What is a Multi-Media Filter?

Multi-media filter is a kind of equipment used for water treatment, mainly used to remove suspended matter, particulate matter, colloid and other impurities in water to achieve the purpose of purifying water quality. It usually uses two or more media as filter layers, such as quartz sand, anthracite, activated carbon, magnetite, etc. These media are arranged in layers and scientifically and orderly distributed in the filter tank according to their specific gravity and particle size.

Working principle of multi-media filter
The working principle of multi-media filter is based on deep filtration, that is, larger particles in the water are removed at the top layer, and smaller particles are removed at a deeper level in the filter medium. When the raw water passes through the filter material from top to bottom, the suspended matter in the water is intercepted by the surface of the filter layer due to adsorption and mechanical flow resistance; when the water flows into the middle of the filter layer, the sand particles in the filter layer are arranged more closely, so that the particles in the water have more opportunities to collide with the sand particles, so the flocculants, suspended matter and sand particles in the water adhere to each other, and the impurities in the water are intercepted in the filter layer, thus obtaining clear water quality.

Characteristics of Multi-media Filters
Wide Application: Multi-media filters are widely used in water treatment processes and can be used alone, but most of them are used as pre-filtration for deep water treatment (exchange resin, electrodialysis, reverse osmosis).
Pretreatment device: Multi-media filters are commonly used pre-treatment devices for deep water purification, and different filter materials can be added according to process requirements.
Various materials: Multi-media filters can be made of fiberglass, A3 steel or rubber lining, stainless steel. There are two modes of operation: fully automatic and manual. Automatic control generally uses imported automatic controllers and gas and hydraulic valves for control, which is easy to operate and maintain.

Application scope of multi-media filters
The application scope of multi-media filters includes but is not limited to:
Pretreatment of reverse osmosis, electrodialysis, ion exchangers, ultrafiltration and other systems.
Pre-filtration and treatment of raw water for power generation, chemical industry, papermaking, beverages, etc.
Decolorization and removal of organic matter in chemical plant feed water.
Pretreatment of domestic water.
Industrial water treatment.
Water treatment for swimming pools.
Circulating water bypass filtration system.
Reducing turbidity and color of surface water and groundwater.
Wastewater treatment.

Maintenance of multi-media filters
Multi-media filters need to be backwashed regularly during use to remove impurities in the filter layer and ensure the filtering effect. During backwashing, the water flows through the filter layer in the reverse direction, causing the filter layer to expand and suspend. The filter layer is cleaned with the help of the shear force of the water flow and the collision friction of the particles, so that the dirt in the filter layer is detached and discharged with the backwash water.