BIRMINGHAM — In Water Technology’s March Professor POU/POE, Technical Editor Dr. Joseph Cotruvo writes about activated carbon (AC) pertaining to water treatment applications.
In the article, Cotruvo explains that AC is carbonaceous organic material that is thermally treated to produce active sites with the capability of biding several chemicals when water (or other liquid/gas) is passed through the medium.
“There are numerous types of AC commercially available, and they are intended to apply to different water treatment purposes,” states Cotruvo. “They are primarily carbon, but also contain some ash. ASTM D2652 defines the properties of AC. Carbon used in drinking water must also meet applicable ANSI/NSF standards. AC as a water treatment medium is manufactured in extruded block, granular or powdered forms.”
Several technologies are used to evaluate ACs, reports Cotruvo, including but not limited to: The iodine number, which is a measure of the micropore content; the molasses number, a measure of the mesopores of the carbon and its ability to adsorb larger molecules; and the dechlorination capacity, which is evaluated as the dechlorination half-length and it is the depth of a carbon column required to “halve the free chlorine content in a test solution.”
Cotruvo continues by taking a closer look at powdered activated carbon (PAC) and granular activated carbon (GAC), explaining that PAC is provided in fine powders or granules and sieved to desired size ranges. When it comes to water treatment, adds Cotruvo, PAC is used intermittently, such as during an algal bloom or a chemical spill, to remove trace synthetic chemicals as well as odor and taste producing chemicals, and is intended for one-pass use. GACS have larger particle sizes, informs Cotruvo, and are used in fixed beds and post contactors.
In the article, Cotruvo notes, “AC is an extremely versatile purifying medium, including gas phase treatment, a drinking water and wastewater treatment component that can remove organic chemicals, dechlorinate and remove tastes, odors and colors, as well as improve the quality of beverage products and other fluids.”
You can find the entire March Professor POU/POE on AC here.