Feasibility study of electricity generation and organics removal for a molasses wastewater by a waterfall-type microbial fuel cell

A membrane electrode assembly (HEM) was incorporated with microbial fuel cell (MFC) to create a HEM-MFC for treating molasses wastewater and converting the pollutant to electrical energy. The most important novelties in this work include the use of polyvinyl alcohol-hydrogel (PVA-H) to replace the less permeable and more expensive proton exchange membrane and the placement of the reactor at an adjustable tilt angle which enabled a proper connection of independent MFC units of the reactor in series to maximize its output voltage, organics removal efficiency, and decolorization. The results showed that the PVA hydrogel introduced into the HEM sustained the moisture for the membrane electrode, thus facilitating proton transmission. When the HEM-MFC was arranged parallel to the wastewater surface and formed a tilt angle (theta) of 0 degrees, the reactor generated electricity by using one MFC only. Increasing the tilt angle enabled inflow wastewater to create differences in the water displacement heights between each chamber of the reactor, thereby forming a set of MFCs connected in series. At tilt angle of 25 degrees, the proposed reactor attained a COD removal efficiency of 95.6% and decolorization of 60.1%. In addition, a tilt angle of 25 degrees yielded a maximum open-circuit voltage (OCVmax) of 2130 mV and power density (PD) of 16.1 mW/m(2), which were higher than those achieved through a tilt angle of 0 degrees (the OCVmax and PD increased 3.9 and 18.7 fold, respectively). Overall, the proposed waterfall-type MFC increased its voltage output by connecting the MFCs in series, effectively treated and decolorized molasses wastewater, and demonstrated considerable potential for scale-up development. (C) 2017 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.