The Abundance And Relationships Between Typical Antibiotics And Corresponding Resistance In Municipal Wastewater Treatment System

Nowadays, the emerging pollution of antibiotics and the relevant resistance has been considered a new threat for human health. This study aimed to detect the occurrence and abundance of8antibiotics (3tetracyclines,4sulfonamides and the trimethoprim),13antibiotic resistance genes (ARGs)(10tet genes,2sul genes and intIl) and4types of antibiotic resistance bacteria (ARB)(no-antibiotics, anti-TC, anti-SMX and anti-double) in residential areas, hospitals and municipal wastewater treatment plants. The removal of the targets in different treatment stages and the influences of the WWTP’s effluents to the downstream water were also evaluated in the study.The concentrations of total/individual targets (antibiotics, genes and bacteria) varied remarkably among different samples. Hospital samples presented lower abundance of detected targets than that in residential areas on average. Except for total tetracyclines concentration and the proportion of anti-TC bacteria (R2=0.330, P<0.05), no significant correlation was found between antibiotics and ARB abundance (P>0.05). Various relationships (P<0.05) between antibiotics and ARGs were identified (e.g. tetracycline and tet(M) with R2=0.432; sulfamethoxazole and sull with R2=0.388), especially sulfamerazine (SMI) with tet(B) and tet(C)(R2=0.710and R2=0.835, P<0.01), probably due to the co-selection or cross-selection. The addition use of trimethoprim may exert little influence to sulfonamide resistance. Moreover, Three ARGs [tet(A), tet(B), tet(M)] showed relationships with anti-TC and anti-double bacteria in the studied areas (P<0.05).Different removal rates were found in different treatment stages of the two WWTPs. In WWTP-Q, antibiotics could be mainly removed in the biological process (about50%) while the ARGs lessened remarkably in both the biological process (about50%) and the secondary sedimentation tank (0.2～1.21og). Abundunce of ARB reduced gradually during the whole process but not markedly in the biological process. In terms of WWTP-L, anaerobic tank could mainly degrade the antibiotics (30%-60%) and reduce the ARB (Ilog) but was not efficient in lessening the ARGs except for only a few ones. Aerobic tank played an important role in eliminating the whole ARGs. The UV treatment in both the two WWTPs had less effect in removing the targets. Besides, high abundance of antibiotics, ARGs and ARB were found in the excess sludge samples (levels of mg/kg,1011copies/g and108CFU/mL, respectively).Different antibiotics had different influences to the downstream water and sulfamethoxazole and sulfamethazine increased the corresponding concentrations. The total abundance of ARGs in downstream water sampling sites had increased by0.1log due to the effluents of WWTP-L, among which several ARGs such as tet(C)、 tet(A) and intll had obvious changes. The afflux of the effluent from WWTP increased the abundance of anti-double bacteria in the downstream water. Besides, abundance of4types of antibiotic resistance bacteria remained steadily in the downstream sampling sites.