Removal of Antibiotics from Livestock Wastewater using Constructed Wetlands

Abstract

The occurrence and removal of antibiotics (sulfamethoxazole (SMZ), sulfathiazole (SFI), sulfamethazine (SMA), trimethoprim (TMP), tetracycline (TC), oxytetracycline (OTC), chlorotetracycline (CTC), and enrofloxacin (EFX)) using constructed wetlands (CWs) system for treating livestock wastewater were investigated by measuring the concentrations of the influents and the effluents in the CWs flowing into the Geum River Basin, Korea. The concentration of antibiotics was measured using solid phase extraction (SPE) followed by LC-MS/MS analysis. The results showed that the levels of antibiotics in the effluents of the CWs were in the order of CTC, SFI, SMA, SMZ, TMP, OTC and EFX, ranging from 47 to 6,834.66 μg/L, respectively. There was an inverse correlation (p < 0.0493) between the removal of sulfonamide-group (SMZ, SFI and SMA) and tetracycline-group (TC, OTC and CTC) in the concentrations of effluents of the CWs, indicating that sulfonamide-group-antibiotics were more effectively removed in the CWs. The sulfonamide-antibiotics have usually higher pKa values, resulting in more effective adsorption with the negative charged soils by the electrostatic interaction. The microcosm antibiotics adsorption experiment by wetlands soil with two sets (biotic system without sterilization and abiotic system with sterilization) showed that average removals of 20, 50 and 100ng/L of antibiotics in biotic system effectively removed (e.g. SMZ (73%), SFI (64%), SMA (76%), TMP (91%) and EFX (87%)) within 48 hours. However, the removals using abiotic system (e.g. SMZ (66%), SFI (36%), SMA (63%), TMP (63%) and EFX (78%)) were relatively low. Sunlight photo-degradation experiments showed that EFX was removed effectively (70%), compared to the removals of sulfonamide-antibiotics with SMZ, SFI and SMA with 23%, 44% and 28%, respectively. The microcosm experiments of antibiotics adsorption by wetlands plants (Phragmites australis) were also performed with two sets (biotic and abiotic systems). The results showed that the biotic system effectively removed sulfonamide-antibiotics such as SMZ (71%), SFI (54%) and SMA (62%) within 3 hours. The effective removals of sulfonamide-group might be attributed to microbial biodegradation compared to lower removals (SMZ (3%), SFI (25%) and SMA (50%)) by abiotic system. Overall, these results imply that the removals of antibiotics are mediated from biodegradation by microbial activity and adsorption into soil and plants which are the main removal mechanisms in the CWs.