The last decade marked a public awareness of the quality of drinking water. The outbreak of cholera and typhoid fever in many towns, as well as E. coli and heavy metal contamination in many rivers and dams made the public aware of and anxious about the drinking water quality in South Africa. Newspapers often report sewage spills or insufficient water treatment due to a lack of skills or sewage plants not being properly maintained. As theb result moe and more responsible concerned consumers now purchase More and more responsible consumers purchase domestic filtration systems for peace of mind. Most filtration systems use activated carbon which is an excellent filter medium. Activated carbon is universally recognised and widely used to remove contaminants such as chlorine, herbicides, pesticides, industrial chemicals, and trihalomethanes (THM).

Carbon Filtration
Carbon filtration is a method of water purification that uses a block or granules of activated carbon to remove contaminants utilizing chemical adsorption. Researchers often refer to activated carbon filters as miracle filters because of their great adsorption properties. Carbon has a long history of being used to adsorb impurities and organic toxins and is the most powerful adsorbent known to man. A half a kilogram (500 gm) of activated carbon contains a surface area of 50 hectares. Activated carbon has a slight electro-positive charge, making it very effective in removing chemicals and impurities.

Most of these filters are rated by the size of particles removed and are measured in microns. The range may vary between 0,5 to 50 microns. The efficiency of carbon filters depends on flow and contact-time. The slower the flow, the more contaminants are exposed to the filter medium and consequently removed.

Adsorption
Adsorption is the binding of one substance at the surface of another, but not being absorbed.

What is Activated Carbon?
Activated carbon is manufactured from carbonaceous materials like coal, peat, wood, or nutshells (i.e. coconut). The processes to activate carbon include the following:

• · Dehydration: All moisture is removed from the raw material.
• · Carbonation: The raw material is carbonated under anaerobic conditions.
• · Activation: The carbon is now treated with steam at 1 800 ^oC. Some carbon atoms are vaporised, leaving behind a highly porous structure, reminescent of a honeycomb.

• Two types of carbon are manufactured this way viz. powdered activated carbon (PAC) and granular activated carbon (GAC). To manufacture an activated carbon block (ACB) a binding material is added to GAC.

Adsorption by activated carbon proceeds through 3 basic steps:

Substances adsorb on the exterior of the carbon granules.

• · Substances move into the carbon pores.
• · Substances adsorb to the interior walls of the carbon.

To find out more about carbon filtration please contact us.

Sources

Wikipedia.
Internet: Ecology Fact Sheet: Treatment Specific Guidance – Carbon Adsorption.
Water Technology. e-News Daily.
The Pure Water Network: www.pwn.com.
Water Treatment Primer, Environmental Information Management, Civil Engineering Dept., Virginia Tech.
KX Industries: www.kxindustries.com.
www.tigg.com.