Fact sheet: Steam Injection

From: Public Services and Procurement Canada

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Description

Steam injection is a variation of the more general in situ soil heating technology. Steam injection involves increasing the temperature of the contaminated medium to promote the volatilization and desorption of volatile and semi-volatile organic compounds, as well as petroleum hydrocarbons. The injection of steam into soils with free-phase contaminants allows the contaminants to be moved to extraction systems. Steam injection is usually done in the unsaturated zone but can also be applied below the groundwater level by steam stripping. The same principles of extraction as stripping apply in this case, namely the transfer of contaminants in the vapour phase by volatilization.

The gaseous emissions that are released into the vadose zone by the process are recovered via a vapour extraction system, followed by a treatment.  

Steam injection therefore applies to free-phase contaminants, dissolved contamination or residual contamination present in both the vadose zone and in the saturated zone.

Sources:

Implementation of the technology

A steam injection system includes the installation of wells, supply lines, trenches, permeable drains or other structures for injecting steam. When steam is injected, monitoring points are installed to track steam migration and temperature changes.

Contaminated gaseous emissions are recovered by a vapour extraction system, also composed of wells, trenches or other, installed around the steam injection wells. The vapours extracted from the soil are usually moist. They are often directed to a gas-liquid separator connected to the extraction system before being treated. Treatment systems are generally composed of combustion units (thermal oxidation, catalytic oxidation) or filtration/adsorption units (activated carbon, biofiltration).

The implementation of this technology may include:

  • Mobilization, access to the site and setting up temporary facilities.
  • The development of steam injection points (wells, trenches, drains or other).
  • The installation of a steam injection system consisting of a boiler to make steam and a steam distribution system to the injection wells.
  • The installation of an extraction system consisting of steam transport pipes, a suction system and, if necessary, atmospheric emission controls.
  • The establishment of the steam treatment unit.
  • Removal of equipment and removal of injection and extraction points.

Materials and Storage

  • This technology is implemented using traditional methods and equipment that are commonly available for well development and installation.
  • Processing units can be built on-site or pre-assembled and transported in shipping containers, trailers or pallets.
  • Equipment requires the establishment of an energy source.
  • Construction and layout generally have little impact and require little on-site storage.

Residues and Discharges

  • The implementation of the system could lead to the management of contaminated soils resulting from drilling or excavation activities. In this case, these soils must be removed off-site.
  • Residues depend on the processes used to treat water and steam. Usually, it is the used activated carbon that will be regenerated or removed off-site.
  • Extraction and treatment systems may periodically require drainage and off-site disposal of contaminated water extracted using air/water separators.
  • The treatment of extracted vapours is usually required before they are released into the atmosphere. The most common air emission control systems use granular activated carbon or an oxidation process (with or without a catalyst).
  • The sorbents used for air treatment may be transported, reclaimed or disposed off-site periodically.
  • In the case of catalytic oxidation devices for the treatment of vapours, the oxidation of chlorinated organic compounds produces acidic vapor. This steam is usually managed by means of a caustic scrubber. In such a case, the wash water must be neutralized and removed periodically.

Recommended analyses for detailed characterization

Physical analysis

  • Temperature
  • Soil granulometry
  • Contaminant physical characteristics including:
    • viscosity
    • density
    • solubility
    • vapour pressure
  • Presence of non-aqueous phase liquids (NAPLs)

Recommended trials for detailed characterization

Physical trials

  • Gas permeability trials
  • Vapour survey
  • Evaluation of the radius of influence
  • Evaluation of operating pressure/vacuum
  • Evaluation of injection and extraction rates

Hydrogeological trials

  • Tracer tests

Notes:

Tests examining the effect of temperature change on hydraulic conductivity and establishing the zone of freezing with a pilot scale tubing system are recommended to properly design the full-scale containment system.

Other information recommended for detailed characterization

Phase II

  • Contaminant delineation (area and depth)
  • Presence of environmental receptors and fragile infrastructures
  • Presence of above and below ground infrastructure
  • The risk of off-site migration

Phase III

  • Soil stratigraphy
  • Identification of preferential pathways for contaminant migration
  • Conceptual site model with hydrogeological and geochemical inputs
  • Characterization of the hydrogeological system including:
    • the direction and speed of the groundwater flow
    • the hydraulic conductivity
    • the seasonal fluctuations
    • the hydraulic gradient

Notes:

Small-scale studies are required to establish the effect of steam injection on treatment efficiency using variables such as the steam injection pressure, the temperature of the steam, the quality of the steam, the time of injection of the steam, etc. Trials are required to determine the optimal design and type of injection and extraction system to be installed (well location, number, type, etc.).

Applications

In situ treatment of soils in the vadose zone.

Applicable for VOCs (chlorinated solvents and fuel) and SVOCs (certain pesticides and diesel) present in the free, dissolved or residual phase.

Efficient in sandy and homogeneous soils.

