Activated Carbon in Water Treatment

Activated carbon is commonly used in water treatment processes because of its large surface area and porous structure that allows it to remove many impurities. Here’s an overview of how activated carbon is used in water treatment:

1. What is Activated Carbon?

• Composition: Activated carbon is derived from carbonaceous materials like coal, wood, coconut shells, or peat that have been processed at high temperatures to develop a porous surface.
• Types: In water treatment, there are two broad categories of activated carbon that are commonly used.
• Granular Activated Carbon (GAC): Coarser particles that are commonly employed in filter beds or columns.
• Powdered Activated Carbon (PAC): Coagulants that are dissolved in the water or used in the form of slurry.

2. Mechanism of Action

• Adsorption: Activated carbon is effective in removing contaminants through the process of adsorption where the contaminants adhere to the surface of the activated carbon. The porous structure of the material means that there is a large surface area for the contaminants to stick to.

Types of Contaminants Removed:

• Organic Compounds: Such as pesticides, herbicides, and industrial chemicals.
• Chlorine and Chloramines: Employed as disinfectants in water treatment plants for municipal water supply.
• Volatile Organic Compounds (VOCs): Such as benzene, toluene, and chloroform.
• Taste and Odor Compounds: Such as geosmin and methylisoborneol (MIB).
• Disinfection Byproducts: For instance, trihalomethanes (THMs).

APPLICATIONS IN WATER TREATMENT

1. Drinking Water Treatment in Municipalities

• Purpose: To eliminate organic impurities, chlorine, and DBPs, enhancing water taste and odor
• Process: GAC filters or PAC is used in the treatment of water by passing through the water or by adding it to the water.

2. Point-of-Use (POU) and Point-of-Entry (POE) Systems

• Purpose: To offer further treatment at the tap or entry point of a building.
• Process: GAC filters are employed in pitchers, under-sink filters, and whole-house systems to filter out contaminants directly before use.

3. Wastewater Treatment

• Purpose: For the elimination of organic pollutants, industrial chemicals, and pharmaceuticals from the wastewater.
• Process: Activated carbon is applied in treatment plants to remove contaminants from industrial effluents and municipal wastewater.

4. Advantages and Limitations

Advantages:

• High Efficiency: Proven to be efficient in the removal of organic and inorganic pollutants.
• Improved Water Quality: Improves the flavor, smell, and general quality of water.
• Versatility: It can be applied in different water treatment processes such as water purification and water recycling.

Limitations:

• Capacity: Activated carbon has a limited adsorption capacity and has to be replaced or regenerated after sometime.
• Selective Adsorption: It is also important to note that some contaminants may not be efficiently removed by activated carbon.
• Cost: The use of activated carbon may also increase treatment costs due to the need for frequent replacement of the material.

5. Regeneration and Disposal

• Regeneration: Activated carbon can be reused by heating or chemical treatment to bring back its adsorption capability. This process is commonly applied in large scale industries.
• Disposal: Used activated carbon that cannot be regenerated is properly disposed off in compliance with environmental laws and can be dumped in landfills or incineration plants.

Conclusion

Activated carbon is a useful aid in water treatment as it is capable of eliminating many impurities and enhancing the quality of water. They include municipal drinking water treatment, point-of-use systems, and wastewater treatment. It is important to understand the benefits and drawbacks of using the technology in order to maximize its effectiveness in providing clean and safe water.