Suitable for use in water which has a solid diameter grater 15 mm at narrow and depth less. Concave portion of circularly produced screen is placed in the Water inlet direction at the channel. Solids hold on the screen surface removed from the system with circular motions by the harrow which moving on the screen surface. Dredged wastes are discharged to the waste collection container. Harrow is not intercept the water flow by staying in top position when the system is not cleaning time.