| 摘要: | 人們平均有80%以上時間待在室內環境，若室內空氣存在高濃度生物性污染物，可能會危害人體健康，因此如何有效控制生物氣膠已成為重要議題。纖維濾材過濾為常見的生物氣膠控制技術，然而薄膜濾材卻鮮少被探討去除生物氣膠。為瞭解薄膜濾材應用於控制室內生物性空氣污染物的可行性，本研究選擇具有良好物理及化學性質的聚四氟乙烯(PTFE)薄膜，探討在不同薄膜孔徑、相對濕度及表面風速下，過濾生物氣膠的能力。 本研究係以差壓計量測不同氣流量通過PTFE薄膜的壓力降。使用卡里遜噴霧器產生三種細菌(大腸桿菌、枯草芽孢桿菌內孢子、金黃色葡萄球菌)及兩種真菌(酵母菌及青黴菌孢子)生物氣膠，並以六階生物氣膠採樣器量測粒徑分布。選擇三種平均孔徑(0.45 m~5.0 m) PTFE薄膜於不同相對濕度(30%~70%)及表面風速(0.25 m/s~1.0 m/s)下，進行五種生物氣膠過濾，以一階生物氣膠採集過濾前後的生物氣膠、培養、菌落數計數及計算過濾效率。結果顯示三種孔徑PTFE薄膜對五種生物氣膠皆具有非常高的去除效率，平均過濾效率皆在99.94%以上，且薄膜孔徑愈小，生物氣膠的過濾效果愈佳。相對濕度並不影響疏水性PTFE薄膜過濾生物氣膠的效率。PTFE薄膜除了對大腸桿菌和枯草芽孢桿菌內孢子生物氣膠的過濾效率會隨著表面速度的增加而降低外，對其他三種生物氣膠的過濾效率並不受表面速度的影響。 結合各種實驗條件下之PTFE薄膜的生物氣膠過濾效率及壓力降評估濾材過濾效能，1.0 m PTFE薄膜在表面速度0.25 m/s的過濾條件下，具有最高的濾材品質因子(qF )。經由本研究瞭解高分子PTFE薄膜雖然較纖維濾材具有較大的壓力降，但即使是平均孔徑大於細菌及真菌生物氣膠粒徑的5.0 m PTFE薄膜，仍具有99.9%以上的高過濾效率，顯示PTFE薄膜確實相當有潛力可發展做為淨化室內生物性空氣污染物的濾材。
People spend average over 80% of their time indoors environments. High levels of indoor bioaerosols may be detrimental to human health. How to effectively control bioaerosols has become an important issue nowadays. Filtration by fiber filter is a commonly bioaerosol control technology. However, membrane filter is rarely to be explored to remove bioaerosols. In order to understand the feasibility to control indoor biological air pollutants by membrane filters, polytetrafluoroethylene (PTFE) membrane with excellent physical and chemical properties was chosen to study the filtration performance for bioaerosols under different membrane pore sizes, relative humidities, and face velocities.The pressure drops across PTFE membrane filters at different air flow rates were measured by using differential pressure gauge. Three types of bacterial (Escherichia coli, Staphylococcus aureus, and Bacillus subtili spore) and two types of fungal (Candida famata var. flareri and Penicillium citrinum endospore) bioaerosls were generated from microbial suspension liquids using a Collison three-jet nebulizer. Bioaerosol size distribution was measured by a six-stage viable particle sampler. The filtration efficiencies of membrane filters for five types of bioaerosols were assessed by sampling bioaerosls, culturing, and counting the numbers of viable colony before and after filtration at different experimental conditions, including membrane mean pore sizes (0.45 m~5.0 m), microbial species (bacteria and fungi), and relative humidities (30%~70%), and face velocities (0.25 m/s~1.0 m/s).The results indicated that the PTFE membrane filters with the three pore sizes of 0.45 m, 1.0 m and 5.0 m have high removal efficiencies of the five types of bioaerosols. The average filtration efficiencies were above 99.94%. The smaller pore size, the higher bioaerosol filtration efficiency. The relative humidities did not affect bioaerosol filtration efficiencies of hydrophobic PTFE membrane filters. The filtration efficiencies of PTFE membrane filters only for E. Coli and B. Subtilis spore bioaerosols were decreased as face velocities increased, however, other three types of bioaerosols were not affected by face velocities.Integrate the bioaerosol filtration efficiencies with pressure drops under all experimental conditions to assess the performance of the filters, the PTFE membrane with the mean pore size of 1.0 m at a face velocity of 0.25 m/s has the highest quality factor (qF). This study clearly indicated that the polymer PTFE membrane filters have higher pressure drop than fiber filters. However, even the PTFE membranes with the pore size of 5.0 m bigger than the sizes of bacterial and fungal bioaerosols, they still have greater than 99.9% of high bioaerosol filtration efficiencies. The results demonstrated that the PTFE membrane does have the potential to be developed as a filter to remove indoor biological air pollutants. |
