https://orcid.org/0000-0002-9912-0349
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ABSTRACT
During wastewater treatment, bioaerosols are generated and, can either remain in suspension for several hours or settle on surfaces and workers may be exposed. The presence of pathogens in the air could contribute to an increased frequency of gastrointestinal or respiratory illness amongst workers. Due to harsh winter conditions in Eastern Canada, many of the steps in the wastewater treatment process occur indoors, leading to a greater risk of significant occupational exposure especially if there is inadequate ventilation or a lack of personal protection. This work has used stationary sampling at various indoor wastewater treatment steps both in winter and summer. Bioaerosols were evaluated using both culture and molecular methods along with ventilation characterization. Endotoxins were quantified, as well as total cultivable and gram-negative bacteria and pathogen indicators using qPCR. This study highlights the presence of potential pathogens at all steps in the treatment process, which may represent a potential occupational hazard. Comparisons between summer and winter data suggest that water temperature is an important factor for microbial activity and suggest that increasing the rate of air changes per hour in summer would be beneficial to reduce the concentration of bioaerosols during this time of the year. The screening, grit/FOGs removal and biofiltration were the most bioaerosol-loaded sites. Based on strong correlations, we suggest the reconsideration of exposure limits in WWTPs. Workers should be encouraged to use personal respiratory protection to limit the risk of health problems, especially during long-term work.
Implications: The work presented herein showcases significant correlations between concentrations of endotoxins, cultivable bacteria, gram-negative bacteria, and total bacteria by qPCR from air collected in indoor wastewater treatment plants. These correlations lead us to propose new limit of exposure values, revisited to fit the endotoxin exposure limits recommendations. The results can serve as guidelines for future proposals for air quality indicators.
Acknowledgment
This work was funded by Institut de Recherche Robert-Sauvé en Santé et Sécurité du Travail du Québec (IRSST Grant 2010-0050). Hamza Mbareche received a postdoctoral fellowship from Fond de Recherche du Québec – Nature et Technologie and is the recipient of the Lab Exchange Visitor Program for the Canadian Society of Virology. Vanessa Dion-Dupont received a CRIUCPQ scholarship. Caroline Duchaine is the holder of Tier-1 Canada Research Chair on Bioaerosols. The authors are thankful to Serge Simard for statistical analyses, Yves Beaudet (IRSST for technical assistance and to Amanda Toperoff and Michi Waygood for English revision of the manuscript. The authors are also indebted to the wastewater treatment plant managers and staff for their participation in the study and their collaborative efforts.
Disclosure statement
No potential conflict of interest was reported by the authors.
Data availability
The data that support the findings of this study are available on request from the corresponding author, CD.
Supplementary material
Supplemental data for this paper can be accessed on the publisher’s website
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Notes on contributors
Hamza Mbareche
Hamza Mbareche is a consultant, researcher and trainer who works at the convergence of microbial occupational exposure, the microbiome and genomics, with implications for public health. He ranks in the top 0.25% of Air Microbiology experts worldwide according to Expertscape. He harnesses cutting-edge technologies to improve the environmental safety of workplaces.
Vanessa Dion-Dupont
Vanessa Dion-Dupont is a microbiologist and has research experience in bioaerosols field sampling and analyses.
Marc Veillette
Marc Veillette has a Master degree in bioaerosols sciences and is a microbiologist and molecular biologist. He is managing major research projects within the Canada Research Chair on Bioaerosols and has published numerous articles and abstracts.
Evelyne Brisebois
Evelyne Brisebois has a master degree in microbiology and has an expertise as an application scientist and regulatory affairs.
Jacques Lavoie
Jacques Lavoie is an industrial hygienist and had a fruitful career in occupational health and bioaerosols research.
Caroline Duchaine
Caroline Duchaine is holder of Tier-1 Canada Research Chair on Bioaerosols and her research is pioneer in molecular methods for bioaerosols assessment, impacts on human health and in vitro bioaerosols behaviour.