Effects of Influent Organic Loading Rates and Electrode Locations on the Electrogenesis Capacity of Constructed Wetland-Microbial Fuel Cell Systems

Three novel constructed wetland-microbial fuel cells (CW-MFCs), based on electrode location, were developed for wastewater treatment and sustainable electricity production by embedding a MFC into a CW system. In the three CW-MFCs, electrodes were placed in different locations, including bottom anode-rhizosphere cathode CW-MFC (BA-RC-CW-MFC), rhizosphere anode-air cathode CW-MFC (RA-AC-CW-MFC), and bottom anode-air cathode CW-MFC (BA-AC-CW-MFC), to investigate the combined effects of organic loading rates (OLRs) and reactor configurations on the electrogenesis capacity of the hybrid system. All the systems operated continuously to treat five types of synthetic wastewater with increasing OLRs: 9.2, 18.4, 27.6, 55.2, and 92.0 g chemical oxygen demand (COD) m(-2) d(-1). The BA-RC-CW-MFC failed to produce electricity at any OLR, whereas the maximum power densities of 0.79 +/- 0.01 and 10.77 +/- 0.52 mW m(-2) were achieved in the RA-AC-CW-MFC with 18.4 g COD m(-2) d(-1) influent OLR and in the BA-AC-CW-MFC with 27.6 g COD m(-2) d(-1) influent OLR, respectively. The coulombic efficiencies of the RA-AC-CW-MFC and BA-AC-CW-MFC decreased gradually with the increase in influent OLRs. (C) 2016 American Institute of Chemical Engineers Environ Prog, 36: 435-441, 2017