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Vertical up-flow constructed wetlands integrating with microbial fuel cell (VFCW-MFC) was evaluated for NH4+-N removal and bioelectricity recovery. The experiments were carried out in lab-scale VFCW-MFC microcosms treating synthetic domestic wastewater under different operational conditions of pH, hydraulic retention time, and mass loading rate. Effects of a wild ornamental grass (Cenchrus setaceus) on treatment performance and voltage output were investigated simultaneously. Experiments demonstrated that the neutral pH of influents favored NH4+-N removal and power generation. Extended retention time improved treatment capacity and power output but likely depending on the substrate availability. COD removal and power output increased, while NH4+-N removal decreased, with the increase of mass loading rates. At the loading rate of 88.31 mg COD/L.day, planted VFCW-MFCs exhibited better NH4+-N treatment performance (36.9%) and higher voltage output (132-143%) than unplanted systems. The presence of plants did not affect COD removal efficiency of VFCW-MFCs (> 95%). Power density varied in the range of 1.26-1.59 mW/m2 in planted microcosms with a maximum CE of 13.6%. The anode layer accounted for a major proportion of NH4+-N removal in VFCW-MFCs. This study implies that NH4+-N in domestic wastewaters with relatively high COD:N ratios can be treated effectively in up-flow CW-MFCs via anaerobic processes, including anammox and heterotrophic denitrifying process. The mass loading rate could be a critical parameter to balance different microbial processes, thus, coincidently determined the potential of power recovery from wastewaters. |
