Request: Information on multi-media filters

A multi-media filter utilizes one or several filtering media to pass water with high turbidity through layers of granular or non-granular materials under certain pressure, thereby effectively removing suspended impurities and clarifying the water. Common filter media include quartz sand, anthracite, and manganese sand. These filters are primarily used for turbidity removal in water treatment, water softening, and as a pre-treatment step for producing pure water; the turbidity of the treated water can be reduced to below 3 NTU. Type: Quartz sand filter. Quartz sand filter: Filled with refined quartz sand, it is used to remove suspended particles from water and improve the temperature of the output water. 　　Functions and working principle of quartz sand filters 　　(1) Functions of quartz sand filtration 　　A quartz sand filter is a type of filter in which quartz sand is used as the filtering medium. It helps to remove impurities from water. It also has advantages such as low filtration resistance, large specific surface area, strong acid and alkali resistance, and good anti-pollution performance. The unique advantage of quartz sand filters lies in the ability to achieve adaptive operation through the optimization of both the filter media and the filter design; the filter media exhibit strong adaptability to factors such as the concentration of the raw water, operating conditions, and pre-treatment processes. That is, during filtration, the filter bed automatically assumes a structure that is loose at the top and dense at the bottom, which helps to ensure the quality of the filtered water under various operating conditions. During backwashing, the filter media spread out fully, resulting in effective cleaning. Sand filters can effectively remove suspended solids from water, and they also have a significant effect on removing pollutants such as colloids, iron, organic substances, pesticides, manganese, bacteria, and viruses from water. It also has advantages such as fast filtration speed, high filtration precision, and large dirt retention capacity. It is mainly used in fields such as electricity, electronics, beverages, tap water, petroleum, chemicals, metallurgy, textiles, papermaking, food processing, swimming pools, and municipal engineering, for the advanced treatment of process water, domestic water, recycled water, and wastewater. 　　(2) Main features of quartz sand filters: Quartz sand filter equipment features a simple structure, automatic operation, high treatment capacity, few backwashing cycles, high filtration efficiency, low resistance, and ease of operation and maintenance. (3) Working principle of quartz sand filters: Quartz sand filters utilize one or several filtering media; they can operate at normal temperatures, are resistant to acids and alkalis as well as oxidation, with a suitable pH range of 2–13. It is equipped with well-configured protective devices and monitoring instruments, as well as a backwashing function that allows contaminants such as sediment to be quickly removed. It consumes little water, and a fully automatic mode can be set according to the user’s requirements. Under certain pressure, the stock solution is passed through this medium, where flocculation, adsorption, and retention occur to remove impurities, thereby achieving the purpose of filtration. The fillers used inside are generally quartz sand, anthracite, granular porous ceramics, manganese sand, etc.; users can choose those that suit their specific needs. Its filtration precision is between 0.005 and 0.01 mm, enabling it to effectively remove colloidal particles and high-molecular-weight organic substances. Activated carbon filter: A filter filled with activated carbon for water treatment, used to remove color, taste, residual chlorine, and organic substances. Multi-media filters, activated carbon filters. Activated carbon filters are widely used in the purification of water for domestic use as well as in industries such as the food industry, chemical industry, and power generation. They serve to remove chlorine, oil, color, and odors from water, thereby eliminating residual chlorine and ensuring that the water quality meets the requirements for feedwater in RO membrane systems. Installing an activated carbon filter before the cation exchanger can also remove organic substances such as humic acid, which are harmful to the cation exchange resin in water. It can typically remove 63% to 86% of colloidal substances, about 50% of Fe, and 47% to 60% of organic substances. Iron and manganese remover: It uses a dual-filter media of refined manganese sand and quartz sand to remove iron and manganese from water. 　　The materials for multi-media filters can be fiberglass reinforced plastic, A3 steel with anti-corrosion treatment or rubber lining, or all stainless steel. There are two operation modes: fully automatic and manual. The automatic control system uses automatically controlled devices imported from the United States, as well as pneumatic and hydraulic valves; it is simple to operate and easy to maintain, and is widely used in pre-treatment units for water treatment processes in various industries. Application areas: Pre-treatment for systems such as reverse osmosis, electrodialysis, ion exchangers, and ultrafiltration; filtration processes in power generation, the chemical industry, paper manufacturing, beverage production, etc.; decolorization and removal of organic substances from water supplied to chemical plants; treatment of domestic water; treatment of industrial water; treatment of water used in swimming pools; secondary filtration systems for circulating water; clarification and decolorization of surface water and groundwater

For multi-media filters, my personal recommendation is to refer to the water treatment standards DL2006; these standards provide all the relevant design parameters, which is sufficient for selection and design purposes. If you need to know more about their internal structure, feel free to contact me

Where does the backwash water for the multi-media filter come from? Is it the water produced by the filter itself?