NOVELTY - Treating sewage utilizing metal membrane co-processing to reach grade III water quality comprises e.g. sedimenting sewage, removing various chunks and processing heavy segments, trapping floating debris, carrying out biochemical treatment of the sewage for water quality regulation, trapping the particulate matter, trapping and separating the heavy metals by heavy metal adsorption process, trapping and separating the heavy metals by infiltration process, treating through biological filter microorganism biodegradation, passing through activated carbon filter and ultrafiltering.    USE - The method is useful for treating sewage utilizing metal membrane co-processing to reach grade III water quality (claimed).    ADVANTAGE - The method saves energy and is easy to operate.    DETAILED DESCRIPTION - Treating sewage utilizing metal membrane co-processing to reach grade III water quality comprises (i) sedimenting sewage, removing various chunks which cannot be subsequently processed and processing heavy segments; (ii) passing the sewage after sedimenting through mechanical grid through a pipeline, trapping floating debris and conveying only sewage into the water quality regulating system (iii) carrying out biochemical treatment of the sewage for water quality regulation, removing most of chemical oxygen demand (COD), biological oxygen demand (BOD), ammonia-nitrogen and suspended solids (SS), adding poly aluminum chloride, poly aluminum ferric chloride, basic aluminum chloride or polyacrylamide and removing total phosphorus in sewage, (iv) taking the resulting sewage obtained in step (iii) and trapping the particulate matter of diameter larger than the normal metal membrane pore size of membrane unit, (v) taking the resulting sewage obtained in the step (iv) and trapping and separating the heavy metals in the sewage by heavy metal adsorption process, (vi) taking the resulting sewage obtained in the step (v) and trapping and separating the heavy metals in the sewage by infiltration process, (vii) taking the resulting sewage obtained in the step (vi) and reducing the content of COD, BOD, ammonia nitrogen and SS content by passing through biological filter containing biodegrading microorganism, (viii) taking the resulting sewage obtained in the step (vii), carrying out deodorization and decolorization by passing through activated carbon filters and removing particulate matter, organic compounds and harmful substance while reducing the total nitrogen content to obtain water, and (ix) taking the resulting water obtained in the step (viii) and removing suspended substance, microorganism, bacteria, virus and organic macromolecule by ultrafiltration to obtain grade III water.