In contrast to a “sand filter,” which normally employs only one grade of sand as the filtration media, multimedia filtration refers to a pressure filter vessel that uses three or more distinct media. There are dozens of different media for various forms of filtration, whether it is to remove chlorine, oxidize iron and manganese, or correct pH and neutralize acid.
For thousands of years, they have been using carbon for filtering and cleaning. Depending on the type, they use carbon for adsorption or as an oxidation catalyst. Bituminous and anthracite coals, bone char, coconut shell, lignite, peat and wood are all sources of activated carbon media. By crushing, sorting and processing these raw materials at high temperatures, we make activated carbon. By using adsorption on the surface and pores of the carbon granules, we remove impurities from activated carbon. This activated carbon granulate is porous and has a large number of activation points both inside and outside. Granular and powdered activated carbon are the most popular types of activated carbon in water treatment. Many carbon block filters and point-of-use filters use powdered activated carbon. The most common are backwash and flow-through filter systems with activated carbon granules. It is common to use activated charcoal to improve the taste and smell of water. Hydrogen sulfide removal, chlorine and chlorine reduction, MTBE removal and PFAS removal are some of the applications. Regeneration requires only backwashing and rinsing. You do not require chemical regeneration.
Birm is a granular filter media that filters out iron and manganese from water. It contains an insoluble sacrificial layer that causes a reaction between dissolved oxygen and iron and/or manganese in the water supply. This activity oxidizes the iron and/or manganese and then filters it out. If iron or manganese remains after the Birm filter, it is in the form of iron bicarbonate and/or manganese. A water softener can easily remove these. For regeneration, you only require backwashing and rinsing. You don’t need chemical regeneration.
Filter Ag, also known as filter aggregate, is a granular filter material that eliminates turbidity in water. It can filter particles as small as 20 microns. Filter Ag is better than sand at removing sediments because it is lighter and uses less water for regeneration. Regeneration requires only backwashing and rinsing. You don’t need chemical regeneration.
Calcite is a white, marble-like calcium carbonate that is crushed and thoroughly sieved to increase the alkalinity, and therefore the pH, of the water supply. The corrosiveness of the feed water is eliminated by increasing the pH. Calcite dissolves in water to raise pH, but at the cost of increasing water hardness. Calcite needs to be added regularly as it is sacrificial due to its dissolving nature. A water softener is recommended as the calcite filter increases hardness. Calcite is also an effective material for removing iron hydroxide (turbid). A water softener is placed after the calcite filter to remove any hardness and iron bicarbonate that the calcite filter missed.