Abstract: A filtration system having: (a) a recirculation loop, (b) a pump, (c) a waste outlet, (d) a valve separating the loop from a waste outlet (d) a control device for said valve, (e) a membrane pressure vessel comprising a feed port, concentrate port and permeate port, and hyperfiltration elements in an axial direction, including an end hyperfiltration element nearest an inlet port or outlet port, (f) a flow distributor located between said end hyperfiltration element and said fluid port to provide a velocity profile with a coefficient of variation of less than 0.1 or a flow resistance of between 10 and 200 kP·sec·m?1, (g) wherein the flow distributor has a proximal surface nearest the end hyperfiltration element and a distal surface nearest said fluid port, and (h) an axial positioner that locates said distal surface at least 50% of the distance between the end hyperfiltration element and the port.