Fate of tetracycline and sulfamethoxazole and their corresponding resistance genes in microbial fuel cell coupled constructed wetlands

Abstract

Pollution by antibiotics and antibiotic resistance genes has become a major health concern. A microbial fuel cell coupled constructed wetland (CW-MFC) is a new installation to simultaneously treat wastewater and produce energy. This study was conducted to assess the removal efficiency of tetracycline (TC) and sulfamethoxazole (SMX) and the development of TC and SMX resistance genes (tetA, tetC, tetO, tetQ, tetW, sulI and sulII) in the CW-MFCs. At the same time, electricity was also produced during the co-metabolism of the antibiotics and glucose. The results indicated that the CW-MFCs could significantly reduce the concentration of TC and SMX in wastewater. Accumulation of antibiotics and the relative abundances of the tet and sul genes in different layers of the CW-MFCs were: anode layer > cathode layer > middle layer > effluent. The relative abundances of ARGs in the substrates ranged from 1.40 × 10⁻⁴ to 6.30 × 10⁻¹ for tet genes and 5.58 × 10⁻³ to 9.27 × 10⁻² for sul genes. The relative abundances of the tetC, tetQ, TetW, sulI and sulII genes were significantly affected by the antibiotics in effluent of the CW-MFCs. In addition, the highest power density obtained under the external resistance of 1000 Ω was 0.0578 W m⁻². However, an obvious drop of power density was observed when the antibiotic concentrations increased from 400 to 1600 μg L⁻¹.