The present invention is three phase separation technology for treating oil-bearing sludge. Oil-bearing sludge is separated into three phases of oil, water and sludge, and the separated raw oil may be recovered. The separation process includes the successive steps of: adding sludge amendment in the amount of 600-1500 mg/L into oil-bearing sludge pumped into the sludge amending chamber for staying of 2-6 hr; collecting scruff from sludge in a airfloat machine; reacting the collected scruff with oil-water separating agent added in the amount of 800-1400 mg/L in a mixing reactor in 40-80 deg.c and continuous stirring for 8-10 hr; and separating the processed oil-bearing sludge in a static separator for over 10 hr to separate oil, water and sand. |