Abstract
Aeration tanks at wastewater treatment plants (WWTPs) emit significant amounts of bioaerosols
containing potentially hazardous infectious material. Occupational exposure to airborne pathogens
can pose health risks to WWTP workers. Bioaerosol samples collected at aeration tanks of two typical
municipal WWTPs that use different aeration modes were analysed to investigate the composition
and diversity of airborne bacteria in wastewater environments, using the Illumina MiSeq platform.
Thirty-six potential airborne bacterial pathogens were identified in the air samples, and these were
dominated by Bacillus, Enterococcus, Clostridium, Streptococcus, Acinetobacter, Enterobacter,
Pseudomonas, Bacteroides fragilis, Acinetobacter baumannii, and Escherichia/Shigella. Bioaerosols
from mechanical aeration tanks (72%, 26/36) had a relatively higher richness and diversity of airborne
bacterial pathogens than diffused aeration tanks (17%, 6/36). Furthermore, most of the identified
airborne bacterial pathogens (78%, 28/36) were classified as Risk Group 2 according to the revised
South African Regulation for Hazardous Biological Agents, 2022, and up to 70% of these were gramnegative
bacteria. The presence of potentially pathogenic bacteria in the ambient air at WWTPs
suggests an elevated risk of bioaerosol exposure for workers. Therefore, further research and sitespecific
risk assessments are recommended to guide the implementation of effective bioaerosol
strategies to protect workers’ health, with special attention paid to WWTPs that use mechanical
aerators.
Keywords Airborne bacteria, Opportunistic pathogens, Occupational exposure, Municipal wastewater