Effects of advanced treatment systems on the removal of antibiotic resistance genes in wastewater treatment plants from Hangzhou, China.

This study aimed at quantifying the concentration and removal of antibiotic resistance genes (ARGs) in three municipal wastewater treatment plants (WWTPs) employing different advanced treatment systems [biological aerated filter, constructed wetland, and ultraviolet (UV) disinfection]. The concentrations of tetM, tetO, tetQ, tetW, sulI, sulII, intI1, and 16S rDNA genes were examined in wastewater and biosolid samples. In municipal WWTPs, ARG reductions of 1-3 orders of magnitude were observed, and no difference was found among the three municipal WWTPs with different treatment processes (p > 0.05). In advanced treatment systems, 1-3 orders of magnitude of reductions in ARGs were observed in constructed wetlands, 0.6-1.2 orders of magnitude of reductions in ARGs were observed in the biological aerated filter, but no apparent decrease by UV disinfection was observed. A significant difference was found between constructed wetlands and biological filter (p < 0.05) and between constructed wetlands and UV disinfection (p < 0.05). In the constructed wetlands, significant correlations were observed in the removal of ARGs and 16S rDNA genes (R(2) = 0.391-0.866; p < 0.05). Constructed wetlands not only have the comparable ARG removal values with WWTP (p > 0.05) but also have the advantage in ARG relative abundance removal, and it should be given priority to be an advanced treatment system for further ARG attenuation from WWTP.