Abstract: The efficiency of membrane separation is enhanced in a hyperfiltration process by scooping off controlled amounts of the boundary layer at desired points along the flow path where useful concentrations have been achieved avoiding the necessity of bringing the entire flow up to desired concentration. The use of porous stainless steel supports with membranes formed therein in situ after fabrication from the pipe sections in a single pass configuration is especially advantageous with scoop apparatus spaced along the length of the stainless supports.