Soil and Groundwater Contamination Survey and Countermeasure Technologies

Category of Tchnology	Treatment	In Situ Extraction Technology
Media	Soil, Groundwater, Soil Gas
Contaminants	Volatile Chlorinated Organic Compounds (TCE, PCE, etc) Volatile Hydrocarbon (Benzene, etc)
	Applied (Demonstrated) Substances	Tetrachloroethylene
Scope	Concentration Range	In principle, the higher concentration of the contaminants is, the higher recovery efficiency of the contaminants is.
	Hydrogeological Conditions	Unsaturated	Permeable Layer
	Chemical Soil Properties
	Other Remarks	Acceleration of aerobic degradation is expected in Europe and U.S.
Technology Description	Classification
	Status	Under Demonstration Soil and Groundwater Countermeasure Test Study (Performed 1995)
	Outline of Technology	This is a technology that make volatile organic compounds vaporise and let them go by injecting air into a vadose zone and groundwater.  Soil gas vacuum extraction method employs the same principle.
	Required Pre- and Post-treatment	Need to collect more air than the injected air in quantity from underground. Absorbed soil gas should be treated.
	Enhance Effectiveness through Combination
	Case History	Installed five wells to send air into the loam layer(down to GL-3m : loam; lower part, clay layer) in a vadose zone polluted with tetrachloroethylene .  Pressed air of 0.8m3/ min  and absorbed soil gas of 4m3/ min. through the vacuum extraction wells installed on the surface of the earth.  Collected 3.19kg of tetrachloroethylene during the test operation that continued for 1110 hours  ( quantity of the collected air this time was 2.87g / hour).  Concentration of the soil gas at the background was 270vol.ppm before the treatment and it restored to 15.1 vol.ppm after the treatment which was about 1/20 of the previous value.
	Application Examples	This technology has been commonly used as restoration technology for pollution by  volatile substances  in Europe and the United States.
	Limitations	Permeability of a target medium (for example, loam layer and sand layer) should be high.Pressed air should be prevented from spreading in the soil of the vadose zone and flowing out.  In the purified vadose zone ,enough soil gas should be absorbed in order to keep the atmospheric pressure always negative.
	Properties of Treated Soil	Properties are Generally Retained
Schematic Flow Process	System of Air Injection Well and Observation Well used for a Proof Examination
Applicability	In Situ Applicability	Possible
	Ground Structures	Applicable even if Ground Structures are Present
	Required Excavation	Digging is required when air injection wells, vacuum extraction wells, and observation wells are installed.
	Groundwater Extraction
	Required Space	It depends on scale of pollution.
	Operational Time	Duration of the operation could be shorter than the vacuum extraction method.
	Installation Time
	Maintenance and Control Requirements	In addition to the measurement of the quantity of the injected air and absorbed air and concentration of the soil gas, it is necessary to monitor the concentration of underground  water and soil gas in the surrounding area.
	Additional Remarks
Secondary Impacts to Environment	Secondary Treatment Required?	Off-gas Treatment
	Effects on Living Environment	Noise
	Additives	Air
	Possibility of Contaminant Spreading	There is a possibility that inappropriate location or operation of the wells would lead to spread of the pollution.
	Secondary By-products	None

• 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