Removal of antibiotic resistance genes from wastewater treatment plant effluent by coagulation

Antibiotic resistance genes (ARGs), as emerging environmental contaminants, have become a threat to human health. Recent studies have demonstrated that the effluent from wastewater treatment plants is a significant point source of ARGs released into the environment. In this study, we investigated the effectiveness of coagulation technology in the removal of ARGs from treated wastewater. Specifically, we measured the removal of five ARGs (two sulfonamide resistance genes, sulI and sulII, and three tetracycline resistance genes, tetO, tetW and tetQ) and the class 1 integron intI1 gene via the application of two coagulants: FeCl3 and polyferric chloride (PFC). Moreover, the removal of dissolved organic carbon (DOC), NH3N and total phosphorus (TP) in the coagulation process was investigated. The coagulation process effectively removed ARGs from the effluent with 0.5-log to 3.1-log reductions. Significant removal correlations were observed between dissolved NH3N and DOC, intI1 and sulI, sulII and tetO, sulII and tetW, and tetO and tetW, implying that the co-removal of DOC, dissolved NH3N, the intI1 gene and different ARGs played an important role in ARG loss during coagulation with Fe-based coagulants. These results indicate that coagulation may play a promising role in ARG reduction in wastewater treatment plants.