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The next group of equipment types to be covered in this Section are all vacuum driven, and nearly all are intended for solids recovery, rather than for decontamination purposes. The simplest vacuum filter is the laboratory Büchner funnel, and the simplest practical embodiment of that is the Nutsche filter, which is found widely distributed throughout a range of industries, taking advantage of its simple, batch format.

The Nutsche filter is a vertical vessel, divided into two chambers by a horizontal perforated plate roughly at its mid-point. This plate may itself be the filter medium, or a sheet of finer medium may be laid onto the plate. In its simplest form, the
upper chamber of the filter is an open feed chamber, into which the feed suspension is poured or pumped. The enclosed lower chamber is the filtrate receiver, to which the vacuum connection is made (at a level above that of the top of the batch of filtrate) to draw the filtrate through the filter medium, leaving the suspended solids from the feed as a cake on the upper surface of the filter medium. This cake will then be dug out of the filter, or lifted out on a removable filter medium, or tipped
out by turning the whole filter unit through 180°.

Filtration in a Nutsche filter will probably start with some sedimentation of the fastest settling solids onto the filter medium, and then filtration under suction of the rest of the suspension. More complicated versions will include a vertically rotating shaft in the upper chamber carrying blades that will smooth out the forming cake or scrape out the formed cake. The upper chamber can be closed, so that the filter can then be operated under pressure rather than vacuum. The most complex form has the capacity to carry out a chemical reaction in the upper chamber, resulting in the precipitation of a solid product, followed by its washing free of reactants, and then sucking dry by the passage of air through the cake, before it is removed from the filter chamber.

The washing of a Nutsche filter cake must be done carefully to avoid the creation of channels through what is usually quite a thin cake, and also to avoid the mixing of filtrate and wash liquor if that is undesirable.