Soil and Groundwater Contamination Survey and Countermeasure Technologies

Category of Tchnology	Treatment	In Situ Extraction Technology
Media	Soil Gas
Contaminants	Volatile Chlorinated Organic Compounds (TCE, PCE, etc)
	Applied (Demonstrated) Substances	Trichloroethylene
Scope	Concentration Range	Dilution of inlet gas may be needed for higher TCE concentration.
	Hydrogeological Conditions	-	-
	Chemical Soil Properties
	Other Remarks
Technology Description	Classification	Decomposition
	Status	Under Demonstration Soil and Groundwater Countermeasure Test Study (Performed 1994)
	Outline of Technology	Gas containing volatile chlorinated compound mixed with hydrogen gas is heated to about 200°C  and passed through layers of precious metal catalysts to cause reductive reaction to dechlorinate the chlorinated compound resulting in detoxification of the contaminated gas.  Trichloroethylene is converted to ethane which further to carbon dioxide and water by the reaction with excess hydrogen.
	Required Pre- and Post-treatment	Neutralization of hydrochloric acid generated in the reaction, as post-treatment.
	Enhance Effectiveness through Combination
	Case History	Gas extracted from a soil gas vapor extraction system containing TCE at 200 ppmv was added with 2,500 ppmv of hydrogen.  The off-gas from the catalyst layers was less than 2-3 ppmv.  The demonstration test showed that carbon and chloride was recovered 100% as carbon dioxide in the off-gas and chloride ion in the neutralized water.
	Application Examples	The demonstration test was carried out at the site where a SVE system was being operated.
	Limitations	In the demonstration test, no dioxins were detected.  As with chlorinated hydrocarbons, reductive reaction can dechlorinate dioxins.
	Properties of Treated Soil	-
Schematic Flow Process	Multistage Catalytic Reduction System
Applicability	In Situ Applicability	Possible
	Ground Structures	-
	Required Excavation
	Groundwater Extraction
	Required Space	20m2, demonstration plant
	Operational Time
	Installation Time
	Maintenance and Control Requirements
	Additional Remarks
Secondary Impacts to Environment	Secondary Treatment Required?	Effluent Water Treatment
	Effects on Living Environment
	Additives	Others (H2 gas)
	Possibility of Contaminant Spreading	None
	Secondary By-products	Dioxins were not detected in the demonstration-test.  Dioxins can be dechlorinated by this process.

• 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