Occurrence and removal of antibiotic resistance genes in municipal wastewater and rural domestic sewage treatment systems in eastern China

Antibiotic resistance genes (ARGs) are emerging environmental contaminants and pose a threat to public health. In this study, four tetracycline resistance genes (tetM, tetO, tetQ and tetW) and two sulfonamide resistance genes (sulI and sulII) were evaluated in 4 municipal wastewater and 8 rural domestic sewage treatment systems with different wastewater handling abilities and treatment processes using quantitative polymerase chain reaction (qPCR). In the influents, the relative abundance of different ARGs showed significant variations among the sampling sites. In addition, significant correlations (tetQ: R2 = 0.712, P < 0.05; tetO: R2 = 0.394, P < 0.05) between the gene copy numbers and wastewater-receiving capacity were observed. Statistical analysis revealed a positive correlation (R2 = 0.756, P < 0.05) between the gene copy numbers of sulI and intI1, whereas the gene numbers of tetM and sulI were strongly correlated with 16S rDNA. Significant reductions (1-3 orders of magnitude) in ARGs were observed in municipal wastewater treatment systems, but a smaller reduction was found in the rural domestic sewage treatment systems. These results provide insights into the occurrence and removal of ARGs in wastewater treatment systems in both rural and urban areas in eastern China.

► We evaluated ARG removal in municipal and rural domestic sewage treatment systems. ► The abundance of ARGs showed significant variation among the sampling sites. ► The tetQ gene number was correlated with wastewater-receiving capacity. ► Higher removal rate of tet genes was found in municipal sewage treatment systems. ► The constructed wetland with plants may play a major role in the removal of ARGs.