霧化無隔膜電解水應用於空氣中細菌抑制效率之研究

Abstract

細菌性氣膠長期以來為環境及食品方面之重要風險因子，無隔膜電解水由於其低廉成本與環境友善等特性，於相關研究中均顯示其應用於細菌氣膠控制之高度潛力，惟其抑菌效能與操作參數有待闡明。本研究以環境控制箱系統模擬室內空間，並採用大腸桿菌 (Escherichia coli) 、枯草桿菌 (Bacillus subtilis) 與金黃色葡萄球菌 (Staphylococcus aureus) 等三種細菌氣膠作為指標污染物。在換氣率為1.0 hr^-1、細菌氣膠濃度為3 × 10^4 CFU m^-3之模擬空間中，使用孔徑8 μm的噴嘴，以70 kg cm^2的水壓，有效氯濃度為100 mg L^-1無隔膜電解水，對於E. coli氣膠可取得一階動力濃度衰減常數ki值為0.236 min^-1之抑菌效果，對於S. aureus氣膠之ki值則為0.419 min^-1。對於細胞壁較為厚實、抑菌劑抵抗性較強之B. subtili氣膠，則需要將有效氯濃度提升至200 mg L^-1，方可取得ki值為0.051 min^-1之抑菌效果。採用能產生較大粒徑霧滴的噴嘴，能夠顯著提升高壓噴霧之抑菌效率。對於E. coli與S. aureus氣膠，若改以超音波震盪方式施放有效氯濃度100 mg L^-1霧化無隔膜電解水，對於E. coli氣膠可取得ki值為0.794 min^-1之抑菌效果，對於S. aureus氣膠之ki值則為1.569 min^-1，抑菌效率均顯著高於高壓噴霧方式。對於B. subtili細菌氣膠，將有效氯濃度設定為300 mg L^-1，換氣率為0 hr^-1時，ki值則可達到為0.634 min^-1。對於兩種霧化方式而言，提升室內空間之換氣率，則均可能造成無隔膜電解水微粒之移除，導致其與細菌氣膠接觸之機率下降。本研究建議未來欲應用霧化無隔膜電解水進行空間的衛生控制時，應事先考量菌株類型及整體換氣等基礎資訊，並應採用適當之霧化方式及有效氯濃度，以提升空氣中無隔膜電解水劑量與均勻擴散混合為原則，方可取得有效細菌氣膠活性抑制效果。

The potential of membran-less electrolyzed water (MLEW) has been revealed as economically, feasible and safe disinfectant for inactivating microorganisms in previous investigations. The aim of this study is to determine the inactivation efficiency to airborne bacteria strains of aerosolized MLEW in an environemtnal-controlled chamber. Two MLEW aerosolizing approaches including air-pressured (with 70 kg cm^-2) spraying and ultrasonic nebulizing were evaluated. Under air exchange (ACH) rate 1.0 hr^-1, air-pressured (spraying MLEW of free available chlorine (FAC) 100 mg L^-1 through 8 μm nozzle achieved first-order concentration decaying constant (ki) 0.236 and 0.419 min^-1 of Escherichia coli and Staphylococcus aureus aerosols (initial counts of 10^4 colony-forming units, CFU m^-3) in the chamber. The FAC 200 mg L^-1 MLEW spraying has to be adopted for obtaining acceptable inactivation efficiency to B. subtilis aerosol with ki value 0.051 min^-1. It is observed in the study that using of a larger orifice-size nozzle facilitates the inactivation efficiency. ultrasonic nebulizing of FAC 100 mg L^-1 MLEW yields better inactivation efficiency than air-pressure spraying while facing E. coli and S. arueus aerosols (ki values were 0.794 and 1.569 min^-1) . The FAC concentration has to be raised to 300 mg L^-1 for effectively inactivate B. subtilis aerosol when ultrasonic nebulizing MLEW (ki values was 0.634 min-1 under ACH rate 0 hr^-1). Besides, the inactivation efficienies to bacteria aerosols were deteriorated while increasing ACH rate of chamber. It may due to ventilating dilution effects which decreased the probability for airborne MLEW particles to contact with bacterial aerosol. We recommend that the FAC concentration and aerosolizing approach should be carefully selected base on the bacterial profile, well-mixing and ventilation rate of target environment before using MLEW for hygiene control.