Abstract: Membrane filtration assembly where the fluid to be filtered is recirculated on the retentate side of a membrane filter and where the filtered fluid, i.e. the permeate, is recirculated on the permeate side of the membrane filter in such a manner that the two streams are cocurrently passed along the membrane filter. The membrane filter comprises several membrane units in form of tubular supporting structures, each supporting structure comprising one or more filter membranes. The membrane units are mounted in parallel inside a common housing in such a manner that one stream flows inside the membrane units while the other stream flows in a space surrounding said membrane units. Each membrane unit is provided with a separate space designed as a narrow passageway on the inner side defined by the membrane unit and on the outer side defined by a channel tube, the inner cross section of which is 4 to 200% larger than the outer cross section of the membrane unit.

Abstract: A plant and a method of treating milk so as to obtain milk with a low content of spores and bacteria. In a centrifugation unit (4) the milk is separated into a cream fraction (CR) and a skim-milk fraction. The skim-milk fraction is separated in a microfiltration unit (8) into a spore and bacteria-containing retentate (R) and a permeate (P) with a low content of spores and bacteria. The cream fraction (CR) is sterilized in a sterilizing unit (16), and the sterilized cream (STCR) or a portion thereof is mixed with the permeate (P) into standardized milk. The retentate is recirculated to the centrifugation unit (4) which is of the type separating the material into the cream fraction (CR), the skim-milk fraction (SM), and furthermore a sludge fraction (SL). The plant and the method ensure a high microfiltration capacity and the cheese formation properties of the milk is maintained.