Experimental data on the pressure gradient-dependent flux through UPM-50M, UFM-50, OPMN-P, and OFAM-K membranes in the separation of molasses distillery slop have been obtained. During the separation of the molasses distillery slop, a dynamic fluid membrane forms above the surface of the active layer on the test semipermeable membrane, which is compacted with increasing pressure and serves as an additional membrane. Evidence has been presented that the reverse osmosis membrane OFAM-K is superior for use at an effective working pressure of P = 4.0 MPa in the separation of the molasses distillery slops to the OPMN-P, UPM-50M, and UFM-50 membranes in terms of performance criteria (environmental friendliness, economy, import substitution, production of a discolored flow (volume) of permeate with good solute permeation and retention parameters) based on the results of statistical processing of experimental data.