An Investigation Of Microbial Aerosol In A Full-scale Constructed Wetland

Aerosolization of microbial pathogens (such as Salmonella spp, Shigella spp and Vibrio cholerae, et al.) is an inevitable consequence of the generation and handling of wastewater. High amounts of microorganisms are not only present in the wastewater but also in bioaerosols that are generated during the different phases of the process in wastewater treatment plants. Bioaerosols can be a vehicle for the dissemination of human and animal pathogens. People work in wastewater treatment plants usually caught the sewage worker's syndrome, and become general malaise, weakness, acute rhinitis and fever.Compared with traditional secondary wastewater treatment process, bioaerosols generated by constructed wetlands should be taken more attention to. For the constructed wetland is an open ecosystem, takes larger area and accepts travelers as tourist sites. In this study, airborne bacteria and airborne fungi were chosen to study the daily, monthly and seasonal variation of the bacterial and fungal concentration and distribution, and its effects on air quality. The conclusions of the research were shown as follows:(1) In daily variation, the bacterial concentration of constructed wetland showed the highest value peak in the morning and lowest value in the afternoon; the fungal concentration showed the highest value peak at noon and lowest value in the afternoon. From March to December the bacterial concentration ranged from 36.0～2292.5CFU·m^-3, and the fungal concentration ranged from 126.0～6200.0 CFU·m^-3. In seasonally variation, the bacterial concentration reached the highest value in spring, and lowest value in winter; the fungal concentration was higher in summer and autumn, and lower in spring and winter. According to the Ecological Research Center of Chinese Academy of Sciences to develop micro-organisms in the atmosphere of the standard 6, Jiaonan constructed wetland was slightly polluted from June to September, and the other months were clean.(2) Escherichia coli(EC), Fecal streptococci(FS), Clostridium perfringens(CP) and salmonellae(SM) were not detected in the bioaerosol.(3) Airborne bacteria and fungi which were easily entering the lungs (particle size range from 0.65 to 4.7μm) accounted for 22.2%～74.9% and 54.2%～87.6%, respectively. The median diameters of airborne bacteria ranged from 1.9 to 4.1μm; and the median diameters of fungal were about 3.0μm.(4) The main predominant fungi included Yeast, Fusarium, Cladosporium, Mucor. Alternaria, Hypocrea, Thamnidium, Penicillium and Aspergillus. The quantity of gram positive bacteria was obviously more than gram negative bacteria.