Briefly describe the arrangement of multilayer filter media in multilayer filter media. Why is this arrangement?

Hello, multi-media filter (filter bed), that is, a media filter with two or more media as the filter layer, is used to remove impurities and absorb grease. In the industrial circulating water treatment system, the water quality can meet the requirements of recycling. The function of filtration is mainly to remove suspended or colloidal impurities in water, especially to effectively remove tiny particles and bacteria that cannot be removed by precipitation technology. There are two-layer and three-layer filters commonly used. Traditional double-layer filters usually use anthracite in the upper layer and quartz sand in the lower layer. With the development of technology, quartz sand can be replaced by garnet with better performance (greater hardness and better acid and alkali resistance). The principle and structure of three-layer filter media are similar to that of double-layer filter media bed, which is equivalent to adding a layer of filter media with higher relative density and smaller particles, usually garnet or magnetite.

This arrangement is mainly due to the fact that the granular layer of the filter material is in the state of large bottom and small bottom, which is beneficial to the filtration process, because when the inlet water enters from the upper part, it first meets the anthracite filter material with larger particles, and the filtration can penetrate into the filter layer to remove the larger particulate impurities in the water. Smaller particles in the lower layer can also intercept a part of sludge and small suspended solids, which plays a role in ensuring the quality of effluent. Moreover, the proportion of filter materials from top to bottom is getting larger and larger, and no mixing layer will be caused during backwashing, so that each filter material can play its role.

I hope it helps you!