The activated carbon sintered or granular form are used in the filtration of liquids. The activated charcoal of plant is not very toxic. In each case the granular carbon layer is enclosed between a porous plastic cage and a thin layer of polypropylene. Activated carbon filters have not, however, effect on bacteria, nitrates and nitrites. Models are available with different filtering capacities, Which Vary from 1 micron to 100 microns.