The disclosed method and apparatus separates solid impurities from a fluid containing solid impurities. The method and apparatus allow the introduction of influent comprising a fluid containing solid impurities into a plurality of channels and allowing at least a portion of the solid impurities initially present in the influent to settle on upward-facing surfaces of a plurality of plates forming the channels or slide down the upward-facing surfaces, while permitting fluid, which has been depleted of at least a portion of solid impurities, to flow upward toward the top edges of the plurality of plates. The influent is introduced into the plurality of channels in a manner that inhibits a disrupting or disturbing of the solid impurities, which have separated from the influent.

Described are systems, methods, and kits for compression sedimentation and whole blood separation. For example, a compression sedimentation system may include a compression stage configured to accept a flexible reservoir configured to contain a liquid mixture. The compression stage may include a base substrate and a compression substrate configured to apply a force to the flexible reservoir effective to create a pressure in the liquid mixture. An apparatus for whole blood separation may include a sedimentation system that separates whole blood into a supernatant including platelet rich plasma and a subnatant including red blood cells. At least one platelet-concentrating device may be included to receive the supernatant including the PRP and to separate a platelet concentrate and a platelet poor plasma from the supernatant.