Landfill leachate and municipal wastewater co-treatment in microbial fuel cell integrated unsaturated and partially saturated tidal flow constructed wetlands

Abstract

This study co-treated landfill leachate and municipal wastewater employing unsaturated, partially saturated microbial fuel cell integrated tidal flow constructed wetlands. The wetland systems were packed with organic or waste materials and planted with Phragmites australis. Leachate and municipal wastewater were mixed in different volumetric proportions (40%: 60%; 20%: 80%; 10%: 90%) for co-treatment under variable wastewater retention periods (i.e., 6 and 24 h). Mean biochemical oxygen demand, chemical oxygen demand, ammonium nitrogen, total nitrogen, phosphorus removal percentage ranged between −35 and 76%, −22 and 76%, 10 and 90%, −0.2 and 71%, 38 and 92%, respectively. The combination of higher influent pollutants load (due to higher leachate volumetric proportion in the mixed wastewater) and longer retention time developed a predominant anoxic/anaerobic environment inside the media of the unsaturated, partially saturated microbial fuel cell integrated tidal flow wetlands. Such environmental conditions diminished organic and nutrient removal by hampering electrochemically active, other removal pathways, particularly in partially saturated wetlands. Leachate volumetric proportion reduction adjusted the influent's pollutant loads, carbon and other chemical composition, increased aerobic gradient inside the media bed, and improved pollutants removal of the unsaturated, partially saturated systems. A longer wastewater retention period supplemented operational performance. Mean voltage production across the microbial fuel cell integrated tidal flow constructed wetlands ranged between 4 and 152 mV; maximum power density production ranged between 50 and 527 mW/m3. Physicochemical properties (voids, roughness, carbon composition) of the media influenced power density production. Waste rubber tire material-based partially saturated wetland was the most efficient bioenergy producing system.