What Should Be Considered When Selecting Filter Media for Multi-media Filters?

It should be noted that while multi-media filters simplify pretreatment systems to some extent, they cannot replace other necessary filters; this depends primarily on the raw water conditions. If tap water is used, a filter is usually unnecessary, and an activated carbon filter can be used directly. If deep well water is used, the content of variable-valence ions such as iron and manganese is very low, so a multi-media filter is sufficient. If shallow well water from riverbeds is used, a fine sand filter should be installed for pre-filtration. If surface water is used, coagulation and multi-stage filtration are necessary.

The filter media of multi-media filters (including dual-media filters) should have sufficient chemical stability, and the relative density and particle size of each media should have certain differences. For dual-media filters composed of anthracite and quartz sand, the anthracite has a relative density of 1.4-1.6 and a particle size of 0.8-1.8 mm, while the quartz sand has a relative density of 2.6-2.65 and a particle size of 0.5-1.2 mm. In addition to the above two types of filter media, three-media filters can also use heavy minerals such as manganese sand and magnetite, with a relative density of 4.7-5.0 and a particle size of 0.5-4 mm.