Multi-Media Filter for Wastewater Treatment

July 25, 2023 Sand Filter

Multi-media filter is the process of using one or several filter media to pass the water with high turbidity through granular or non-granular materials of a certain thickness under a certain pressure, so as to effectively remove suspended impurities and clarify the water. The commonly used filter media are quartz sand, anthracite, manganese sand, etc., which are mainly used for water treatment to remove turbidity, softened water, pre-treatment of pure water, etc. The turbidity of the effluent can reach below 3 degrees. The meaning of filtration, in the process of water treatment, filtration generally refers to the process of intercepting suspended impurities in water with filter layers such as quartz sand and anthracite, so as to clarify the water. The porous material used for filtration is called filter material, and quartz sand is the most common filter material. The filter material is granular, powdery and fibrous. Commonly used filter materials are quartz sand, anthracite, activated carbon, magnetite, garnet, ceramics, plastic balls, etc. Multi-media filter (filter bed) is a media filter that uses more than two kinds of media as the filter layer. In the industrial circulating water treatment system, it is used to remove impurities in sewage, absorb oil, etc., so that the water quality meets the requirements of recycling. The function of filtration is mainly to remove suspended or colloidal impurities in water, especially to effectively remove tiny particles and bacteria that cannot be removed by sedimentation technology. BODs and COD also have a certain degree of removal effect. The filter body mainly includes the following components: water distribution component, support component, backwash air pipe, filter material, exhaust valve (external), etc.

How to choose the suitable filter media:

(1) It must have sufficient mechanical strength to avoid rapid wear and tear during backwashing; (2) The chemical stability is better; (3) It does not contain harmful and toxic substances that are harmful to human health, and does not contain substances that are harmful to production and affect production; (4) The selection of filter materials should try to use filter materials with high adsorption capacity, high sewage interception capacity, high water production, and good effluent quality.

In the filter material, pebbles mainly play a supporting role. During the filtration process, because of their high strength, the gaps between them are stable and the pores are large, which is convenient for the smooth passage of filtered water in the normal washing process; similarly, in the backwashing process, backwashing water and backwashing air can pass through smoothly. In the conventional configuration, pebbles are divided into four specifications, and the bedding method is from bottom to top, first big and then small. Commonly used multi-media filters for water treatment are: anthracite-quartz sand-magnetite filter, activated carbon-quartz sand-magnetite filter, activated carbon-quartz sand filter, quartz sand-ceramic filter, etc.