What Is Activated Carbon Filtration?
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 very 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.
Bed Filtration
There are a few couple options Integrity Water Inc. has for bed filtration. 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 would require calculations of bed depth, water flow, and other factors.
Granular activated carbon can be reactivated through thermal oxidation, which allows it to be used multiple times. Meaning that it is sustainable because it can be used more than once. 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 to study 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.
Integrity Water Inc. uses multimedia and activated carbon filtration to remove suspended solids for treating process water in industrial settings, but in many cases, reverse osmosis (RO) 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. This would include chloride, some heavy metals, tannins, unwanted water disinfection byproducts, toxins created by algae, and trihalomethanes.
Granular activated carbon filters
GAC filters contain loose granules of activated carbon that allow water to flow through easily. Water flows in one direction through the cartridge and contacts carbon in the process.
Advantage: Not as restrictive. Water flows through the carbon at a faster rate.
Disadvantage: Channeling. Water can cut a path through the carbon and allow contaminants through.
Carbon block filters
Carbon block is made of fine granules held together with a bonding agent, which only takes up 15% of the surface area. Impure water flows in through the side of the filter and sends filtered water our through the top. As carbon is ground to a finer granule, the surface area increases.
Advantage: Gives 7-10 times more surface area than GAC filters, and the compact carbon prevents channeling.
Disadvantage: More flow restrictive.
Radial flow GAC carbon filters
Radial flow carbon filters combine the surface area of the carbon block with the flow rate of the GAC filter. Water flows to the filter through the side of the cartridge radially like a carbon block but contains granules for increased flow like the GAC.