NOVELTY - Wastewater is filtered in sedimentation tank, supernatant is extracted to anaerobic tank, anaerobic treatment is carried out, resultant product is provided into anoxic tank, denitrification process is carried out, denitrified product is provided into aerobic tank, activated sludge is added and mixed. Resultant product is provided into secondary sedimentation tank, sodium alginate solution and polyferric sulfate are added, processed, resultant product is provided into tertiary sedimentation tank, immobilized microorganisms are added, processed, and sterilized.    USE - Wastewater treatment (claimed).    ADVANTAGE - Wastewater is economically treated by simple and environmentally-friendly process. Ornamental fish can be efficiently grown in treated odorless water.    DETAILED DESCRIPTION - Wastewater is filtered in sedimentation tank for 8 hours, such that large-sized floating debris and other impurities are settled, supernatant is extracted into anaerobic tank and anaerobic treatment is carried out. Resultant product is provided into anoxic tank and denitrification process is carried out, in which denitrification rate is more than 80%. Denitrified product is provided into aerobic tank, activated sludge is added and mixed, such that carbon-containing organic pollutants are removed. Resultant product is provided into secondary sedimentation tank, 15-20 mg/L sodium alginate solution and 15-20 mg/L polyferric sulfate as coagulant aid are added and processed. Resultant product is provided into tertiary sedimentation tank, immobilized microorganisms are added and processed. Resultant product is provided into sterilizing tank, 5 mg/L chlorine dioxide as disinfectant, dodecyldimethylbenzylammonium bromide as sterilizing agent and 80 mg/L additive are added, mixed and processed. Additive is prepared by adding polymaleic acid and hydroxyethylidene diphosphonic acid in a ratio of 1:1, zinc chloride and water, mixing, adjusting pH value to 10 using 10 pts. wt. borax buffering solution, adding polyvinyl alcohol, stirring at 110 degrees C for 5 hours, adding dodecyldimethylbenzylammonium chloride, crushing, adding epoxy resin and mixing. The molar ratio of polymaleic acid and hydroxyethylidene diphosphonic acid, zinc chloride, polyvinyl alcohol, dodecyldimethylbenzylammonium bromide, epoxy resin and water is 15:30:9:10:5:35. Sodium alginate solution is prepared by providing 1 kg dried seaweed, cutting into small pieces, performing steam explosion treatment under pressure of 1 MPa for 10 minutes, adding 10 L of 2 wt.% sodium carbonate solution to treated seaweed, maintaining at 45 degrees C for 1 hour, 10 kg water is added, stirred and filtered.