Bioaerosols emission characteristics from wastewater treatment aeration tanks and associated health risk exposure assessment during autumn and winter

• Published in: The Science of the total environment 2022-12, Vol.851, p.158106-158106, Article 158106
• Main Authors: Zhao, Xiao-yan, An, Dong-zi, Liu, Man-li, Ma, Jia-xin, Ali, Wajid, Zhu, Hao, Li, Ming, Ai, Xiao-jun, Nasir, Zaheer Ahmad, Alcega, Sonia Garcia, Coulon, Frederic, Yan, Cheng
• Format: Article
• Language: English
• Subjects: Aerosolization ratio; Annual infection risk; Bioaerosols; Disease burden; Quantitative microbial risk assessment; Wastewater treatment plants
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2022.158106

Aeration tanks from activated sludge wastewater treatment plants (WWTPs) can release a large amount of bioaerosols that can pose health risks. However, risk characterization of bioaerosols emissions form wastewater treatment plants is currently not systematically carried out and still in its infancy. Therefore, this study investigated emission characteristic of two indicator model bioaerosols Staphylococcus aureus and Escherichia coli, emitted from aeration tanks of a municipal WWTP. Monte Carlo simulation was then used to quantitatively assess microbial risk posed by different aeration modes under optimistic and conservative estimates. Further to this, two different exposure scenarios were considered during 3 days sampling campaign in autumn and winter. Results showed that the bioaerosol concentration from microporous aeration tank (20–262 CFU m−3) was one order of magnitude lower than rotating disc aeration tank. Average aerosolization rate was 7.5 times higher with mechanical aeration mode. Health risks of exposed populations were 0.4 and 9.6 times higher in winter than in autumn for E. coli and S. aureus bioaerosol, respectively. Health risks of staff members were 10 times higher than academic visitors. Interesting results were observed for academic visitors without personal protective equipment (PPE) respectively exposed to S. aureus and E. coli bioaerosol in autumn and winter: while the derived infection risk met the United States Environmental Protection Agency (U.S. EPA) benchmark under optimistic estimation, the disease risk burden was over the World Health Organization (WHO) benchmark under conservative estimation. These revealed that only satisfying one of the two benchmarks didn't mean absolute acceptable health risk. This study could facilitate the development of better understanding of bioaerosol quantitative assessment of risk characterizations and corresponding appropriate risk control strategies for wastewater utilities. [Display omitted] •Health risks of exposed populations are 1–2 orders of magnitude higher in winter.•Health risks of staff members are 10 times higher than academic visitors.•Health risks of staffs without PPE exposed to bioaerosols unsatisfied the benchmarks.•Results of risk assessment under optimistic and conservative estimation are different.•Satisfying one benchmark doesn't mean absolute security or acceptable health risk.