Removal of Tetracycline and Tetracycline Resistance Genes from Municipal Wastewater in Microcosm Fill-and-Drain Constructed Wetlands

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 × 10 2 -2 × 10 4 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 nonplanted 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.