Developing Benthic Sediment and Emergent Plants‐Based Electroactive Surface Flow Wetlands to Treat Strong Wastewater: The Effect of External resiStance and Wastewater Contact Periods

The pollutant removal pathways and the influencing catalysts have been assessed in benthic sediment and emergent plants-based two electroactive surface flow (SF) wetlands operated under variable wastewater contact and treated strong wastewater, that is, landfill leachate. The two SF systems achieved mean removal percentages of 68%-81% for organic matter, 33%-52% for nitrogen, 42%-70% for phosphorus, and 31%-84% for coliforms, respectively. The positive impact of electrogenic bioreactions on the removal routes in the reductive environment-dominated anode compartment, as well as the supplementary contribution from the cathode zone, improved overall organic, phosphorus, and coliform removals in the closed circuit-based (with external resistance) SF wetland. The open circuit-based SF wetland (without external resistance) achieved better nitrogen removal due to the availability of oxygen as an electron acceptor for oxidizing NH₄-N, particularly in the anode compartment. A higher wastewater contact period improved the organic removal in both systems, supporting both physicochemical and microbial-based routes. However, it also triggered oxygen consumption by the aerobic-based organic removal pathways, thereby restricting nitrification in the cathode compartments. The higher phosphorus composition of the benthic stone dust than the fresh (i.e., before being utilized as the benthic sediment) samples reflects the effect of the chemical route-based adsorption route. The mean voltage production within the two systems ranged from 50 to 215 mV; the bioenergy and wastewater contact period increments showed a positive correlation in both systems. This study investigated the interactions among benthic sediment, plants, electrodes, circuit connections, and wastewater pollutants in electrode-coupled SF wetlands operated under variable wastewater contact periods and higher influent organic strength.