Organic matter and nutrient removal in tidal flow-based microbial fuel cell constructed wetlands: Media and flood-dry period ratio

This study assessed the integrated impact of tidal flow, microbial fuel cell (MFC), flood (F)-dry (D) period ratio, and media on organic matter, nutrient removal pathways in subsurface flow constructed wetlands that received municipal wastewater. The tidal flow-based MFC constructed wetlands were filled with organic (biochar, coal, jute fiber), waste (slag), construction materials (concrete, brick), and planted with Phragmite australis or Chrysopogon zizanioides (i.e., Vetiver). The tidal flow-based MFC wetlands were operated under sequential flood-dry periods; three F:D ratio values (i.e., 8hrs: 16hrs; 16 hrs: 8 hrs; 24 hrs: 0 hrs) were employed within three operational periods. Mean input chemical oxygen demand (COD), nitrogen (N), and phosphorus (P) load across the tidal flow-based MFC wetlands ranged between 45 and 1130, 6–71, and 0.1–25 g/m²d, respectively; removal percentages ranged between 75 and 100, 57–86, and 80–100%, respectively. Nutrient accumulation percentage in wetland plants was <7% with respect to total removal. Electrochemically active-inactive microbial degradation and media-based adsorption supported nutrient, organics removals. Flood-dry period variation influenced N removal kinetics; organics and P removals were stable throughout the experimental run. Maximum power production rates (within the experimental systems) ranged between 63 and 982 mW/m². Tidal flow-based MFC wetlands filled with organic media achieved high N removal and power production than waste, construction materials based systems.