A rotary disc filtration device having a fluid filtration gap between a filtration surface and a disc is disclosed. The disc and/or filter has one or more spiral grooves in fluid communication with fluid in the gap. The disc and/or filter is rotated and one or both may be axially oscillated and/or vibrated to create the shear at the filter surface that increases permeate flux through the filter. Several discs and filters may be interleaved to increase filtration device capacity and make more efficient use of equipment space. In such a device, the discs can be mounted on a common shaft for rotation in unison and can have spiral grooves on both major faces of each disc. The filters are held stationary in that device and are fluidly connected to facilitate collection of the permeate.