Fact sheet: Bioventing

From: Public Services and Procurement Canada

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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.


Implementation of the technology

Bioventing may include:

  • mobilization, site access, site preparation and setting up temporary facilities;
  • installation of wells, collection trenches and/or permeable drains;
  • the installation of air injection and extraction networks;
  • the implementation of a monitoring network for the migration of vapour effluents;
  • installation, if required, of off-gas or vapour treatment units.

Materials and Storage

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.

Residues and Discharges

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.

Recommended analyses for detailed characterization

Biological analysis

  • Total heterotrophic and specific bacterial counts (according to the contaminants of interest)

Chemical analysis

  • pH
  • Alkalinity
  • Conductivity
  • Organic matter content
  • Contaminant concentrations present in the following phases:
    • adsorbed
  • Nutrient concentrations including:
    • total phosphorus
    • organic nitrogen
    • potassium
  • Redox potential
  • Dissolved gas concentration (for the saturated zone, if necessary)

Physical analysis

  • Temperature
  • Soil water content
  • Soil granulometry
  • Presence of light or dense immiscible liquids

Recommended trials for detailed characterization

Biological trials

  • In situ respirometry trials
  • Biodegradation trial

Physical trials

  • Soil permeability tests with air (pneumatic tests)

Other information recommended for detailed characterization

Phase II

  • Regional climatic conditions (precipitation, temperature, etc.)
  • Presence of potential environmental receptors
  • Presence of above and below ground infrastructure

Phase III

  • Soil stratigraphy
  • Identification of preferential pathways for contaminant migration
  • Volume of contaminated material to treat


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).

Applications to sites in northern regions

  • The technology is achievable in northern environments, however, remote sites require greater mobilization, resulting in higher on-site monitoring costs. In addition, equipment availability is limited and work windows are relatively short.
  • Passive bioventing systems or low-intensity autonomous bioventing systems may be viable in northern environments.
  • Deep freezing, permafrost and freeze/thaw cycles may limit the depth at which the technology can be effectively implemented.
  • The cold climate will impact the biodegradation processes and may extend the treatment time compared to that in a temperate climate.
  • It may be necessary to heat and/or insulate the soils to improve the effectiveness of the treatment.

Treatment type

Treatment type
Treatment typeApplies or Does not apply
In situ
Ex situ
Does not apply
Does not exist
Does not exist
Dissolved contamination
Does not exist
Free Phase
Does not exist
Residual contamination
Does not exist

State of technology

State of technology
State of technologyExist or Does not exist
Does not exist

Target contaminants

Target contaminantsApplies, Does not apply or With restrictions
Aliphatic chlorinated hydrocarbons
With restrictions
With restrictions
Does not apply
Does not apply
Monocyclic aromatic hydrocarbons
Non metalic inorganic compounds
Does not apply
With restrictions
Petroleum hydrocarbons
Phenolic compounds
With restrictions
Policyclic aromatic hydrocarbons
With restrictions
Polychlorinated biphenyls
Does not apply

Treatment time

Treatment time
Treatment timeApplies or Does not apply
Less than 1 year
1 to 3 years
3 to 5 years
More than 5 years

Long-term considerations (following remediation work)

There is minimal long-term consideration for sites where remediation goals have been met when equipment and facilities have been dismantled.

Secondary by-products and/or metabolites

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.

Limitations and Undesirable Effects of the Technology

  • Soils with significant heterogeneity.
  • Low permeability soils combined with high moisture content.
  • Lack of moisture or nutrients in the soil can slow down the biodegradation process.
  • The depth and extent of the contamination.
  • High contaminant concentrations can be toxic to microorganisms.
  • The performance of the technology may be affected by local climatic conditions.
  •  Depth and fluctuations of the groundwater level may limit the applicability of this technology if contaminated soils are close by.
  • The presence of receptors sensitive to vapour migration.
  • Shallow soils (usually less than 1 m) can be more difficult to treat.
  • A cover for the ventilated area may be required.
  • In the presence of stratified soils, the implementation of the technology may require bioventing wells installed at different depths.
  • The technology may be limited by very hydrophobic (less bioavailable) contaminants, high organic content and high molecular weight contaminants.

Complementary technologies that improve treatment effectiveness

  • Biostimulation (such as the addition of nutrients or carbon).
  • Bioaugmentation (addition of microorganisms).
  • Adding warmth to increase the temperature of the soil (20 °C to 35 °C) to stimulate the growth of bacteria.
  • Soil fracturing to increase air circulation.
  • Addition of a surface cover (paving, membrane).

Required secondary treatments

An off-gas treatment system must be installed if bioventing is performed by the air extraction method.

Application examples

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.

Measures to improve sustainability or promote ecological remediation

  • Use of renewable energy and energy-efficient equipment for the implementation and operation of the technology.
  • Optimization of the schedule to promote resource sharing and reduce the number of mobilization days.
  • Minimizing the number of field visits by using telemetry for remote monitoring of site conditions.
  • Review of historical data to reduce the number of samples required.
  • Evaluation of the advantages of a pulsed injection system compared to a continuous injection system and to an injection system without extraction.
  • Allow for a longer processing time to avoid operation in winter conditions, eliminating the need to isolate the system while reducing the amount of energy required.
  • Use of the TRIAD approach for planning and executing site characterization steps to optimize characterization efforts and reduce the environmental footprint of this work.
  • Technology implementation and site remediation that optimizes the protection of ecological habitats and/or improves the quality of these habitats.

Potential impacts of the application of the technology on human health

Unavailable for this factsheet


Author and update

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