The filtration sand bed is frequently used and it is a very valuable method to remove suspended solids from water.
The operation and 'quite simple, usually a sand filter is constituted by a cylindrical container, inside which is inserted washed silica sand, monolayer (that is, all of the same grain size), multi-layer (ie layers of different grain size) or particle size variable.
The pump draws water from the tank and sends it to the filter, allowing it to enter from the top, the water passes through all the filtering layer and is collected at the bottom by "candles" or "plates" which convey it again in tank through the feeder.
During the transition, the water removes suspended particles, wiping.
Sand filters are available in different sizes and materials and operate either manually or fully automatically.