NOVELTY - The microbial fuel cell comprises an anode chamber (10) containing an anodic electrode and having an inlet for effluent, a cathode chamber (11) containing a cathodic electrode and having an outlet for effluent, a separator that allows flow of ions from the anode chamber to the cathode chamber, an electrical pathway that allows flow of electrons from the anodic electrode to the cathodic electrode, an effluent pathway that allows flow of effluent from the anode chamber to the cathode chamber, and an inlet for flow of air or oxygen gas through the cathode chamber.    USE - The fuel cell is useful for removing organic compounds from wastewater and generating electricity.    ADVANTAGE - The fuel cell reduces the operating cost of wastewater treatment plants by producing the power required to drive electrical equipment at the plant, such as pumps and fans.    DETAILED DESCRIPTION - The microbial fuel cell comprises an anode chamber (10) containing an anodic electrode and having an inlet for effluent, a cathode chamber (11) containing a cathodic electrode and having an outlet for effluent, a separator that allows flow of ions from the anode chamber to the cathode chamber, an electrical pathway that allows flow of electrons from the anodic electrode to the cathodic electrode, an effluent pathway that allows flow of effluent from the anode chamber to the cathode chamber, and an inlet for flow of air or oxygen gas through the cathode chamber. The effluent pathway allows control of pH in the cell. The cathodic electrode is open to the air. The effluent pathway includes a reactor for conversion of ammonia to nitrate and/or nitrite (nitrification) of effluent from the anode chamber. The cathode chamber enables both nitrification and denitrification processes. The anode chamber contains micro-organisms that catalyse transfer of electrons from an electron donor to the anode and/or the cathode compartment contains microorganisms that catalyze transfer of electrons from the cathode to an electron acceptor. The effluent is waste water and the electron donor includes organic materials or sulfur. The electron acceptor is oxygen, nitrate, nitrite or a halogenated hydrocarbon or any pollutant that can be degraded through a reductive pathway. Either the anodic or cathodic electrode is selected from woven carbon fiber, woven graphite, granular graphite or any material that is conductive and has a surface area of more than 1 m2 per cubic meter of material. Reactions in the anode chamber include generation of oxidants for oxidation of ammonium and/or ammonia. The separator is cation selective, anion selective or a non-selective separator. The pathway enables fluid to pass from the anode to the cathode and allows pH control of the fluid. The pathway includes a reactor for oxygenation or nitrification of the fluid. The anode and/or the cathode contain micro-organisms, which catalyse the respective transfer of electrons. The cathode is open to the air. INDEPENDENT CLAIMS are included for:    (1) a method of operating a microbial fuel cell; and    (2) a microbial fuel cell for treatment of a fluid containing organic or inorganic compounds.    DESCRIPTION OF DRAWING(S) - The drawing shows a microbial fuel cell having an effluent pathway between anode chamber and cathode chamber.    Anode chamber (10)    Cathode chamber (11)    Ion exchange membrane (12)    Anode (13)    Cathode (14)    External circuit (15)    Pathway. (18)