Absorption
The uptake of water, other fluids, or dissolved chemicals by a cell or an organism (e.g., as tree roots absorb dissolved nutrients in soil).

Activated carbon
A highly adsorbent form of carbon used to remove odors and toxic substances from liquid or gaseous emissions. In waste treatment, it is used to remove dissolved organic matter from waste drinking water. It is also used in motor vehicle evaporative control systems.

Adsorption
Removal of a pollutant from air or water by collecting the pollutant on the surface of a solid material; e.g., an advanced method of treating waste in which activated carbon removes organic matter from waste-water.

Aerobic
Life or processes that require, or are not destroyed by, the presence of oxygen.

Aerobic treatment
Process by which microbes decompose complex organic compounds in the presence of oxygen and use the liberated energy for reproduction and growth. Such processes include extended aeration, trickling filtration, and rotating biological contactors.

Air sparging
Injecting air or oxygen into an aquifer to strip or flush volatile contaminants as air bubbles up through the ground water and is capturedby a vapor extraction system.

Anaerobic
A life or process that occurs in, or is not destroyed by, the absence of oxygen.

Attentuation
The process by which a compound is reduced in concentration over time, through absorption, adsorption, degradation, dilution, and/or transformation.

Biochar
Charcoal produced from plant matter and typically buried underground in order to remove from the atmosphere carbon dioxide (fixed during photosynthesis) that would otherwise contribute to the greenhouse effect.

Bioremediation
Use of living organisms to clean up oil spills or remove other pollutants from soil, water, or wastewater

Carbon adsorption
A treatment system that removes contaminants from ground water or surface water by forcing it through tanks containing activated carbon treated to attract the contaminants.    

Dechlorination
Removal of chlorine from a substance

Dense Non-Aqueous Phase Liquid (DNAPL)
An acronym for denser-than-water nonaqueous-phase liquid -- an organic liquid, composed of one or more contaminants, that does not mix with water and is denser than water. The most common DNAPL contaminants in ground water are chlorinated solvents. (National Research Council)

Dredging
Removal of mud from the bottom of water bodies. This can disturb the ecosystem and causes silting that kills aquatic life. Dredging of contaminated muds can expose biota to heavy metals and other toxics, including PCBs.

Ex situ remediation
Involves the removal of contaminated material to be treated elsewhere.

Hydrophilic
Having a strong affinity for water

Hydrophobic
Having a strong aversion to water

Impermeable
Not easily penetrated. The property of a material or soil that does not allow, or allows only with great difficulty, the movement or passage of water.    

In situ
Involves treating contaminated material at the site.

In-situ flushing
Introduction of large volumes of water, at times supplemented with cleaning compounds, into soil, waste, or ground water to flush hazardous contaminants from a site.

In-situ oxidation
Technology that oxidizes contaminants dissolved in ground water, converting them into insoluble compounds.    

In-situ stripping
Treatment system that removes or "strips" volatile organic compounds from contaminated ground or surface water by forcing an airstream through the water and causing the compounds to evaporate.

In-situ vitrification
Technology that treats contaminated soil in place at extremely high temperatures, at or more than 3000 degrees Fahrenheit

Incineration
A treatment technology involving destruction of waste by controlled burning at high temperatures; e.g., burning sludge to remove the water and reduce the remaining residues to a safe, non-burnable ash that can be disposed of safely on land, in some waters, or in underground locations.    

Injection well
A well into which fluids are injected for purposes such as waste disposal, improving the recovery of crude oil, or solution mining.    

Light Non-Aqueous Phase Liquids (LNAPLs)
Less-dense-than-water nonaqueous-phase liquid. LNAPLs do not mix well with water and are less dense than water. Gasoline and fuel oil are common LNAPLs.

Oxidation
The chemical addition of oxygen to break down pollutants or organic waste; e.g., destruction of chemicals such as cyanides, phenols, and organic sulfur compounds in sewage by bacterial and chemical means.    

Permeability
The rate at which liquids pass through soil or other materials in a specified direction.    

Petroleum
Crude oil or any fraction thereof that is liquid under normal conditions of temperature and pressure. The term includes petroleum-based substances comprising a complex blend of hydrocarbons derived from crude oil through the process of separation, conversion, upgrading, and finishing, such as motor fuel, jet oil, lubricants, petroleum solvents, and used oil.

Phytoremediation
Phytoremediation is the direct use of green plants and their associated microorganisms to stabilize or reduce contamination in soils, sludges, sediments, surface water, or ground water.  Sites with low concentrations of contaminants over large cleanup areas and at shallow depths present especially favorable conditions for phytoremediation.

Phytotreatment
The cultivation of specialized plants that absorb specific contaminants from the soil through their roots or foliage. This reduces the concentration of contaminants in the soil, but incorporates them into biomasses that may be released back into the environment when the plant dies or is harvested.    

Plasma arc reactors
Devices that use an electric arc to thermally decompose organic and inorganic materials at ultra-high temperatures into gases and a vitrified slag residue. A plasma arc reactor can operate as any of the following: (1) integral component of chemical, fuel, or electricity production systems, processing high or medium value organic compounds into a synthetic gas used as a fuel. (2) materials recovery device, processing scrap to recover metal from the slag. (3) destruction or incineration system, processing waste materials into slag and gases ignited inside of a secondary combustion chamber that follows the reactor.    

Polychlorinated biphenyls (PCBs)
A group of toxic, persistent chemicals used in electrical transformers and capacitors for insulating purposes, and in gas pipeline systems as lubricant. The sale and new use of these chemicals, also known as PCBs, were banned by law in 1979.    

Remediation
Cleanup or other methods used to remove or contain a toxic spill or hazardous materials from a Superfund site.    

Sparge
Injection of air below the water table to strip dissolved volatile organic compounds and/or oxygenate ground water to facilitate aerobic biodegradation of organic compounds.