Carbon Filtration: Better water through Adsorption…
“Activated” Carbon (AC) Filtration is often used to:
- Remove Chlorine from municipal water supply to prevent oxidation, and subsequent degradation, of Reverse Osmosis (R O) Membranes
- Removal of Organic Contaminants
- Improve the Aesthetic quality of water, such as Color, Odor, and Taste
Activated Carbon Filter (ACF) Filters take advantage of the amazingly vast surface area possessed by activated carbon. One pound of AC boasts between 60 and 150 acres of surface area! This property allows a relatively small amount of media to attract, hold, and contain large amounts of contaminants.
Advantages of Activated Carbon Filtration Include:
- Highly Effective and Efficient at removing Organic Contaminants
- Highly Effective and Efficient at removing Chlorine to protect RO Membranes
- Relatively Inexpensive with no Recurring Cost of Consumable Chemicals
- Easily Cleaned and Maintained
- Resistant to Fouling (Clogging)
- Filtration Media is Inexpensive and Long-Lasting
- Systems are Robust with no Moving Parts inside the Tanks
- Control Valves are Modular and Designed for Operational Flexibility
Factors Affecting Activated Carbon Filtration:
Water Temperature and pH: Adsorption usually increases as pH and Temperature decrease. Many organic chemicals become more adsorbable at lower pH and Temperature.
Concentration of Contaminants: Generally, the higher the concentration of contaminants, the less effective the Activated Carbon filter will be in adsorbing those contaminants.
Exposure Time: Adsorption of contaminants is also a factor of how long the process water is in contact with the Activated Carbon “bed.” Longer contact times may be obtained by increasing the size of the filter, and therefore, the amount of carbon, by reducing demand in terms of flow rate, or by a combination of the two techniques.
Activated Carbon Filtration Operating Cycles:
Service Cycle: Carbon Filters remove contaminants from water. As the water flows downward through the carbon, contaminants are adsorbed. The contaminants accumulate in the carbon bed, while the purified water passes through to downstream processes.
Backwash Cycle: When the filter begins to clog or when the head loss (pressure drop) though the bed increases, flow rates are reduced. To prevent water channeling, or “break through”, and the resulting degradation of water quality, the Service Cycle flow is reversed, fluidizing the media bed. The reverse flow is directed, by the control valve(s) to drain, carrying with it, some of the contaminants that have been trapped during the Service Cycle. The life of the Carbon Bed will depend on how effective the Backwashing Cycle is, but the Carbon Bed will inevitably require replacement. The flow required is specific to the media and is essential to properly cleaning the Carbon Bed.
Continuous Versus Periodic Service: In most operations, demand for process water is tied to work shifts. If those work shifts consume all 24 hours each day, and the demand for process water is constant, the Activated Carbon Filtration system may need to be designed to operate in stages across multiple tanks, so that the Backwash Cycle can occur in one or more tanks while the other tanks are operating in the Service Cycle mode. If the demand for process water is periodic, Backwashing can usually occur during off hours, which decreases the size and complexity of the Activated Carbon Filtration system. Our standard products are designed to accommodate either scenario up to 400 gallons per minute; however, specific applications may require additional design modifications.