The ZQXN peripheral drive full bridge type sludge suction machine is used in circular secondary sedimentation tanks of sewage treatment plants. The sludge settled at the bottom of the tank is scraped and collected to a set of suction pipe openings arranged along the radius direction, and then discharged through the central discharge pipe for sludge reflux or concentration dewatering. At the same time, the floating slag on the tank surface is directed towards the slag collection hopper and discharged outside the tank through the slag collection hopper for further treatment.