Wastewater treatment plants (WWTPs) have increased dramatically in number due to rapid urbanization. However, these facilities release significant amounts of potentially hazardous airborne microorganisms, including Staphylococcus aureus bioaerosol, which poses health risks to employees and nearby residents. Therefore, this study estimated the direct exposure risks of bioaerosols in WWTPs using a quantitative microbial risk assessment (QMRA) framework evaluated through sensitivity analysis methods. The results showed that the sludge yard had the highest mean bioaerosol concentration but the lowest aerosolization ratio. The disease health risk burden values followed a descending order: residential area >
office >
sludge yard >
inverted umbrella aeration tank >
microporous aeration tank >
control room. Meanwhile, the risk values were shrunken by 14.1-17.3 times when personal protective equipment (PPE) was used. Sensitivity analysis for individual and multifarious contributions showed that the removal fraction achieved by using PPE was consistently the most influential parameter, followed by aerosol ingestion rate or exposure concentration. This suggests that isolation strips, such as green belts, between the WWTP and residential area is alternative effective measures for residents and wearing masks is essential measure for on-site employees. Furthermore, the multifarious contribution analysis showed that stepwise risk mitigation approaches were equally effective as one-step solutions, as indicated by their identical sensitivity coefficient rankings. This indicates that, when resources for mitigating risk are limited, taking a stepwise approach to risk reduction can be equally effective as allocating all resources at once. This study can advance the understanding of the characteristics and health risks of WWTP bioaerosol emissions and supplement the multifarious contributions of the sensitivity analysis implemented in the QMRA model, which contributes to public wellness development. The findings of this study will help in the optimization of control strategies for local wastewater utilities and implicated surrounding residents.