Airborne enteric coliphages and bacteria in sewage treatment plants Helvi Heinonen-Tanski a, *, Tiina Reponen b , Jari Koivunen a a Department of Environmental Science, University of Kuopio, POB 1627, FIN-70211 Kuopio, Finland b Department of Environmental Health, University of Cincinnati, POB 670056, Cincinnati, OH 45267-0056, USA article info Article history: Received 17 October 2008 Received in revised form 6 March 2009 Accepted 9 March 2009 Published online 17 March 2009 Keywords: Bioaerosol Coliphages Impactor Impinger Indicator bacteria Salmonella abstract The concentrations of airborne culturable microorganisms were determined in wastewater and sludge treatment processes of seven sewage treatment plants. Two types of coli- phages, Salmonella and total viable bacteria were sampled by the BioSampler and the numbers of faecal coliforms and enterococci were obtained from the Andersen 6-stage impactor. The BioSampler recovered higher numbers of airborne coliphage viruses than has been measured with other liquid samplers in previous studies, suggesting that this sampler has improved efficiency for sampling airborne coliphages. Airborne coliphages were detected in many stages of the wastewater or sludge treatment process. The highest microbiological air contaminations were found in pre-treatment and aerated grit separation stages of the operation. This was attributed to aerosolisation of microorganisms by mechanical handling or forced aeration. Aeration and settling processes located outdoors caused low microbial concentrations, but the brush aerator released more microorganisms into the air. Our results emphasize the necessity for controlling the exposure of sewage workers to airborne microorganisms, especially in process areas that involve mechanical agitation or forced aeration of wastewater. ª 2009 Elsevier Ltd. All rights reserved. 1. Introduction Wastewater treatment plants are recognized as being impor- tant sources of microbial aerosols and may constitute a health risk for plant workers and the surrounding population (Fannin et al., 1985; Carducci et al., 1995, 2000; Pillai et al., 1996; Orisini et al., 2002; Fracchia et al., 2006; Grisoli et al., 2009). Municipal wastewaters may contain pathogenic viruses, bacteria, protozoa and parasite eggs. Aerosolized microorganisms may be present in many stages of the wastewater and sludge treatment process (Sanchez-Monedero et al., 2008). Thus, wastewater treatment plant workers may be exposed to pathogens and endotoxins, most likely through the inhalation of aerosols or by the hand-to-mouth route. Exposure to bioaerosols, especially to pathogenic or allergenic microor- ganisms, may cause respiratory and other health disorders. Some studies as reviewed by Thorn and Kerekes (2001) have revealed a significant association between exposure to aero- sols and the incidence of respiratory and enteric illness. Rylander (1999) characterized many symptoms, including weakness and fever, among wastewater treatment plant workers, and named the disease ‘‘sewage workers syndrome’’. The levels of bioaerosols in the ambient air surrounding treatment plants have been reported to vary considerably (Carducci et al., 2000; Sanchez-Monedero et al., 2008; Grisoli et al., 2009). The greatest emphasis has been placed on sampling at outdoor locations, mainly near activated sludge aeration tanks, at irrigation sites, or downwind of treatment * Corresponding author. Tel.: þ358 40 3553152. E-mail address: heinotan@uku.fi (H. Heinonen-Tanski). Available at www.sciencedirect.com journal homepage: www.elsevier.com/locate/watres 0043-1354/$ – see front matter ª 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.watres.2009.03.006 water research 43 (2009) 2558–2566