Dissimilar emission characteristics between bioaerosol and suspended particles from gaseous biofilters and bioaerosol health risk evaluation

Abstract

Biofiltration is a common technology for treating volatile organic compounds (VOCs); however, bioaerosols may be emitted in the gas flow, indicating a potential risk to human health. In this study, we analyzed the emission characteristics of bioaerosol and suspended particles (mainly nonbiological particles) emitted from biofilters and their health risk at different gas velocities and temperatures and with different amounts of moisture in the packing bed. Results showed that a high gas velocity enabled easy transport of microbes from the carriers. The maximum bacterial aerosol outlet concentration was 223 CFU m−3 at 50°C, although the fungal aerosol concentration decreased at temperatures above 25°C. The peak bacterial concentration was 349 CFU m−3, with a moisture content of 70%, whereas the highest fungi concentration was nearly 267 CFU m−3, with a moisture content of 40%. The bioaerosol concentrations also changed with the experimental conditions: A high gas velocity, low temperature, and high moisture content favored the emission of fine particles; however, changes in the concentration and size distribution of coarse particles were not obvious. The relationship between bioaerosols and suspended particle emissions demonstrates that biofilters are a source of bioaerosol emissions despite the removal of nonbiological suspended particles due to filtration. The health risk evaluation indicates that bioaerosol emissions from biofilters pose the highest risk of infection via inhalation to adult males.