FILTRATION

Filtration indicates the retention of particles from a gas or a liquid with a filter medium.

A distinction is made between surface filtration and depth filtration. Both filtration methods are applied for water and wastewater treatment.

Surface filtration:
The use of filter screens and reversible flow filters are always surface filter, where the particles are restrained on the surface of the filter medium. Another typical example of surface filtration is sludge drainage using belt filter press or chamber filter press. In this method, a filter cake is formed which supports filtration and thus provides a better filtration result.

Depth filtration:
In the depth filtration, the particles are restrained within the filter medium. Mostly granular materials such as filter sand used as filter medium. The particle to be filtered flow through the gaps in the filter medium until they come in contact with the medium and are stuck on its surface.