In a device for separating solid particles from liquids and gases in flexible disposable plastic containers, a plurality of filter elements, consisting of flat, elongate support grids with filtrate drain channels and a covering, all-round closed filter medium, are connected to form a filter package and enclosed by a flexible plastic container. This disposable filter system is operated in a pressure vessel and can be compressed there by applying an external pressure in such a way that the residual volume of the suspension is considerably reduced. As a result of the stable design, backwashing of the filter elements is possible, which prevents the build-up of a dense layer of solid particles and can therefore lead to increased filtrate flow. As a result of the completely sealed, sterile filter elements, the increased filter surface area and the resulting high filter efficiency and complete filtration with reduced residual volume shares, this system proves to be a cost-effective filtration device with high flow rates, minimized cleaning costs and short changeover times when changing products.