NOVELTY - Treating wastewater, comprises e.g. removing impurities from wastewater by passing through screen, bio-adsorbing organic matter of sludge components by transferring into a bio-adsorption tank, precipitating organic matter in a bio-adsorption precipitation tank and transferring to an anaerobic sludge digestion tank, biologically treating in biological treatment tank and a final precipitation tank, anaerobically digesting by transferring precipitated and separated sludge to the anaerobic sludge digestion tank, releasing the dehydrated sludge cake, and treating by anaerobic ammonium oxidation.    USE - The method is useful for treating waste water (claimed).    ADVANTAGE - The method saves energy of greater than or equal to 50%; and reduces greater than or equal to 70% amount of sludge (claimed).    DETAILED DESCRIPTION - Treating wastewater, comprises (a) removing impurities from wastewater by passing through a screen, (b) bio-adsorbing organic matter in the sludge components by transferring the impurities removed wastewater into a bio-adsorption tank (21), (c) precipitating organic matter adsorbed bio-sludge by a bio-adsorption precipitation tank (22) and transferring to an anaerobic sludge digestion tank, (d) biologically treating by discharging after removing contaminants including organic matter, solids and nitrogen through a biological treatment tank (31) and a final precipitation tank (32), (e) anaerobically digesting the sludge by transferring the precipitated and separated sludge from the bio-adsorption precipitation tank and precipitated and separated excess sludge from final precipitation tank of biological treatment process to the anaerobic sludge digestion tank (41) for producing biogas, dissolving nitrogen and moisture within the sludge, and removing the organic matter by decomposing bio-sludge of the bio-adsorption precipitation tank and excess sludge of bio-adsorption precipitation tank of biological treatment process introduced into the anaerobic sludge digestion tank, and (g) releasing the dehydrated sludge cake by dehydrating the sludge to the moisture content of 70-80% from a dehydrator when the discharge of anaerobic digestive fluid by anaerobic digestion from the anaerobic sludge digestion tank is complete, where the anaerobic digestion effluent includes high concentration of nitrogen and phosphorus during dehydration from the dehydrator, and anaerobic digestion effluent is removed by chemical flocculation or by pressure increase. The nitrogen present in the form of ammonium nitrogen is removed by anaerobic ammonium oxidation process by performing nitrite forming reaction and anaerobic ammonium oxidation reaction. The anaerobic ammonium oxidation treatment is processed by reducing nitrogen load of wastewater treatment plant through enhancing biological treatment, and increasing energy independent rate of sewage treatment plant to maximize biogas energy production through anaerobic digestion by bio-absorption while reducing amount of sludge and amount of energy required for aeration. An INDEPENDENT CLAIM is also included for device for treating waste water mentioned above.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic representation of the device for treating waste water.    Bio-adsorption tank (21)    Bio-adsorption precipitation tank (22)    Biological treatment tank (31)    Final precipitation tank (32)    Anaerobic sludge digestion tank (41)