By Gary Battenberg
In Part 1 of this series, we looked at activated carbon (AC) application and its use in drinking water point-of-use (POU) products and point-of-entry (POE), commercial, industrial, or institutional installations. AC has long been accepted as the best all-around adsorbent for improving the taste and aesthetics of water. Additionally, its ability to address many other contaminants, such as color, detergents, odor, organics, pesticides, phenols, tannins, toxic organic compounds, trihalomethanes, and many more, has been proven to be effective for remediation.
In the last issue, we first looked at a group of contaminants for which AC has very high (excellent) affinity and listed them with a brief description of their uses. In this installment, we will look at another list of contaminants for which AC has high affinity and is a proven application.
Remember, obtaining an accurate water analysis for types of contaminant species is crucial to properly size the treatment array to yield the customer’s desired quality and/or specification.
High Carbon Affifinity
This list of contaminants has shown that AC has a high affinity for remediation, which makes it a proven application.
• Acetaldehyde: Used in the manufacture of disinfectants, drugs, perfumes, room air deodorizers, lacquers, and varnishes.
• Acetone: Used to make nail polish remover and paint remover.
• Alcohols: Three main types of alcohol (isopropyl, methyl, and ethyl). All are toxic, and only ethyl or grain alcohol can be consumed by humans.
• Antifreeze: Lowers the freezing point and increases the boiling point of water in internal combustion engines.
• Chloramine: Formed when ammonia is combined with chlorine to treat drinking water. Intended to reduce the formation of trihalomethanes and provide longer-lasting disinfection of piping systems.
• Chlorophyll: The natural compound in green plants that gives them their color and is used in medicine and health products.
• Citric acid: Used as a food additive to enhance flavor and preserve ingredients, soft drinks, juices, medicines, and dietary supplements. Also used as a resin bed cleaner for iron-fouled softeners.
• Ethyl alcohol: Grain alcohol used in making beer, wine, and spirits. Also known as ethanol.
• Ethylamine: Naturally occurring in fruits and vegetables and present in tobacco smoke.
• Ethyl chloride: Previously used in preparation of the gasoline additive tetraethyl lead. Commonly used as a cooling substance to relieve deep muscle pain.
• Ethyl ether: Used as a solvent in the production of plastics such as cellulose acetate.
• Lactic acid: Used as a food preservative, flavoring agent, and curing agent during meat processing.
• Mercaptans: Used as an odorant, which, when added to natural gas, gives a distinct odor and provides warning of a gas leak.
• Methyl acetate: Used as a solvent in glues, paints, and nail polish removers.
• Methyl alcohol: Used as fuel for camp stoves and as a paint remover, de-icing agent, and softening agent for plastics.
• Methyl chloride: Used as a catalyst solvent for butyl rubber production and as an aerosol propellant.
• Organic acids: Used for oil and gas wells in which long contact time between acid and pipe is needed to maintain production.
Organic salts: Used in processed foods for flavoring and as a preservative.
• Ozone: Converted back to oxygen by AC.
• Potassium permanganate: Oxidizer used to regenerate manganese greensand.
• Propionic acid: Used as fungicides and bactericides on stored grain, hay, and silage.
• Propyl acetate: A solvent commonly used in fragrances.
• Propyl alcohol: A solvent used in cosmetics, pharmaceuticals, and lacquers.
• Propyl chloride: Industrial solvent.
• Radon: A short-lived radioactive gas considered carcinogenic when inhaled by humans. Removed from water by aeration and/or activated carbon.
• Solvents: Collectively used to dissolve another substance to form a solution.
• Sulfonated oils: Water-soluble oils, such as olive, cod liver, tea seed, and castor, treated with concentrated sulfuric acid.
• Tannins: Organic phenolic compounds from decayed vegetation. Use anion exchange to treat tannins in water with pH above 6. Water with pH below 5 is better treated with AC.
• Tar emulsion: The liquid byproduct of mixing water with tar, used to create products for sealing, such as asphalt, roofing, and timber products.
• Tartaric acid: Used as a food additive and in ceramics, textile printing, tanning, photography, and pharmaceuticals.
• Taste (deionized water): Polishes chemical taste from deionized water to below the taste threshold.
• Taste (from organics): Polishes taste contributed by chemical and/or chemical compounds from water.
• Xanthophyll: Yellow crystalline pigment eluted into ground and surface water from fallen autumn leaves.
Empty Bed Contact Time
As stated in Part 1, when sizing for toxic organics, empty bed contact time (EBCT) must be taken into consideration, which specifies 8-10 minutes/0.7 gpm per sq ft – 0.9 gpm per cu ft. In the case of organics reduction, let’s use the same example we used in Part 1.
EXAMPLE: One cubic foot (cu ft) of activated carbon is equal to 7.48 gallons. Organic contaminant removal requires a service fellow rate of 1.4 gallons per minute (gpm) per cubic foot of media. A 10- inch diameter tank that is 48 inches tall will hold 2 cubic feet (44-inch bed depth) of activated carbon. Therefore, the calculation formula is 7.48 x 2 = 14.96 gallons capacity in 2 cubic feet.
1.4 gpm x 2 = 2.8 gpm, so 14.96 [gallons]/2.8 gpm = 5.3 minutes EBCT
For reference, use the following EBCT for designing a contactor for removing organic chemicals: 5-7 minutes/1.0 gpm per sq ft – 1.4 gpm per cu ft.
Follow the recommendations for building an activated-carbon contactor described in Part 1. and remember that industry bed depth standards for AC is 36 inches minimum. Use a good-quality water-washed or acid-washed carbon to minimize carbon fines for a better soaking, flushing, and rinse up prior to installation.
In Part 3, we will look at the good and acceptable results of using AC for other contaminant(s) remediation.
About the author
Gary Battenberg is a senior business development manager for Argonide Corporation. His four decades of experience in the water industry covers mechanical and adsorptive filtration, ion exchange, UV sterilization, reverse osmosis, and ozone technologies. He has worked in the domestic, commercial, industrial, high-purity, and sterile water treatment arenas. A contributing author to WC&P and a member of its Technical Review Committee since 2008, Battenberg was voted one of the magazine’s Top 50 most influential people in the water treatment industry in 2009. He can be reached by email at [email protected] or by phone at (407) 488-7203.
About the company
Founded in 1994, Argonide Corporation is a family-owned business focused on water filter manufacturing. Today, Argonide sells filtration cartridges and systems all over the world, commercially and residentially, across many applications and markets. Products include NanoCeram, DEAL carbon blocks (diatomaceous earth media coated with aluminum oxide-hydroxide), and the COOL-BLUE Microbiological Water Purifier System.