Method for selectively degrading trace polycyclic aromatic hydrocarbon in water

The invention relates to a method for selectively degrading trace polycyclic aromatic hydrocarbon in water. According to the invention, a molecular imprinting modified catalyst (C) is prepared; a photo-catalytic reactor (6) with an ejector (4) on the top and an ultraviolet lamp (7) in the middle, a reflux water tank (33) with a high-speed mixer (32) inside, a coagulation and sedimentation tank (14) which is divided into a coagulation zone (15) and a sedimentation zone (17) inside by using a separation plate (16), and a membrane separator (21) are connected. The injector (4) injects the molecular imprinting modified catalyst (C), inlet water (A) comprising trace polycyclic aromatic hydrocarbon, and air (B) into the photo-catalytic reactor (6), such that a convection is formed with reflux water (G) entered from the bottom of the photo-catalytic reactor (6), and the molecular imprinting modified catalyst (C) is in a suspension state. With the method provided by the invention, trace polycyclic aromatic hydrocarbon in water can be continuously, stably and selectively degraded, and the molecular imprinting modified catalyst (C) can be circulated or recycled. Also, frequent backwash to the membrane separator (21) is not needed.