Normally, the filter materials have a grain size of 300-700 μm and the space between the particles is 25-500 μm. The ability to filter out grain sizes that are smaller than the "screening gap" depends on various influencing variables such as gravity separation, particle diffusion, hydrodynamics, particle absorption, etc. These variables are influenced by physical properties such as the filter size, filtration rate, temperature, filter material density, size and shape of the suspended particles, etc. Not to be forgotten are influencing variables such as electrostatic pulsating forces and the Van der Waals forces, in which electrons dipolarly react to subatomic particle movements. Then there are also the properties of the filter materials, including oxidative, reductive or neutralizing type.
All filter materials require a backwash to remove the filtered substances, some require regeneration agents and many have limitations and conditions of use with regard to the water constituents. As a consequence of the complex filtration processes, data on filtration rates are often only assumptions. The filter rates must be related to the adsorption criteria. Filter materials as well as the water constituents can show a small, medium or high surface area, which considerably influences the absorption properties for absorption and separation.
If the filtration rates are too high, a poor filtration effect can be expected.
The backwash raises the filter bed and depends on the density of the material.
Too low backwash speeds prevent a good cleaning of the filter bed and result in poor filtration during operation. Excessively high filter rates can lead to loss / flushing of the filter material.
Hardening / deacidification