EX-SITU REMEDIATION SERVICES: Soil Vapour Extraction Systems

Effectively removing volatile compounds from the vadose zone.
Ex-Situ Remediation - Soil Vapour Extraction System

Experience

IRSL has designed and implemented numerous Soil Vapour Extraction (SVE) systems in various geologies.

We have mobile equipment for the treatment of soil vapour impacted by petroleum hydrocarbons, volatile organic compounds, and PAHs, using activated carbon or gas and electrical catalytic oxidation.

For our Province of Ontario clients, our Mobile Certificates of Approval enable us to be on-site within two weeks.

Approach

Soil Vapour Extraction Systems effectively remove volatile compounds from the vadose zones and can be coupled with Air Sparging to address saturated zone impacts.

A well-established remediation technology, SVE is the vadose zone equivalent of pump-and-treat technology for groundwater remediation. It uses a vacuum to extract volatile contaminant vapours from vadose zone (unsaturated) soils. The extracted vapours are subsequently treated and released into the environment.

Advantages

SVE has several advantages:

  • Minimal site disturbance.
  • Relatively quick mass removal method for volatile compounds.
  • Can potentially treat large soil volumes at reasonable costs.

Geology Addressed

  • Fill Materials
  • Fluvial Deposits
  • Fractured Carbonate Rock
  • Fractured Shale
  • Glacial Till

Treatment Trains Used

  • Activated Carbon
  • Permanganate Impregnated Activated Carbon
  • Electric and Natural Gas Catalytic Oxidizers (Catox)
  • Biofilters

Contaminates Mitigated

  • Aromatic Volatile Organic Compounds
  • Chlorinated Ethenes and Ethanes
  • Petroleum Hydrocarbons

Treatment Trains

Treatment trains may include:

Activated Carbon

Composed of black granules of bituminous coal, wood, nutshells or other carbon-rich materials, Granular Activated Carbon (GAC) can treat a wide range of contaminants dissolved in groundwater, such as fuel oil, solvents, polychlorinated biphenyls (PCBs), dioxins, and other industrial chemicals, as well as radon and other radioactive materials.

As contaminated water or air flows through the activated carbon, the contaminants are chemically bound, or sorbed, to the surface of the carbon, removing them from the water or air. Various types and grades of GAC exist, including virgin and regenerated. IRSL aids our clients in determining which carbon type and carbon material is best for their application.

Permanganate Impregnated Activated Carbon

Activated carbon’s adsorptive capacity can be greatly enhanced through impregnation with permanganate or other options. This option is especially useful in addressing vinyl chloride.

Electric and Natural Gas Catalytic Oxidizers (Catox)

Electric or Natural Gas Catalytic Oxidizers (Catox) use the organic compounds within the impacted air as fuel to combust the compounds prior to discharge to the atmosphere.

Sand, Particulate and Green Biofilters

Extracted groundwater is filtered trough various sand, particulate or “green” filters to remove fine particles that can plug down gradient filters and media as well as removing some contaminants such as iron and lead. IRSL provides technical advice to our clients on which filters are most effective for their application. Various types of filters can be utilized, including:

  • Canister
  • Sand
  • Bag
  • Organoclay
  • Chemical filters, such as Greensand

Considerations

  • Effective Soil Vapour Extraction requires a comprehensive understanding of the constraints of the site geology.
  • On sites with high groundwater levels, water table depression pumps may be required to offset the effect of upwelling induced by the vacuum.
  • Airflow across a site is key to the program’s success; soil moisture and subsurface heterogeneity can result in less vapour flow across some zones, thus requiring detailed engineering and placement of screens.
Ex-Situ Remediation - Soil Vapour Treatment Systems - Equipment

Details

Also called “in situ soil venting” or “vacuum extraction”, Soil Vapour Extraction systems reduce concentrations of volatile constituents absorbed into the subsurface by converting them from the solid (sorbed) and liquid (aqueous or non-aqueous) phases into the gaseous phase, and then removing them through extraction wells. Vapours are then treated above-ground.

The system relies on vapour flow through the subsurface and extraction via wells specifically installed for vapour extraction. Vacuum extraction promotes vapour flow across a site, thus increasing the mass transfer driving force from aqueous (soil moisture), non-aqueous (pure phase), and solid (soil) phase into the gas phase.

SVE is most effective for contaminants with higher Henry’s Law constants, such as benzene, toluene, ethylbenzene and xylenes, TCE and PCE.

Soil Vapour Extraction + Air Sparging

SVE can be enhanced by combining it with Air Sparging. Air sparging is the process of blowing air directly into the groundwater. As the bubbles rise, the contaminants are removed from the groundwater by physical contact with the air (i.e., stripping) and are carried up into the unsaturated zone (i.e., soil).

As the contaminants move up into the soil (unsaturated zone), a soil vapour extraction system collects the vapours and removes the contaminates for treatment. Air sparging can also enhance aerobic biodegradation reactions by introducing oxygen to the groundwater, which the native micro-organisms utilize to degrade compounds such as petroleum hydrocarbons.

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