Fate of tetracycline at high concentrations in enriched mixed culture system: Biodegradation and behavior

Abstract

BACKGROUND: Tetracycline (TC), a group of broad-spectrum synthetic antibiotics, has been detected in wastewater at concentrations ranging from ng L-1 to mg L-1. However, low biodegradation efficiencies of TC, especially at high concentrations, were obtained in conventional activated sludge processes. This study aimed to investigate the biodegradation and behavior of TC at high concentrations in an enriched mixed culture system. RESULT: High TC removal efficiencies of 83.6 ± 4.3% and 93.2 ± 2.2% were obtained in two reactors with the addition of TC at 10 mg L-1 and 1 mg L-1, respectively. In the presence of TC, activated sludge floc size kept increasing and aggregation phenomena were observed. In addition, TC exposure decreased the microbial diversity and enriched the dominant bacteria. These effects were more prominent with higher TC concentration. CONCLUSION: TC at high concentrations could be effectively removed in enriched mixed culture, and biodegradation was the primary mechanism. TC induced the aggregation of activated sludge and the effect was more prominent under higher TC stress. The TC exposure affected the microbial communities of activated sludge, resulting in a decrease in microbial diversity and the enrichment of dominant bacteria.