Powdered activated carbon (PAC) is a highly porous adsorptive material that plays a central role in industrial water and wastewater treatment due to its large specific surface area. PAC is primarily used to remove organic pollutants, heavy metals, odors and flavors as well as toxic substances from water and wastewater. Their high effectiveness and versatility make PAHs an indispensable component in various treatment processes.

Chemical and physical principles of powdered activated carbon

Powdered activated carbon is produced by activating carbon sources such as wood, peat, coconut shells or hard coal. The activation process is carried out either by chemical treatment or thermal processes (steam activation). This produces a highly porous material with the following properties:

  1. High specific surface area:

    • Values of 500 to 1500 m²/g are typical.
    • Responsible for the adsorption capacity.

  2. Pore structure:

    • Mikroporen (< 2 nm): Adsorption kleiner Moleküle.
    • Mesopores (2-50 nm): Adsorption of larger molecules.
    • Macropores (> 50 nm): Allow access to deeper pores.

  3. Chemical modification:

    • Can be adapted to specific applications by treatment with acids, bases or oxidizing agents.

Adsorption is based on physical and chemical interactions, in particular van der Waals forces and electrostatic bonds.

Areas of application for powdered activated carbon

  1. Drinking water treatment:

    • Removal of organic pollutants such as pesticides, herbicides, pharmaceutical residues and chlorine compounds.
    • Reduction of odors and flavors.

  2. Industrial wastewater treatment:

    • Adsorption of poorly degradable organic substances, AOX reduction and micropollutants.
    • Removal of colorants and aromas in the textile industry.

  3. Water recycling and recycled water treatment:

    • Removal of disruptive residual materials to enable them to be fed back into production processes.

  4. Pre-treatment in reverse osmosis:

    • Removal of organic substances that could impair the service life of the membranes.
Filter technology from ALMAWATECH as gravel and sand filters or activated carbon filters

Photo: Our activated carbon filters in GRP tanks(ALMA FIL AK)

Dosage and application

PAHs are usually applied in suspension form. The process comprises the following steps:

  1. Storage and dosage:

    • PAH is stored in silos or big bags.
    • It is added to water or waste water via dosing systems.

  2. Suspension production:

    • PAH is mixed with water in agitator tanks to ensure even distribution.
    • Typical dosing quantities are between 10 and 100 mg/l, depending on the pollutant load.

  3. Contact time:

    • To ensure effective adsorption, a contact time of 15 to 60 minutes is required.
    • The efficiency depends on the concentration of pollutants and the temperature.

  4. Separation and disposal:

Advantages of powdered activated carbon

  1. High adsorption capacity:

    • Effective removal of even low-concentration pollutants.

  2. Flexibility:

    • Simple adaptation to different requirements by varying the dosing quantity.

  3. Wide range of applications:

    • Can be integrated into various process stages, e.g. pre-treatment or post-treatment processes.

  4. Fast effectiveness:

    • Due to the fine particle size and the high specific surface area.

  5. Economic efficiency:

    • Cost-efficient, especially in the case of intermittent pollutant loads, as use can be demand-driven.

Challenges and solutions

  1. Handling and storage:

    • PAH is dusty and requires dust-tight silos and special dosing equipment.
    • Solution: Use of closed conveyor systems.

  2. Separation after use:

  3. Disposal:

    • The disposal of loaded PAHs can be costly.
    • Solution: Thermal utilization to recover energy from the loaded coal.

  4. Regeneration:

    • Compared to granular activated carbon (GAC), regeneration of PAC makes less economic sense.
    • Solution: Optimization of use and minimization of residual quantities.

Conclusion

Powdered activated carbon (PAC) is an indispensable aid in industrial water and wastewater treatment. Its high adsorption capacity, flexibility and versatility enable the effective removal of pollutants from various water streams. Careful process integration and optimized operational management can maximize the benefits of PAC and minimize potential challenges. 

For further information on our products, please feel free to contact us at any time!

info@almawatech.com

06073 687470