Distribution, fate and removal efficiency of anthelmintic drugs in wastewater treatment plants.

The distribution and fate of 19 anthelmintic drugs (ADs) were investigated in two wastewater treatment plants (WWTPs) using different wastewater treatment technologies, including anaerobic-anoxic-aerobic (A2/O) biological process and cyclic activated sludge system (CASS) process. All the 19 ADs were found in the two WWTPs, with concentrations ranging from N.D. to 324.6 ng/L in the influent and from N.D. to 1579.2 ng/L in the effluent. Benzimidazoles were the primary pollutants in the wastewater and suspended particulate matter, accounting for more than half of the total concentration. The concentrations of macrocyclic lactones in the sludge were significantly higher than that of other two media. The ADs removal efficiency of A2/O ranged from -330 % (albendazole sulfoxide) to 100 % (fenbendazole, mebendazole and pyrantel). While the ADs removal efficiency of CASS process ranged from -425 % (albendazole sulfoxide) to 100 % (abamectin, moxidectin and ivermectin). There was no significant difference in the average removal efficiency of the ADs between the two processes (64 % and 63 %, except albendazole sulfoxide). The removal efficiencies of the ADs in the biodegradation stage were better than them in the sedimentation stage. The load per capita of the 19 ADs in two WWTPs ranged from 0 (moxidectin) to 36 μg.d-1.p-1 (albendazole), and the emission in the effluent ranged from 0 (moxidectin) to 163 μg.d-1.p-1 (albendazole sulfoxide). This study provided the first comprehensive data on the occurrence and fate of the 19 ADs and evaluated the removal efficiencies of the 19 ADs in two WWTPs using A2O process and CASS process in the city.