Nanofiltration to Address Membrane Fouling from Antibiotic Resistance Genes in Secondary Effluent

Antibiotic resistance genes (ARGs) have been defined as new environmental pollutants, which have been frequently detected in secondary effluent from wastewater treatment plants and have become a potential threat to human health and ecological security. In this study, the combined process of slow filtration and low-pressure nanofiltration (NF) was used to thoroughly remove ARGs and dissolved organic carbon (DOC) from secondary effluent. In addition, the removal efficiency of ARGs was discussed and the influence of the combined process on the membrane fouling mechanism was analyzed. The results showed that the combined biofilm slow filtration-NF process can effectively reduce ARGs and DOC in the secondary effluent. The removal amount of the four ARGs (tet A, tet W, sul I, and sul II) was in the range of 4.83- to 5.67-log and the removal rate of DOC was 82.5%. Four ARGs present in the water had a significant positive correlation with the total number of microorganisms, integron intI 1, and DOC concentration, validating that the removal of the above indicators could help reduce different types of ARGs. Compared with the direct NF and slow filtration-NF, the rate of decline of the membrane specific flux of biofilm slow filtration-NF was the lowest, with a minimal membrane fouling index. The membrane fouling characteristic curve also showed that the combined biofilm slow filtration-NF process exhibited mild membrane fouling. Overall, the combined slow filtration-NF process is considered to be a better process for removing ARGs.