Fact sheet: Hot water injection

From: Public Services and Procurement Canada

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Description

Hot water injection is an in situ remediation technology that was developed to facilitate the movement of free phase products or the desorption of adsorbed phases to an extraction system or an in situ treatment zone. This technology is a variation of the most general soil heating technology.

The injection of hot water into the aquifer increases the ambient temperature, which consequently reduces the viscosity of the free-phase products, decreases their adsorption onto soil particles or organic matter and increases the dissolution of contaminants.

Sources:

Implementation of the technology

A hot water injection system includes the installation of a network of wells or other structures that are used to inject water into the treatment area.

A vapour containment and recovery system above the hot water treatment area are recommended to prevent volatilization of contaminants and emission of gas to the soil surface. The hot water injection technique must be combined with a system for extracting products in dissolved and/or free phases, such as a pumping system or an in situ system for the treatment of contaminants.

The implementation of this technology may include:

  • Mobilization, access to the site and setting up temporary facilities.
  • The development of water injection points (wells, trenches or drains).
  • The installation of a system for heating the water to be injected.
  • The installation of a water injection system consisting of a pumping system and a set of distribution pipes.
  • The development of an extraction system or the recovery of products in free phase as well as the development of a reservoir for products in free phase.
  • Extraction, recovery and treatment of vapours.
  • Dismantling of equipment and removal of injection and extraction points if applicable.

Materials and Storage

  • This technology is implemented using traditional methods and equipment that are commonly available for well development and installation or trenching.
  • Injection and extraction units can be built on-site or pre-assembled and transported in shipping containers, trailers or pallets.
  • The equipment requires the installation of a large energy source for heating the water.
  • The installations generally have minimal impact and require little on-site storage.

Residues and Discharges

The development of wells or trenches generally requires drilling or excavation activities in contaminated areas. This results in the handling of contaminated soils that will have to be removed off-site.

Recovered free-phase products will be accumulated inside a tank. These products will then have to be managed off-site.

Recommended analyses for detailed characterization

Physical analysis

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

Recommended trials for detailed characterization

Physical trials

  • Vapour survey
  • Evaluation of the radius of influence
  • Evaluation of operating pressure/vacuum

Hydrogeological trials

  • Permeability test
  • Pumping 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.

  • Free product recovery tests
  • Other information recommended for detailed characterization

    Phase II

    • Contaminant delineation (area and depth)
    • Presence of receptors:
      • presence of potential environmental receptors
      • presence of above and below ground infrastructure
      • the risk of off-site migration

    Phase III

    • Soil stratigraphy
    • Characterization of the hydrogeological system including:
      • the direction and speed of the groundwater flow
      • the hydraulic conductivity
      • the seasonal fluctuations
      • the hydraulic gradient
    • Hydrogeological modelling

    Notes:

    Small-scale studies are recommended to determine the effect of increased temperatures on the free-phase products. These trials will also provide important information for the design of the hot water injection system (injection pressure, water temperature, time of injection, type of injection wells, zone of influence, etc.) and the design of the extraction system.

    Applications

    • In situ treatment of soils in the saturated zone.
    • Applies mainly to free-phase contamination but can also treat dissolved and residual contamination (adsorbed).
    • Applicable to semi-volatile organic compounds such as coal tar, creosote and heavy fuel and oil present in the free phase.
    • Can be used to treat volatile organic compounds.
    • Applicable to homogeneous soil with a hydraulic conductivity of 10-4 cm/s or higher, such as sandy and gravelly soils.
    • An increase in the ambient temperature (up to 40 °C) can enhance microbial activities and bioremediation processes.

    Applications to sites in northern regions

    Hot water injection is not always appropriate in remote areas that do not have easy access to utilities or local labour to operate and maintain the system. The development of this type of system in a northern environment may require climate-adapted techniques that consider, deep freezing of the soil, seasonal changes in soil conditions and long periods without intervention by the system operator. The operating costs of this type of system, in northern environments, could be high, because of the energy required for heating water.

    Treatment type

    Treatment typeApplies or Does not apply
    In situ
    Applies
    Ex situ
    Does not apply
    Biological
    Applies
    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 technologyExist or Does not exist
    Testing
    Exist
    Commercialization
    Exist

    Target contaminants

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

    Treatment time

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

    Long-term considerations (following remediation work)

    Free-phase product levels and thicknesses should be monitored when the recovery work is stopped and recovery devices may be required again if free-phase product is newly measured.

    Secondary by-products and/or metabolites

    • Hot water injection enhances the mobility of contaminants by changing their physical properties. This technology does not directly produce by-products.
    • Increasing temperature may induce volatilization of some contaminants and could potentially release contaminated vapours.

    Limitations and Undesirable Effects of the Technology

    • Hot water injection is efficient in homogeneous, coarse material aquifers with a high hydraulic conductivity (10-4 cm/s and above).
    • Heterogeneous hydrogeological properties reduce the performance of the technology.
    • Increased contaminant mobility can cause contaminants to migrate out of the treatment area or contaminated site.
    • This technology does not treat the contamination and must be combined with other remediation technologies.
    • The pressure at which hot water can be injected into an aquifer is limited.
    • Very high temperature water injection may decrease the microbial population and temporarily reduce the potential for bioremediation.
    • If hot water injection is intended to promote biodegradation processes, the injected water must be non-chlorinated water.

    Complementary technologies that improve treatment effectiveness

    In highly contaminated sites where the goal is to reach specific residual levels, this technology may not be able to achieve low concentrations. Potential polishing techniques are soil washing by adding solvents or surfactants, bioremediation or chemical oxidation.

    Required secondary treatments

    A vapour extraction and treatment system may also be required.

    Application examples

    The following site provides in application example:

    Performance

    Hot water injection is rarely effective because it is affected by soil permeability, solubility of the contaminant, and it is very energy intensive and requires a lot of control methods. Its use is limited to very specific conditions.

    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 days of mobilization.
    • Use of renewable energy and low-energy equipment (geothermal or solar energy for extraction).
    • Allow a longer treatment time to avoid winter operation, eliminating the need to winterize the system while reducing the amount of energy required.

    Potential impacts of the application of the technology on human health

    Main exposure mechanisms

    Applies or does not apply

    Monitoring and mitigation

    Dust

    Does not apply

    N/A

    Atmospheric/Steam Emissions—Point Sources or Chimneys

    Applies

    Emissions monitoring (choice of parameters and levels of intervention depending on source, risk and local requirements).

    Atmospheric/Steam Emissions—Non-point Sources

    Applies

    Modelling the effects of water injection, model validation and soil vapour migration monitoring.

    Air/steam—by-products

    Applies

    Emissions monitoring (choice of parameters, types of samples and type of intervention [source, risk or local requirements]).

    Runoff

    Does not apply

    N/A

    Groundwater—displacement

    Applies

    Modelling of the water injection network and mobilization of the free phase and monitoring of the groundwater level using pressure sensors

    Groundwater—chemical/ geochemical mobilization

    Does not apply

    N/A

    Groundwater—by-product

    Does not apply

    N/A

    Accident/Failure—damage to public services

    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 vapour)

    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

    Updated by : Martin Désilets, B.Sc., National Research Council

    Updated Date : April 17, 2013

    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

    Date Modified: