Activated Carbon Filtration
Activated Carbon is the most effective tool when it comes to removing Taste, Odor, organic contaminants and chlorine, which are responsible for the unpleasant flavors and smells in water.
Activated carbon (AC) is particles of carbon that have been treated to increase their surface area and increase their ability to adsorb a wide range of contaminants, activated carbon is particularly good at adsorbing organic compounds.
Contaminant reduction in AC filters takes place by two processes, physical removal of contaminant particles, blocking any that are too large to pass through the pores (obviously, filters with smaller pores are more effective), and a process called adsorption by which a variety of dissolved contaminants are attracted to and held (adsorbed) on the surface of the carbon particles. The characteristics of the carbon material (particle and pore size, surface area, surface chemistry, density, and hardness) influence the efficiency of adsorption.
AC is a highly porous material; therefore, it has an extremely high surface area for contaminant adsorption. This high concentration of pores within a relatively small volume produces a material with a phenomenal surface area
AC is made of tiny clusters of carbon atoms stacked upon one another. The carbon source is a variety of materials, such as peanut shells, coconut husks, or coal. The raw carbon source is slowly heated in the absence of air to produce a high carbon material. The carbon is activated by passing oxidizing gases through the material at extremely high temperatures. The activation process produces the pores that result in such high adsorptive properties. Activated carbon is one of the best tools which can be used to reduce risks to human health and provide an aesthetically pleasing product at reasonable cost.
The adsorption process of the AC depends on:
1) Physical properties of the AC, such as pore size distribution and surface area.
2) Chemical nature of the carbon source, or the amount of oxygen and hydrogen associated with it.
3) Chemical composition and concentration of the contaminant.
4) Temperature and pH of the water.
5) The flow rate or time exposure of water to AC.
Activated carbon (AC) cartridge Filters:
There are two basic kinds of activated carbon cartridge filters; Granular Activated carbon (GAC) and solid block activated carbon (SBAC).
Granular Activated Carbon Filters (GAC):
In this type of filter, water flows through a bed of activated carbon granules which trap some particulate matter and remove some chlorine, organic contaminants and undesirable tastes and odors.
The advantages of GAC filters include;
Simple GAC filters are primarily used for water treatment, since they can reduce chlorine and particulate matter as well as improve the taste and odor of the water.
The bottom line is that GAC filters are effective and valuable water treatment devices, but their limitations always need to be considered. A uniform flow rate, not to exceed the manufacture's specifications, needs to be maintained for optimal performance, and the filter cartridge must be changed after treating the number of gallons.
The disadvantages of GAC filters include;
Water flowing through the filter is able to "channel" around the carbon granules and avoid filtration. Water seeks the path of least resistance. When it flows through a bed of loose carbon granules, it can carve a channel where it can flow freely with little resistance. Water flowing through the channel does not come in contact with the filtration medium. The water continues to flow but it is not completely treated.
Unless the filter plugs up or you notice an odor in the "filtered water", it may be difficult to know when the filter has become saturated with contaminants and ineffective.
Solid Block Activated Carbon (SBAC):
Activated carbon is the primary raw material in solid carbon block filters; but instead of carbon granules comprising the filtration medium, the carbon has been specially treated, compressed, and bonded to form a uniform matrix. The effective pore size can be very small (0.5 - 10 micron). SBAC, like all filter cartridges, eventually become plugged or saturated by contaminants and must be changed according to manufacturer's specifications.
The advantages of SBAC filters include;
Provide a larger surface area for adsorption to take place than Granular Activated Carbon filters for better contaminant reduction, adsorption of many different chemicals (pesticides, herbicides, chlorine, chlorine byproducts, etc.) and greater particulate filtration of parasitic cysts, asbestos, etc. than many other purification processes available.
Customized SBAC filters can be produced for specific applications or to achieve greater capacity ratings for certain contaminants like lead, mercury, arsenic, etc. (Heavy metals).
Provide a longer contact time with the activated carbon for more complete contaminant reduction.
SBAC filters are useful in emergency situations where water pressure and electricity might be lost.
SBAC filters do not require electricity to be completely effective, SBAC filters do not waste water only Simple economical maintenance. Typically, an inexpensive filter cartridge needs to be changed every few months depending on water use and the manufacturer's recommendation.
The disadvantages of SBAC filters include;
SBAC filters, like all activated carbon filters, do not naturally reduce the levels of soluble salts (including nitrates), fluoride, and some other potentially harmful minerals like arsenic (unless specially designed) and cadmium, SBAC filters remove contaminants from the water, gradually lose effectiveness until they are no longer able to adsorb the contaminants.
