Filters are devices that pass light and filter out certain wavelengths. There are many different types of filters, each with its own unique characteristics and applications. Gravity filters are the oldest and simplest type, and are commonly used in city water plants. These filters involve the use of tanks that are usually constructed of concrete.
At the bottom of the tank, there is a grate or false bottom, above which is a layer of coarse-grained gravel or crushed rock of gradual size. The top layer consists of uniformly sized quartz sand. In industrial filtrations, graduate-sized crushed coke is used to filter sulfuric acid, while graduate-sized crushed limestone is used for alkaline liquors. Charcoal beds are used to purify organic liquids by filtration and adsorption. Activated alumina is an excellent choice for purifying drinking water for domestic use, as well as in industrial applications, water treatment facilities or in the cleaning of toxic waste.
In complex systems, it is possible to combine several different types of filters to achieve the desired overall response characteristic. The biochemical properties of the water in your area, the water pressure, the type of pipes it runs through, and even the water source in your home all influence the water content. Active and passive filter circuit filters are the difference between active and passive filters and types of filter circuits. The four main types of filters include the low-pass filter, the high-pass filter, the band-pass filter, and the notch filter (or the band-stop or band-stop filter).