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)
	Applied (Demonstrated) Substances	Hexavalent Chromium Cr (VI)
Scope	Concentration Range
	Hydrogeological Conditions	Saturated Unsaturated	Permeable Layer
	Chemical Soil Properties	The care must be taken in dealing with the soil containing a large quantity of chloride (halogen) ion.
	Other Remarks
Technology Description	Classification
	Status	Under Demonstration Soil and Groundwater Countermeasure Test Study (Performed 1995)
	Outline of Technology	The contaminated ground is saturated with water, and a direct current is passed through the ground.  Chromium in the form of Cr (VI) are attracted to the anode by electric charge, and so could be removed by draining the water around the anode.  This treatment derives its supply of water from ground water pumped up.
	Required Pre- and Post-treatment	It is necessary to treat draining water containing contaminants.
	Enhance Effectiveness through Combination
	Case History	The 10m3 tank was filled with Chromium contaminated soil (Cr content is 8,590-10,100mg/kg), and 40-60V DC was passed through this soil for 88 days.  It was shown that water-soluble chromium content decreased from the initial value of 32-36 mg/l to 11mg/l.
	Application Examples	None
	Limitations	When this technology apply to partially saturated soil, the soil must be saturated with water by setting up a cut-off wall.
	Properties of Treated Soil	Properties are Generally Retained
Schematic Flow Process	(Example in case of Cr (VI) contaminated soil)
Applicability	In Situ Applicability	Possible
	Ground Structures	Not Applicable
	Required Excavation	There are some cases where the establishment of cut-off wall needs excavation of soil.
	Groundwater Extraction
	Required Space
	Operational Time	This remedial speed is not so fast, so it takes a lot of time occasionally.
	Installation Time
	Maintenance and Control Requirements	water supply, drainage, disposal of sludge
	Additional Remarks
Secondary Impacts to Environment	Secondary Treatment Required?	Effluent Water Treatment
	Effects on Living Environment	Others (stray current)
	Additives	Water
	Possibility of Contaminant Spreading	None
	Secondary By-products	It can be considered theoretically that Cl2 gas occur by electrolysis in the case of this treatment applying to the soil containing a large quantity of Cl ion.

• 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