Bioaerosols from outdoor wastewater treatment facilities: dispersal behavior, exposure risks and protection strategies

Bioaerosols released into the atmosphere from wastewater treatment processes can contaminate the surrounding air environment and threaten the health of people living in the vicinity of wastewater treatment plant. Bioaerosols had migratory properties and are easily diffused and spread in the air. This paper investigated the escape characteristics of bioaerosols from outdoor wastewater treatment facilities, simulated their dispersion using Gaussian plume model, and assessed the risk of exposure via the inhalation route. The results showed that the fugitive concentrations of airborne bacterial aerosols range from 58 to 1218 CFU/m³ and fungal aerosols range from 0 to 79 CFU/m³. Bacterial aerosols showed seasonal variations with high concentration in autumn and low value in winter. Coarse particle (>2.1 μm) dominated the bioaerosols detected, accounting for more than 70 % of all detections. The concentration of bioaerosols accumulated to the highest level within a range of 90 m. After that, it decreased as the diffusion distance increases. When the diffusion distance reached 3,000 m, the concentrations of both bacterial aerosols and fungal aerosols were lower than 5 CFU/m³. The exposure risk of bioaerosols was the highest within a range of 100 m, with the HQ ranging from 0.000 to 0.104. As the diffusion distance increases, the exposure risk was lower than 0.02 at a distance of 500 m, and it drops to as low as 0.001 at a distance of 3000 m. The non-carcinogenic health risk of bioaerosols from wastewater treatment facilities to workers operating wastewater treatment plants and neighboring residents was low and negligible.