Introduction:
Sand filter is a common and important water treatment equipment, widely used in various fields such as drinking water treatment, sewage treatment, industrial water treatment, etc. One of its core components is the filter material, and different filter materials play their unique roles in the sand filter, jointly achieving effective purification of water quality. This article will provide a detailed introduction to the different types of filter media commonly used in sand filters and their respective roles.
Quartz sand filter material
1.Principle of filtration action
Mechanical interception
Quartz sand filter material forms a filter layer with a certain particle size distribution in the sand filter. When water passes through the filter layer, larger impurities in the water, such as sediment, suspended solids, colloids, etc., will be intercepted by the pores between quartz sand particles. These impurities, due to their larger size than the pores of the filter material, cannot pass through the filter layer and are therefore separated from the water.
For example, in drinking water treatment, some visible sediment particles in the raw water may be intercepted on the surface or in the internal pores of the quartz sand filter layer, resulting in a significant reduction in the turbidity of the effluent.
Adsorption effect
Although the chemical properties of quartz sand are relatively stable, its surface still has a certain degree of activity. In water, the surface of quartz sand will adsorb some small impurity particles and soluble substances. This adsorption is mainly achieved through physical adsorption, that is, van der Waals forces between molecules.
For example, for some trace organic compounds in water, quartz sand can partially remove them through surface adsorption, thereby improving the chemical properties and taste of the water.
2.Widely applicable fields
Quartz sand filter material has been widely used in many fields due to its excellent filtration performance and relatively low cost. In drinking water treatment plants, it is an important link in ensuring the safety of drinking water quality, which can effectively remove suspended solids, colloids and other impurities in the water, and make the effluent meet the national drinking water standards. In sewage treatment, quartz sand filter material is also commonly used for deep filtration after secondary treatment to further remove residual pollutants in sewage, improve effluent quality, and meet discharge or reuse requirements. In industrial water treatment, such as the electronics industry, pharmaceutical industry, and other industries that require high water quality, quartz sand filters are also widely used in the pretreatment process to provide high-quality water sources for subsequent production processes.
Activated carbon filter material
1.Principle of filtration action
physical adsorption
The huge specific surface area of activated carbon provides it with a large number of adsorption sites. Through physical adsorption, it can adsorb various organic pollutants, odorous substances, and some heavy metal ions in water. For example, for volatile organic compounds (VOCs) in water, activated carbon can utilize its pore structure to adsorb these molecules on the surface, effectively removing odors and harmful chemicals from the water.
When water passes through the activated carbon filter layer, organic molecules are adsorbed into the pores of the activated carbon under the action of van der Waals forces, achieving purification and improvement of water quality.
chemical adsorption
The surface of activated carbon also contains some functional groups, such as carboxyl, hydroxyl, carbonyl, etc. These functional groups can undergo chemical reactions with certain substances in water, thereby achieving chemical adsorption. For example, the hydroxyl groups on the surface of activated carbon can undergo ion exchange reactions with heavy metal ions in water, fixing heavy metal ions on the surface of activated carbon and achieving the goal of removing heavy metals.
For some oxidative substances in water, the functional groups on the surface of activated carbon can also undergo redox reactions, changing the chemical properties of these substances and making them easier to remove from water.
2.Application scenarios
Advanced treatment of drinking water: In drinking water treatment, activated carbon filter media is commonly used to remove trace organic matter, odors, and residual chlorine from water. It can effectively improve the taste and odor of drinking water, and enhance the quality of drinking water. For example, in some cities’ water plants, the water that has undergone conventional treatment is further processed through activated carbon filters to ensure that residents can drink higher quality water.
Advanced treatment in sewage treatment: In the advanced treatment stage of sewage treatment plants, activated carbon can be used to remove recalcitrant organic pollutants and chromaticity from sewage. For some industrial wastewater, such as printing and dyeing wastewater, pharmaceutical wastewater, etc., activated carbon filter media can effectively adsorb harmful substances such as dye molecules and drug residues, making the effluent meet higher discharge standards or reuse requirements.
Industrial water purification: In industries such as electronics and food that require extremely high water quality, activated carbon filter media is often used to remove trace organic impurities and heavy metal ions from water to ensure the quality of water used in the production process and prevent adverse effects on product quality.
Anthracite Filter Media
1.Principle of filtration action
Mechanical screening and interception
Anthracite filter material is usually used in combination with quartz sand and other filter materials in sand filters to form a multi-layer filter material structure. Due to its relatively large particle size, anthracite filter material first plays a role in mechanical screening during the filtration process. It can intercept larger sized impurity particles in water, such as larger suspended solids, sediment, etc., providing preliminary support for more refined filtration in the future.
At the same time, the pores of anthracite filter material can also intercept some smaller impurity particles, complementing quartz sand filter material and jointly improving the filtration effect. For example, in the primary treatment of sewage, anthracite filter material can remove larger solid particles from the sewage and reduce the load on subsequent treatment units.
Adsorption and ion exchange interactions
The surface of smokeless coal has certain activity and can adsorb some organic compounds and metal ions in water. Compared with activated carbon, its adsorption capacity is relatively weak, but it can also improve water quality to a certain extent. In addition, smokeless coal also contains some mineral components that can undergo ion exchange reactions with ions in water.
For example, cations such as calcium and magnesium in anthracite can exchange with some heavy metal ions in water, thereby reducing the concentration of heavy metal ions in water.
2.Application scenarios
Pre treatment of drinking water: In drinking water treatment, anthracite filter material is often used as a pre-treatment filter material to remove large particle impurities, suspended solids, and some organic matter from raw water, creating favorable conditions for subsequent fine filtration and deep treatment. It can effectively extend the service life of subsequent filter materials such as quartz sand filter and activated carbon filter, and improve the operational efficiency of the entire water treatment system.
Industrial water filtration: In industrial water treatment, such as chemical and power industries, anthracite filter material can be used for pre-treatment of circulating water systems, removing impurities and microorganisms from water, and preventing equipment scaling and corrosion. At the same time, in some industrial production processes where water quality requirements are not particularly high, anthracite filter media can also be used as the main filtration medium to meet the basic requirements of production water.
Conclusion:
Different filter materials in sand filters play an indispensable role in the process of water purification. Quartz sand filter material is used as the basic filter material to remove large impurities and some small particles in water through mechanical interception and adsorption; Activated carbon filter material, with its strong adsorption performance, effectively removes organic matter, odors, and heavy metal ions from water; Anthracite filter material has a certain role in mechanical screening and adsorption, and is moderately priced, with high mechanical strength, and works well with other filter materials
