Abstract
BackgroundIn many parts of the world, health problems and diseases have often been caused by discharging untreated or inadequately treated wastewater. In this study, we aimed to control physico-chemical parameters in wastewater samples. Also, microbiological analyses were done to reveal Salmonella strains and each Escherichia coli (E.coli) pathotype.FindingsSixty wastewater samples were collected from fifteen different regions of Tunisia. All physico-chemical parameters (pH, residual free chlorine, total suspended solids, biological oxygen demand, and chemical oxygen demand) were evaluated.For microbiological analyses, samples were filtered to concentrate bacteria. DNA was extracted by boiling and subjected to polymerase chain reaction (PCR) using different pairs of primers.The mean pH values recorded for the sampling point were above the WHO pH tolerance limit. The total suspended solids (TSS) concentrations varied between 240 mg/L and 733 mg/L in entrance points and between 13 mg/L and 76 mg/L in exit points. In entrance points, the studied wastewater has an average COD concentration that varied between 795 mg/mL to 1420 mg/mL. Whereas, BOD concentration of the wastewater ranged between 270 mg/L to 610 mg/L. In exit points, COD concentration varied between 59 mg/L and 141 mg/L, whereas BOD concentration ranged from 15 mg/L to 87 mg/L.The bacteriological control of wastewaters showed that, in entrance points, Escherichia coli (E.coli) was detected at the rate of 76.6%. Three E.coli pathotypes were found: ETEC (53.3%), EAEC (16.6%) and EIEC (6.6%).Concerning the ETEC isolated strains, 8 of 16 (50%) have only the heat-labile toxin gene, 5 of 16 (31.2%) present only the heat-stable toxin gene and 3 of 16 (18.7%) of strains possess both heat-labile toxin gene and heat-stable toxin gene. In exist point, the same pathotypes were found but all detected ETEC strains present only the "est" gene.Concerning Salmonella isolated strains; percentages of 66.6% and 20% were found in entrance and exit points respectively.ConclusionsWastewaters contain a large amount of pathogenic bacteria that present a real impact on human health. Assessment wastewater treatment stations have to consider in account enterobacterial pathogens as potential pathogens that should be correctly controlled.
Highlights
In many parts of the world, health problems and diseases have often been caused by discharging untreated or inadequately treated wastewater
Wastewaters contain a large amount of pathogenic bacteria that present a real impact on human health
The aim of this study is on physico-chemical indicators of wastewaters and on human enteropathogenic bacteria (Salmonella spp., and Escherichia coli pathotypes) detection that may be present in reclaimed water using the multiplex polymerase chain reaction (PCR) method
Summary
In many parts of the world, health problems and diseases have often been caused by discharging untreated or inadequately treated wastewater. The need to conserve water has resulted in an increase in the use of treated sewage effluent, or reclaimed water, for many non-drinking purposes such as irrigation especially in places where numerous recreational resort zones, such as golf courses. In these areas, it is very important to implement water conservation and recycling plans for a more efficient use of water [1]. Reclaimed water used for irrigation contains parasites, bacteria, and disease-causing viruses This can create potential health hazards for the exposed human population [2]
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