Abstract: A scum removal system for a sewage treatment or clarification tank having a feedwell or skimmer flight includes a scum trough disposed within the settling tank. A floating weir is disposed proximate to the scum trough. A membrane or sheet is partially wrapped or wound about the weir, at least one cable being connected to the membrane for pulling the membrane and concomitantly lowering the weir entrained therewith to permit surface scum to enter the trough from the settling tank. A mechanism for exerting increased tension on the cable to thereby lower the weir below the surface of the liquid in the clarification tank includes a camming lever or arm and an actuator. The lever is connected to the cable, while the actuator is mounted to the feedwell or a skimmer wiper arm so as to engage the camming lever and pivot the actuator lever about an axis.