12. Vacuum Drum Filters Rotary vacuum filter drum consists of a drum rotating in a tub of liquid to be filtered. The technique is well suited to high solids liquids that would blind or block other forms of filter. The drum rotates through the liquid and the vacuum sucks liquid and solids onto the drum pre-coat surface, the liquid portion is "sucked" by the vacuum through the filter media to the internal portion of the drum, and the filtrate pumped away.

The solids adhere to the outside of the drum, which then passes a knife, cutting off the solids and a small portion of the filter media to reveal a fresh media surface that will enter the liquid as the drum rotates. The knife advances automatically as the surface is removed.