What is Activated Carbon Filtration?
The process may have ancient roots, but still plays a role in modern water treatment
Activated carbon filtration is one of many processes commonly used in water treatment to remove contaminants such as organic materials, and since it also can remove odor-causing contaminants, it’s often used to make drinking water more palatable.
The first known carbon filtration devices date back to ancient Minonan Crete, according to a paper by M. Sklivaniotis and A.N. Angelakis, “Water for Human Consumption through the History.” The water was carried through a 3-km aqueduct, and several cone-shaped terra cotta filters filled with charcoal were discovered in the system.
Activated carbon filter technology has improved with time, and today the activated carbon market is predicted to grow, with water treatment driving the growth, although the COVID-19 pandemic has introduce some uncertainty in activated carbon market predictions.
Activated carbon is frequently chosen for potable water applications because it efficiently adsorbs synthetic organic chemicals, PFAS, chlorine, compounds that affect smell and taste, and naturally occurring organic compounds. As pollution and contamination gets worse, particularly in the developing world, activated carbon filtration is poised to grow.
Water treatment plant operators have two choices when using granular activated carbon filtration, according to Water Tech Online: Retrofitting an existing multimedia filter — typically a bed filter — by replacing its medium, or installing a new filter. Both methods require calculations of bed depth, water flow, and other factors. Operators must also allow for seasonal changes in water that may mean more frequent backwash is required.
Granular activated carbon can be reactivated through thermal oxidation, which allows it to be used multiple times. Granulated activated carbon filtration can be used on its own or paired with other technologies for disinfection or other processes to achieve desired water quality. For example, it can be used with ozone in a treatment known as a biological activated carbon process.
Activated Carbon Filtration as a Stage in Treatment
Researchers continue studying the medium, which is still being widely applied in a variety of applications, for instance, activated carbon used with coagulation and filtration for advanced wastewater treatment. A granulated activated carbon unit is most often placed in a water treatment plant after conventional filtration processes, or after a process such as flocculation and sedimentation, according to the U.S. Environmental Protection Agency.
Fluence uses multimedia and activated carbon filtration to remove suspended solids for treating process water in industrial settings, but in many cases, reverse osmosis (RO), like that used in Fluence NIROBOX™ units, removes significantly more contaminants from water than activated carbon filtration. Yet pretreatment with activated carbon filtration can still protect reverse osmosis membranes from premature fouling.
Granulated activated carbon filters can also remove specific organic and inorganic substances from the water, including chloride, some heavy metals, tannins, unwanted water disinfection byproducts, toxins created by algae, and trihalomethanes.
Activated Carbon Filtration Cases
Although activated carbon filtration has ancient roots, it’s still being used in modern applications:
- Activated carbon filtration is one of many treatment technologies used in the village of Hoosick Falls, New York, since its water was contaminated by perfluorinated compounds, which are unregulated contaminants.
- In Florida, this type of filter is being applied to remove dieldrin, an insecticide used in the 1960s and 1970s, from local water supplies.
- The U.S. Army Corps of Engineers is cleaning up groundwater under an ordnance plant in Nebraska with a granular activated carbon system that includes air stripping and ultraviolet and ozone oxidation stages.
- In Fountain, Colorado, activated carbon filtration was deployed to clean up so-called “forever chemicals” from firefighting foam used at a U.S. Air Force base. Because the method was not as efficient as hoped, another remediation project on the same aquifer at Security-Widefield, Colorado, used ion exchange instead.