Lexikon

see also ex situ soil treatment

see ex situ soil remediation

thermal desorption is the process whereby wastes are heated so that organic contaminants and water volatilize. Typically, a carrier gas or vacuum system transports the volatilized water and organics to a gas treatment system, such as a thermal oxidation or recovery system. Based on the operating temperature of the desorber, thermal desorption processes can be categorized into two groups: high temperature thermal desorption (320 to 560°C or 600 to 1000°F) and low temperature thermal desorption (90 to 320°C or 200 to 600°F).

ex situ thermal treatment of soil contaminants generally involves the destruction or removal of contaminants through exposure to high temperature in treatment cells, combustion chambers, or other means used to contain the contaminated media during the remediation process. The main advantage of ex situ treatments is that they generally require shorter time periods, and there is more certainty about the uniformity of treatment because of the ability to screen, homogenize, and continuously mix the contaminated media; however, ex situ processes require excavation of soils, which increases costs and engineering for equipment, permitting, and materials handling worker safety issues.

Thermal processes use heat to separate, destroy, or immobilize contaminants. Thermal desorption and hot gas decontamination are separation technologies. Pyrolysis and conventional incineration destroy the contaminants. Vitrification destroys or separates organics and immobilizes some inorganics.

Incineration is a heat-based technology that has been used for many years to burn and destroy contaminated materials. Because it is considered to be a conventional rather than an innovative technology, its treatment here is limited to information listed under "Additional Resources."

EX SITU THERMAL DESORPTION involves the application of heat to excavated wastes to volatilize organic contaminants and water. Typically, a carrier gas or vacuum system transports the volatilized water and organics to a treatment system, such as a thermal oxidation or recovery unit. Based on the operating temperature of the desorber, thermal desorption processes can be categorized as either high-temperature thermal desorption (320 to 560ºC or 600 to 1,000ºF) or low-temperature thermal desorption (90 to 320ºC or 200 to 600ºF).

HOT GAS DECONTAMINATION involves raising the temperature of contaminated solid material or equipment to 260ºC (500ºF) for a specified period of time. The gas effluent from the material is treated in an afterburner system to destroy all volatilized contaminants. This method will permit reuse or disposal of scrap as nonhazardous material.

PLASMA HIGH-TEMPERATURE RECOVERY uses a thermal treatment process applied to solids and soils that purges contaminants as metal fumes and organic vapors. The vapors can be burned as fuel, and the metals can be recovered and recycled.

PYROLYSIS is defined as chemical decomposition induced in organic materials by heat in the absence of oxygen. Pyrolysis typically occurs under pressure and at operating temperatures above 430ºC (800ºF). The pyrolysis gases require further treatment. The target contaminant groups for pyrolysis are SVOCs and pesticides. The process is applicable for the separation of organics from refinery wastes, coal tar wastes, wood-treating wastes, creosote-contaminated soils, hydrocarbon-contaminated soils, mixed (radioactive and hazardous) wastes, synthetic rubber processing wastes, and paint waste.

THERMAL OFF-GAS TREATMENT is one of several approaches that can be used to cleanse the off-gases generated from primary treatment technologies, such as air stripping and soil vapor extraction. In addition to the established thermal treatments, organic contaminants in gaseous form can be destroyed using innovative or emerging technologies, such as alkali bed reactors.

VITRIFICATION technology uses an electric current to melt contaminated soil at elevated temperatures (1,600 to 2,000ºC or 2,900 to 3,650ºF). Upon cooling, the vitrification product is a chemically stable, leach-resistant, glass and crystalline material similar to obsidian or basalt rock. The high temperature component of the process destroys or removes organic materials. Radionuclides and most heavy metals are retained within the vitrified product. Vitrification can be conducted in situ or ex situ.

Source: US-EPA, Clu-In:

http://www.clu-in.org/techfocus/default.focus/sec/Thermal_Treatment%3A_Ex_Situ/cat/Overview/

explosive substances are in itself capable by chemical reaction of producing gas at such a temperature and pressure and at such a speed as to cause damage to the surroundings. Pyrotechnic substances are included even when they do not evolve gases. Means a solid or liquid substance (or mixture of substances).

Source: REACH

explosive material s or explosives are substances that contain a great amount of stored energy that can produce an explosion, a sudden expansion of the material after initiation, usually accompanied by the production of light, heat, and overpressure.

