Bioaerosol emission from wastewater treatment plants

In this report we describe the results of astudy conducted to better estimate airbornemicroorganisms present in wastewater treatmentplants (WWTP) environments. Air samples weretaken with the Air Sampler MAS 100 impactor(Merck) at each stage of an activated-sludgeWWTP (pre-treatment, primary clarifiers,aeration basins and sludge processors), inorder to determine levels of contaminationaccording to work stations. Culture methodswere used to investigate heterotrophic platecount, moulds and yeasts, total and fecalcoliforms, Pseudomonas aeruginosa andspecies belonging to Mycobacteriumtuberculosis complex, whereas these lastmicroorganisms were also analysed by PolymeraseChain Reaction (PCR) methods. Statisticalanalysis showed that pretreatment and primaryclarifiers were the stages with the highestemission of bioaerosols, and that bioaerosolconcentration at each stage depended on windspeed and daily inflow at the WWTP. Lowconcentrations of P. aeruginosa werefound isolated at pretreatment and primaryclarifiers; however, species of M.tuberculosis complex were not detected at anystage of the treatment plant.