Free-draining two-stage microbial fuel cell integrated constructed wetlands development using biomass, construction, and industrial wastes as filter materials: Performance assessment

This study reports organic, nutrient, and coliform removal performances in free-draining, three parallel two-stage microbial fuel cell (MFC)-based wetlands that were filled with organic, construction, industrial waste materials and planted with Canna indica. Two hydraulic load rates, i.e., 260 (Phase I) and 520 mm/d (Phase II), were employed. Mean ammoniacal nitrogen (NH₄-N), total nitrogen (TN), total phosphorus (TP), coliform removal percentages of the organic, construction, industrial waste materials packed two-stage MFC-based wetland systems ranged between 88 and 96%, 83 and 94%, 59 and 78%, 72 and 100%, respectively, throughout the two operational periods. Chemical oxygen demand (COD) removal percentage in construction, industrial waste materials packed systems ranged between 66 and 79%. The organic waste media packed system achieved low COD removal (33%) during the first operational period that improved substantially (84%) during the last phase. Wastewater organic, nutrient removals were achieved by plant uptake, media-based adsorption, and microbial transformation. Nitrogen, phosphorus accumulation percentages in the plants tissue (with respect to total removal) ranged between 0.3 and 64%, 0.2 and 6%, respectively. Nitrogen, phosphorus concentration in the used media ranged between 0.4 and 13.5 g/kg, 0.7 and 1.1 g/kg, respectively. Maximum voltage and power density production across the construction waste jhama brick packed MFC-based wetland (i.e., 119 mV and 86 mW/m², respectively) exceeded the bioenergy production of organic, industrial waste materials packed wetlands. Input organic load increment adversely impacted voltage production across all MFC-based wetlands. The carbon composition of the waste media partially supported electrochemical removal mechanisms. This study demonstrates a relatively stable pollutant removal performance of the free-draining construction, industrial waste media packed two-stage MFC-based wetlands despite input pollutant load increment.