However, the authors of such study did not usually present the detailed qualitative characteristics of anaerobic bacteria (Fracchia et al. Limited data indicate that they may occur at all stages of wastewater treatment and their concentrations may be higher in winter (10 1–10 4 CFU/m 3) than in summer (10 1–10 2 CFU/m 3). Despite the progress in research concerning physiological characteristics of anaerobic bacteria, the knowledge about their presence in working environments is still scarce.
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At WWTPs, bacterial concentrations in the air usually range from 10 1 to 10 4 CFU/m 3 (Korzeniewska 2011) and can adversely affect the health of sewage workers being responsible for respiratory, digestive tract, eye and skin infections (Cyprowski and Krajewski 2003). 2015).ĭuring the wastewater treatment processes, bioaerosol is released into the air in the form of nuclei droplets, where the fine particles of water serve as carriers of microorganisms. 2010) as well as Clostridium perfringens (Ajonina et al. In treated effluent, there may be faecal bacteria of the genera Bifidobacterium and Bacteroides (Wery et al. 2008 Zinder and Mah 1979) and Clostridium (Lisle et al. Among the bacterial genera involved in the anaerobic methane fermentation process are Methanosarcina, Methanosaeta (Van Lier et al. They are responsible for methane fermentation of sewage sludge, facilitating decomposition of macromolecular organic matter into simpler compounds. Furthermore, anaerobic bacteria are an important element in the wastewater treatment processes. ( 2015a), 18 species of Longilinea, Georgenia, Desulforhabdus, Thauera, Desulfuromonas and Arcobacter genera were identified in the sewerage system.
A substantial part of the anaerobic bacteria is delivered to the wastewater treatment plant (WWTP) by the sewage network. However, some of them can also survive having only temporary access to the oxygen (facultative anaerobes) or even without it (obligate anaerobes). 2005 Gerardi and Zimmerman 2005).įrom the oxygen demand standpoint, a majority of bacteria which may occur in this environment are aerobic ones. In wastewater can be also found obligate pathogens from Salmonella and Shigella genera or enteropathogenic strains of Escherichia coli, which are responsible for salomonellosis, shigellosis or gastroenteritis, respectively (Cyprowski et al. Wastewater can carry many opportunistic pathogens (e.g., Enterobacter cloacae, Enterococcus faecalis, Escherichia coli, Klebsiella pneumoniae, Proteus vulgaris or Pseudomonas aeruginosa), which can cause different systemic infections, especially among people with a weakened immune system. Among them, pathogenic bacteria pose the most serious epidemiological risk. Wastewater is always contaminated with different biological agents such as bacteria, viruses, protozoa, fungi, flatworms or roundworms (Sorber and Sagik 1980). Anaerobic bacteria formed small aggregates with both wastewater droplets and dust particles of sewage sludge origin and as such may be responsible for adverse health outcomes in exposed workers. ConclusionsĪnaerobic bacteria were widely present both in the sewage and in the air at workplaces from the WWTP, especially when the technological process was performed in closed spaces. In both the sewage and air samples, Clostridium perfringens pathogen was identified. The analysis revealed that mechanical treatment processes were responsible for a substantial emission of anaerobic bacteria into the air. In total, 16 bacterial species were determined, from which the predominant strains belonged to Actinomyces, Bifidobacterium, Clostridium, Propionibacterium and Peptostreptococcus genera. In turn, the average airborne bacterial concentration was at the level of 50 CFU/m 3 (GSD = 5.83) and the highest bacterial contamination (4.06 × 10 3 CFU/m 3) was found in winter at the bar screens. The average concentration of anaerobic bacteria in the sewage samples was 5.49 × 10 4 CFU/mL (GSD = 85.4) and in sludge-1.42 × 10 6 CFU/g (GSD = 5.1). Additionally, the determination of Clostridium pathogens was carried out using 16S rRNA gene sequence analysis. Qualitative identification of all isolated strains was performed using the biochemical API 20A test.
Samples of both sewage and sludge were collected at six sampling points and bioaerosol samples were additionally collected (with the use of a 6-stage Andersen impactor) at ten workplaces covering different stages of the technological process. The objective of this study was to assess exposure to anaerobic bacteria released into air from sewage and sludge at workplaces from a wastewater treatment plant (WWTP).
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