NOVELTY - A gas-liquid contact part with its cross-sectional shape changing continuously, with axially expanding flow paths, connected to an oxygen supply chamber is formed in a treatment tank. Fat and oil suction pipes, whose one end contacts water surface and other end opens to oxygen chamber suctions fats and oils. Gas-liquid contact is enabled by suctioning fats and oils in oxygen supply chamber and by mixing with air bubbles.    USE - As fat-splitting purifier for degradation-purification of fats and oils in waste water from kitchens, restaurants and hotels.    ADVANTAGE - The apparatus carries out the decomposition-purification of fats and oils in waste water, by using aerobic degradation microorganism which is activated efficiently. Fat and oil wastes floating on surface of waste water in the grease trap installed in kitchens and cooking area in hotels and restaurants is accumulated and decomposed. The sludge precipitated at the bottom is separated and only purified waste water is drained out.    DETAILED DESCRIPTION - The fat-splitting purifier (10) is immersed in waste water tank, and it performs degradation-purification of fats and oils in waste water. A gas-liquid contact part (12) is formed in a vertical flow path of waste water and on the lower part of the gas liquid contact part, an oxygen supply chamber (13) is connected. One or more surface fat and oil suction pipes (17) are arranged on the waste water tank, whose one end (17a) contacts the waste water surface and other end opens to the oxygen supply chamber and one end of gas liquid contact part. A pressurized air supply unit (19) and an air bubble generating unit (18) connected to it, supplies air into the oxygen chamber. The gas-liquid contact part comprises an inlet and an outlet, such that its cross-sectional shape in-between the two parts, changes continuously. In the gas liquid contact part, deforming flow paths which carry out axial expansion, are arranged. The gas bubbles from oxygen supply chamber rise continuously through the deformation part to the surface outlet (21a). Gas-liquid contact for aeration and degradation of fats, is enabled by suctioning the fats and oils near the waste water surface, in tank, from the upper end opening of the fats suctioning pipe, by a drift condenser, receiving in the oxygen supply chamber and mixing with the air bubbles. An INDEPENDENT CLAIM is also included for the grease trap used in the fat-splitting waste water purifier.    DESCRIPTION OF DRAWING(S) - The figure shows front elevation of fat-splitting purifier in waste water treating installation.    Fat-splitting purifier (10)    Gas-liquid contact part (12)    Flange parts (12a,12b)    Oxygen supply chamber (13)    Housing (14)    Fat and oil suction pipe (17)    Surface opening (17a)    Air bubble generating unit (18)    Pressurized air injector (19)    Exit cone of gas-liquid contact part (21a)