Microbiological quality of atmospheric air at sewage treatment plants operating with different treatment technologies

This article presents a study of bioaerosol emissions in a constructed wetland treatment plant with all technical facilities located outdoors compared to emissions from four other treatment plants using different technologies. Air analysis was performed based on microbiological indicators using culture methods. The concentration of bacteria determined at the aeration pond did not exceed 60cfu/m3 and was comparable to the boundary of the treatment plant's protection zone on both the windward (66cfu/m3) and leeward (60cfu/m3) sides. Measurements of the remaining microbiological indicators did not indicate a significant impact of the plant on the ambient air. A comparison of the constructed wetland with four treatment plants with partially enclosed process rooms showed that the operation of activated sludge bioreactors is a source of significantly higher microbial concentrations (up to 284 cfu/m³), and particularly high concentrations of bioaerosols are generated during the operation of the sludge dewatering centrifuges (up to 9460cfu/m³). The study showed that bioaerosol emissions from the constructed wetland did not exceed the permissible values for air without microbiological contamination. The obtained results indicate that the constructed wetland treatment plant does not pose a significant microbiological threat to the personnel or the immediate surroundings of the treatment plant.