Filter (water)
From Wikipedia, the free encyclopedia
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 people 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 outdoorspeople, by aid organizations during humanitarian emergencies, and by the military. These filters are usually small, portable and light (1-2 pounds), and filter water by working a hand pump. Dirty water is pumped via a tube through the filter, then out into another flexible tube and directly into a water bottle. 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, Katadyn, and Mountain Safety Research.
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.
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[edit] External links
- History of Water Filters - History of water and water treatment.
- Water Filter and Equipment Various type of water filters
- 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 - Southwest Biotechnology and Informatics Center
