Frontal filtration with additives

Filtration is a general technique for separating two phases - liquid and solid - by passing them through a porous element.

The cake of porous elements, or media made up of one or more additives, retains the particles and allows a purified liquid called filtrate to flow freely. The system passes from a disordered state to a more ordered one. This operation consumes energy, which will determine the use of different filtration techniques.

Filtration processes are classified according to the following criteria :

• the force involved (vacuum filtration or pressure filtration, for example) ;

• particle size (coarse filtration, fine filtration) ;

• desired efficiency (clarifying or sterilizing filtration) ;

• filter media (diatomaceous earth precoat, cellulose plate, polypropylene or nylon cartridge filtration).

Frontal filtration, a technique adapted to lightly loaded liquids, involves applying a pressure gradient to the liquid to force it through the media. Additives can be of various kinds. The most common are cellulose and diatomaceous earth (kieselguhrs or perlites). After studying front-end filtration with additives, we'll move on to the special case of cheese-making brines.