Abstract: The present concentration device includes a membrane module having a first and a second flow paths that are separated by a semipermeable membrane, the module including a U-shaped tube in which the semipermeable membrane is disposed, a first flow-path-inlet and a first flow-path-outlet connection parts, and a second flow-path-inlet and a second flow-path-outlet connection parts, the device including an introducing unit for introducing a subject solution with a predetermined pressure into the first flow path from the first flow-path-inlet connection part, separating the subject solution into a concentrate and a permeate through the semipermeable membrane, passing the permeate through the second flow path, draining the concentrate from the first flow-path-outlet connection part, introducing the subject solution with a pressure lower than the predetermined pressure into the second flow path from the second flow-path-inlet connection part, and draining a diluent diluted with the permeate, from the second flow-path

Abstract: A precipitation system for precipitating the target component is provided. The precipitation system includes: a reverse osmosis module; a precipitation device; a membrane separation device that includes a semipermeable membrane module including a first chamber and a second chamber separated by a semipermeable membrane, and that makes the feed solution after precipitation of the target component in the precipitation device flow to each of the first chamber and the second chamber and pressurizes the feed solution in the first chamber to transfer water into the second chamber via the semipermeable membrane and thereby concentrate the feed solution in the first chamber and dilute the feed solution in the second chamber; first return means for returning the feed solution concentrated in the membrane separation device to the precipitation device; and second return means for returning the feed solution diluted in the membrane separation device to the reverse osmosis module.