Disclosed herein is a single pass cross flow filtration system comprising : a filtration module comprising two or more filtration segments fluidly connected in series, each having an upstream side and a downstream side; wherein each filtration segment comprises hollow fiber filter membranes, and wherein, when in use, the desired permeate flux is controlled by a configuration comprising; each filtration segment having a selected length; the hollow fiber filter membranes of each filtration segment having a selected inner diameter, wherein the selected inner diameters may be the same or different, provided that at least one of the selected inner diameters differs from the others, and provided that the two or more filtration segments are arranged such that no inner diameter is larger on the upstream side; and one or more pumps, mounted in the permeate channel.