Abstract
The adverse impact of sewage treatment plants on the environment, resulting from the emission of harmful biological agents to the atmosphere, depends mainly on the size of the facility, the quantity and composition of treated sewage as well as the technologies and equipment used. The aim of the conducted research was to determine the microbiological quality of atmospheric air at Municipal-Industrial Sewage Treatment Plant in Oświęcim, which is one of the largest treatment plants in Lesser Poland. Bioaerosol measurements were made at four points (raw sewage inlet, aeration chamber, purified sewage outlet and 150 m from the treatment plant, at the background point) in the period from January to December 2018. Bioaerosol samples were collected using Microbiological Air Sampler MAS-100 by Merck. The tested atmospheric air was characterized by a qualitatively and quantitatively diverse microflora. The largest source of emission of microorganisms to the atmosphere was the mechanical part of the sewage treatment plant (raw sewage inlet) and the biological reactor. The highest number of mesophilic bacteria was observed near the biological reactor (in the summer), the least at the control point. During the research, the least β-hemolytic bacteria was isolated at the purified sewage outlet—on average 3 CFU m−3, the highest at the biological reactor 16 CFU m−3. Most of α-hemolytic bacteria was observed near the raw sewage inlet and was not found at the control point. Actinomycetes also occurred in a small amount (0–40 CFU m−3). A high concentration of mildew fungi occurred in summer when the air temperature was highest, the smallest quantities of these microorganisms were found in January and February.
Highlights
Microbiological contaminants occurring in the atmospheric air come from various sources, including, among others, municipal facilities, e.g., sewage treatment plants, landfills and composting
The number of microorganisms isolated from atmospheric air at individual research points and the dependence between the number of microorganisms, temperature and air humidity are shown in Tables 1, 2, 3, 4, 5, 6 and 7 and illustrated graphically in Figs. 1, 2, 3, 4 and 5
At the inlet of raw sewage and the outflow of purified wastewater, the largest amount of bacteria was isolated in September (1320 colony forming units (CFU) m-3 and 670 CFU m-3, respectively), and at the control point constituting the background in June (130 CFU m-3)
Summary
Microbiological contaminants occurring in the atmospheric air come from various sources, including, among others, municipal facilities, e.g., sewage treatment plants, landfills and composting. The bioaerosol formed in wastewater treatment plants includes viruses, bacteria and fungi, the form of which may be different, e.g., spores, conidia, parts of the mycelium, vegetative forms (Bawiec et al 2016; Lee et al 2016). Their survival in air compared to wastewater changes significantly, because the air does not contain nutrients and does not provide adequate physicochemical conditions (Bawiec et al 2016; Lee et al 2016). The threat to health and the environment resulting from the emission of bioaerosol makes it necessary to control the microbiological contamination of air in the sewage treatment plant and in its immediate vicinity (Li et al 2013; Bauer et al 2002; Korzeniewska 2011)
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