ADMS simulation and influencing factors of bioaerosol diffusion from BRT under different aeration modes in six wastewater treatment plants

Wang, Yanjie and Yang, Liying and Wild, Oliver and Zhang, Song and Yang, Kai and Wang, Wenwen and Li, Lin (2023) ADMS simulation and influencing factors of bioaerosol diffusion from BRT under different aeration modes in six wastewater treatment plants. Water Research, 231: 119624. ISSN 0043-1354

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Abstract

Bioaerosols produced by municipal wastewater treatment plants (MWTP) can spread in air, thereby polluting the atmosphere and causing safety hazards to workers and surrounding residents. In this study, the biological reaction tanks (BRTs) of six MWTPs undergoing typical processes in North China, Yangtze River Delta, and the Greater Bay Area were selected to set up sampling points and investigate the production characteristics of bioaerosols. The Atmospheric Dispersion Modelling System method was used to simulate the diffusion of bioaerosols in the MWTPs. The concentrations of bacteria and, specifically, intestinal bacteria in the bioaerosols ranged from 389 CFU/m3 to 1,536 CFU/m3 and 30 CFU/m3 to 152 CFU/m3, respectively, and the proportion of the intestinal bacteria was 8.85%. The concentration of soluble chemicals (SCs) in the bioaerosols was 18.36 μg/m3–82.19 μg/m3, and the main SCs found were Mg2+, Ca2+, and SO4 2−. The proportion of intestinal bacteria (75.79%) produced via surface aeration by a BRT attached to large-sized bioaerosol particles was higher than that of a BRT undergoing the bottom aeration process (37.28%). The main microorganisms found in the bioaerosols included Moraxellaceae, Escherichia–Shigella, Psychrobacter, and Cyanobacteria. The generation of bioaerosols exhibited regional characteristics. The wastewater treatment scale, wastewater quality, and aeration mode were the main factors influencing bioaerosol production. Model simulation showed that, after 1 h, the diffusion distance of bioaerosol was 292 m–515 m, and the affected area was 42,895 m2–91,708 m2. The diffusion distance and range of the bioaerosols were significantly correlated with the concentration at the bioaerosol source and the aeration mode adopted by the BRTs. Wind speed and direction were two environmental factors that affected the diffusion of bioaerosols. With an increase in the diffusion distance, the concentration of microorganisms, intestinal bacteria, ions, and fine particles in the bioaerosols decreased significantly, resulting in a corresponding reduction in the exposure risk. This study provides new insights to help predict bioaerosol risks at MWTPs and identify safe areas around MWTPs. The study also provides a basis for selecting safe MWTP sites and reducing bioaerosol pollution risks.