Applications to sites in northern regions

  • In situ treatment of soils in the saturated or vadose zones.
  • Applies to contaminants present in free, dissolved or residual phases.
  • Steam injection is efficient for treating sandy and homogeneous soils.

Treatment type

Treatment type
Treatment typeApplies or Does not apply
In situ
Applies
Ex situ
Does not apply
Biological
Does not exist
Chemical
Does not exist
Control
Does not exist
Dissolved contamination
Applies
Free Phase
Applies
Physical
Applies
Residual contamination
Applies
Resorption
Applies
Thermal
Applies

State of technology

State of technology
State of technologyExist or Does not exist
Testing
Does not exist
Commercialization
Exist

Target contaminants

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

Treatment time

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

Long-term considerations (following remediation work)

For the mobilization of the free phase, the level and thickness must be monitored at the end of the recovery work, and the installation of recovery devices may be required again if the free-phase product is once more measured in the wells.

Secondary by-products and/or metabolites

Steam injection enhances the volatilization and desorption of volatile and semi-volatile organic compounds. This technology does not produce by-products or metabolites because the contaminants are transferred to the aqueous or gaseous phase. The free, aqueous or gaseous phases must be collected and treated.

Limitations and Undesirable Effects of the Technology

  • Steam injection technology is efficient in a homogeneous coarse material aquifer, and/or aquifers with a high permeability and hydraulic conductivity.
  • Heterogeneous soil hydrogeological properties reduce the performance of the steam injection technique.
  • Steam injection pressure is limited by the pressure of the soil above the contaminated aquifer, and by the risk of fracturing, which can create preferential pathways.
  • The presence of buildings or infrastructure near the contaminated site may require monitoring of vapour intrusions into buildings.
  • Steam injection can cause gases to seep through preferential pathways such as foundation drains, utility trenches for public services, etc.
  • The technology is not applicable to inorganic contamination.

Complementary technologies that improve treatment effectiveness

Treatment efficiency can be increased by adding soil fracturing to increase airflow (hydraulic or pneumatic fracturing), or by sealing the soil surface to avoid "short-circuiting".

Required secondary treatments

The steam injection must be combined with a system for extracting and treating the extracted vapours.

Application examples

The following site provides an application example:

Performance

The first field trials of steam injection for groundwater treatment occurred in 1983 (Davis 1998). Since then, numerous studies have examined various aspects of the steam injection system. Today, many private companies offer steam injection as a remediation technique.

Measures to improve sustainability or promote ecological remediation

  • Choice of equipment and optimization of the size of each equipment.
  • Optimization of the calendar to promote the sharing of resources and reduce the number of mobilization days.
  • Use of energy efficient equipment.
  • Use of biofilters for air treatment.
  • Allow a longer treatment time to avoid winter operation, eliminating the need to winterize the system while reducing the amount of energy required.
  • On-site treatment of condensate and purged water from air lines.
  • Limit the number of field visits using telemetry for remote monitoring of site conditions.

Potential impacts of the application of the technology on human health

Main Exposure Mechanisms Applies or Does Not Apply Monitoring and Mitigation
Dust Applies Emissions monitoring at the source (choice of parameters, types of samples and type of intervention (source, risk or local requirements))
Atmospheric/Steam Emissions - Point Sources or Chimneys Applies Emissions monitoring at the source (choice of parameters, types of samples and type of intervention (source, risk or local requirements))
Atmospheric/Steam Emissions - Non-point Sources Applies Modeling the effects of steam injection, model validation and monitoring of soil vapour migration.
Air/steam – by-products Does not apply N/A
Runoff Does not apply N/A
Groundwater - displacement Applies Modeling of the water injection network and mobilization of the free phase and monitoring of the groundwater level using pressure sensors
Groundwater - chemical/ geochemical mobilization Applies (variation of groundwater level) Modeling required barrier effects, pressure sensor monitoring, groundwater migration monitoring and gradient change monitoring
Groundwater - by-product Does not apply N/A
Accident/Failure - damage to public services (sewers, electricity, high pressure water, natural gas, oil, fuel transportation) Applies File verification and licensing of pre-drilling or excavation work, development of special excavation or drilling procedures, and emergency response.
Accident/Failure - leak or spill Applies Risk review, development of accident and emergency response plans, monitoring and inspection of unsafe conditions
Accident/Failure – fire or explosion (inflammable vapours) Applies Risk review, development of accident and emergency response plans, monitoring and inspection of unsafe conditions
Other - Handling contaminated soils or other Solids Applies Risk review, development of accident and emergency response plans, monitoring and inspection of unsafe conditions

References

Author and update

Composed by : Josée Thibodeau, M.Sc, National Research Council

Latest update provided by : Nathalie Arel, P.Eng., M.Sc., Christian Gosselin, P.Eng., M.Eng. and Sylvain Hains, P.Eng., M.Sc., Golder Associés Ltée

Updated Date : March 22, 2019

Version:
1.2.1