Bioaerosol emission and exposure risk from a wastewater treatment plant in winter and spring

The potential health risks posed by bioaerosols containing pathogens originating from wastewater treatment plants (WWTPs) have gaining intensive attention. This study designated sampling locations within a WWTP situated in Xi'an, a major city in northwest China. The airborne bacterial concentration, taxonomic composition, and the associated health risks were analyzed in the aeration tanks with bottom microporous aeration system. The Anaerobic-Anoxic-Oxic (AAO) tank emitted significantly higher culturable bacteria (1.58×10⁴ CFU m^-3 in spring, 6.69×10³ CFU m^-3 in winter) compared to Double-ditch (DE) oxidation ditch and aerated grit chamber (AGC) chamber, aligning with 16S rDNA quantification results. The bacterial concentrations are higher in spring than that in winter, with the AAO tank posing the highest exposure risk during the spring season. The dominant genera in the air samples include Cutibacterium, Lawsonella, Acinetobacter, Pseudomonas, and Aeromonas. Among the identified genus, 139 bacterial genera were identified as potential human pathogens like Neisseria, Moraxella, Haemophilus, Escherichia-Shigella and Streptococcus. These pathogens further elevate exposure risks from WWTP bioaerosols. This study provides relevant information on the seasonal health risk variations tied to bioaerosol emissions from diverse aeration tanks with bottom microporous aeration system in the mega city of northwest China, emphasizing the imperative to enhance the management and control measures for bioaerosols originating from the AAO tank.