The contaminants that people want to remove most often and that are not easily removed by carbon filtration are fluoride, nitrates, and sodium. Reverse osmosis and distillation are the only two methods that can eliminate all three, so combining them with a high-quality carbon filter provides a complete treatment. If you only want to remove fluoride, you can get a double filter with a fluorine cartridge and a carbon cartridge. A granular activated carbon (GAC) filter is a great option for removing certain chemicals, particularly organic ones, from water.
It can also be used to remove chemicals that produce unpleasant odors or flavors in water, such as hydrogen sulfide (the smell of rotten eggs) or chlorine. Carbon filters can also remove some toxins, including chemicals and volatile organic compounds, from water. However, they don't produce 100% toxin-free water. The only way to remove all toxins from water is with a reverse osmosis system or a water distiller. Reverse osmosis units contain one or more carbon filters, which can eliminate some of the most common pesticides that currently exist in the environment, such as lindane, chlordecone, kepone, heptachlor and chlordane.
It's not recommended for the removal of coliforms or cysts, although some of the very airtight solid carbon block filters currently on the market easily eliminate bacteria (though manufacturers rarely make this claim) and cysts like giardia and cryptosporidium quite easily. Activated carbon water filter media has a capacity similar to that of a sponge to absorb chemicals, flavors and odors. Most heavy metals are not attracted to carbon media, so they are retained during the carbon filtration process. A new special carbon called catalytic carbon is now available that removes hydrogen sulfide gas (which produces the smell of rotten eggs in the water of some wells) and is very effective in eliminating chloramines (the mixture of ammonia and chlorine used as a disinfectant in some water supplies). Most carbon filters will start to let other chemicals escape long before they start to let chlorine through. Multipure and some other very compact carbon block filters eliminate cysts simply because of their restricted pore size.
Most carbon filters are made from charcoal, but other substances are also used, such as wood and nut shells. Heat, in the absence of oxygen, is used to increase (activate) the surface area of carbon; this is why these filters are sometimes called “carbon filters”. Look for a carbon water filter combined with a KDF medium, which reduces water-soluble metals such as copper, zinc, iron and cadmium. Granular activated carbon is made from raw organic materials (such as coconut shells or charcoal) that have a high carbon content. Tap water must always be filtered with charcoal before distillation, otherwise VOCs and chlorine will re-enter the distilled water or be released into the air so you can breathe.
An example is a unit located under the sink; the water passes through the carbon filter and goes to a separate water faucet, next to the main faucet. In conclusion, it's important to understand that while carbon filters can be effective at removing certain contaminants from your drinking water, they cannot remove all contaminants. For complete protection against toxins in your drinking water, you should consider using a reverse osmosis system or a water distiller.
