There are many different ways to filter water. You can use media filters, which employ sand to filter water as it travels from underground to the surface. Screen filters, which utilize a thin screen that separates fine particles out of water for irrigation and other uses. Disk Filters are generally the main form of filtration for irrigation. This process is much like using a screen filters, but instead of a screen a small disks are used. The disks are stacked on top of each other separating the water from its impurities.

Slow sand filters are used to treat raw water found on the surface of the earth. They are usually between one and two meters deep. This system uses a layer of earth called the Schmutzdecke layer which contains bacteria and fungi. This layer purifies the water leaving exceptionally clean water at the top.

Rapid sand filters or rapid gravity filters are forms of filtration used municipal water treatment facilities. Coarse sand is used to remove the particles that were previously trapped in flocks by salts of aluminum or iron. The simplest filter still in use today is the cloth filter. This filter can be dangerous because it is not very effective. It is done by using a folded cloth placed in a container. The container is dipped in water and then raised. The cloth is lifted from the container and the filtered water will move through the cloth and into the container.

Filtration has several more complex forms that do not employ physical screens in order to filter the impurities out of water. Using ultra violet rays, water can be purified very effectively. Exposing water to the rays will remove any virus and bacteria that would have previously been in the water. Raw water is normally put through this process but drinking water has more recently been filtered in this way. A drinking water disinfection facility has already been approved for construction in New York that will use ultra violet rays. The facility should be able to produce up to two billion gallons of drinking water on a daily basis.

Reverse osmosis is a process in which pressure is applied to a membrane forcing water through it. The impurities in the water are trapped within the membrane as the water flows out the other side. Most of the separation occurs within the polymer matrix, which is the outer layer of the membrane. The membrane is known as the semi permeable, because it only lets the solute pass through while collecting the solvent.

Catalytic converters are devices using filtration for the benefit of the environment instead of strictly humans. The converter is put on automobiles in order to reduce toxic emissions into the environment that are made by the vehicle.

Water filtration is among the most beneficial ideas man has ever conjured. Early in human existence water filters were used to allow man to live in some of the most difficult of environments. It can only continue to prove its usefulness as we further discover all of its capabilities.