Abstract: An assembly for separating particulate matter from an influent carrier comprises a perforated plate for separating an inner compartment from an outer compartment, and for transferring the influent between the inner and outer compartment with a minimum amount of a convective momentum that is associated with disturbing the settling matter. In practicing the process, suspensions are introduced into the assembly at the inner compartment. An agitator subassembly, within the inner compartment, sequentially fast mixes and slow mixes the influent to respectively insure mixing of the influent with additives and to promote agglomeration of the suspensions. Flow paths in the perforated plate function to cancel all velocity components of the momentum, except for vertical downward acting velocity components, thereby maximizing the rate of settlementation.