FILTERS: Screen or disc filters have mainly the function of retaining inorganic solid particles suspended in water, such as lime, fine sand and other slags, depending on the construction features of the filters.These filters are particularly suitable for very dirty water requiring frequent backwash.
In a disc filter, impurities are retained by the mesh that can be steel or plastic.
Disc filters have a filtering body composed by a stack (or column) of discs with rough surface. During operation, the discs are tightly held in cohesion and the suspended particles are retained by the interstices (or porosity) between the contact surfaces of the discs.
During backwash, the adherence between the discs is loosened, supporting the rapid removal of retained impurities.
In screen and disc filters the size of filtering net is expressed in “mesh”. The higher the value of this parameter is, the smaller the size of the particles retained will be.