Great For Removing Chemical Impurities Says The EPA
Activated carbon, otherwise known as activated charcoal, a general term used to describe carbon material derived from charcoal. This material is considered by the EPA to be the best technology used in water filters to remove a wide variety of industrial contaminants such as volatile organic compounds(VOCs) and trihalomethanes(THMs).A carbon filter removes contaminants by the process of absorption and adsorption. Absorption occurs when contaminants in your water become trapped in the porous element within your filter. Adsorption occurs when impurities are removed from your tap water by attaching themselves to a solid surface.
Activated carbon can be derived from different type of materials such as coconut shells, coal and wood. The rate at which chemical impurities in your water supply is adsorbed depends on the size of the pores and water temperature.
Ideally, your carbon water filter media should be small and have have many pores. This reduces the distance the impurities have to travel from your tap water to the adsorption surface. However, the colder your tap water, the slower the water moves and the lower the adsorption rate.
There a various types of carbon elements used within a filter cartridge.
One type is the carbon pleated media. Cartridges using this element are usually made of cellulose or polyester and impregnated with activated carbon. Carbon-pleated cartridges can remove sediments, chlorine and odors. Some consumers however, have reported a bad smell coming from water filtered by this device.
You also have filter cartridges that uses granular activated carbon(GAC). This type improves filtration in two ways.
One, by using a compression pad to reduce the flow of water that bypasses the filtering mechanism, thus increasing the amount of water that is filtered.
Secondly, by its design. Water is able to travel the entire length of the carbon bed which again, increases the time that the contaminants come in contact with the filtering elements. GAC also improves water taste and odor.
The third type is considered the most efficient; the carbon block element. GAC or powered carbon are mixed with polyethylene or some other binder and molded into a tubular shape. The outside of the cartridge is treated and acts as a sediment screen.
Carbon block is excellent at removing chlorine and the industrial chemicals mentioned at the top of this page. Furthermore, unfiltered water is unable to bypass the filtering mechanism and flow through your tap.
A carbon block filter is able to remove particles in your water that are as small as 0.5 microns, which is about 2 millionth of a meter. To give you an idea of how small that is, the human eye can only detect particle sizes down to 40 microns.
Before you buy a carbon filter, bear the following in mind:
1. No matter what you have been told, this type of filtration does not remove bacteria, heavy metals, inorganics and radioactivity. Carbon filters that use silver may partially remove bacteria but silver is considered toxic.
2. A carbon filtration system doesn’t produce pure water and therefore cannot be classified as a water purifier. Distillation is the closest thing to producing pure water(albeit pure water devoid of minerals). A water filter is only designated as a “purifier” if it can remove 99.75% of all bacteria.
3. Depending on the material in which the activated carbon is derived, low levels of metallic impurities such as aluminum and arsenic may be left in the carbon. These could leach into your drinking water. Activated carbon derived from coconut is the least likely to leach arsenic.
It is important therefore, that when a carbon filter is used in a reverse osmosis system, it should be placed before the filter membrane and not after. This would reduce the likelihood of cross contamination of your drinking water.
For a drinking water system that uses carbon filtration, and what Consumer Digest calls, “Best Buy,” see the recommendation below.
>>> Recommended Carbon Block >>>
These countertop and under the sink water filters are multi-media block carbon filters, that use and a dual filter submicron process to remove chlorine, cryptosporidium, giardia, lead, MTBE, PCBs and organic chemicals.
Counter Top Water Filter
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