Patent ID: 7179636

Claim:
A method of filtering with a filter comprising a housing (2) in which there are arranged, parallel to one another, a plurality of hollow fibers (3), the porous wall (3a) of each of which determines an aperture (4) so that said means comprises an internal path (A) consisting of the plurality of the parallel apertures (4) of said respective hollow fibers and an external path (B) corresponding to the volume available between the fibers and the housing, for treating a starting liquid sample of large volume comprising, in the dilute state, a plurality of microorganisms of different sizes, to obtain a final liquid sample of small volume, comprising, in the concentrated state, the same relative composition of microorganisms, said method comprising, during at least one concentrating step, the steps of: a. using a single filtering means b. using said means in frontal mode, c. determining the cut-off threshold of the porous wall (3a) of the fibers, so as to retain the smallest-sized microorganism of the starting sample, and, discontinuously: d. introducing during a filtering phase, all of the starting liquid sample through the internal path (A) of the filtering means, removing a filtrate via the external path (B) of the filtering means, and accumulating a concentrate in said path via which the liquid sample was introduced, e. during a collection phase, having passed all of the starting liquid sample, halting the passage of this sample through the filtering means (1) from said path to said other path and obtaining the outlet liquid sample, namely the concentrate, f. circulating during a backwash phase, a liquid flow which may be free of microorganisms from said path to said other path.