A microbial fuel cell for generating electricity. The microbial fuel cell includes an anode and a cathode electrically coupled to the anode. The anode is in contact with a first fluid including microorganisms capable of catalyzing the oxidation of ammonium. The anode is in contact with a second fluid including microorganisms capable of catalyzing the reduction of nitrite. The anode and the cathode may be housed in a single compartment, and the cathode may rotate with respect to the anode. The microbial fuel cell can be used to remove ammonium from wastewater, to generate electricity, or both.