Intensified interactions of triclosan and diclofenac mitigation and nitrogen removal in manganese oxide constructed wetlands

Abstract

Pharmaceuticals and personal care products (PPCPs) have received increasing attention due to their potential threats to the environment and human health. To explore economic and effective methods to treat wastewater containing triclosan (TCS) and/or diclofenac (DCF), six lab-scale CWs using birnessite modified sand (B-CWs) or sand (C-CWs) as substrate were operated for one year. The removal efficiency of TCS and DCF are affected by seasonal and temperature changes. In summer, the mean removal efficiency of TCS and DCF reached 91.7% ± 2.5% (C-CWs) and 97.7% ± 1.4% (B-CWs), and 85.8% ± 10.1% (C-CWs) and 80.8% ± 9.5% (B-CWs), respectively. B-CWs showed a better removal performance than control groups in ammonium nitrogen and TCS removal, especially under low temperatures. Degradation of TCS and DCF promoted the simultaneous occurrence of denitrification coupled with Mn2+ oxidation. The mechanisms of birnessite sand enhanced nitrogen nutrients and PPCPs removal was proposed as, both ammonium oxidation and PPCPs degradation were promoted by manganese oxide reduction to Mn2+, intermediates of PPCPs promoted denitrification coupled to Mn2+ oxidation. Overall, we propose the addition of birnessite sand is an effective way to enhance the removal performance of both PPCPs and nitrogen nutrients in subsurface flow CWs.