Wind tunnel experiments on bioaerosol dispersion and exposure risk assessment in wastewater treatment plants under natural ventilation

Natural ventilation in wastewater treatment plants can introduce bioaerosols into uncontaminated environment, which poses significant threats on susceptible human health. In this study, the dispersion and deposition of bioaerosols in two different plants were comparatively investigated with wind tunnel experiments. Quantitative risk assessment was conducted to evaluate exposure to Escherichia coli using dose-response modeling under two distinct meteorological conditions. The results indicated the predominant influence of thermal buoyancy on natural ventilation pattern between outdoor and indoor circulation. And the exposure risk was significantly elevated under unstable thermal stratification conditions. The removal and migration of the airborne bioaerosols generated during the indoor implementation of effluent treatment were accelerated with stronger air circulation. Deposition of bioaerosol particles were primarily found on the vertical surface below 2 m and at the corner of the leeward side. A notable finding was that the likelihood of infection at the surrounding area was much higher than that within the plant. The study's findings can serve as scientific references for the design and layout of industrial buildings that release infectious bioaerosols, and also offers valuable recommendations for mitigating bioaerosol concentrations in industrial plants.