By processes of solid-liquid separation or separation of macromolecule of different species, one of the technologies that is affirming even more is the use of porous semi-permeable membranes.
These filtering processes operate continually with reduced energy-consumptions, they do not involve phase’s changes, they do not require the add of chemical and/or filter aids substances, they can be conducted to a ambient temperature and they can operate until a molecular level.
By a classic filtration the liquid to filtrate crosses the filter-surface only in a perpendicular way (frontal).
By a cross-flow filtration, where the filter-surface is set up from a semi-permeable membrane, the liquid to filtrate that crosses the filter-surface has also a flow which is parallel to itself.
In this way you can assure middling in the time a great filter-surface cleanliness, preventing that on this last a coat of stopping material forms and accumulates (membrane fouling).
According to the size of the semi-permeable membrane’s pores you can talk of micro filtration, ultra filtration, dwarf filtration, reverse osmosis.
The membranes can be selected on the ground of the most different separating requirements, making possible both the recovery of the interest solution and the formation of an effluent with a organic load which is practically null to recycle in the process or to get rid of without other treatments.