Application of Ozone on Indoor Biohazard Control

• Main Authors: Jen-Hsuan Tai, 戴仁軒
• Other Authors: none
• Format: Others
• Language: zh-TW
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/14778617445247402198

碩士 === 嘉南藥理科技大學 === 產業安全衛生與防災研究所 === 98 === 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- IV 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.