Abstract: An improved membrane separation system is provided, which comprises a plurality of discrete membrane separation units, each membrane separation unit:(a) comprising at least two membranes;(b) comprising inlet for process fluid and, optionally, outlet for process fluid; and(c) being located within a container for permeate, said container comprising a permeate outlet,and wherein the container is such as to enable the membrane separation units to be at least partially immersed in permeate.Also provided is a method of membrane separation utilizing such a system.