Abstract: A method of treating a fluid containing matter in suspension and/or in solution by using separation membranes, in which method a "feed" additive for adsorption and/or filtration purposes is added to the fluid to be treated, and a "backwash" additive for the purpose of improving backwashing is added to the membrane backwash fluid, wherein a backwash additive is chosen that is capable of being neutralized by the feed additive, the backwash fluid which contains the backwash additive and which has washed away unused feed additive is collected as a backwash discharge, the backwash discharge is allowed sufficient contact time to enable neutralization to take place in said discharge, and the resulting product is separated into a residual product that is concentrated in solid matter and a fluid that is recycled to the inlet of the installation.

Abstract: The invention relates to an extrusion plate for the production of membranes of an organic material including at least one longitudinal passageway. This extrusion plate includes an annular body (1) provided with a cylindrical cavity into which opens at least one radial fluid conduit (5), an upper ferule (3) adapted to be inserted into the cavity of the body and comprising at least one hollow needle (8) extending in the extension of said insert and a longitudinal centering fluid feed conduit (9), and a lower insert (4) adapted to be inserted into the cavity of the body and having a bore (6) defining an extrusion chamber around the needles (8). The upper (3) and lower (4) inserts are in abutment at assembly faces at the level of which open the fluid conduits (5), and a fluid passage (7) is provided on these opposing faces in continuity with the passages (5), for communicating with the extrusion chamber.