Granular activated carbon (GAC) is materials of organic carbon filtration in domestic water purifying and waste water treatment. Normally they used to to make UDF and T33 activated carbon for domestic water purifiers.
According to type of granular activated carbon materials, they are classified as woods, coals, peat, coconut shells, and other kind shells, such as apricot shells, walnut shells, palm kernel husks and peach kernels. Nuts shell GAC are used to replacing coconut shells activated carbon because they are with much cheaper but with similar effect. Baiyun carbon granular nuts shell activated carbon are made by mixed apricot shells and peach kernel.
Generally, a UDF with GAC can remove certain chemicals, particularly organic contaminants, from water, as well as chemicals that produce odors or tastes to water such as hydrogen sulfide or chlorine and kill germs, especially residual chlorine from tap water because residual chlorine can damage and reduce RO membrane lifetime very much.Granular activated carbon notably assists with the removal of per- and polyfluoroalkyl substances (PFAS), which have become an increasing contaminant of concern for regulators. For coconuts granular activated carbon, the main uses is make to kill germs and improve tasty of pure water. That is why pure water is tasted a little bit sweet.
Usually coals activated carbon UDF is used as 3rd grade filter and T33 is placed as 5rd in the 5 grade water purifiers that is the cheapest and most common water purifiers. Meanwhile, filter pots usually used granular activated carbon and Ion exchange resin as cheaper alternatives for 5 grade water purifiers.
However, other chemicals, specifically iron and nitrate, can not be removed with GAC. GAC should be changed based on contaminant levels and water use, as higher levels or use may require more frequent change-outs.
How does granular activated carbon work?
According to EPA, granular activated carbon is a porous adsorption media with extremely high internal surface area, much like granular salt or granular sugar.
Granular activated carbon is made from raw organic materials that are high in carbon, such as coconut shells, coal, peat and wood. Heat is used to activate the surface area of the carbon, removing certain chemicals dissolved in water as they pass through a filter containing granular activated carbon. The GAC adsorbs the chemical due to its porous qualities.
The adsorption occurs on the internal surface of activated carbon. During adsorption, liquids or gases pass through the porous structure of the activated carbon, diffusing the compounds to be removed to the surface of the adsorbent, and are retained because of attractive forces.
How to judge the quality of activated carbon and activated carbon filter?
1. General speaking, more high iodine takes higher effective of absorption.
2. Quality. Many people think that the heavier the activated carbon filter represents the better the quality, which is wrong. In the same volume, the lighter the activated carbon, the better the void development, and the stronger the adsorption capacity.
Many activated carbon filter manufacturers try to use recycled activated carbon to reduce costs. This activated carbon is only 80% effective, which means that 20% of the voids are filled, and the corresponding weight is greater.
3. Nuts shell activated carbons are more expensive than coals activated carbon, even in the same iodine value, because there are some heavy metal elements in coals activated carbon.
4. For coals Granular activated carbon, the material is another key point of quality. Only high carbon, low sulfur anthracite is the best material for coals granular activated carbon. So normally most coals activated carbon factories are built near the anthracite mine.
History of GAC for water purification
Granular activated carbon for water purifying began over 100 years ago in Reading of England. The activation process was applied to charcoal in 1906. The first application of activated carbon in the form of GAC was in the year 1910 in Reading, England, for dechlorination of chlorinated water.
GAC for dechlorination purposes is no longer feasible or used because of the formation of additional haloforms and other chlorine compounds within the filters, however.
The use of carbon in gas masks for the absorption of poisonous gases in Ⅰ World War paved the way for the development and large-scale production of GAC. After Ⅰ World War, Europe progressed in the manufacturing of activated carbons using new raw carbonaceous materials such as coconut and almond shells.
The first granular activated carbon filters were installed in Germany in 1929 and in the U.S. in 1930, targeting taste and odor issues.
Other notable GAC milestones in history include:
· The first major GAC filter for public water supply, which was installed in a Hopewell, Virginia, water treatment plant in 1961;
· And the first full-scale advanced tertiary wastewater treatment plant in South Lake Tahoe, California, which began incorporating GAC in its operations in 1965.
Domestic water purifying system or household water purifying system
A point of use (POU) filter is installed in the water supply pipe just before the faucet where people get water and are commonly found under the sink.
Industrial or commercial water purifying system
The water purifiers are placed outside of buildings, usually they used Quartz sand filter to replace PPF, and normally they use Ion exchange resin to replace RO membranes.
Is GAC harmful?
In water treatment GAC is not considered hazardous, nor does it create hazardous outcomes for the water when used properly. However, GAC used improperly or inhaled can be hazardous, as wet activated carbon in an enclosed space depletes oxygen.
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