for bulk fluid flow over upstream surface 20 of the filtration medium cross flow filtration through the filtration medium and filtrate collection from the downstream side such a configuration may reduce air entrapment on the bulk fluid side of the filtration medium a suitable housing configuration of this type in accordance with the present invention is illustrated in the drawing as containing a planar filtration medium and is now described in the context of bulk fluid flow as depicted in fig1 with reference to fig2 a bulk fluid enters preferred apparatus 10 through an inlet port 30 in housing member 18 and is spread laterally from the conveniently centrally located inlet port to ends 32 34 of a distribution groove 36 formed in member 18 the distribution groove or manifold is spaced apart from filtration medium 12 by a wall portion 38 of housing member 18 so as to prevent the entering bulk fluid from encountering the filtration medium fluid flow into manifold 36 is advantageously from a direction countercurrent to flow through filtration medium 12 depicted in fig3 and circumvents the filtration medium until fluid contact with upstream surface 20 of the filtration medium occurs housing member 16 has recessed areas 40 for channeling fluid flow separated by ribs 42 for bearing upon upstream surface 20 of the filtration medium ends 44 of channels 40 overlie and are in fluid communication with distribution manifold 36 and.