From Wikipedia, the free encyclopedia

An industrial water filter with geared motor

A water filter is a device which removes impurities from water by means of a fine physical barrier, chemical processes and/or biological process. Filters are used to cleanse water for irrigation, drinking water, aquariums, and swimming pools.

Water filters are primarily used to soften water and remove chemicals such as chlorine. Some scientists believe that the contaminants found in drinking unfiltered drinking water can be harmful to your health, even increasing the risk of developing cancer. The most common problem with unfiltered water, however, is a bad taste or smell.

Water filters are also used by recreational hikers, by aid organizations during humanitarian emergencies, and by the military. These filters are usually small, portable and light (1-2 pounds or less) and usually filter water by working a mechanical hand pump, although some use a siphon drip system to force water through. Dirty water is pumped via a screen-filtered flexible silicon tube through a specialized filter, ending up in a water bottle (or other container, such as a Camel Back). These types of filters work to remove bacteria, protozoa and cysts, all of which can cause disease. Popular and reliable makers of these small, portable water filters include General Ecology, Innova Pure Water, Katadyn,Mountain Safety Research, and Pure Water 2GO. Filters include fine meshes, which must be replaced, and ceramic filters which must have their outside abraded off when it becomes clogged with impurities.

These water filters should not be confused with devices or tablets that are water purifiers. Water purifiers satisfy higher EPA standards, and also remove viruses, such as hepatitis A and rotavirus, among others.

In a domestic emergency, where water needs will last beyond those of stored, bottled water, a device that is specifically certified as a water purifier, and not a water filter, is preferred.

The physics of filters is based on sieving, adsorption, ion exchanges and other processes. Unlike a sieve or screen, a filter can remove particles much smaller than the holes through which the water passes.

• Media filter
• Screen filter
• Disk filter
• Slow sand filter bed
• Rapid sand filter
• Cloth filter

• Backwashing
• Water purification
• Reverse osmosis
• Distillation
• Sand separator
• Settling basin
• Swimming pool sanitation

• History of Water Filters - History of water and water treatment.
• Types of Filters - a comparison of the Slow sand filter, Rapid sand filter, Pressure filter & Diatomaceous earth filter. (Mountain Empire Community College, Water/Wastewater Distance Learning)
• Filtration info from New Mexico State University