S1 Supplementary information Transport and transformation of selenium and other constituents of flue-gas desulfurization wastewater in water-saturated soil materials Madhubhashini B. Galkaduwa, Ganga M. Hettiarachchi, Gerard J. Kluitenberg, Stacy L. Hutchinson, Lawrence Davis and Larry E. Erickson Pages: 33 Figures: 13 Tables: 10 Pilot-scale constructed wetland treatment system at Jeffrey Energy Center Westar’s Jeffrey Energy Center (JEC), St. Marys, Kansas is the largest coal-fired power plant in Kansas. It consists of three separate 720 MW units for electricity generation and uses low-sulfur subbituminous coal. In 2010, the upgrade of a flue-gas desulfurization (FGD) scrubber unit was completed to enhance the removal efficiencies of sulfur dioxide, mercury, and particulate matter in the flue gas, complying with air emission regulations. Scrubber design is a limestone forced-oxidation (wet) FGD process (Westar Energy, 2017). These systems create wastewater with elevated concentrations of trace elements (such as selenium), dissolved solids, and other constituents including boron, sulfur, fluorine, etc. Therefore, the FGD wastewater needs to be treated before releasing into the Kansas River to meet surface water quality regulations. As an economically and environmentally feasible option, a pilot-scale constructed wetland treatment system (CWTS) was implemented at the JEC in December 2010. The CWTS composed of two lines, side by side, with four wetland cells per line (total of eight cells) and the total area of the wetland system was two acres (see Figure S1 a, and b). These cells included two free water surface (FWS), four vegetated submerged bed (VSB), and