NOVELTY - A membrane-less and barrier-less microbial fuel cell comprises a cathode module (17), an anode module (16), and a device for feeding source water from the anode module to the cathode module. The fill (4) used in the cathode module comprises at least one rolled silver foil and where both the anode and cathode rolled foil fill further comprises stacking material attached to at least one side of the foil.    USE - For reducing biological oxygen demand in water (claimed) and for treating nutrient containing source water, such as food processing effluent or wastewater (sewage).    ADVANTAGE - The membrane and barrier-free microbial fuel cell lowers capital costs, cleans wastewater, and converts wastewater treatment into energy; is operated without using a cation-exchange membrane or any barrier between the cathode and the anode modules, such as glass wool or glass beads; allows for continuous flow, prevents fouling issues, and promotes scalability to fit the particular application; and is an improved device capable of being utilized in a process of treating nutrient containing source water, such as food processing effluent or wastewater (sewage) with electricity generation. The present membrane-less and barrier-free microbial fuel cell is based on a novel and unique concept of first anaerobically treating the nutrient containing source water in an anode module and then aerobically treating the source stream from the anode module in a cathode module; does not require a particular distance between a cathode module and an anode module, and preferably uses a conductive, non-biocidal material, such as graphite as an electrode in the anode module and silver, silver coated, copper, copper coated, or other conductive contacts with biocidal or antibiotic properties as an electrode in the cathode module. The microbial fuel cell is operated without using an expensive cation-exchange membrane or similar glass wool or glass bead barrier or interface between the cathode and anode with an expectation of greater efficiency by limiting fouling.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for a method of reducing biological oxygen demand in water using the microbial fuel cell involving introducing source water into the anode module and discharging from the cathode module, and introducing the air to the source water after the anode module.    DESCRIPTION OF DRAWING(S) - The figure shows a diagram of microbial fuel cell.    Anode (1)    Anode inlet (2)    Anode outlet (3)    Fill (4)    Collection device (12)    Anode module (16)    Cathode module (17)    Distribution screen (18)