NOVELTY - A 1,4-dioxane-containing organic wastewater (1) is processed within an aerator (2) containing activated sludge and in aerator (4) containing microorganism support. 1,4-Dioxane is decomposed by the microorganism support at preset condition to obtain process liquid (5). Liquid (5) is subjected to solid-liquid separation process and separated into treated water (7) and thickened sludge (8). The thickened sludge is returned to aerator (2), in the biological treatment of 1,4-dioxane-containing organic wastewater.    USE - Biological treatment of 1,4-dioxane-containing organic wastewater e.g. wastewater of manufacturing plant of chemicals and semiconductor, leachate of garbage land reclamation field and sewage.    ADVANTAGE - The method enables stable and rapid biological treatment of 1,4-dioxane containing organic wastewater and decomposition of 1,4-dioxane.    DETAILED DESCRIPTION - A 1,4-dioxane-containing organic wastewater is processed within an aerator (2) containing an activated sludge to obtain process liquid (3). Liquid (3) is introduced into aerator (4) containing microorganism support which supports the microorganisms which decompose 1,4-dioxane and activated sludge. The 1,4-dioxane in liquid (3) is decomposed by the microorganism support in presence of the activated sludge to obtain process liquid (5). Liquid (5) is subjected to solid-liquid separation process and separated into treated water and thickened sludge. The thickened sludge is returned to aerator (2), in the biological treatment of 1,4-dioxane-containing organic wastewater. An INDEPENDENT CLAIM is included for biological treatment apparatus of 1,4-dioxane containing organic wastewater.    DESCRIPTION OF DRAWING(S) - The drawing shows the flowchart of biological treatment of 1,4-dioxane containing organic wastewater. (Drawing includes non-English language text)    Dioxane-containing organic wastewater (1)    Aerators (2,4)    Process liquid (3,5)    Solid-liquid separator (6)    Treated water (7)    Thickened sludge (8)