Water filtration using carbon filters: What are carbon filters?

Carbon filters are extremely effective in removing contaminants from water. They can remove or reduce bad tastes, unpleasant odors, chlorine, VOCs, lead, pesticides, heavy metals, gaseous pollutants, and more. Due to its high effectiveness, carbon is the most popular filter media used in water treatment. Almost every type of water filtration system uses carbon filtration in some way.

What are Carbon Filters?

Carbon filters are made by grinding up carbon from coconut shells, bituminous coal, peat, or other raw organic materials that are high in carbon. Most carbon filters are made from coconut. Charcoal is a type of carbon that sometimes is used interchangeably with carbon however carbon is a better choice because it’s purer and better quality than charcoal.

To create the carbon that makes up a carbon filter, the organic material is heated to an extremely high temperature without oxygen. This bakes off any impurities. Next, it undergoes the activation process in which an even hotter steam creates pores and cracks in the carbon surface. These pores and cracks give active carbon its really high contaminant holding capabilities.

There are two styles of carbon filter: loose carbon granules (granular activated carbon or GAC) or compressed particles of carbon (carbon block). Further, there are two types of activated carbon filter media: activated carbon and catalytic activated carbon. We’ll discuss the differences among the options for carbon media filters below.

10 inch CTO GAC UDF Activated Active Carbon Block Filter for water purifier

What do carbon filters remove?

Carbon filters have a high adsorption and can potentially remove and reduce a wide variety of organic compounds and organic chemicals. Activated carbon filters are best at removing chlorine and bad tastes or odors. Some activated carbon filters may be capable of removing and reducing other contaminants (check with the manufacturer to be sure). Keep in mind that not all carbon filters are created equal and may not tackle some or most of the contaminants in the following list. Again, check with the manufacturer to determine if the filter is capable of removing a specific contaminant.

Some carbon filters may remove or reduce these contaminants including: accetone, alcohols, amyl acetate, amyl alcohol, antifreeze, bacteria, bad tastes, benzene, bleach, butyl alcohol, butyl acetate, calcium hypochlorite (chlorine powder), chloramines, chloroform, chlorine, chlorine by-products, chlorobenzene, chlorophenol, chlorophyll, citric acid, cresol, diesel fuel, dirt, dyes, ethanol, ethyl acrylate, ethyl alcohols, ethyl acetate, ethyl amine, ethyl ether, gasoline, glycols, heavy metals, herbicides, hydrogen peroxide, hydrogen sulphide (rotten egg smell), hypochlorous acid, insecticides, iodine, iron, isopropyl accetate, isopropyl alcohol, ketones, lactic acids, lead, methyl acetate, methyl alcohol, methyl bromide, methyl chloride, methyl ethyl ketone, microplastics, naphtha, nitrobenzene, nitrotoluene, odors, organic acids, organic esters, oxalic acid, ozone, pesticides, phenol, polychlorinated biphenyls (PCBs), potassium permanganate, propioic acid, propyl acetate, propyl alcohol, propyl chloride, radon, sediment, sodium hypochlorite, solvents, sulphonated oils, tannins, tar emulsion, tartaric acid, trihalomethanes (THM’s), toluene, toluidine, trichlorethylene, trichloroacetaldehyde, turpentine, unpleasant odors, volatile organic compounds (VOCs), xanthophyll, xylene, and more.

Carbon filters are not effective at removing dissolved minerals, dissolved salts, and other dissolved inorganic substances – you will need reverse osmosis to remove these.

Activated Carbon versus Catalytic Activated Carbon

What is a Granular Activated Carbon (GAC) Water Filter?

A granular activated water filter (GAC) contains loose pieces of carbon granules. Whole house / point of entry and point of use water filter systems may use GAC filters. This type of carbon filter can be used as a pre-filter and “polishing” or final filter in the water filtration process.

GAC filters work by adsorption in which the surface of the activated carbon attracts and holds on to contaminants.

With GAC filters, the longer the water has contact with the loose carbon granules the better. This is one of the disadvantages of GAC compared to carbon block since the later, doesn’t require as much contact time. Also, a granular activated carbon filter may have a higher flow rate than a carbon block filter because it’s a looser medium in which it’s less difficult for the water to pass through the loose granules.

A GAC filter is typically used to improve taste and odor of water by removing chlorine, hydrogen sulfide (that rotten egg smell), and other offensive tastes and odors.

What is a Carbon Block Water Filter?

A carbon block filter is contains compressed pieces of carbon granules to form a solid block. Residential whole house / point of entry, commercial water treatment, and point of use water filter systems may use carbon block water filters. This type of carbon filter can be used as a pre- or post-filter in the water filtration process.

An important distinction with carbon block filters is that they have a micron rating depending on how much the carbon is compressed. For example, a 0.5 micron filter will filter out much finer contaminants than a 5 micron filter. This also means that activated carbon block has lower flow rates than GAC filters because the filter medium is much more compact.

Active carbon block filters adsorb and filter contaminants. This style of filtration adsorbs chemical contaminants and mechanically separates particles as water is pushed through through the pores of the dense carbon block filter media.

An activated carbon block filter is one of the most absorbent materials in the world. In fact, a standard 10″ activated carbon block cartridge has the equivalent surface area as 160 acres – that’s roughly 121 football fields or 2,560 tennis courts!

How Often Should Carbon Water Filters Be Changed?

The lifespan of a carbon filter can vary based on the quality of the filter itself, how contaminated the water is, and water usage Typically, a carbon filter should be replaced once every 3 months to 1 year. Please check with the manufacturer for guidance.

With carbon block water filters, they will essentially plug when they’ve reached capacity. You’ll know it’s time to replace the filter when there is a significant drop in water flow coming from the filter.