Soil and Groundwater Contamination Survey and Countermeasure Technologies

Category of Tchnology	Treatment	In Situ Extraction Technology
Media	Soil, Groundwater
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) Volatile Hydrocarbon (Benzene, etc)
	Applied (Demonstrated) Substances	Pb, As
Scope	Concentration Range
	Hydrogeological Conditions	Saturated Unsaturated	Permeable Layer
	Chemical Soil Properties	Care should be taken when high concentration of chloride is contained in soils.
	Other Remarks
Technology Description	Classification
	Status	Under Demonstration Soil and Groundwater Countermeasure Test Study (Performed 1997)
	Outline of Technology	Direct current causes the migration of cations migrate to the cathod and anions to the anode in moist soils.  This is applied to contaminated soils to collect heavy metals near the electrodes and remove from soils.  The electrodes used in the demonstration test was covered with semipermeable membranes and EDTA added in the membrane cell was circulated in the system and picked up heavy metals.  Two actual contaminated soils, Pb and As, were treated with use of a small and a medium size electrolytic cells.
	Required Pre- and Post-treatment	Treatment of the extracted metals (ion exchange resin adsorption was used in the demonstration test)
	Enhance Effectiveness through Combination
	Case History	Removal of 3%/day of Pb from 5,300 mg/kg-soil, 1.5%/day of Pb from 1,000 mg/kg-soil and 1.5%/day of As from 1,800 mg/kg-soil was demonstrated.
	Application Examples	Commercially applied in Europe and U.S.
	Limitations	Impermeable walls may be needed when applied in unsaturated zone.
	Properties of Treated Soil	Properties are Generally Retained
Schematic Flow Process	Principle of Electromigration
Applicability	In Situ Applicability	Possible
	Ground Structures	Not Applicable
	Required Excavation	May need the excavation for cut-off wall installation.
	Groundwater Extraction
	Required Space
	Operational Time
	Installation Time
	Maintenance and Control Requirements	Management of EDTA solution (ion exchange columns were used in the test.
	Additional Remarks	Sufficient soil flushing is needed to remove residual extrant (EDTA) after the electrode withdrawal.
Secondary Impacts to Environment	Secondary Treatment Required?	Effluent Water Treatment
	Effects on Living Environment
	Additives	Water Others (EDTA solution)
	Possibility of Contaminant Spreading	None
	Secondary By-products	Chlorine gas may be generated when the medium contains high concentration of chloride.

• 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