Bioaerosol emission from wastewater treatment plants.

In this report we describe the results of a study conducted to better estimate airborne microorganisms present in wastewater treatment plants (WWTP) environments. Air samples were taken with the Air Sampler MAS 100 impactor (Merck) at each stage of an activated-sludge WWTP (pre-treatment, primary clarifiers, aeration basins and sludge processors), in order to determine levels of contamination according to work stations. Culture methods were used to investigate heterotrophic plate count, moulds and yeasts, total and fecal coliforms, Pseudomonas aeruginosa and species belonging to Mycobacterium tuberculosis complex, whereas these last microorganisms were also analysed by Polymerase Chain Reaction (PCR) methods. Statistical analysis showed that pretreatment and primary clarifiers were the stages with the highest emission of bioaerosols, and that bioaerosol concentration at each stage depended on wind speed and daily inflow at the WWTP. Low concentrations of P. aeruginosa were found isolated at pretreatment and primary clarifiers; however, species of M. tuberculosis complex were not detected at any stage of the treatment plant. [ABSTRACT FROM AUTHOR]