From: Public Services and Procurement Canada
Bioventing is a treatment technology that is performed by injecting air into the unsaturated zone (and/or the water table fluctuation zone) of the soil to stimulate the activity of microorganisms and promote contaminant biodegradation processes.
Bioventing can be performed in several modes of operation, including air injection or extraction from the bioventing wells. For this last mode of operation, a vapour treatment unit is required.
Nutrients such as nitrogen, phosphorus and potassium can be added to stimulate the growth of microorganisms. It is also possible to use irrigation (with or without nutrients), gaseous nutrients (such as nitrous oxide and triethyl phosphate), added moisture, or gases other than air (such as methane, propane, and hydrogen). However, such applications are rare.
Bioventing should not be confused with ventilation. Ventilation involves the use of large amounts of energy to create negative pressures and relatively high vapour displacement rates to remove volatile contaminants from soils. Bioventing, on the other hand, requires lower energy inputs to provide the necessary oxygen supply to the soil to stimulate biodegradation processes. Low-energy “passive” bioventing systems and solar-powered bioventing systems have been successfully tested. A “passive” bioventing system uses pressure differentials between the vadose zone of the soil and the atmosphere to move air in or out of the bioventing wells.
Sources:
Bioventing may include:
Bioventing may involve the use of specialized equipment for the development and installation of bioventing wells and the service lines between the wells and the treatment unit. On-site storage may include the matrix used for air treatment if required, nutrients for bacterial stimulation, as well as fuels, lubricants and other site materials required for the operation of machinery or equipment for the process.
If an air extraction and off-gas treatment system is used, the used materials (such as active carbon) from the air treatment may periodically need to be transported and regenerated or disposed of off-site. This is also necessary for contaminated water (condensate) from the air/water separator if applicable.
The bioventing technology is suitable for the treatment of permeable to semi-permeable soils present in the unsaturated zone and/or in the fluctuating water table zone. The technology is applicable to chemical compounds that can be biodegraded under aerobic conditions (presence of oxygen).
There is minimal long-term consideration for sites where remediation goals have been met when equipment and facilities have been dismantled.
Biodegradation of organic contaminants generally does not generate toxic by-products.
However, this is possible for some organic contaminants. For example, vinyl chloride and 1,2-dichloroethylene (cis) are produced during the biodegradation of trichloroethylene and tetrachloroethylene.
An off-gas treatment system must be installed if bioventing is performed by the air extraction method.
The following links provide application examples:
The time required to treat contaminants with a bioventing system is highly variable and depends mainly on the properties of the contaminant and the environmental conditions.
The treatment of soils contaminated with petroleum hydrocarbons has demonstrated a 98% reduction in contaminants.
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Composed by : Serge Delisle, Eng. M.Sc., National Research Council
Updated by : Karine Drouin, M.Sc., National Research Council
Updated Date : January 1, 2008
Latest update provided by : Nathalie Arel ing., M.Sc., Frédéric Gagnon CPI., Sylvain Hains ing., M.Sc., Golder Associates Ltd.
Updated Date : March 27, 2022
