Mechanical Operations
Filter aids like asbestos, kieselguhr, diatomaceous earth etc. are used to increase the porosity of the final filter cake & reducing the cake resistance during filtration. Filter aid is

Added to the feed slurry
All of these
Separated from the cake by dissolving solids or by burning it off
Precoated on the filter medium prior to filtration

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Mechanical Operations
Higher is the mesh number, smaller will be the aperture size of the screen. It means that the aperture size of a 200 mesh screen will be smaller than that of 20 mesh screen. This is valid for

German standard screens (DIN 1171) etc
British standard screens
All of these
American standard screens (ASTM and Tyler standard screens)

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