The energy stored in an explosive material may be

• chemical energy, such as nitroglycerine or grain dust
• pressurized compressed gas, such as a gas cylinder or aerosol can
• nuclear, such as fissile isotopes of uranium-235 and plutonium-239

Some chemical compounds are unstable in that, when shocked, they react, possibly to the point of detonation. Each molecule of the compound dissociates into two or more new molecules (generally gases) with the release of energy. The above compositions may describe the majority of the explosive material, but a practical explosive will often include small percentages of other materials. For example, dynamite is a mixture of highly sensitive nitroglycerin with sawdust, powdered silica, or most commonly diatomaceous earth, which act as stabilizers. Plastics and polymers may be added to bind powders of explosive compounds; waxes may be incorporated to make them safer to handle; aluminium powder may be introduced to increase total energy and blast effects. Explosive compounds are also often "alloyed": HMX or RDX powders may be mixed (typically by melt-casting) with TNT to form Octol or Cyclotol.

Amongst chemical explosives the followings are the most well-known:
Nitroglycerin: a highly unstable and sensitive liquid.
Acetone peroxide: a very unstable white organic peroxide.
TNT: yellow insensitive crystals that can be melted and cast without detonation.
Nitrocellulose: a nitrated polymer which can be a high or low explosive depending on nitration level and conditions.
RDX, PETN, HMX: very powerful explosives which can be used pure or in plastic explosives.
C-4 (or Composition C-4): an RDX plastic explosive plasticized to be adhesive and malleable.

exposure is the concentration or dose of the substance to which humans and the environment are or may be exposed by producing or using the chemical substance or by using contaminated land.

exposure assessment aims to make a quantitative or qualitative estimate of the dose / concentration, which the users are exposed to. exposure assessment under REACH consists of two steps: 1) Development of exposure Scenarios and 2) exposure Estimation, which have to be iterated until it can be concluded that the resulting exposure scenarios would ensure adequate control of risks upon implementation. (Source: REACH Glossary)

The Exposure Information required for substances registered in the 1 to 10 tonne band is defined in Annex VI, 6, of REACH, and is given in the table below.

This information is required in place of the CSR which is required for substances in higher tonnage bands.

Source: http://www.reach-serv.com/index.php?option=com_content&task=view&id=160&Itemid=64

set of conditions, including operational conditions and risk management measures, that describe how the substance is manufactured or used during its life-cycle and how the manufacturer or importer controls, or recommends downstream users to control exposure of humans and the environment. These exposure scenarios may cover one specific process or use or several processes or uses as appropriate. Source: REACH Glossary

method to separate components based on their relative solubilities (partition) in two different, immiscible solvents. In extraction" target="_blank">liquid/liquid extraction the solvent (usually organic) dissolves only the desired compounds from the sample solution (usually aqueous solution). In supercritical extraction the solvent is supercritical carbon dioxide. Soxhlet extraction is the tradional way for extracting solid samples, when the sample is connected with freshly boiled solvent in a special apparatus several times. The extraction of soild samples can be intensified by ultrasound (sonication assisted extraction, SAE) or elevated pressure and temperature (pressurized fluid extraction or accelerated fluid extraction, ASE). The solid phase extraction (SPE) is characterized by decreased sample and solvent need. Further miniaturization resulted in solid phase microextraction (SPME), stirbar+extraction and the membrane assisted extraction (MASE) techniques used for sample preparation for chromatography.

solvent extraction uses an organic solvent as an extractant to separate organic and metal contaminants from soil. The organic solvent is mixed with contaminated soil in an extraction unit. The extracted solution then is passed through a separator, where the contaminants and extractant are separated from the soil. Organically bound metals may be extracted along with the target organic contaminants.

solvent extraction from soil uses an organic solvent as an extractant to separate organic and metal contaminants from soil. The organic solvent is mixed with contaminated soil in an extraction unit. The extracted solution then is passed through a separator, where the contaminants and extractant are separated from the soil. Organically bound metals may be extracted along with the target organic contaminants.

eye corrosion is defined in OECD TG 405 as ”the production of tissue damage in the eye, or serious physical decay of vision, following application of a test substance to the anterior surface of the eye, which is not fully reversible within 21 days of application”. In the EU, this effect is assigned “Xi”, and R41.

Eye irritation is defined in OECD TG 405 as “the production of changes in the eye following application of a test substance to the anterior surface of the eye, which are fully reversible within 21 days of application”.
In the EU this effect is assigned “Xi” and R36.

eye irritation is defined in OECD TG 405 as “the production of changes in the eye following application of a test substance to the anterior surface of the eye, which are fully reversible within 21 days of application”.
In the EU this effect is assigned “Xi” and R36.

Eye corrosion is defined in OECD TG 405 as ”the production of tissue damage in the eye, or serious physical decay of vision, following application of a test substance to the anterior surface of the eye, which is not fully reversible within 21 days of application”. In the EU, this effect is assigned “Xi”, and R41

Source: REACH