Vapor phase Granular Activated Charcoal (GAC) is a treatment technology that removes contaminants from air. Contaminated air is passed through one or more vessels containing GAC. Contaminants stay onto the surfaces of the activated carbon grains. The thermal processing of carbon, often from coconut shells, creates small porous particles with a large internal surface area. This processing activates the carbon. The activated carbon attracts and adsorbs organic molecules as well as certain metal and inorganic molecules. When the concentration of contaminants in the vapor exceeds a certain level, the carbon must be replaced.
Limitations and Concerns
- Some degradation products such as vinyl chloride and smaller molecules are not sorbed well, and consequently must be monitored carefully.
- All spent carbon eventually needs to be disposed in landfills or regenerated. There are few regeneration facilities.
- The carbon used for some contaminants (g.,metals) can not be regenerated.
- Relative humidity greater than 50% can reduce carbon capacity
- Some compounds, such as ketones, may cause carbon bed fires because they release heat upon adsorption.
This technology is used to treat off-gas contaminats with VOCs and some fuels.
Contamination, the introduction of a pollutant or undesirable material into the air, soil, or water, has many negative and far-reaching effects. Thus it is important to protect drinking water from contamination for public health, economic, and environmental reasons.
Water is necessary to all living things. It makes up approximately 70% of the human body’s weight and plays a role in its functions, such as digestion and cooling. Without clean drinking water, we could not survive. If the drinking water is contaminated, many health risks can result: bacteria can result in illnesses such as hepatitis or cholera; a component of gasoline, benzene, is known to be a carcinogen; lead causes kidney, liver, and nerve damage as well as pregnancy risks.
Protecting drinking water also makes good environmental sense. In the past, people thought that if we buried chemicals in the ground they would disappear. This is now a proven fallacy that has resulted in dire consequences for our environment. Everything we put into the environment accumulates. Contamination can take years to clean up and not all ground water contamination can be treated successfully with current technology. This is why pollution prevention is crucial.
What is contamination?
Contamination is the introduction of a pollutant or undesirable material into air, soil, or water. There are three types of contaminants: microorganisms, inorganic chemicals, and organic chemicals. Microorganisms are living organisms such as bacteria, viruses, and Giardia. Inorganic chemicals such as nitrate, arsenic and metals are another type of contaminant. Microorganisms and some inorganic chemicals are naturally occurring substances that taken out of drinking water through treatment at our local water systems. Organic chemicals can be solvents, fuels, and pesticides.
In the last decade, the number of products designed to reduce contaminants in tap water has expanded significantly. In this article, I summarized a quick lesson on home water purification systems.
- Know the TASTE. Does your water taste funny or smell bad? Does it look reddish or leave
- Look for products that tackle specifically your problem. Filters reduce chemical contaminants, some metals, parasites, sediment. Provide about 1/2 to 1 gallon of water a minute.
- DEVICE. Choose a style that fits your needs: Pitchers with filters: Inexpensive. No installation; frequent filter changes (every 40 gallons).
Faucet with builtin filter — may require pro to install; filter changes every 100 gallons or so.
Device that mounts on existing faucet; filter changes every 100 gallons or so.
Countertop device that connects to faucet via hose; filter change starting at about every 100 gallons. Plumbed-in: Systems that install under sink and refrigerator filters that install directly to plumbing line. Both have long filter lives; generally require pro to install.
CERTIFY/VERIFY. Look for an NSF-certified product. And be sure to read the owner’s manual to make sure you change the filter appropriately.