FIELD: waste water treatment. SUBSTANCE: waste water containing suspended solid particles, ammonia nitrogen, phosphate, and biologically degradable substances is passed consecutively through aerobic biooxidation zone, intermediate sedimentation zone, oxygen-free zone, aerobic mixing zone, and final sedimentation zone wherein purified water and final sludge are separated. Part of final sludge is fed into oxygen-free anaerobic zone which receives volatile acid to release phosphate. Part of sludge and waste water recycle from oxygen-free anaerobic zone into oxygen-free zone. Another part of sludge is fed into fermentation zone to form volatile acid. EFFECT: improved separation of solids, reduced oxygen biological demand, and increased nitrogen and phosphorus removal. 32 cl, 33 dwg, 8 tbl, 2 ex
