NOVELTY - Organic wastewater (11) is introduced into an anaerobic tank (1a) of a biological treatment tank (1) consisting of an equalizing tank (6), a denitrifying tank (1b), and an aerobic tank (1c), and biological dephosphorylation-denitrogenation is carried out. The effluent (12) of tank (1) is separated into treated water (20) and sludge. Some activated sludge in tank (1a, 1b or 1c) is supplied for liquefying. A portion of activated-sludge liquid mixture (15) of tank (1a) is solid-liquid separated, and phosphorus is recovered from the supernatant (17).    USE - Processing of organic wastewater, such as foodstuff wastewater with high phosphorus concentration.    ADVANTAGE - The method prevents increase in phosphorus and chemical oxygen demand in treated water, reduces generation amount of surplus sludge, and increases ozone utilization efficiency.    DETAILED DESCRIPTION - Organic wastewater (11) is introduced into an anaerobic tank (1a) of a biological treatment tank (1) consisting of an equalizing tank (6), an anaerobic tank, a denitrifying tank (1b), and an aerobic tank (1c), and biological dephosphorylation-denitrogenation is carried out by activated sludge. The wastewater is processed through anaerobic tank, denitrifying tank, and aerobic tank. The effluent (12) of biological treatment tank is solid-liquid separated into treated water (20) and sludge. The separated sludge (13a) is returned to the anaerobic tank. Some activated sludge in the anaerobic tank, denitrifying tank, or aerobic tank is supplied for liquefying process by ozone. The liquefied activated sludge (13b) flowing out of the liquefying apparatus (3) is supplied to an equalizing tank, and souring is carried out by stirring and mixing. The effluent (21) of equalizing tank is supplied to the anaerobic tank with organic wastewater. A portion of activated-sludge liquid mixture (15) of the anaerobic tank is introduced into anaerobic-tank mixed-liquid solid-liquid separation tank (4) and solid-liquid separator. The separated sludge (16) is returned to the denitrifying tank, and the supernatant (17) is supplied to a phosphorus recovery equipment (5). Phosphorus (19) is recovered as hydroxyapatite by hydroxyapatite crystallization. The liquid (18) after phosphorus recovery is returned to the denitrifying tank. An INDEPENDENT CLAIM is included for organic-wastewater-processing apparatus.    DESCRIPTION OF DRAWING(S) - The drawing shows a flow sheet of the processing method of organic wastewater. (Drawing includes non-English language text)    Biological treatment tank (1)    Anaerobic tank (1a)    Denitrifying tank (1b)    Aerobic tank (1c)    Liquefying apparatus (3)    Anaerobic tank-mixed-liquid solid-liquid separator (4)    Phosphorus recovery equipment (5)    Equalizing tank (6)    Organic wastewater (11)    Biological treatment tank effluent (12)    Return sludge (13a,13b)    Liquefying-process effluent (14)    Anaerobic-tank liquid mixture (15)    Anaerobic-tank liquid mixture separated sludge (16)    Anaerobic-tank liquid mixture supernatant (17)    Liquid from phosphorus recovery equipment (18)    Phosphorus (19)    Treated water (20)    Equalizing tank effluent (21)