How To Filter

According to the nature of the filtering equipment used, the filtering medium and the processed material system and the requirements of product collection, the filtering operation is divided into two main methods: intermittent and continuous.

According to the way of providing the driving force of filtration, there are gravity filtration, pressure filtration, vacuum filtration and centrifugal filtration, the purpose of which is to overcome filtration resistance.

Filtration is a water purification process that removes suspended solids and microorganisms in the water when the water passes through the filter material. The filter tank is usually located after the sedimentation tank or clarification tank. The purpose is to make the turbidity of the filtered water meet the requirements of water quality standards. After the water is filtered, the remaining bacteria and viruses lose the protective effect of suspended solids, thereby creating conditions for disinfection after filtration. Therefore, in the purification of drinking water using surface water as the source of water, precipitation or clarification can sometimes be omitted, but filtration is indispensable.

⑴ The principle of water purification by filtration. ① Screening effect: When water passes through the filter material, particles larger than the pores of the filter layer are intercepted; subsequently, the pores of the filter layer gradually become smaller, and smaller particles are also intercepted. ②Contact agglomeration: the small flocs or destabilizing particles that have not been removed by precipitation are adsorbed due to contact with the filter material; after the filter material adsorbs the flocs, its adsorption is further enhanced.

⑵ Water purification efficiency of filtration. Depends on factors such as water quality, filter particle size, filter layer thickness, filter structure, filtration speed and management. Filtration speed refers to the amount of water passing through a unit filter area per hour. The higher the filtration rate, the deeper the penetration of impurities in the filter layer. However, if the filtration rate is too high, the water quality after filtration will be affected.

⑶ Requirements for filter media. It has sufficient mechanical strength, does not deteriorate water quality, has a certain particle gradation, and is economical and easy to obtain.

⑷ Commonly used filter type. ①Ordinary fast filter, the plane is square or round. When filtering, the influent water flows from the distribution channel to the drain, and then is evenly distributed on the surface of the filter, and then passes through the filter layer and the supporting layer; finally, the filter tube system After being collected, it is discharged through a clear water pipe. When washing sand, clean water is backwashed from bottom to top through the filter pipe system, so that the sand layer swells and floats, the number of sand rubs against each other, and the sludge is washed down; the sewage flows from the water distribution and drainage tanks to the distribution channel, and finally is discharged from the washing tank sewage channel . The fast filter is reliable in operation and can improve the effluent quality by reducing the filter speed; ②Double and three-layer filter media are added with a layer of smokeless filter with a larger particle size and a smaller specific gravity on the quartz sand layer. Due to the large pores of the anthracite coal seam, the mud interception capacity is higher than that of the fast filter; ③Siphon filter, valveless filter and mobile flushing hood filter: The water purification principle of these filters is the same as that of ordinary fast filters. Their common advantage is that they reduce valves and facilitate operation and management; but the structure is complex.