TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Method: The method further involves: injecting air from a bottom of a space, which includes the anode, when treating the sewage wastewater by electrocoagulation; and stirring the treated water introduced into the mixing tank. The method further involves introducing a metal ion-reducing agent into the mixing tank in order to remove color from the treated water and enhance settlement of sludge generated by the electrocoagulation. In method (M1), the step of placing the electrode assembly in electrocoagulation tank is performed such that a space including the anode is larger than a space including the cathode. The method (M1) further involves injecting air from a bottom of a space, which includes the anode, into the electrocoagulation tank, in order to uniformly mix metal ions, generated by electrocoagulation, with phosphate ions contained in the sewage wastewater. The method (M1) further involves stirring the treated water introduced into the mixing tank, when further treating the treated water; introducing a metal ion-reducing agent into the mixing tank in order to remove color from the treated water and enhance the settlement of sludge generated by the electrocoagulation. Preferred Components: The electrodes are iron or aluminum electrodes, and the metal ion-reducing agent is sodium borohydride (NaBH4).    TECHNOLOGY FOCUS - INSTRUMENTATION AND TESTING - Preferred Components: The electrode assembly is placed in the electrocoagulation tank such that a space including the anode of the electrode assembly is larger than a space including the cathode. Preferred Apparatus: The apparatus further comprises an air injection device, which serves to inject air into electrocoagulation tank in order to uniformly mix phosphate ions of the sewage wastewater with metal ions dissolved from the electrodes, where the air injection device is placed at a bottom of the space including the anode; or a device which serves to introduce a metal ion-reducing agent into the mixing tank in order to remove color from the treated water and enhance the settlement of sludge generated by the electrocoagulation. In the apparatus, the anode and cathode of the electrode assembly are made of iron or aluminum, the porous membrane of the electrode assembly is made of nonwoven fabric, and the metal ion-reducing agent is sodium borohydride (NaBH4). In the apparatus, a distance between the porous membrane and the anode and a distance between the porous membrane and the cathode are such that migration of charges between them is possible, and a distance between the cathode and a partition wall of the electrocoagulation tank is shorter than a distance between the cathode and the partition wall of the electrocoagulation tank. EXAMPLE - No suitable example given.