A device or substance that partially or completely absorbs certain light rays. Filter Bed 1. A tank, covered trench. Etc. with a sand or gravel bottom which is used to filter water, sewage, etc. Filter material layer through which fluid is passed.
Water is purified of certain chemicals when it is passed through a layer of activated charcoal.
Filter Block Flooring, of hollow vitrified clay masonry units, which is used in a sewage treatment plant. Filter Fabric 1. This fabric is fastened down against the soil to prevent erosion. Synthetic fabric, which sieves out the fine materials from ones that are coarser and also filters particles from fluids. Filter Paper Porous paper, which is used for filtering.