Method for removing heavy oil by dense medium surface modifying process

The invention discloses a technical method applicable to removal of heavy oil in sewage. The technical method is that dense medium magnetic powder subjected to surface modification is used as a carrier; electric charge is combined and absorbed by the surface of the magnetic powder, and the effect of a coagulant is achieved; the heavy oil in suspension state in sewage can be absorbed by the magnetic powder; a tower-shaped magnetic system is additionally arranged at the bottom of a pond in an efficient separating area, so that the settling velocity of the magnetic powder can be increased; the hydraulic load in the separating area is up to 25 to 50m/h, and therefore, the area used can be greatly reduced; the magnetic powder absorbing oily mud can be recycled through a magnetic powder recovering system. According to the method, the recovery rate of the magnetic powder is up to 99%; the removal rate of the heavy oil is more than 85%.