Characterization, factors, and UV reduction of airborne bacteria in a rural wastewater treatment station

Highlights: • Most of the airborne bacteria from rural wastewater treatment was coarse particles. • Intestinal bacteria presented in the air surrounding the treatment facility. • Airborne bacteria mainly from those originated in water be treated and sludge. • Wind speed affected the level and particle size distribution of airborne bacteria. • Over 60% of the airborne bacteria can be reduced by ultraviolet-light radiation. Bioaerosols containing pathogens released from wastewater will pose potential health risks to workers on site. The emission of airborne bacteria from a rural wastewater treatment station and their inactivation by ultraviolet were investigated in this study. High-throughput sequencing technique was utilized to assay airborne bacterial population while the health risks associated with airborne bacteria exposure were estimated based on average daily dose rates. The recorded emission level of airborne bacteria in the air surrounding the multi-point inlet contact oxidation bioreactor (MTB) was 4795 ± 1475 CFU/m³, containing 2233 ± 471 CFU/m³ of intestinal bacteria, and most of them (70.3%) was coarse particles with size over 2.1 μm. Wind disturbance had significant effects on the diffusion and particle size distribution of the bioaerosols emitted from MTB. The identified opportunistic pathogens in bioaerosols were Enterobacter sp., Acinetobacter sp., Pantoea sp., Achromobacter sp., and Curtobacterium sp. They were originated in the water and active sludge in MTB. Inhalation was one of the main ways through which onsite workers were exposed to airborne bacteria. Exposure to ultraviolet radiation caused an apparent decrease in the level of bioaerosols in the air, thereby indicating that it can be utilized as an effective method for the reducing of bioaerosols. This study aims to provide preliminary data for the bioaerosols control in rural wastewater treatment process.