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Volume 13, No. 6, December 2013, Pages 1807-1814 PDF(255 KB)  
doi: 10.4209/aaqr.2012.09.0245   

Dispersion and Risk Assessment of Bacterial Aerosols Emitted from Rotating-Brush Aerator during Summer in a Wastewater Treatment Plant of Xi’an, China

Yanpeng Li1,2, Haifeng Zhang1, Xionghui Qiu3, Yanru Zhang1, Huanran Wang4

1 School of Environmental Science and Engineering, Chang’an University, Xi’an 710054, China
2 Key Laboratory of Subsurface Hydrology and Ecology in Arid Areas, Ministry of Education, Xi’an 710054, China
3 Technology and Standard of Environmental Protection Research Professional Committee of All-China Environment Federation, Beijing 100032, China
4 School of Energy and Power Engineering, Xi’An Jiaotong University, Xi’an 710049, China




A microbial risk assessment was carried out for the rotating-brush aerator used during summer in a wastewater treatment plant (WWTP) of Xi’an, China. Bacterial aerosols were first collected by an Andersen cascade impactor at selected sampling sites near the rotating-brush aerator. The concentrations of airborne bacteria were used to obtain microbial emission rate by back calculation. The downwind concentrations of airborne bacteria were then calculated by a modified Gaussian dispersion model accounting for environmental impact and microorganism decay. Subsequently, the exposure parameters suitable for Chinese people were incorporated into a risk assessment model to evaluate non-carcinogenic risks of airborne mesophilic bacteria to sewage workers and surrounding residents. The results indicate that both mean bacterial concentrations at ground level and the exposure hazard quotient decrease rapidly with downwind distance. The exposure hazard quotient by inhalation route is over 105 times more than by dermal contact route for both children and adults, suggesting that inhalation route is the major exposure pathway of microbial aerosol intake for surrounding people. Although the present model gives acceptable low risk values at various downwind distances, it is worth noting that health risks of microbial aerosols associated with rotating-brush aeration for children are generally much more than those for adults.



Keywords: Wastewater treatment plant; Microbial aerosols; Dispersion; Risk assessment; Rotating-brush aerator.



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