Soil and Groundwater Contamination Survey and Countermeasure Technologies

Category of Tchnology	Treratment	In Situ Containment Technology
Media	Soil
Contaminants	Heavy Metal (Cd, Pb, As, Hg, Se, etc) Inorganic Compounds (total CN, etc) Reducible Inorganic Compounds (Cr6+, etc) Volatile Chlorinated Organic Compounds (TCE, PCE, etc) Semi Volatile Chlorinated Organic Compounds (PCB, etc) Volatile Hydrocarbon (Benzene, etc) Agricultural Chemicals (Organic Phosphorus Compounds, etc) Others (Dioxin)
	Applied (Demonstrated) Substances	Pb, As, Organic Mercury, HCH, DDT, Aldrin, Endrin, Dieldrin, Parathion, EPN, etc.
Scope	Concentration Range
	Hydrogeological Conditions	Unsaturated	Permeable Layer Semi to Impermeable Layer
	Chemical Soil Properties	Organic contents: less than 10%
	Other Remarks	Application to wet land requires more energy for dehydration.
Technology Description	Classification
	Status	Under Demonstration Soil and Groundwater Countermeasure Test Study (Performed 1993 & 1995)
	Outline of Technology	Contaminated soil is fused and solidified at 1600-2000°C by Joule heat generated by applying high-voltage electric current to the soil via graphite anode inserted.  Volatile contaminants, which vapor in the process, are caught, by off-gas hood, and treated by wet scrubbing, HEPA/active carbon-filter and oxidization/decomposition.
	Required Pre- and Post-treatment	After the scrubbing process, some contaminants will remain in the waste water, which should appropriately be treated of.  The pit, resulting from the vitrification, should be filled up.
	Enhance Effectiveness through Combination
	Case History	The vitreous substance obtained by fusing the soil mixed with discarded agricultural chemicals in a test, was crushed and subjected to an elution test. The elution of lead, etc., of which the contents in the fused substance were a few percent collectively, was within the limitation set by the Soil Environmental Quality Standards, and no elution was found of organic matters, such as HCH, whose concentrations in the fused matter were ten-odd percent.  Another test of the soil containing hexavalent chromium slag proved that chromium was effectively immobilized in the vitreous material, with the elution remaining within the limit set by the Soil Environmental Quality Standards.
	Application Examples	In the U.S., where this method has been in use on a large scale, the staging treatment method, in which the contaminated soil is Excavated and gathered to a central plant for fusing and solidification, is being adopted recently.
	Limitations	The process will leave a large, vitreous solid block in the ground, which needs to be crushed depending on the use of the site.
	Properties of Treated Soil	Properties Change to Major Extent
Schematic Flow Process	Principle of In Situ Vitrification
Applicability	In Situ Applicability	Possible
	Ground Structures	Not Applicable
	Required Excavation	Excavation is not necessary.  In the U.S., however, soils are generally Excavated and gathered to one place for processing.
	Groundwater Extraction	Because larger energy will be required if the soil is watered, it is necessary to set up water walls or lower the groundwater level by pumping.
	Required Space
	Operational Time	It takes from one to ten days to complete the process of fusing/solidification, which also completes the remediation of the fused and solidified portion of the soil.
	Installation Time	Once the fusing and solidification begin, the operation has to continue without a break until the process completes.
	Maintenance and Control Requirements	Only the trained personnel should operate the system.  Uninterrupted control of the operation is required until the process ends.
	Additional Remarks	Because contaminants may vapor by fusing and spread to the soil in the neighborhood, it may be necessary in certain cases to shield the operational area by steel sheet piles, etc.
Secondary Impacts to Environment	Secondary Treatment Required?	Effluent Water Treatment    Off-gas Treatment
	Effects on Living Environment	Noise
	Additives
	Possibility of Contaminant Spreading	A demonstrative test found a slight spread of contaminants to the soil in the neighborhood.
	Secondary By-products	It will be necessary to pay due attention to the unintended formation of toxic substances, depending on the nature of the contaminants and soils.

• Understanding the Contamination Survey and Countermeasure Technology Description Sheet
• Where to make contact

Soil Environment Management Division, Water Environment Department, Environmental Management Bureau, Ministry of Environment
Tel: +81-3-5521-8319
E-mail: MOE@env.go.jp