What is Activated Carbon and how does it work ?
Activated Carbon for water treatment and consumption
Activated Carbon is a form of carbon that has been processed to make it extremely porous, which in turn creates a large amount of surface area. This process allows for excellent adsorption. Adsorption is the adhesion of gas, liquid or dissolved solid to a surface. This is different than absorption, which is where a fluid permeates or is dissolved by a liquid or solid. Activated Carbon comes in granular or extruded forms. Activated Carbon comes from a few different materials such as coal, coconut shells, peat or wood. The Activated Carbon is made from these materials by exposing them to a very high temperature in an oxygen deficient environment which " carbonizes " the material. Then it is " activated " by exposing it to an oxidizing agent at a very high temperature. This process is what creates the porous nooks and crannies in each particle, which creates the high surface area, which is great for " collecting " contaminants from the water in your home.
Extruded carbon is a fine powdered carbon that is combined and fused with a thermoplastic binder AND specialty adsorbents like oxidizing filtration media, and then extruded into a cylindrical form for numerous apllications, including water filtration. Extruded Carbon has an even higher amount of surface area which is extremely uniform, compared to Granular Activated Carbon. Extrusion provides High Performance adsorption and particulate reduction while also providing a low flow resistance. These types of filters meet exacting performance requirements, and many of them meet NSF International standards.
So what is the purpose of Activated or Extruded Carbon ? They are both excellent at removing chlorine and bad tastes and odors from your water, along with other various organic compounds. What they will not remove is inorganic compounds, microbes, sodium, nitrates, flourides, lead and hardness minerals. There are some special carbon filters that do remove cryptosporidium and giardia cysts from you drinking water.
Granular Activated Carbon vs. Extruded Block Carbon
Extruded Carbon generally out performs Granular Activated Carbon because of its higher adsorbant capacity along with higher contaminent reduction. Extruded Carbon also gives low pressure drop, higher dirt holding capacity and low to very few carbon fines. Extruded Carbon typically has higher integrity and strength and an overall ability to produce the highest possible effluent quality when compared to GAC. Granular Activated Carbon is sometimes loosely packed in a non rigid cartridge, which can allow for water channeling. Sometimes you will get some carbon fines released from a GAC filter cartridge as well. GAC filters also sometimes allow water to bypass the carbon because of the loosley design of the filter cartridge, and it is not a good idea to mount the filter housing horizontally, as the carbon will settle to the bottom side of the cartridge and allow water to flow thru the open channel.
Most Extruded Carbon Block filters have an NSF Certification. NSF is National Sanitation Foundation International, and it is an organization that certifies products. A filter that meets NSF material requirements has been certified to not leach chemicals in excess of established standards. All filter components are tested during certification and evaluations.