There are three major groups of in-situ treatments for remediation of soils.
- Physical/chemical treatment technologies,
- Biological treatments technologies,
- Thermal treatment technologies.
Each treatment method has its particular advantages and disadvantages for the removal of specific groups of contaminants. One of the important overall features of in situ treatment methods is that these methods allow the recovery and monitoring of fluids and other reactants as they are brought to the subsurface.
The Environmental Protection Agency’s Federal Technologies Roundtable summarizes the effectiveness of available in situ methods as follows.
In Situ Physical/chemical methods have mixed results.
- Soil vapor extraction methods work comparatively well for some volatile organic compounds (VOCs) and some fuel extractions, but have poorer than average results on more than half of contaminants.
- Solidification/stabilization methods have good results with inorganic and radio-nuclides pollutants but have worse than average results for most other contaminants.
- Chemical oxidation methods are not especially effective in removing most contaminants, except for certain particular inorganic contamination types.
- Soil flushing methods work well against inorganic contaminants but are not recommended against radio-nuclides and explosives.
- Electrokinetic separation methods are effective for inorganic contaminants but much less effective against explosive contaminants.
In situ biological treatments are widely effective.
- Bioremediation methods are effective against the whole range of contaminants.
- Bioventing methods are effective against contamination from fuels but largely less effective in decontaminating inorganic contaminants, radio-nuclides and explosives.
- Phytoremediation methods are only moderately effective and notably less effective against radio-nuclides and explosives.
In situ thermal methods include electrical resistivity, heating, steam injection, radiofrequency heating and vitrification.
- These in situ thermal methods are widely effective against VOCs, but notably less effective against nuclides, inorganic contaminants and explosives.
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Soil Remediation for the Environment
Soil contamination or soil pollution is often caused by industrial mining or agricultural activity that leaves chemicals in the ground. Sometimes contaminated soil sites are the locations of
- chemical leached from waste sites and landfills,
- where dissolved or suspended chemicals are carried by waste water,
- leaking underground storage tanks,
- improper disposal of agricultural or industrial chemicals,
- lead from bullets contaminating gun ranges.
The biggest pollutants are
- mineral tailings and waste-flows from mining,
- lead in soil from various sources,
- fertilizers and insecticides that are applied incorrectly,
- oil and fuel dumping.
Prosecution of polluters:
The United States Environmental Protection Agency (EPA) and other agencies monitor and try to regulate levels of contamination in soil in accordance with the so-called “Superfund,” or the Comprehensive Environmental Response, Compensation, and Liabilities Act. Under the law the EPA can require those responsible for contamination to clean up polluted soil or pay for the cost of cleanup. Each day of non-compliance after the order can cost the polluter $37,500 for each day of non-compliance.
Soil Washing—uses surfactants and water. The soil is placed in a wash solution that either dissolve contaminants, or suspend the particles of contaminant in the wash, separated by size, then carrying them away. Bioremediation makes use of microorganisms of fungi to break down organic contaminants (or even petroleum products) so they can be separated from the soil and removed or destroyed.
Thermal Desorbtion—is used for non-organic waste contamination. Contaminated solids are heated to the boiling point of the oil or other contaminants. The liquidized contaminants are pumped away and either to a thermal oxidizer or condensed in a vapor recovery process to be reclaimed (if the contaminant can be re-used).
Thermal soil remediation uses steam and hot air injection, electric current, or other powerful heat-producing methods to bring contaminants to the vapor point along with steam from trapped moisture. The vaporized (or volatilized) contaminants can be stripped away and removed.
Please contact us to learn more.