NOVELTY - Metals recycling involves utilizing microbial fuel cell, which comprises hexavalent chromium ions as cathode electron acceptor and cuprous ions as cathode electron acceptor and cadmium (II) ions as anodic material. Chromium microbial fuel cells (MFCs), copper microbial fuel cells and cadmium microbial electrolysis cells (MECs) are connected with series of resistor. The cathode of chromium microbial fuel cells and copper microbial fuel cells is carbon rod, and cadmium microbial electrolysis cell is made of titanium or stainless steel.    USE - Method for recycling metals used for clarifying sludge sewage treatment plant containing electrochemically active microorganisms. (all claimed).    ADVANTAGE - The method is simple and eco-friendly.    DETAILED DESCRIPTION - Metals recycling involves utilizing microbial fuel cell, which comprises hexavalent chromium ions as cathode electron acceptor and cuprous ions as cathode electron acceptor and cadmium (II) ions as anodic material. Chromium microbial fuel cells (MFCs), copper microbial fuel cells and cadmium microbial electrolysis cells (MECs) are connected with series of resistor. The cathode of chromium microbial fuel cells and copper microbial fuel cells is carbon rod, and cadmium microbial electrolysis cell is made of titanium or stainless steel. The anode of chromium microbial fuel cells, copper microbial fuel cells and cadmium microbial electrolysis cells are made of carbon felt or carbon rod. The solution of chromium microbial fuel cells, copper microbial fuel cells and cadmium microbial electrolysis cells are hexavalent chromium ions , cuprous ions and cadmium (II) ions salt solution, respectively. The cathodic potential and catholyte pH of chromium microbial fuel cells is 0.3 -0.4 Volts, and 3.5-12, respectively. The cathodic potential of copper microbial fuel cells and the catholyte pH is 0.10-0.20 Volts, and 4-6, respectively. The cathodic potential of cadmium microbial electrolysis cells, and the catholyte pH is -0.51 Volts, and not more than 8.0, respectively.