied practically in small of-fice. Then, the research also focus on evaluating the germicidal efficacy of ozone to bioaerosols at two different air change rates (air changes per hour, ACH=0.45/hr and 3.89/hr).
The results indicated that the needed concentrations of ozone to reach dis-infection efficacy of 90% (at relative humidity of 70% and expose time of 10sec) for Escherichia coli, Candida famata var. flareri and Penicillium citrinum spore bioaerosols were 50, 100 and 150ppm respectively. However, it was ineffective to Bacillus subtilis endospore bioaerosols even at high concentration of 175ppm ozone under the same relative humidity and exposure time. As MnO2/AuO and MnO2/AC catalysts, and at gas hourly space velocity (GHSV) of 1.03�104h-1, the concentration of 175ppm ozone in tail gas was decomposed to under detect-able range.
The orders of germicidal efficacy of ozone to bioaersols were Escherichia coli > Candida famata var. flareri > Penicillium citrinum spore > Bacillus sub-tilis endospore. Increasing of relative humidity and exposure time could enhance the germicidal efficacy of ozone to the three bioaerosols but no efficacy to Ba-
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cillus subtilis endospore bioaerosols. Compared the results with literature in this study, ozone has higher contribution to disinfect the vegetative cell type of bio-aerosols but lower contribution to hard spore type of bioaerosols within the dis-infection mechanisms in DBD plasma system. The concentrations of indoor bioaerosols (total bacteria and fungi) and ozone in tail gas were reduced to be-low 50 CFU/m3 after 2 hours lasting treatment of using the hybrid system of ozone and catalyst in small office. The ventilation rate had no significant effect on germicidal efficacy in indoor environment. The annual cost was economical by using the hybrid system of ozone disinfection and catalyst to purify indoor air.
Summary, the germicidal efficacies of ozone to three types of bioaerosols (two vegetative cells and one spore) were above 90%. Ozone also had good dis-infection efficiency after hours treatment applied in small office. In addition, catalyst could completely decompose residual ozone in tail gas. Therefore, the hybrid system of ozone disinfection and catalyst not only had high germicidal efficacy and low cost but also can protect people indoor from exposing to ozone directly. Preliminary assessment of this study had showed that ozone combined with catalyst was a feasible method to control indoor biohazards and improve indoor air quality. |
