Treatment performance of stone dust packed tidal flow electroactive and normal constructed wetlands: Influence of contact time, plants, and electrodes

This study reports the pollutant removal performance of unplanted, planted tidal flow constructed wetlands (with and without electrodes integration) that received municipal wastewater. The wetland systems were operated under two wastewater dosing/fill (F)-drain (D) time ratios, i.e., 1 hour (h) F:3 hour D, 3 h F:1 h D, and three contact (retention time) periods, i.e., 20, 10, 5 h. Overall mean total Kjeldahl nitrogen (TKN), ammoniacal nitrogen (NH₄-N), total nitrogen (TN), total phosphorus (TP), biochemical oxygen demand (BOD), chemical oxygen demand (COD), coliform removal percentages (of the wetland systems) ranged between 51 and 65 %, 40 and 64 %, 54 and 71 %, 64 and 90 %, 85 and 94 %, 73 and 85 %, 64 and 87 %, respectively. The presence of plants influenced electrochemically active, inactive-based pollutant removal routes. Organic removal with electrodes integrated unplanted, planted wetlands was dependent upon wastewater fill and contact periods variation. NH₄-N, NO₃-N, TN removal of the unplanted, planted wetlands with or without electrodes relied upon the former operational factor. The chemical composition of the stone dust media supported nutrient adsorption and microbial pollutant removal routes. Power density production of the electrodes integrated wetlands decreased during 3 h fill and 5 h wastewater contact periods when pollutant removal performance was higher. The maximum power density produced across the electrodes integrated unplanted and planted wetlands was 113 and 147 mW/m³, respectively.