By Tamara Bostwick
Submitted On April 06, 2010
The most common filtering agent used in water filters, including those in refrigerators, is activated charcoal. Charcoal can adsorb contaminants, removing them from the water as the water flows past the charcoal (aDsorb means to stick to a surface in a thin layer as opposed to soaking in like aBsorb). The use of activated carbon in filtering mechanisms is an effective way of removing chlorine (and its by-products) as well as volatile organic compounds such as atrazine, benzene, radon, PCBs and toluene, along with many others.
There are two main types of activated carbon that are used for water filtration. Granular activated carbon (GAC) and solid carbon block (CB). Activated carbon is very porous and has large surface areas over which water can pass to be cleansed. It is hard to imagine, but on a microscopic level, activated charcoal has numerous cracks and pores which expose the surface of the charcoal. To give you an idea of this surface area, a teaspoon of activated carbon has a surface area the size of a football field. Also, activated carbon has a mild positive electrical charge added to it which attracts negative ions in the contaminants drawing them to the surface of the carbon like a magnet, removing them from the water.
The effectiveness of GAC depends on how slow the flow is through the carbon and how long the water makes contact with the carbon surfaces. The longer the water stays in the carbon filter, the higher the filtration and vice versa. The trick is timing exposure so that the water flows through the carbon long enough to filter it adequately without it taking so long that the consumer gets impatient.
A more effective method of filtering water is through a solid carbon block (CB) made from blended carbon types combined with plastic polymers and then shaped under high pressure. CB filters are given a micron rating, unlike GAC filters. Water takes longer to move through carbon blocks than it does carbon granules so carbon blocks can adsorb and remove more contaminants from the water than GAC filters. A 1/2 micron CB filter can significantly reduce asbestos and cysts, though not eliminate them from the water.
Water filters should be changed regularly according to the manufacturer recommendation. In the case of refrigerator water filters, they should be changed at least every six months for optimal performance. Filters are designed to purify a specific number of gallons of water. However, you do not want to use a refrigerator water filter for any longer than six months whether or not the specified amount of water has been processed through the filter because bacteria builds up on the carbon of the filter, and after six months, the number of bacteria build-up may raise to dangerous levels. Also, failing to change the water filter every six months allows the filter to become saturated with contaminants and bacteria and the clogged filter may then leak unwanted contaminants into the processed water.
Make sure that your refrigerator keeps dispensing safe and fresh-tasting drinking water by changing your water filter every six months without fail.