Abstract: A container is provided that is disposable, for first collecting blood delivered from a patient, preferably by a vacuum draw of blood into a container, and then the blood in the container is treated. The treatment is provided by an at least partial a back-and-forth or reciprocating motion of blood along membranes, such that filtrate components of the blood pass through the membrane walls and are collected, whereby retentate components of the blood are retained, with the back-and-forth motion being provided by a substantially constant vacuum draw, that provides a pumping action by a diaphragm pump. A replenishment liquid is automatically added, substantially proportional to the amount of filtrate components of the blood that are withdrawn. The membranes are protected by a device which removes body fat or other potentially harmful materials.