Factors Affecting Wastewater Treatment and Power Generation of Constructed Wetland Microbial Fuel Cell Systems

Although there have been many studies on the process conditions of Constructed Wetlands (CW) and Microbial Fuel Cells (MFC), there are few studies on the Constructed Wetlands coupled with Microbial Fuel Cells. Currently, low power production is the main problem faced by Constructed Wetlands-Microbial Fuel Cell systems (CW-MFCs). This experiment intends to research the effects of HRT, influent COD and electrode spacing on wastewater treatment and power generation performance. In this experiment, CW-MFCs with two different electrode spacings (18 cm for reactor A and 28 cm for reactor B) were set up under continuous flow conditions. The effects of HRT, influent COD and eletrode spacing on wastewater treatment and power generation performance were explored using a single-factor controlled variable method. Experiment results showed that the extension of HRT was beneficial for contaminants removal and the power generation of the CW-MFCs, but the excessive extension was ineffective for the electricity output. The optimal HRT of the CW-MFCs was 24 h when influent COD was 500 mg.l(-1). Improving influent COD within the appropriate range (500 similar to 1000 mg.l(-1)) facilitated the power generation and contaminant removal performance of the CW-MFCs. The maximum output voltage and power density were obtained in reactor A when influent COD was 1000 mg.l(-1) and HRT was 24 h, which were 548 mV and 120 mW.m(-3), respectively. Compared with reactor B, reactor with smaller electrode spacing achieved better electricity generation and contaminant degradation under the optimal condition. Its average output voltage could be improved by 5.1 similar to 46.1% and the removal rates of COD and NH4+-N could also be improved by 0.2 similar to 4.9 % and -0.9 similar to 13.7 %, respectively. This phenomenon indicates that there was a significant positive correlation between the number of Gram-negative bacteria and the electricity production performance of the CW-MFCs, which was due to the difference in electron transfer efficiency. This study can provide operation parameters for the CW-MFCs process.