A disposable kit for washing a suspension of cellular material containing target and non-target components comprising: a) a spinning membrane separator having an inlet for flowing the suspension of cellular material to be washed and a wash medium into the spinning membrane separator, a first outlet for flowing retentate comprising a target component from the spinning membrane separator, and a second outlet for flowing filtrate comprising a non-target component of the cellular suspension and wash medium from the spinning membrane separator; b) a container for receiving the retentate; c) a container for receiving the filtrate; d) a container of the wash medium; and e) a flow control cassette comprising a housing and having a first fluid pathway with a first inlet configured to be in fluid communication with a source of the suspension of cellular material to be washed, a second inlet configured to be in fluid communication with the container of wash medium, and an outlet in fluid communication with the inlet of the spinning membrane separator; a second fluid pathway with an inlet in fluid communication with the first outlet of the spinning membrane separator for flowing retentate, a first outlet in fluid communication with the container for receiving the retentate, and a second outlet in fluid communication with a first syringe; a third fluid pathway with an inlet in fluid communication with the second outlet of the spinning membrane separator for flowing filtrate, a first outlet in fluid communication with the container for receiving the filtrate, and a second outlet in fluid communication with a second syringe; at least one device (78, 80, 82, 84, 86, 88) for selectively occluding the fluid pathways associated with each of the first, second and third fluid pathways (54, 62, 70); and at least one fluid interface detector (90, 92, 94) associated with each of the first, second and third fluid pathways. a) a spinning membrane separator having an inlet for flowing the suspension of cellular material to be washed and a wash medium into the spinning membrane separator, a first outlet for flowing retentate comprising a target component from the spinning membrane separator, and a second outlet for flowing filtrate comprising a non-target component of the cellular suspension and wash medium from the spinning membrane separator; b) a container for receiving the retentate; c) a container for receiving the filtrate; d) a container of the wash medium; and e) a flow control cassette comprising a housing and having a first fluid pathway with a first inlet configured to be in fluid communication with a source of the suspension of cellular material to be washed, a second inlet configured to be in fluid communication with the container of wash medium, and an outlet in fluid communication with the inlet of the spinning membrane separator; a second fluid pathway with an inlet in fluid communication with the first outlet of the spinning membrane separator for flowing retentate, a first outlet in fluid communication with the container for receiving the retentate, and a second outlet in fluid communication with a first syringe; a third fluid pathway with an inlet in fluid communication with the second outlet of the spinning membrane separator for flowing filtrate, a first outlet in fluid communication with the container for receiving the filtrate, and a second outlet in fluid communication with a second syringe; at least one device (78, 80, 82, 84, 86, 88) for selectively occluding the fluid pathways associated with each of the first, second and third fluid pathways (54, 62, 70); and at least one fluid interface detector (90, 92, 94) associated with each of the first, second and third fluid pathways.