Remediation Techniques

Environmental remediation restores a site to healthy and productive use.

Environmental remediation is the practice of removing pollution or contaminants from elements of the environment to restore an area to healthy, productive use. According to its publication "Green Remediation" (EPA 542-R-08-002), the U.S. Environmental Protection Agency actively supports site remediation and reuse. Soil and water remediation techniques include excavation, soil vapor extraction, stabilization, oxidation, pumping and treating, and surfactant-enhanced aquifer remediation (SEAR).

Excavation

Excavation in its simplest form is the removal of contaminated soil. According to the EPA's Best Management Practices, excavation is useful for addressing immediate risks to human health and in cases where other methods are not feasible. When possible, excavation is used as part of other remediation techniques where the excavated soil is cleaned and restored.

Soil Vapor Extraction

Soil vapor extraction is also called soil venting and vacuum extraction. It utilizes a vacuum applied via horizontal or vertical wells drilled near the source of the contamination. The vacuum draws off the volatile constituents of the contaminants; after the collected vapor is treated, it is released into the atmosphere.

Stabilization

Soil stabilization uses chemical reagents added to the soil to create more chemically stable materials or to physically encapsulate the volatile material, thus reducing its mobility. Lime is often used to neutralize acids and to convert metals to more chemically stable forms, and both lime and cement can be used to solidify contaminants so that they don't leach out or react further.

In Situ Chemical Oxidation

In situ chemical oxidation relies on injected oxidants to convert contaminated media into harmless, naturally occurring compounds. The most common oxidant is a hydroxyl-free (OH-free) radical created by applying hydrogen peroxide with iron. The resulting radical is useful for oxidizing complex organic compounds. Other powerful oxidants such as ozone or potassium permanganate may be used, and in some cases the injection of oxygen or simply the ambient air is sufficient.

Pump and Treat

The pump-and-treat remediation technique for contaminated groundwater is self-descriptive in that it consists of pumping contaminated water out of the ground and treating it. The treatment involves absorption of the contaminated material by passing the water through different absorbing materials. Flocculants (substances, including clay, that help separate the contaminant from the water) may also be added to the water, which is then passed through filters.

SEAR (Surfactant-Enhanced Aquifer Remediation)

Chlorinated hydrocarbons are found in many U.S. aquifers.

SEAR is a technique used to remove nonaqueous phase liquids (NAPLs) from water. These NAPLs are common groundwater contaminants that, according to the environmental engineering department of the University of Texas, are found in many U.S. aquifers. They are produced by chlorinated hydrocarbons widely used as solvents. Because they don't mix with water, the addition of surfactants (agents to lower surface tension) is required for their recovery. The increased solubility and mobility of the contaminant allows for its removal.

References

• EPA: Green Remediation
• EPA: Best Management Practices for Excavation and Surface Restoration
• EPA: Soil Vapor Extraction (SVE)
• HSI: Chemical Stabilization
• EPA: Chemical Oxidation

Resources

• "Modern Project Management Techniques for Environmental Remediation," Timothy J. Havrane; 1999