Controlling Indoor Bioaerosols Using a Hybrid System of Ozone and Catalysts

Abstract

As people spend a greater portion of their time indoors, the likelihood of exposure to biohazards in indoor air is increasing. This study developed a system to disinfect indoor bioaerosols while protecting occupants from direct exposure to ozone. This hybrid approach combines high concentrations of ozone generated by a non-thermal dielectric barrier discharge system, and an ozone decomposition unit using MnO 2 /Al 2 O 3 and MnO 2 /AC catalysts. Four types of common bioaerosols were used to test the germicidal efficacy of 0-175 ppm ozone at a relative humidity of 30-70% and retention time of 1-10 s. The results indicate that the germicidal efficacy of ozone on E. coli, C. famata and P. citrinum spore bioaerosols increased with ozone concentration, relative humidity, and retention time; however, the process was less effective with the hardy endospores of B. subtilis. Germicidal efficacy of 90% was obtained for bioaerosols (two vegetative cells and one spore) using high concentrations of ozone at a relative humidity of 70% and exposure time of 10 s. Residual ozone in the tail gas was decomposed to undetectable levels using catalysts at a gas hourly space velocity of 3.287 × 10 3 1/h. The concentration of indoor bioaerosols (total bacteria and fungi) in a small office was reduced to below 50 CFU/m 3 and ozone in the tail gas was reduced to undetectable levels following treatment for 2 h. The hybrid system of ozone disinfection and catalysts provides high germicidal efficacy while protecting occupants from direct exposure to ozone.

Characterization of Indoor-Air Bioaerosols in Southern Taiwan

“…(Huang et al, 2012). In this study, ClO 2 was used as a disinfectant to control the indoor TFC level.…”

Investigation of Antimicrobial Activity of Grapefruit Seed Extract and Its Application to Air Filters with Comparison to Propolis and Shiitake

“…Various techniques have been used to mitigate the viability of biological contaminants in indoor environments, such as ultraviolet (UV) irradiation (Lin and Li, 2002), air electric ion emission (Huang et al, 2008), ozone (Huang et al, 2012), and photocatalytic oxidation (Chen et al, 2010), among others. One promising method is an antimicrobial filtration system that physically captures bioaerosols on air filters and then inactivates the airborne microorganisms on the surface of the filters by treatment with antimicrobial materials such as silver or titanium-based nanoparticles (Li et al, 2006;Jin et al, 2007,), iodine powders (Lee et al, 2008), and carbon nanotubes (Brady-Estévez et al, 2008;Jung et al, 2011a).…”

Preparation of TiO2-Coated Polyester Fiber Filter by Spray-Coating and Its Photocatalytic Degradation of Gaseous Formaldehyde

“…The reasons for this include: people spend the majority of their time indoors; there is a wide and varied range of emission sources indoors; and for certain kinds of pollutant, e.g., formaldehyde and environmental tobacco smoke (ETS), the concentration levels are always higher in indoors compared with outdoors. Various of control technologies, such as filtration (Klimov et al, 2009), adsorption (Jee et al, 2005), ionization (Nishikawa and Nojima, 2001), ozone oxidation (Huang et al, 2012), etc., have been used for indoor air purification of different pollutants.…”