Filter is the use of one or several filter media, under a certain pressure to high turbidity of the water through granular or particulate material of a certain thickness, so as to effectively remove suspended impurities in the water clarification process, commonly used media quartz sand, anthracite, manganese sand, mainly for water turbidity, water softening, water pretreatment stage before, up to 3 degrees below the water turbidity. Multi-media filter within the filter for high-quality grain are gravel, quartz sand, magnetite, anthracite and other media, the media according to the size of its specific gravity and particle size distribution in an orderly filter tank body of science, such as the proportion of small the larger particle size of anthracite in the top of the filter bed, the proportion of moderate and small diameter quartz sand filter bed in the middle, heavy and large particle size gravel on the lowermost layer of the filter bed. Such a ratio ensures that the filter during the backwash when no turbostratic phenomenon, thus ensuring the retention capacity of the filter.
