Abstract
This study investigated the capacity of fill-and-drain constructed wetlands (CWs) for removal of a common antibiotic, tetracycline (TC), and tetracycline resistance genes (tet genes) from municipal wastewater. TC (230 μg/L) containing wastewater was treated in the CWs planted or non-planted with common reed (Phragmites australis). TC was removed significantly in the planted (95.4 % removal) and non-planted (87.2% removal) CWs with a treatment time of 1 day. Both CWs, with longer treatment times, completely removed TC from the wastewater. Adsorption of TC to soil materials might be the major mechanism of removal by the CWs over the short-term. Biodegradation of TC by native microorganisms present in wastewater also contributed in TC removal in CWs. In addition, the planted CWs showed higher TC removal efficiency than did the non-planted ones. The presence of five tet genes (tetC, tetM, tetO, tetQ, and tetW) was monitored in the planted CWs. The influent wastewater had 1.7 × 102-2 × 104 copies/mL of these genes. All the tet genes were completely removed from wastewater by the planted CWs with 1 day treatment. In 28 days sequencing batch experiments using planted and non-planted CWs treating TC containing wastewater (250 μg/L) with treatment time of 2 days, the planted CWs completely and repeatedly removed TC from the wastewater. TC removal by non-planted CWs was 98.9-99.8%, and low concentration of TC persisted in the effluents. The presence of plants provided the effective TC removal in the CWs for a long-term. The planted CWs also maintained about 3 log reduction of tet genes from wastewater during the sequencing batch experiments. These results suggest the potential of planted CWs for use in the removal TC and tet genes from municipal wastewater.
