Emerging contaminants (ECs) represent a risk for health and the environment at concentrations as low as nanograms per liter. In this study, acesulfame-K (ACK), acetaminophen (ACE), caffeine (CAF), and N, N-diethyl-m-toluamide (DEET) were selected based on their ubiquity and concentrations of 16.9 μg ACK/L, 4.7 μg ACE/L, 3.1 μg CAF/L, and 3.7 μg DEET/L measured in real domestic wastewater. Biological oxygen consumption by activated sludge in the presence of ECs, at the milligram per liter level, suggested a biodegradability degree of ACE > DEET > CAF > ACK, supported by removal of 100% ACE, 99% DEET, 97% CAF, and 90% ACK, verified by liquid chromatography on parent compounds. Metagenomic analysis of the activated sludge identified Aeromonas, Macellibacteroides, Ottowia, Tetrasphera, and Bdellovibrio among the most abundant bacterial genera. Sequential plate cultures, matrix-assisted laser desorption ionization-time of flight mass spectrometry, and 16S rRNA gene sequencing allowed us to report here for the first time four strains of Aeromonas tolerant to 100 mg DEET/L isolated from activated sludge. Also, single bacterial strains of Aeromonas, Shewanella, and Bacillus tolerant to 100 mg ACE/L were equivalently isolated and identified. These strains represent promising candidates for further studies in bioremediation and biodegradation of ECs. The findings enhance our understanding of ECs occurrence, fate, and biological degradation in wastewater treatment systems and highlight the potential of native microbial communities to mitigate pollutant persistence.
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