Abstract: A bar screening apparatus for the efficient screening and removal of solid materials from a liquid flow stream. The bar screen includes a plurality of bars that are disposed in substantially parallel adjacent relation to each other and each have an upstream face disposed at an acute angle to the direction of flow of the liquid flow stream for enhancing screening of even relatively thin solid waste materials without significantly impeding the flow stream. The bars of the screen preferably are formed with a plurality of flow apertures in their active region which further minimizes head losses in the system and enhances screening of solid materials. A power operated two-directional rake is provided for more efficiently removing solid material that accumulate on the bar screen. Projections on the rake engage the bar screen only in one direction of the rake's movement and means are provided for forcing a close-fitting relationship between the rake projections and the screen bars during the raking operation.

Abstract: A comminutor for comminuting solid materials carried by flowing fluids, such as industrial wastes or sewage, in which cutter elements carried by a plurality of rotating rings forming a cone shaped rotor co-act with stationary cutter elements supported alongside the rotor, and a method of comminuting. The stationary cutter elements are reversable so that upon repositioning, new stationary cutting edges are presented to the cutter elements carried by the rotating rings. A plurality of stationary cutter elements are formed on a single structure, each stationary cutter element forming a cutting station. The cutting action is further increased by providing co-acting cutting edges in planes perpendicular as well as parallel to the rotor axis at each cutting station.