Abstract: Phosphatic wastes produced during the mining and beneficiation of phosphate ore are concentrated by treatment in a crossflow filter under conditions which prevent the formation of a filter cake on the filtering surface. Slimes having an initial concentration of suspended solids, usually less than about 5% suspended solids, can be treated in series of crossflow filters to concentrate the solids to 24% or higher. In one embodiment a series of three spiral-wound crossflow filters followed by a fourth stage tubular crossflow filter is used to concentrate a slime having about 3% suspended solids to a concentrate having 30% or more suspended solids. By maintaining the linear velocity over the surface of the filter medium at 5 ft/sec. or higher a relatively high permeation rate can be achieved while producing a permeate having an extremely low suspended solids concentration. Proper selection of filter medium and flow rates can produce permeates having a turbidity less than about 5 Jackson Turbidity Units.