A powder discharge system is installed in a circulating water tank for collecting powder generated when an exhaust gas is treated in an exhaust gas treatment apparatus. The powder discharge system includes at least one eductor provided in the circulating water tank. The eductor has a nozzle configured to throttle a flow of water supplied from a pump for pumping water in the circulating water tank, a suction port configured to suck water in the circulating water tank into the eductor by utilizing a reduction of pressure generated when the flow of water is throttled by the nozzle, and a discharge port configured to eject the water sucked from the suction port together with the water discharged from the nozzle toward a bottom of the circulating water tank.