*Microbial Fuel Cells Used in Laboratory Studies for Scale-Up Purposes*

Several MFCs have been used in the laboratory for scale-up studies. These include single or dual-chambered cylindrical and cubic MFCs. Similarly, tubular or flat-plate designs have been employed for most scale-up studies. The MFC configuration mostly used in scale-up studies includes a tubular anode surrounded by a separator to isolate the anode from the cathode [66] electrically. Moreover, the MFCs, usually tubular or a product of cylindrical construction materials, can easily be upscaled. Most of the materials that are used as support materials to scale-up reactors include polyvinyl chloride, cylindrical glass, polypropylene, measuring cylinders, cation exchange membranes produced in a tubular shape, and nylon tubing. Most recent studies have shown the mechanism of operation of tubular designs in a continuous flow mode. This resulted in further opportunities for scale-up because of the tube length extension. As such, this culminated in the extension and additional tubular MFC modules to form an MFC stack. However, when considering the flat-plate and tubular designs, multiple MFCs configured this way can only be hydraulically controlled in parallel or series. In another arrangement in series, the effluent flow goes through each of the MFC modules sequentially; on the other hand, each MFC module obtains the same influent when a parallel connection is used. Overall, this means modules of MFCs can be connected in parallel or series to increases voltage and current generation, respectively [53].
