Abstract: Apparatus for and a method of reducing solids and controlling surges in the flow of effluent from the clarifier chamber of an aerobic wastewater treatment plant. The apparatus is mounted inside the clarifier chamber of the wastewater treatment plant and connected to an outlet pipe of the plant. The apparatus includes a cylindrical tubular weir positioned in a cylindrical housing connected to the outlet pipe of the clarifier. The surge control weir assembly restricts the flow of the effluent from the clarifier resulting in an accumulation of effluent in the surge control weir assembly from which it flows at a rate proportioned to the volume retained in the assembly and resulting in a settling of minute suspended solids in the clarifier chamber. The surge control weir provides a final screening of the effluent through aerobic bacteria which grow in the slots of the assembly to digest the last solid particles from the water as the water slowly passes through the assembly.