Comparison of the elimination effectiveness of tetracycline and AmpC β-lactamase resistance genes in a municipal wastewater treatment plant using four parallel processes

Abstract

Municipal wastewater treatment plants (mWWTPs), considered reservoirs ofantibiotic resistance genes (ARGs), are selected to compare the contributions oftechnology and process to ARG removal. Fifteen ARGs (tetA, tetB, tetC, tetE,tetG, tetL, tetM, tetO, tetQ, tetS, tetX,MOX, CIT,EBC, and FOX) and two integron genes (intI1, intI2) were tracked anddetected in wastewater samples from a large-scale mWWTP with four parallelprocesses, including three biological technologies of AAO (anaerobic-anoxic-oxic),AB (adsorption-biodegradation), and UNITANK, two different disinfectiontechnologies, and two primary sedimentation steps. The results showed that ARGs werewidely detected, among which tetA and tetM had the highest detection rate at 100%. AAO wasthe most effective process in removing ARGs, followed by the AB and UNITANKprocesses, where the separation step was critical: 37.5% AmpC β-lactamase genes were reduced by the secondaryclarifier. UV disinfection was more efficient than chlorination disinfection by47.0% in ARG removal. Both disinfection and primary sedimentation processes couldeffectively remove integrons, and the swirling flow grit chamber was a moreeffective primary settling facility in total ARG removal than the aerated gritchamber. The tet genes and AmpC β-lactamase genes were significantly correlatedwith the water quality indexes of BOD5,CODCr, SS, TP, TOC, pH andNH4+-N (p < 0.05). In addition, thecorrelation between efflux pump genes and AmpC β-lactamase genes was strongly significant (r2 = 0.717,p < 0.01). This studyprovides a more powerful guide for selecting and designing treatment processes inmWWTPs with additional consideration of ARG removal.