What is in situ thermal treatment?
In situ thermal treatment methods move or “mobilize” harmful chemicals in soil and groundwater using heat. The chemicals move through soil and groundwater toward wells where they are collected and piped to the ground surface to be treated using other cleanup methods.
How is in situ heating used to treat VOCs?
In situ heating is used primarily to treat high dissolved concentrations of halogenated and nonhalogenated VOCs, gasoline-range fuels, and light/dense non-aqueous phase liquids (LNAPLs/DNAPLs) (USACE, 2014; ESTCP, 2010). VOCs and SVOCs are vaporized by increasing their vapor pressure.
What factors affect the cost-effectiveness of in situ thermal technologies?
The amount of contaminant mass contained in the in situ thermal treatment zone also has some impact on cost-effectiveness. The higher the contaminant concentrations, the more cost effective in situ thermal technologies become (in terms of dollars per pound of contaminant recovered).
What is in situ thermal treatment?
What is In Situ Thermal Treatment? In situ thermal treatment methods move or “mobilize” harmful chemicals in soil and groundwater using heat. The chemicals move through soil and groundwater toward wells where they are collected and piped to the ground surface to be treated using other cleanup methods.
How does thermal soil remediation work?
How Does It Work? In situ thermal treatment methods heat contaminated soil, and sometimes nearby groundwater, to high temperatures. The heat vaporizes (evaporates) the chemicals and water, changing them into gases. These gases, also referred to as “vapors,” can move more easily through soil than liquids.
What is thermal desorption unit?
Thermal Desorption Units (TDU) are now used in many industries to heat contaminated material to a high enough temperature for a long enough time to dry it and vaporize the contaminants from it.
How much does thermal desorption cost?
SOIL TECHNOLOGY:Thermal DesorptionRACER PARAMETERSEasyEasyCOST PER CUBIC FOOT$2$1COST PER CUBIC METER$81$44COST PER CUBIC YARD$75$404 more rows
How do you remove chemicals from soil?
Common treatment methods for contaminated soilBiological treatment/bioremediation uses bacteria to break down substances in the soil.Chemical oxidation converts contaminated soils into non-hazardous soils.Soil stabilisation involves the addition of immobilizing agents to reduce a contaminants' leachability.More items...
What is thermal desorption process?
Thermal desorption removes organic contaminants from soil, sludge or sediment by heating them in a machine called a “thermal desorber” to evaporate the contaminants. Evaporation changes the contaminants into vapors (gases) and separates them from the solid material.
How do thermal desorption tubes work?
How does TD work? TD is a two stage process. In the first step, a thermal desorption tube containing the sample is lowered into the thermal desorber by a multifunctional robotic autosampler. Once in in place, the tube is leak checked and then heat and flow are applied to the tube to drive off compounds of interest.
What is thermal disruption?
Thermal breakdown occurs when a car's internal heat causes a chemical reaction in the motor oil, which causes the oil's viscosity to change. The high level of heat actually causes the oil to degrade, or break down.
What is in situ thermal remediation?
In situ thermal remediation is a very aggressive treatment technology, and the cost to implement it typically is high compared to other less aggressive technologies. In situ thermal technologies are typically selected when treatment time needs to be minimized or when concentrations are very high (especially when NAPL is present). In many cases, in situ thermal remediation may be the only technology that can meet the cleanup objectives. The most critical cost factor is the treatment volume. As with all in situ technologies, application costs vary according to site and contaminants. Major cost drivers include equipment, utilities, and number/spacing of electrodes and vapor recovery wells.
What is in situ heating?
In situ heating is used primarily to treat high dissolved concentrations of halogenated and nonhalogenated VOCs, gasoline-range fuels, and light/dense non-aqueous phase liquids (LNAPLs/DNAPLs) (USACE, 2014; ESTCP, 2010). VOCs and SVOCs are vaporized by increasing their vapor pressure. Compounds that have a boiling point higher than water (such as tetrachloroethene [PCE]) can still be effectively removed using in situ thermal technologies because the co-boiling temperature of a VOC NAPL in the presence of groundwater is lower than the boiling point temperature of the pure compound. The water vapor and organics generated by heating are collected by multi-phase vacuum extraction wells and separated and treated aboveground. High temperature in situ heating using TCH is used primarily to treat halogenated and non-halogenated SVOCs, polychlorinated biphenyls (PCBs), diesel and oil-range fuels, and DNAPLs (USACE, 2014; ESTCP, 2010).
What is thermal treatment?
In situ thermal treatment is a general term for three different technologies that are used today – electrical resistance heating (ERH), thermal conduction heating (TCH), and steam enhance extraction (SEE). These technologies can accomplish steam stripping, volatilization, and boiling of volatile organic compounds (VOCs) and semi-volatile organic compounds (SVOCs) from in situ soils and groundwater. In situ thermal treatment is supplemented by vapor collection within the subsurface and aboveground treatment of recovered separated gaseous and liquid phases. For SEE and some implementations of ERH, multiphase extraction is included.
How does thermal well work?
The heating elements operate at up to 1,000°C to heat the surrounding soil. Heat transfer from the wells into the soil occurs by simple conduction and through advection (via flowing groundwater or flowing steam). The wells are sometimes installed with an outer perforated screen and their top outlets may be connected to a common manifold. In other cases, the extraction wells are separate from the heating wells. A vacuum applied to the manifold removes air and contaminants for aboveground treatment. The ground surface is covered by an insulating vapor barrier.
How long does it take to remediate a soil?
Soil remediation by in situ heating typically can be accomplished within six to nine months; however, longer treatment durations may be required at large sites. In many cases portions of the site reach treatment goals prior to other portions of the site and treatment of these areas is discontinued, with operation continuing for an extended period in recalcitrant areas. Treatment duration is site specific and depends on the following conditions:
How does heat work in the subsurface?
The voltage required to heat the subsurface will depend on the conductivity of soil moisture and groundwater in the contaminated zone. Heating vaporizes water from the subsurface, sometimes requiring a continual dripped supply of water to be added around each electrode to maintain adequate electrical conductivity.
Is in situ heating cost effective?
The feasibility and cost-effectiveness of in situ heating depends upon site hydrogeology and other site conditions. Therefore, it is important to conduct a thorough site assessment to determine the expected outcome of heating and elucidate geological properties (soil type, etc.), hydrologic properties (groundwater flow, degree of saturation, etc.), extent of contamination (the nature and extent of the plume, the extent of the source zone, and locations of known or suspected NAPL), and properties of target contaminants (which is generally available for common contaminants).
Schematic
Introduction
Other Technology Names
Description
Development Status and Availability
Applicability
Cost
Duration
- Soil remediation by in situ heating typically can be accomplished within six to nine months; however, longer treatment durations may be required at large sites. In many cases portions of the site reach treatment goals prior to other portions of the site and treatment of these areas is discontinued, with operation continuing for an extended period i...
Implementability Considerations
Resources