Comparing the Effects of Deep and Surface Aeration Methods on Density and Type of Airborne Bactria and Fungi in Municipal Wastewater Treatment Plant

Background and purpose: Emission of bioaerosols from wastewater treatment plants is a potential hazard to human health. In this study aimed at investigating the effects of surface and deep aeration techniques on density and type of airborne bacteria and fungi in two municipal wastewater treatment plants. Materials and methods: This descriptive cross-sectional study was done in two wastewater treatment plants in Tehran equipped with surface and deep aerations. Microbial samples were taken from air beside aeration tank, grit chamber, secondary sedimentation basin and two control points (upwind and downwind) every 6 days during summer and autumn 2017. Samples were analyzed for density of bioaerosols and types of bacteria and fungus applying standard methods. Results: Wastewater treatment plant with surface aeration tank had the greatest effect on emission of bioaerosols than the plant with deep aeration. Mean values for density of bacterial bioaerosols and fungal emission were 6845 and 15784 CFU/m2/h in summer and 535 and 899 CFU/m2/h in autumn, respectively. Different gram-positive and gram-negative bacteria were identified in both wastewater treatment plants investigated. Conclusion: According to current study, emission of bioaerosol in wastewater treatment plants with surface aeration is more than that of those with deep aeration and has greater potential hazard.