Removal of bioaerosols by the combination of a photocatalytic filter and negative air ions

This study focused on the investigation of the effectiveness of negative air ionization (NAI), photocatalytic oxidation (PCO), and the combination of NAI and PCO on the removal of aerosolized Escherichia coli, Candida famata  , and λλ vir phage under different relative humidity. The experiments were conducted with a stainless steel reactor equipped with a negative air ion generator, a photocatalytic filter, and two ultraviolet lamps with 365 nm wavelength. The removal efficiency (η)(η), defined as one minus the ratio of the outlet concentration to the inlet concentration of the appropriate bioaerosol, was used to evaluate the effectiveness of the removal methods. The combination of NAI and PCO was the most efficient removal method for aerosolized E. coli  (η=0.304±0.06–0.364±0.008)(η=0.304±0.06–0.364±0.008), C. famata  (η=0.433±0.08–0.598±0.047)(η=0.433±0.08–0.598±0.047), and λλ vir phage (η=0.689±0.02–0.903±0.06)(η=0.689±0.02–0.903±0.06). In this removal method, the contributions of NAI were higher than those of PCO for the removal of E. coli and C. famata  ; for the removal of λλ virus phage the contributions of NAI and PCO were comparable NAI was the least efficient removal method for bioaerosols, and the removal efficiencies are: η=0.175±0.04–0.245±0.03η=0.175±0.04–0.245±0.03 for E. coli  ; η=0.216±0.007–0.297±0.044η=0.216±0.007–0.297±0.044 for C. famata  ; and η=0.299±0.12–0.384±0.02η=0.299±0.12–0.384±0.02 for λλ vir phage.