Abstract
Water reuse is now becoming a global necessity. However, one of the drawbacks in releasing wastewater into the environment is some persistent pollutants that are not completely removed in wastewater treatment plant. Residual bacteria and antibiotics in the inflowing wastewater can contribute to the antibiotic resistance spread in the aquatic environment. This study determined the effectiveness of activated sludge process for fecal coliform bacteria elimination, and also the Escherichia coli resistance to antimicrobial agents as erythromycin, azithromycin, clarithromycin, ofloxacin, ciprofloxacin, trimethoprim, and metronidazole in treated wastewater. The research was carried out using the membrane filtration technique, and the susceptibility of isolates to antimicrobial agents was tested by the disc diffusion method. The concentrations of fecal coliform bacteria and Escherichia coli differed significantly depending on the seasonal period in which it was carried out. Despite up to 99% reduction in the number of sanitary indicators in biologically treated wastewater, 89% of E. coli isolates resistant to the tested antibiotics was found, while 100% of the isolates were susceptible to metronidazole. Most of the isolates showed resistance to trimethoprim, and the fewest isolates were resistant to ofloxacin, indicating that some strains may react differently to antibiotics.
Highlights
The constantly deepening world water deficit makes it necessary to ensure the appropriate quality of available water resources
Utilities and regulatory agencies rely on an assumed relationship between the indicator organism and pathogen survival/transport through wastewater treatment plants to ensure that the reclaimed water is safe for public use
The number of fecal coliforms and Escherichia coli, including isolates resistant to antimicrobial agents, was determined as the basic indicator of bacterial contamination in sanitary analyses to assess the degree of contamination with fecal contamination
Summary
The constantly deepening world water deficit makes it necessary to ensure the appropriate quality of available water resources. The unquestionable benefits of wastewater treatment plants are followed by certain difficulties. The most important of which are the problems of wastewater sludge management and discharging to water bodies. Microbiological contamination is one of the basic threats to surface waters which are receivers of wastewater and potential sources of drinking water. Apart from physical and chemical pollutants, wastewater contains numerous pathogenic and opportunistic microorganisms, mainly of intestinal origin. Raw wastewater is the largest reservoir of human intestinal bacteria. Treated wastewater, even with the use of highly effective methods, may pose a serious microbiological threat to the receiving waters in terms of bacteriology
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