Effects of selection and compiling strategy of substrates in column-type vertical-flow constructed wetlands on the treatment of synthetic landfill leachate containing bisphenol A.

A constructed wetland (CW) is a low-cost, eco-friendly, easy-to-maintain, and widely applicable technology for treating various pollutants in the waste landfill leachate. This study determined the effects of the selection and compiling strategy of substrates used in CWs on the treatment performance of a synthetic leachate containing bisphenol A (BPA) as a representative recalcitrant pollutant. We operated five types of lab-scale vertical-flow CWs using only gravel (CW1), a sandwich of gravel with activated carbon (CW2) or brick crumbs (CW3), and two-stage hybrid CWs using gravel in one column and activated carbon (CW4) or brick crumbs (CW5) in another to treat synthetic leachate containing BPA in a 7-d sequential batch mode for 5 weeks. CWs using activated carbon (CW2 and CW4) effectively removed ammonium nitrogen (NH-N) (99-100%), chemical oxygen demand (COD) (93-100%), and BPA (100%), indicating that the high adsorption capacity of activated carbon was the main mechanism involved in their removal. CW5 also exhibited higher pollutant removal efficiencies (NH-N: 94-99%, COD: 89-98%, BPA: 89-100%) than single-column CWs (CW1 and CW3) (NH-N: 76-100%, COD: 84-100%, BPA: 51-100%). This indicates the importance of the compiling strategy along with the selection of an appropriate substrate to improve the pollutant removal capability of CWs.