Constructed wetland-microbial fuel cells enhanced with zero-valent iron for wastewater treatment and power generation

Abstract

The performance of constructed wetland microbial fuel cells (CWMFC) was enhanced by synergy with zero-valent iron-activated carbon (ZVI/AC) micro-electrolysis reactions. The experimental group (“Group-ZVI”) removed 12.7% more chemical oxygen demand (COD; 79%) than the control group (“Group-CK”) through ZVI micro-electrolysis oxidation reactions. The presence of ZVI significantly increased the average voltage (326 ± 1.08 mV in Group-ZVI, 176 ± 1.15 mV in Group-CK) and power density (2.03 mW m−2 in Group-ZVI, 1.32 mW m−2 in Group-CK) compared with the control group by accelerating the electron transfer rate and enriching the community of electrochemically active bacteria (p < 0.05). The removal of COD dominant bacterial Sphingomonadceae was promoted and the main microorganisms that provided electricity, such as the Proteobacteria phylum, were also enriched under the action of the primary cell closed loop. The concentrations of the functional microbes Rhizobium and Alphaproteobacter also increased significantly (p < 0.05) in Group-ZVI (anode) compared with Group-CK. These observations led us to propose a new strategy to improve the performance of CWMFCs for wastewater treatment and power generation.