Drinking water filtration systems include carbon or ceramic filters, distillers, and reverse osmosis systems. Some systems filter all the water coming into the house, while others filter only the water in the kitchen. There are also countertop filters and portable UV wands for purifying water while camping or travel. Drinking water filtration is needed for water supplies that are contaminated with pathogens, or for water that contains dangerous or undesirable sediment, such as heavy metals or excess hardness.
Carbon filters, also called charcoal filters, are made with replaceable cartridges filled with activated charcoal. Activated charcoal is a highly porous material made by burning organic material at extremely high temperatures. The tiny pores are capable of trapping chlorine, heavy metals, and many pathogens as small as .01 microns. Carbon is a common and economical method of drinking water filtration that improves the taste of water and significantly improves its quality. The filters need to be changed regularly to maintain their effectiveness.
The carbon in some filters might be treated with silver to make them more effective against bacteria and viruses. Some viruses and other pathogens can pass through the carbon, so some carbon filters also have a ceramic filter. The pores in the ceramic are much smaller, making them effective against pesticides and some types of radioactivity as well as viruses smaller than .01 micron. Carbon filters are inexpensive, but must be scrubbed and disinfected regularly to prevent the buildup of pathogens.
Distillers are the most effective way of removing all harmful pathogens because the water is boiled. They also can remove some chemicals such as chlorine that affect the water's taste. A distiller can be used for home drinking water filtration, usually as a counter top device. Portable distillers are also useful for travel or camping, where safe drinking water sources are unavailable. Another portable device used for drinking water filtration is the UV wand, which uses ultraviolet light to kill bacteria, viruses, and microscopic cysts that cause giardia. The wand is stirred in a small amount of water for several minutes before drinking.
Reverse osmosis is a type of drinking water filtration that might be used for a whole house, or as an under-sink filter. It works by forcing water through a semi-permeable membrane using enough pressure to overcome osmotic pressure. The contaminants stay behind the filter while the clean water passes through. Reverse osmosis filters are expensive and waste a lot of water, but they can remove most harmful chemicals and microorganisms.