1、 Working principle and filter layer design

The core of multimedia filters lies in the "deep filtration" mechanism. The filter bed is usually composed of filter materials with different densities such as anthracite, quartz sand, and magnetite, which are filled in layers from large to small particle size (such as 1-2mm anthracite in the upper layer, 0.5-1mm quartz sand in the middle layer, and 0.3-0.5mm magnetite in the lower layer). When the water flow passes from top to bottom, suspended solids are first intercepted by the coarse filter material, and then smaller particles are adsorbed by the lower layer of fine filter material, forming a gradient filtration effect. This design significantly extends the filtration cycle and improves the interception capacity (up to 15-20kg/m ³).

2、 Application scenarios and advantages

Industrial water treatment: used for pre-treatment of circulating cooling water and boiler feedwater, removing iron, manganese, and turbidity.

Municipal water supply: As an upgraded solution for sand filters, it can cope with high turbidity raw water (such as river water in rainy season).

Wastewater reuse: Used as a protective filter before MBR or RO systems to extend membrane life.

Compared to single medium filters, its advantage lies in an increase of over 30% in pollutant holding capacity and a 40% reduction in backwash frequency.

3、 Maintenance and common problems

Filter material compaction: Due to incomplete backwashing or microbial growth, it is necessary to strengthen the combined backwashing of air and water or add chemical cleaning agents.

• Material running phenomenon: Check if the supporting layer has collapsed or if the backwash strength exceeds the standard.

• Deterioration of effluent quality: It may be due to unreasonable grading of filter media or deviation of operating parameters from design values, requiring re screening of filter media or calibration of flow rate.